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Body SystemsEyes
Other Names
Synopsis
The Eyes: Anatomy, Physiology, Health Assessment, Nutritional Support, and Associated Conditions
Overview
The eyes are light-gathering sensory organs at the front of the head that send signals the brain uses to create the "picture" we see. The main task of the eye is to capture incoming light and convert it into electrical signals, which are then transmitted to the brain where they are interpreted and result in the information of a visual image. Vision is one of the most complex and critical of the human senses, and the integrity of the visual system depends on the coordinated function of numerous anatomical structures, neural pathways, and biochemical processes.
Anatomy and Structural Components
The Outer Tunic (Fibrous Layer)
The sclera is the tough, white outer layer of the eye that provides protection and structural support and maintains the eye's shape, also known as the "white of the eye." The main function of the sclera is to provide a stable shell, and it is bordered by eye muscles for the movement of the eyeball and the optic nerve at the back of the eye.
The cornea is a unique biological tissue that is transparent to light and contains no blood vessels. This small transparent dome at the front of the eye is approximately 11 mm in diameter and 500 ÎĽm thick in the center, thickening to around 700 ÎĽm at the periphery. One of the cornea's most important functions is to refract incoming light and direct it onto the retina, playing a crucial role in vision. In addition, the cornea acts as a protective barrier against external agents such as dust or debris. The cornea functions predominantly as a refractive lens, contributing approximately three-fourths of the eye's focusing power, with the remaining one-fourth attributed to the actual lens.
The Middle Tunic (Uveal Tract)
The iris, the colored part of the eye, regulates the amount of light entering the eye and controls the size of the pupil, which itself can dilate or constrict in response to light intensity. The iris is actually an extension of the ciliary body, a structure that has multiple functions in the anterior segment, from production of the fluid that fills the anterior segment (aqueous humor) to suspension and control of the shape of the crystalline lens of the eye.
The ciliary body is a structure that contains the ciliary muscle, surrounds the lens, and is responsible for changing the shape of the lens to focus on objects at different distances. The ciliary body also produces aqueous humor.
The Inner Tunic (Retina)
The retina is the innermost layer of the eye. It contains special photoreceptor cells — rods and cones — which are responsible for detecting and converting light into electrical signals that are transmitted to the brain via the optic nerve. Ten different layers of cells work together in the retina to detect light and turn it into electrical impulses. The retina is one of the most metabolically active tissues in the body.
The Lens
Located behind the cornea, iris, and pupil, the lens is a transparent, flexible structure that further focuses incoming light onto the retina. Changes in the lens shape, known as accommodation, allow the eye to adjust its focus for objects at different distances.
Vitreous and Aqueous Humors
Light passes through the pupil and the lens before reaching the retina, traversing the vitreous humour, a gel-like substance that maintains ocular shape, supports the retina, and facilitates proper optical functioning. Vitreous humor is a gel-like substance that fills the back part of the eye (the vitreous chamber), filling the space between the lens and the retina. It maintains the eye's shape and transmits light to the retina.
The Optic Nerve
Rays of light fall into the eye and pass through the cornea, eye chambers, pupil, lens, and vitreous body before finally landing on the retina. The focal point is on the retina and an image is created. The visual impression is transmitted to the brain via the optic nerve and processed there, resulting in visual perception.
The Lacrimal Apparatus
The lacrimal glands are responsible for producing tears. Tear production keeps the eye moist, protects it from foreign objects, and washes away debris or foreign particles.
Eyelids and Conjunctiva
The eyelids, with lashes at their leading edges, help to protect the eye from abrasions by blocking particles that may land on the surface of the eye. The external eye structures include the eyelids and surrounding tissues, conjunctiva, lacrimal apparatus, cornea, and anterior chamber.
Autonomic Innervation
The majority of intraocular muscles of the eyes are dominantly controlled by the autonomic nervous system (ANS). The pupillary light reflex (PLR) has been widely used for the detection of ANS dysfunction. The eyes are innervated by sympathetic, parasympathetic, and trigeminal sensory nerve fibers.
Physiological Functions
The anatomy and function of the various structures are closely linked, enabling clear vision, color discrimination, and distance estimation. The different layers of the eye, such as the cornea, retina, and choroid, play a central role in this process.
- Light refraction and focusing: The eye structure lets light enter and pass through a series of clear components and sections, including the cornea, aqueous humor, lens, and vitreous humor. Those structures bend and focus light, adjusting how far the light beams travel before they come into focus. The focus needs to be precise; if it isn't, what is being viewed appears blurry.
- Accommodation: An important aspect of the eye's function is accommodation, which enables vision of objects in focus at different distances.
- Phototransduction: The main task of the eye is to capture incoming light and convert it into electrical signals, which are then transmitted to the brain where they are interpreted as a visual image.
- Peripheral vision: Visual field (VF) describes how far one can see to the side. A normal visual field is 180 degrees, which is a half-circle.
- Visual acuity: Visual acuity (VA) is defined as the clarity of the image seen by the eye and is measured using an eye chart at a distance of 20 feet. 20/20 vision does not mean perfect vision; it is normal, average vision.
Assessment of Eye Health
A routine assessment of the eyes by registered nurses in inpatient and outpatient settings typically includes external inspection for signs of a medical condition, as well as screening for vision problems. A vision screening test and assessment of pupillary response are often included in the physical exam.
The examination of a person's eyes involves the performance of one or more tests for monitoring and diagnosing eye health, such as detecting glaucoma and retinal disorders, inspecting the pupil, and measuring corneal sensitivity, and/or tests for evaluating visual ability and acuity, such as determining refractive error and detecting color blindness.
Comprehensive eye examinations, according to established clinical standards, may include:
- Objective and subjective refraction and/or other tests to check visual acuity; examination of the extraocular muscles; peripheral vision test (e.g., by checking the visual field by confrontation); examination of the external eye; examination of the pupils; color vision test; test for stereopsis for depth perception; evaluation of central vision field (e.g., using the Amsler grid); cover test for strabismus; an optical coherency tomography (OCT) scan and/or slit lamp examination using biomicroscopy; examination of eyelids, conjunctiva, cornea, anterior chamber, iris, and lens; and measurement of eye pressure.
The sclera should be white and the conjunctiva should be pink. There should not be any drainage from the eyes. The astute clinician can frequently gain helpful diagnostic information about a patient by briefly but meticulously studying the external eyes.
Regular visits and checkups enable practitioners to monitor and track the health of the eyes and to detect and diagnose certain disorders, diseases, and other changes. This allows for early detection, diagnosis, and treatment of many conditions, which frequently increases the likelihood that treatment will be successful.
Nutrients, Herbs, and Natural Ingredients
Vitamin A (Retinol)
Traditional Use
The link between diet and night vision has been recognized since ancient times. Historical records from ancient Egypt describe using liver (rich in vitamin A) as a remedy for night blindness. One of the oldest diseases known to man is nutritional night blindness. Across many traditional medicine systems, including Ayurveda, dietary manipulation with liver and orange and yellow vegetables was employed to address visual deterioration at night.
Scientific Evidence
Vitamin A is required for the formation of the photoreceptor rhodopsin — a photopigment found in rod cells of the retina that is especially helpful in allowing the eyes to see at night. To see the full spectrum of light, the eye needs to produce certain pigments for the retina to work properly. Vitamin A deficiency stops the production of these pigments, leading to night blindness. The eye also needs vitamin A to nourish other parts of the eye, including the cornea. Without enough vitamin A, eyes cannot produce enough moisture to keep them properly lubricated.
Night blindness is one of the first signs of vitamin A deficiency. In its more severe forms, vitamin A deficiency contributes to blindness by making the cornea very dry, thus damaging the retina and cornea. An estimated 250,000–500,000 children who are vitamin A-deficient become blind every year, and half of them die within 12 months of losing their sight. Deficiency of vitamin A is the world's leading preventable cause of childhood blindness.
Other symptoms of deficiency include dryness of the conjunctiva (xerosis), corneal ulcers and necrosis (keratomalacia), hyperkeratotic skin lesions, and development of small white patches on the conjunctiva (Bitot's spots). Current data do not support dietary supplementation with vitamin A for glaucoma. Evidence strength for vitamin A supplementation in glaucoma and AMD prevention is weak; its primary established role is in the correction of deficiency states.
Lutein and Zeaxanthin
Traditional Use
Lutein and zeaxanthin are not associated with a distinct pre-scientific traditional medicinal use comparable to herbs. However, diets rich in dark leafy green vegetables — the primary food sources of these carotenoids — have been historically associated with good health in numerous cultures.
Scientific Evidence
Lutein, zeaxanthin, and meso-zeaxanthin are xanthophyll carotenoids found within the retina and throughout the visual system. The retina is one of the most metabolically active tissues in the body, and the highest concentration of xanthophylls is found within the retina, generating many theories regarding their role in supporting retinal function.
Lutein and zeaxanthin constitute the main pigments found in the yellow spot of the human retina, which protect the macula from damage by blue light, improve visual acuity, and scavenge harmful reactive oxygen species. They have also been linked with reduced risk of age-related macular degeneration (AMD) and cataracts.
They work as a filter protecting the macula from blue light and also as structurally bound antioxidants which protect surrounding ocular cells against oxidative stress. Many observational and interventional studies have indicated that lutein and zeaxanthin might reduce the risk of various eye diseases, especially age-related macular degeneration.
Observational studies have reported that increased dietary intake and higher serum levels of lutein and zeaxanthin are associated with lower risk of AMD, especially late AMD. Randomized, placebo-controlled clinical trials have demonstrated that xanthophyll supplementation increases macular pigment levels, improves visual function, and decreases the risk of progression to late AMD, especially neovascular AMD. Current publications on the preventive and therapeutic effects on cataracts, diabetic retinopathy, and retinopathy of prematurity have reported encouraging results.
The AREDS2 trial — a major NIH-sponsored randomized controlled trial — specifically examined these carotenoids. In AREDS2, begun in 2006, researchers compared the beta-carotene formulation to one with 10 mg lutein and 2 mg zeaxanthin instead. Like beta-carotene, lutein and zeaxanthin are antioxidants with activity in the retina. At the end of the five-year AREDS2 study period, the researchers concluded that lutein and zeaxanthin did not increase risk for lung cancer, and that the new formulation could reduce the risk of AMD progression by about 26%. Current evidence suggests lutein and its isomers play important roles in ocular development in utero and throughout the life span, in vision performance in young and later adulthood, and in lowering risk for the development of common age-related eye diseases in older age.
These xanthophyll carotenoids are found in a wide variety of vegetables and fruits, and in especially high concentrations in leafy green vegetables. Additionally, egg yolks and human milk appear to be bioavailable sources. Evidence for lutein and zeaxanthin in AMD prevention and management is among the strongest in the ocular nutrition literature, grounded in large-scale RCT data.
The AREDS/AREDS2 Formulation (Vitamins C, E, Beta-Carotene/Lutein+Zeaxanthin, Zinc, Copper)
Scientific Evidence
The Age-Related Eye Disease Studies (AREDS and AREDS2) established that dietary supplements can slow progression of age-related macular degeneration (AMD), the most common cause of blindness in older Americans. The original AREDS study, launched in 1996, showed that a dietary supplement formulation (500 mg vitamin C, 400 international units vitamin E, 2 mg copper, 80 mg zinc, and 15 mg beta-carotene) could significantly slow the progression of AMD from moderate to late disease.
Taking AREDS or AREDS2 supplements reduces the risk of progression from intermediate to advanced AMD by about 25 percent. AREDS and AREDS2 supplements do not prevent AMD onset. AREDS and AREDS2 supplements do not have an effect on cataract. Omega-3 fatty acid supplements do not have an effect on cataract or AMD.
Long known to help slow the progression from intermediate to late AMD, analysis of AREDS2 data further showed that taking AREDS2 supplements can also slow disease progression in people with late dry AMD, supporting the continued use of AREDS2 supplements by people with late dry AMD. In the new analysis, the researchers reviewed the original retinal scans of participants in the AREDS (318 participants, 392 eyes) and AREDS2 (891 participants, 1,210 eyes) trials who developed dry AMD.
However, two concurrent studies revealed that people who smoked and took beta-carotene had a significantly higher risk of lung cancer than expected. The AREDS2 formula, which substituted antioxidants lutein and zeaxanthin for beta-carotene, not only reduces risk of lung cancer due to beta-carotene, but is also more effective at reducing risk of AMD progression, compared to the original formula.
Oxidation and inflammation are implicated in the etiology of age-related eye diseases, and there is evidence that dietary antioxidants and anti-inflammatories may provide benefit in decreasing risk. Nutrients of interest are vitamins C and E, β-carotene, zinc, lutein, zeaxanthin, and the omega-3 fatty acids EPA and DHA. Overall, the AREDS/AREDS2 evidence base represents the highest quality clinical evidence in ocular nutrition.
Omega-3 Fatty Acids (DHA and EPA)
Traditional Use
Consumption of fatty fish has been traditional in many coastal and Nordic cultures. While not identified specifically as an eye remedy, omega-3-rich diets have been part of traditional medicine in various forms, particularly in Scandinavian and Japanese traditions, where fatty fish formed a large part of the diet.
Scientific Evidence
There is some limited evidence suggesting that omega-3 supplements may have a role in managing dry eye; however, more research is needed before any firm conclusions can be drawn. A 2019 Cochrane review of 34 randomized controlled trials involving more than 4,314 adult participants concluded that long-chain omega-3 supplements may have a role in managing dry eye; however, the evidence is currently limited.
A 2015 Cochrane systematic review of two randomized controlled trials involving 2,343 participants found that omega-3 fatty acid supplementation in people with AMD for periods up to 5 years does not reduce the risk of progression to advanced AMD or the development of moderate-to-severe visual loss. Much more research will need to be conducted before anything conclusive can be asserted with respect to the effects of omega-3 fatty acids on eye health. Evidence for omega-3 supplementation in dry eye is preliminary and mixed; evidence for AMD prevention is currently negative based on the best available data.
Zinc
Traditional Use
Zinc-containing compounds have been used in topical eye preparations since antiquity, notably in ancient Egyptian and Roman medicine. Zinc sulfate eye drops were used historically as antiseptic eye treatments.
Scientific Evidence
Zinc helps vitamin A produce melanin to protect the eye and may help delay AMD progression, while a zinc deficiency also has been linked to poor night vision. Zinc deficiency may also produce nyctalopia by worsening vitamin A deficiency, as zinc is critical for vitamin A metabolism.
Zinc is a key component of the AREDS/AREDS2 formulations at 80 mg/day, and as part of that combination has demonstrated the capacity to reduce AMD progression in clinical trials. However, the evidence for zinc supplementation in isolation for eye conditions remains less well-characterized than its role within the full AREDS formulation.
Saffron (Crocus sativus)
Traditional Use
Saffron (Crocus sativus L.) and its main constituents, crocin and crocetin, are natural carotenoid compounds that have been reported to possess a wide spectrum of properties and induce pleiotropic anti-inflammatory, anti-oxidative, and neuroprotective effects. Saffron has been used in Persian, Indian (Ayurvedic), and Mediterranean traditional medicine for centuries, including as a remedy for visual fatigue and eye inflammation, administered both orally and as an eye wash in some traditions.
Scientific Evidence
An increasing number of experimental, animal, and human studies have investigated the effects and mechanistic pathways of saffron and its compounds to assess their potential therapeutic use in ocular diseases, including age-related macular degeneration, glaucoma, and diabetic maculopathy.
Saffron and its active compounds, crocin and crocetin, have shown promising results in improving visual function and delaying AMD progression. Several clinical studies have found that daily supplementation with 20–50 mg of saffron or 5–15 mg of crocin for 3–12 months significantly improved best-corrected visual acuity, contrast sensitivity, and retinal function as measured by electroretinogram and microperimetry, with benefits observed in both dry and wet forms of AMD.
The results of clinical studies showed that saffron and its active compounds, such as crocin and crocetin, in oral form, have been effective in reducing inflammation in eye diseases such as diabetic retinopathy, open-angle glaucoma, and age-related macular edema. The effect of crocin is dose-dependent, since crocin at a dose of 15 mg compared to 5 mg per day significantly reduced the thickness of macular degeneration in patients with diabetic retinopathy.
The results of this review indicated that saffron and its main ingredients such as crocin could be a potential candidate for the treatment of ocular disease, especially eye inflammation; however, further clinical studies are needed to confirm such efficiency. Evidence for saffron in AMD and diabetic maculopathy is promising based on multiple small-to-moderate RCTs, but overall evidence strength remains preliminary due to small sample sizes and limited long-term data.
Bilberry (Vaccinium myrtillus)
Traditional Use
Bilberry (Vaccinium myrtillus) has a long history of traditional use to support eye health, particularly in Europe. Folklore claims, especially from World War II, suggest that British Royal Air Force pilots consumed bilberry jam to improve night vision. In European herbal traditions, bilberry preparations (berries, leaf extracts, and jams) were used for a range of visual complaints including impaired night vision, eye strain, and vascular fragility in the eye.
Scientific Evidence
Bilberries are rich in anthocyanins — plant pigments with antioxidant properties — that are thought to benefit eye health by supporting blood vessel integrity and reducing oxidative stress. Some small clinical studies and animal research have explored bilberry extracts for potential benefits in conditions such as night vision, retinal health, and diabetic retinopathy, but results are inconsistent and not conclusive.
Systematic reviews generally find that high-quality evidence supporting bilberry for improving vision or treating eye diseases is lacking. The European Medicines Agency recognizes bilberry as a traditional herbal remedy, not as a clinically validated treatment. In summary, while bilberry has a strong tradition of use for supporting the eyes and contains compounds of biological interest, robust scientific validation for its effectiveness in eye health remains limited. Most claims are based on historical use and preliminary research rather than large, well-controlled clinical trials.
Ginkgo Biloba
Traditional Use
Ginkgo biloba has been used in Traditional Chinese Medicine for thousands of years. Its seeds and leaves have historically been employed for a wide range of conditions, including visual disturbances and dizziness. Ginkgo biloba has been celebrated for centuries across European, Ayurvedic, and Chinese medicine traditions for its ability to support clear vision, reduce inflammation, and defend delicate retinal tissue from oxidative damage.
Scientific Evidence
Ginkgo biloba may have a benefit in protecting the optic nerve of the eye in certain vascular conditions. Increasing evidence is pointing to glaucoma being more than simply an intraocular pressure-dependent degeneration of the optic nerve. Ginkgo biloba extract has numerous properties which may be beneficial in treating non-pressure related mechanisms of damage in glaucoma, including increased ocular blood flow, antioxidant activity, platelet activating factor and nitric oxide inhibition, and neuroprotective activity. Some researchers are beginning trials where ginkgo biloba extract is used in selected glaucoma patients, especially in those with "normal tension glaucoma" or those with progressing glaucomatous damage despite adequate ocular pressure control. The overall body of clinical evidence for ginkgo biloba in eye disease remains preliminary, with limited and small RCTs; larger well-controlled trials are needed.
Vitamin C (Ascorbic Acid)
Scientific Evidence
Vitamin C is a component of the validated AREDS formulation for AMD. Oxidation and inflammation are implicated in the etiology of age-related eye diseases, and there is evidence that dietary antioxidants may provide benefit in decreasing risk of age-related eye disease. Current data do not support dietary supplementation with vitamin C for glaucoma. Good dietary sources include citrus fruits, berries, tomatoes, and broccoli.
Vitamin E (Tocopherol)
Scientific Evidence
Vitamin E is part of the AREDS formulation. Vitamin E protects cells in the eyes from damage caused by free radicals, which break down healthy eye tissue. This damage can increase risks of developing AMD and cataracts. Current data do not support dietary supplementation with vitamin E alone for glaucoma. As with vitamin C, its strongest evidence is as part of the combined AREDS/AREDS2 formulation rather than as a standalone supplement for eye disease.
Conditions and Concerns Associated with the Eyes
The leading causes of blindness and low vision in the United States are primarily age-related eye diseases, including age-related macular degeneration, cataract, diabetic retinopathy, and glaucoma.
Age-Related Macular Degeneration (AMD)
AMD results in damaged sharp and central vision. Central vision is needed for seeing objects clearly and for reading and driving. AMD is a common eye disease characterized by the deterioration of the macula, the part of the retina responsible for sharp, central vision. This condition is primarily age-related and is a leading cause of vision loss among people older than 50. There are two principal forms: "dry" (atrophic) and "wet" (neovascular) AMD. A high prevalence of AMD, over 14%, as the cause of blindness and vision impairment, in adults aged 50 years and older in 2015, has been predicted in high-income subregions.
Cataracts
A cataract is the clouding of the eye's transparent lens that causes blurry vision. This condition usually develops gradually over time and is the most common cause of vision loss in people over age 45. Cataracts affect more than 50% of all adults above the age of 80. By the age of 60, more than half of all adults will begin to develop a cataract. With more than 20 million cases, cataracts are one of the leading causes of blindness worldwide. A cataract does not cause pain or significant ocular discomfort and generally takes many decades before any signs of the condition are noticeable.
Glaucoma
Glaucoma is a group of diseases that can damage the eye's optic nerve and result in vision loss and blindness. Glaucoma occurs when the normal fluid pressure inside the eyes slowly rises; however, recent findings show that glaucoma can occur with normal eye pressure. With early treatment, the eyes can often be protected against serious vision loss. Elevated intraocular pressure (IOP) due to inadequate ocular drainage is the primary cause of glaucoma. Glaucoma often develops as the eye ages, or it can occur as the result of an eye injury, inflammation, tumor, or in advanced cases of cataract or diabetes.
Diabetic Retinopathy
Diabetic retinopathy is a diabetes-related condition that affects the eyes. This eye problem is caused by damage to the retina's blood vessels, the light-sensitive tissue at the back of the eye. It can develop in anyone who has type 1 or type 2 diabetes, and the chances of developing this complication become higher the longer someone has diabetes and the less controlled their blood sugar is. As many as 50% of patients are not getting their eyes examined or are diagnosed too late for treatment to be effective. An estimated 4.1 million Americans have retinopathy and 899,000 have vision-threatening retinopathy.
Refractive Errors
Refractive errors are the most frequent eye problems in the United States. They include myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia, which occurs between age 40–50 years and involves loss of the ability to focus up close. Short-sightedness (myopia) is a very common eye condition that causes distant objects to appear blurred, while close objects can be seen clearly. Worldwide, the prevalence of myopia is increasing. Myopia begins at younger ages and progresses faster, leading to more adults with high myopia and risk of sight-threatening complications.
Dry Eye Disease
Dry eye disease is a multifactorial condition of the ocular surface characterized by disruption of the tear film. There is some limited evidence suggesting that omega-3 supplements may have a role in managing dry eye; however, more research is needed before any firm conclusions can be drawn. Dry eye is among the most common reasons for eye clinic visits globally.
Amblyopia and Strabismus
Other common eye disorders include amblyopia and strabismus. Amblyopia and strabismus are disorders that most commonly occur in children. Amblyopia (often called "lazy eye") is a condition in which vision in one eye fails to develop properly. Strabismus refers to misalignment of the eyes.
Vitamin A Deficiency and Ocular Manifestations
The eye signs of vitamin A deficiency include night blindness, conjunctival xerosis, Bitot's spots, corneal xerosis, corneal ulcers, keratomalacia, and corneal scarring. Many nutritional deficiencies can result in vision impairment. Ocular manifestations include those of vitamin A, vitamin B1, B12, vitamin C, vitamin D, and vitamin E deficiencies, as well as minerals such as zinc, and encompass dry eye disease, corneal xerosis, decreased night vision, subconjunctival hemorrhage, and retinal changes.
Other Eye Conditions Catalogued by the NIH National Eye Institute
Additional conditions recognized by the NIH NEI include blepharitis, blepharospasm, central retinal vein occlusion, coloboma, color blindness, convergence insufficiency, corneal conditions, floaters, Graves' eye disease, idiopathic intracranial hypertension, low vision, macular edema, retinal detachment, and pink eye (conjunctivitis), among others.
References
- PMC: Ocular Autonomic Nervous System: An Update from Anatomy to Physiological Functions
- arXiv: Introduction to Eye Tracking: A Hands-On Tutorial (Eye Anatomy Section)
- Ophthalmology24: Parts of the Eye: Physiology and Eye Anatomy
- AboutKidsHealth: Eye Anatomy and Function
- USAARL: Basic Anatomy and Physiology of the Human Visual System
- arXiv: The Eye as a Window to Systemic Health — Ocular Anatomy and Physiology
- Cleveland Clinic: Eyes — How They Work, Anatomy and Common Conditions
- NIH/NCBI Clinical Methods: The External Eye Examination
- NIH/NCBI Nursing Skills: Chapter 8 Eye and Ear Assessment
- NIH NCCIH: Dietary Supplements for Eye Conditions
- NIH NCCIH: Dietary Supplements for Eye Conditions — What the Science Says
- PMC: Lutein and Zeaxanthin Isomers in Eye Health and Disease
- PMC: Lutein, Zeaxanthin, and meso-Zeaxanthin in the Clinical Management of Eye Disease
- PMC: Zeaxanthin and Lutein in the Management of Eye Diseases
- PMC: Dietary Sources of Lutein and Zeaxanthin Carotenoids and Their Role in Eye Health
- PMC: Nutrients for the Aging Eye
- NIH National Eye Institute: NIH Study Confirms Benefit of Supplements for Slowing AMD
- NIH National Eye Institute: AREDS/AREDS2 Clinical Trials
- NIH National Eye Institute: AREDS2 Supplements for AMD
- NIH: Supplements Slow Disease Progression During Late Stage Dry AMD
- NIH/AHRQ NCBI: Effects of Omega-3 Fatty Acids on Eye Health — Evidence Report Summary
- CDC: About Common Eye Disorders and Diseases
- NIH/NCBI StatPearls: Blindness
- WHO: Vitamin A Deficiency
- American Academy of Ophthalmology: What Is Vitamin A Deficiency?
- PMC: The Eye Signs of Vitamin A Deficiency
- PMC: Ophthalmic Manifestations of Nutritional Deficiencies: A Mini Review
- PMC: Reversible Nyctalopia and Bilateral Optic Neuropathy due to Combined Vitamin A, Zinc, and Copper Deficiency
- PMC: Pharmacological Effects of Saffron and its Constituents in Ocular Disorders — Systematic Review
- PMC: Crocus sativus (Saffron) and Age-Related Macular Degeneration
- PMC: Saffron (Crocus sativus L.) in Ocular Diseases: A Narrative Review
- PMC: A Longitudinal Follow-Up Study of Saffron Supplementation in Early AMD
- NIH National Eye Institute: Eye Conditions and Diseases (Full Index)
- American Optometric Association: Vitamin A — Beneficial for Eyes
Natural Remedies
Ingredients
These ingredients are often used in alternative medicine to support eyes.
- ALA (alpha-lipoic acid)Scientific
Alpha-lipoic acid is an endogenous antioxidant and mitochondrial cofactor that regenerates vitamins C and E and glutathione. Preliminary human evidence suggests potential benefit for geographic atrophy in dry AMD, and animal models demonstrate protection of retinal ganglion cells and photoreceptors from oxidative injury.
- algal oilScientific
DHA from algal oil is a primary structural and functional fatty acid of the retina, accounting for approximately 20% of retinal weight. Algal DHA supplementation in infant formula improves visual acuity at 12 months. DHA is essential for photoreceptor function and protection against age-related retinal damage including dry eyes and macular degeneration.
- alpha-caroteneScientific
Alpha-carotene is a provitamin A carotenoid whose conversion to retinol is essential for the visual cycle, specifically the synthesis of rhodopsin required for dim-light vision. NIH identifies provitamin A activity as the only firmly established in-human health function of carotenoids including alpha-carotene. Vitamin A deficiency—which adequate alpha-carotene intake can prevent—is a leading cause of preventable blindness globally.
- alpha-glycosyl isoquercitrinScientific
Two human double-blind, placebo-controlled RCTs of 100 mg AGIQ/day for 8 weeks in seasonal pollinosis subjects found significant improvement in ocular comfort and eye-related quality of life, attributable to mast cell stabilization and antihistamine activity in conjunctival tissue.
- anchoviesScientific
DHA from anchovies is a primary structural component of retinal photoreceptor membranes, essential for phototransduction. Vitamin A from anchovies is required for rhodopsin synthesis. Epidemiological and clinical studies link oily fish omega-3 intake with reduced risk of AMD and support for general visual function.
- annattoScientific
Norbixin from annatto has been evaluated in animal models of AMD and Stargardt disease, demonstrating protection of retinal pigment epithelium cells, reduction of A2E accumulation, and preservation of photoreceptor function. In vitro, norbixin outperformed lutein and zeaxanthin in retinal photoprotection. A drug candidate (BIO201/norbixin) is in preclinical development for AMD.
- anthocyaninsScientific
Anthocyanins (especially from bilberry and dark berries) reach retinal tissue intact after oral intake and are documented to reduce retinal inflammation, improve retinal sensitivity, and reduce eye strain in clinical studies. They protect retinal capillary integrity and accelerate rhodopsin regeneration in preclinical studies.
- anthocyanosidesScientific
Anthocyanosides are the glycoside forms of anthocyanins from bilberry, documented to accelerate rhodopsin regeneration in rod photoreceptors and to protect retinal capillary integrity. A standardized bilberry extract with 36% anthocyanosides improved retinal sensitivity as measured by computerized perimetry in clinical studies.
- apricotScientific
Apricots are a rich source of beta-carotene, lutein, and zeaxanthin—the principal nutrients associated with retinal and macular health in peer-reviewed literature. Vitamin A (from beta-carotene) is essential for photoreceptor function; lutein and zeaxanthin concentrate in the macula and protect against AMD and cataract. Multiple population studies associate dietary carotenoid intake with reduced risk of blinding eye diseases.
- astaxanthinScientific
Astaxanthin is a xanthophyll carotenoid with uniquely potent antioxidant properties that crosses the blood-retinal barrier. Clinical studies document improvements in dry eye syndrome, eye fatigue, and accommodation in screen users, and a growing body of evidence covers AMD, glaucoma, cataract, and asthenopia. A 2020 PubMed review (PMID 32370045) comprehensively documented its ocular clinical applications.
- benfotiamineScientific
Benfotiamine blocks the three major hyperglycemia-driven pathways (polyol, PKC, AGE) responsible for retinal microvascular damage, and completely prevented diabetic retinopathy in a seminal Nature Medicine animal study. It also suppresses ocular inflammation in uveitis animal models. Small human studies suggest potential benefit in early diabetic retinopathy; no large human RCT has confirmed this.
- beta-caroteneScientific
Beta-carotene is a provitamin A carotenoid included in the original AREDS formula that reduced advanced AMD progression risk by 25% in a landmark NEI RCT. It also serves as a precursor to retinol, supporting rhodopsin synthesis and night vision. AREDS2 replaced it with lutein/zeaxanthin due to lung cancer risk in smokers.
- bilberryScientific
Bilberry (Vaccinium myrtillus) has been used in European traditional medicine for eye ailments since the Middle Ages. Standardized extract (36% anthocyanins) improves retinal sensitivity by computerized perimetry and reduces eye strain in clinical studies. Evidence for night vision improvement is mixed in controlled trials but preclinical mechanistic evidence for retinal protection is robust.
- blueberryScientific
Large prospective epidemiological evidence (36,000+ women) assessed blueberry and anthocyanin intake in relation to cataract and AMD. Anthocyanins localize to retinal tissue and have established protective mechanisms, providing mechanistic and observational support for eye health.
- bovine liverScientific
Bovine liver is the richest food source of preformed vitamin A (retinol), the direct precursor of 11-cis-retinal in rhodopsin required for photoreception. Zinc in liver facilitates vitamin A transport to the retina. B vitamins from liver reduce homocysteine associated with optic neuropathy. This is one of the most historically and scientifically validated nutritional relationships for bovine liver.
- boxthorneScientific
Boxthorn is one of the primary herbs for ocular health in East Asian medicine, supported by multiple clinical trials and extensive preclinical research. LBPs protect RGCs, retinal pigment epithelium, and retinal vasculature. Human RCTs demonstrate preserved macular thickness and visual acuity in retinitis pigmentosa. Zeaxanthin from boxthorn raises macular pigment optical density.
- brussel sproutsScientific
Brussels sprouts supply lutein, zeaxanthin, beta-carotene (provitamin A), and vitamin C — nutrients with established roles in retinal protection, macular health, and prevention of age-related macular degeneration and cataract. Brussels sprouts are specifically listed among foods high in lutein and zeaxanthin.
- butcher's broomScientific
Butcher's broom extracts have been studied in diabetic retinopathy, a microvascular condition affecting the retina. A small clinical study (N=60, Archimowicz-Cyrylowska 1996) reported positive findings on retinopathy and lipid parameters in diabetic patients using Ruscus extract. The vasoprotective and anti-elastase mechanisms of ruscogenins provide biological plausibility for retinal microvascular protection.
- calamari oilScientific
DHA is a major structural component of retinal photoreceptors, and EPA and DHA together modulate ocular inflammation. Clinical evidence supports marine omega-3s for dry eye disease, AMD risk reduction, and general retinal health. Calamari oil's high DHA content makes it particularly relevant for eye health support.
- capsanthinScientific
Capsanthin has documented preclinical activity across multiple ocular endpoints: reducing intraocular pressure, improving tear film stability in dry eye, protecting corneal epithelium, and shielding ocular cells from UVB-induced DNA damage. It is structurally comparable to lutein in antioxidant photoprotection.
- caroteneScientific
Beta-carotene is the principal dietary precursor of vitamin A, an indispensable component of rhodopsin in retinal rods and a regulator of corneal epithelial and conjunctival health. Beta-carotene's antioxidant activity in ocular tissues provides additional protection against oxidative damage from light exposure. The AREDS RCT demonstrated benefit of a beta-carotene-containing formula in slowing AMD progression.
- carrotScientific
Carrots are among the best-known dietary sources for eye health, providing beta-carotene (provitamin A for rhodopsin and corneal integrity), lutein, and zeaxanthin (retinal macular pigment). Clinical and epidemiological evidence supports carotenoid-rich diets in reducing AMD risk and maintaining visual function, particularly in vitamin A deficient populations.
- chondroitinScientific
Chondroitin sulfate is used in ophthalmic solutions for dry eye disease, functioning as a lubricating agent and drug-delivery vehicle. Multiple clinical trials demonstrate improvements in tear film stability, goblet cell density, and ocular surface symptoms. CS also shows potential as a drug vehicle for enhanced corneal permeation and drug retention.
- chrysanthemumScientific
Chrysanthemum is one of the most prominent traditional and modern herbal interventions for ocular health. It has both deep TCM documentation and emerging clinical and preclinical scientific evidence for dry eye, eye strain, and related inflammatory conditions.
- chymotrypsinScientific
Alpha-chymotrypsin has an established and long-standing medical use in cataract surgery via enzymatic zonulolysis—dissolution of the zonular fibers holding the lens, facilitating intracapsular lens extraction. This application has been studied in multiple clinical series and controlled trials since the 1950s–1960s. It is an FDA-approved ophthalmic use.
- citicolineScientific
Citicoline has the most extensive ophthalmic clinical trial evidence among supplements, with multiple RCTs demonstrating neuroprotection of retinal ganglion cells, improved visual evoked potentials, visual field preservation, and retinal nerve fiber layer support in open-angle glaucoma. Both oral and topical formulations have been tested. A 2023 systematic review in PLOS One confirmed clinical evidence across multiple endpoints while noting that conclusive evidence of slowing glaucoma progression requires further study.
- cod liver oilScientific
Cod liver oil directly supports ocular health through two key nutrients: vitamin A (essential for rhodopsin in photoreceptors and conjunctival goblet cells) and DHA (the dominant structural fatty acid in retinal photoreceptor outer segments). Both prevent deficiency-related eye disease and may reduce risk of AMD and dry eye.
- coleus forskohliiScientific
Forskolin from Coleus forskohlii reduces intraocular pressure (IOP) and provides retinal neuroprotection via cAMP-mediated mechanisms. Multiple clinical trials support its efficacy as eye drops in open-angle glaucoma, with one RCT showing superiority over timolol. Oral formulations have also been investigated.
- collardScientific
Collard greens are one of the highest dietary sources of lutein and zeaxanthin (~14.6mg/cup), carotenoids that concentrate in the macula and retina to protect against blue-light damage and oxidative stress. They also provide vitamin A (beta-carotene) required for rhodopsin synthesis and maintenance of corneal health. Clinical evidence from CAREDS and AREDS2 trials supports these carotenoids in reducing AMD progression.
- CoQ10 (coenzyme Q10)Scientific
The retina is one of the most metabolically active tissues in the body and is highly vulnerable to mitochondrial dysfunction and oxidative stress. Clinical studies have investigated CoQ10 (topical and oral) for diabetic retinopathy, glaucoma, retinal vascular diseases, and retinopathy of prematurity. Topical CoQ10/vitamin E drops improved oxidative stress markers in a randomized glaucoma trial.
- crocetinScientific
Crocetin is the aglycone metabolite of crocin from saffron with anti-angiogenic, neuroprotective, and antioxidant mechanisms in retinal tissue. Multiple clinical studies show crocetin/crocin supplementation improves visual acuity and retinal function in AMD, supports myopia control in children, and may regulate intraocular pressure.
- crocinScientific
Crocin is the water-soluble glycosidic carotenoid from saffron that is the active precursor to crocetin. Multiple clinical studies document improvements in best-corrected visual acuity, contrast sensitivity, and retinal function in AMD patients. A 2025 AAO review confirmed benefits across several RCTs with 5–15 mg/day for 3–12 months.
- cryptoxanthinScientific
BCX is present in human serum and contributes provitamin A for retinal visual cycle function. It protects retinal photoreceptors from light-induced oxidative damage in animal models. Case-control studies find lower serum BCX in AMD patients, supporting a role in retinal health maintenance.
- currantScientific
The most comprehensively studied body system benefit of blackcurrant. Multiple human RCTs support improved ocular blood flow, slowed glaucoma progression, improved dark adaptation, reduced digital eye fatigue, and retinal protection against oxidative blue-light damage.
- d-alpha tocopherolScientific
The eye is highly susceptible to oxidative stress, and alpha-tocopherol has been investigated in major RCTs for prevention of AMD and cataracts. As a component of the AREDS formula (with vitamins C, beta-carotene, and zinc), vitamin E supplementation reduced progression to advanced AMD by 25%, though vitamin E alone has not shown consistent benefit.
- DHA (docosahexaenoic acid)Scientific
DHA is the primary structural fatty acid in photoreceptor outer segment membranes, comprising 50–60% of their total fatty acid content, and is essential for retinal function. Epidemiological data and Mendelian randomization (UK Biobank, n=258,350) link higher plasma DHA with significantly lower AMD risk. RCTs support DHA+EPA for dry eye disease.
- docosahexaenoic acidScientific
DHA is the dominant structural fatty acid of the retina, essential for photoreceptor rod cell function and visual signal transduction. DHA accumulates rapidly in the retina during the third trimester and early postnatal life. Clinical relevance spans retinal development, AMD, dry eye disease, and diabetic retinopathy.
- EGCG (epigallocatechin gallate)Scientific
EGCG has demonstrated beneficial effects across multiple ocular tissues and diseases including glaucoma, AMD, diabetic retinopathy, cataracts, dry eye, and retinitis pigmentosa in preclinical studies. It protects RPE cells, photoreceptors, and retinal ganglion cells from oxidative damage, inflammation, and mitochondrial dysfunction.
- eggScientific
Egg yolk lutein and zeaxanthin are the exclusive dietary carotenoids deposited in the human macula and lens, providing blue-light filtration and antioxidant protection. RCTs confirm egg consumption raises serum and macular L/Z levels significantly, with enriched eggs producing changes equivalent to 5 mg/day supplements.
- eicosapentaenoic acidScientific
EPA reduces ocular surface inflammation in dry eye disease and contributes to retinal anti-inflammatory defense. A meta-analysis of 19 RCTs (n=4,246 DED patients) found EPA percentage in omega-3 formulations was a significant predictor of dry eye symptom improvement across all key parameters.
- EPA (eicosapentaenoic acid)Scientific
EPA is an omega-3 fatty acid with anti-inflammatory properties that generate specialized pro-resolving mediators supporting tear film health. Along with DHA, it is supported by meta-analyses of RCTs for dry eye disease. Epidemiological data also associate higher EPA intake with lower AMD risk.
- fish oilScientific
DHA is a major structural fatty acid of the retinal photoreceptor outer segment membrane (~50% of photoreceptor PUFA), essential for phototransduction and visual acuity. Fish oil EPA and DHA also reduce ocular surface inflammation relevant to dry eye disease and AMD via production of resolvins and protectins. Adequate omega-3 status has been shown critical for visual development in infants.
- forskohlii rootScientific
Topical forskolin eye drops significantly lower IOP by reducing aqueous humor production in the ciliary epithelium. Multiple clinical trials confirm IOP reduction in both healthy subjects and glaucoma patients. Neuroprotective effects on retinal ganglion cells are supported by preclinical and early clinical evidence.
- ginkgo bilobaScientific
Ginkgo biloba extract (GBE, EGb 761) has been used in TCM for centuries and has at least four RCTs evaluating its role in glaucoma and visual field loss. It improves retinal microcirculation and has documented antioxidant and neuroprotective effects on the optic nerve and retina. Studies also support benefits in diabetic retinopathy and AMD.
- goji berryScientific
Goji berry (Lycium barbarum) has been used in Traditional Chinese Medicine for over 2,000 years specifically for brightening the eyes. Its polysaccharides (LBP) protect retinal ganglion cells, increase macular zeaxanthin levels, and clinical trials show neuroprotection against glaucoma-related retinal nerve fiber layer loss and possible AMD protection.
- grapeScientific
Grape seed and skin extracts contain oligomeric proanthocyanidins (OPCs) and resveratrol with documented preclinical protective effects against AMD and retinal neurodegeneration. Grape seed OPCs protect retinal capillaries and inhibit VEGF-driven neovascularization. Life Extension's AMD protocol includes grape seed extract as a preclinically supported agent.
- grape seedScientific
A multicenter, randomized double-blind RCT (n=124, 150 mg/day GSPE for 12 months) in non-proliferative diabetic retinopathy patients showed GSPE reduced hard exudates in the retina at a higher rate than both placebo and the standard drug calcium dobesilate. Preclinical studies demonstrate GSPE protects retinal cells via Nrf2 pathway activation and suppresses VEGF-driven angiogenesis in diabetic rat retinas.
- huckleberryScientific
Vaccinium genus anthocyanosides, chemically identical to those in huckleberry, have the best-characterized relationship of any herbal compound with eye health. Clinical and preclinical evidence supports retinal protection, rhodopsin regeneration, and protective effects against macular degeneration and diabetic retinopathy. The evidence for the Vaccinium genus on eye health is among the strongest in botanical medicine.
- hyaluronic acidScientific
HA eye drops are among the most widely studied and used treatments for dry eye disease (DED). A meta-analysis of 19 RCTs (n=2,078) found HA eye drops significantly improved tear production versus non-HA drops. A 2026 systematic review and meta-analysis of 39 RCTs (n=3,469) further supports HA as first-line treatment for mild-to-moderate dry eye.
- kaleScientific
Kale is the highest dietary source of lutein (~39 mg/100 g raw) and provides zeaxanthin—the only two carotenoids that accumulate in the retinal macula. These macular pigments filter blue light and provide antioxidant protection to photoreceptors. AREDS2 and multiple cohort studies support lutein/zeaxanthin's role in AMD and cataract prevention.
- krill oilScientific
The Deinema et al. 2017 double-blind RCT (n=60, Ophthalmology) found krill oil for 90 days significantly reduced tear osmolarity, improved OSDI dry eye symptom scores, and reduced IL-17A inflammatory cytokine in tears — with krill oil showing effects superior to fish oil on symptom measures. Astaxanthin in krill oil also has documented ophthalmic antioxidant effects.
- L-carnosineScientific
L-carnosine is an endogenous dipeptide concentrated in the crystalline lens that protects against oxidative damage and glycation of lens crystallins. When delivered to the eye as its prodrug N-acetylcarnosine in eye drops, clinical studies document improvements in visual acuity and lens transparency in age-related cataract.
- luteinScientific
Lutein is a xanthophyll carotenoid concentrated in the macular pigment of the human retina, where it filters high-energy blue light and acts as an antioxidant. The landmark AREDS2 RCT (n=4,203, 5-year follow-up) demonstrated that 10 mg/day lutein with zeaxanthin reduces risk of progression to advanced AMD. It is also studied for cataract prevention and visual function improvement in adults with screen exposure.
- luteolinScientific
Luteolin is a flavone found in eyebright and other herbs that inhibits mast cell histamine release (relevant to allergic conjunctivitis), protects retinal ganglion cells from excitotoxicity, and inhibits VEGF in RPE cells. A 2014 study confirmed its immunomodulatory effects on human corneal cells; it is a key active constituent of eyebright for eye health.
- lyciumScientific
Lycium (Lycium barbarum/chinense) is the botanical genus of Goji berry, used in TCM for over 2,000 years specifically for liver and eye health. Its polysaccharides (LBP) protect retinal ganglion cells, and clinical RCTs demonstrate preservation of retinal nerve fiber layer in glaucoma patients and enhancement of macular zeaxanthin.
- lycopeneScientific
Epidemiological studies show that low serum lycopene is associated with increased risk of age-related macular degeneration (AMD); persons in the lowest lycopene quintile were twice as likely to have AMD in one case-control study. Lycopene levels are specifically reduced in AMD patients but not in controls. In vitro studies show lycopene protects retinal pigment epithelium cells and inhibits pathological angiogenesis.
- mangoScientific
Mango contains beta-carotene (provitamin A essential for rhodopsin/visual pigment), lutein, and zeaxanthin — carotenoids that concentrate in the macula and lens and protect against AMD, cataracts, and blue-light damage. These are scientifically well-characterized ocular nutrients with established clinical evidence.
- maqui berryScientific
The eyes represent the most clinically validated body system for maqui berry. Multiple human trials (pilot and RCT) confirm increased tear fluid production and relief of dry eye and fatigue symptoms. Additional cell-line and animal evidence supports photoreceptor protection from light-induced oxidative damage.
- melatoninScientific
The eye contains multiple melatonin receptors, and melatonin is synthesized locally in retinal photoreceptors. It acts as a potent antioxidant protecting photoreceptors and may reduce intraocular pressure via MT2 receptors. A clinical study found AMD patients receiving melatonin did not experience further vision loss and had reduced pathological macular changes.
- methylcobalaminScientific
The retina and optic nerve are vulnerable to MeCbl deficiency, as demonstrated by the severe retinal degeneration seen in inborn errors of cobalamin metabolism. MeCbl is required for methionine synthase activity in ocular tissues, and deficiency leads to macular atrophy, pigmentary retinopathy, and optic neuropathy.
- mucinScientific
Mucins produced by conjunctival goblet cells are essential components of the tear film, stabilizing its aqueous layer over the corneal epithelium and preventing dry eye disease. Mucin secretagogue drugs are approved and clinically validated for dry eye treatment. Alterations in both secretory and membrane-associated ocular mucins are documented in dry-eye-related conditions.
- N-acetyl carnosineScientific
N-Acetyl Carnosine (NAC) is a prodrug of L-carnosine formulated as eye drops specifically for age-related cataract. It penetrates the cornea and is metabolized to L-carnosine, which protects lens crystallins via antioxidant and anti-glycation mechanisms. A clinical trial of 96 cataract patients and a 9-month study of 75 patients showed improvements in visual acuity and lens transparency.
- NAC (N-acetyl cysteine)Scientific
NAC has documented clinical evidence for effects on ocular conditions including dry eye syndrome in Sjögren's syndrome and preliminary evidence for glaucoma and cataracts. A double-blind clinical study found oral NAC improved dry eye symptoms including ocular soreness, irritability, and daytime thirst in Sjögren's syndrome patients.
- omega-3 fatty acidsScientific
Omega-3 fatty acids (EPA and DHA) are essential structural components of retinal photoreceptors and are supported by meta-analyses of RCTs for dry eye disease and by large epidemiological evidence (Mendelian randomization) for AMD risk reduction. Their anti-inflammatory SPM generation underlies both ocular surface and retinal benefits.
- omega-6 fatty acidsScientific
Omega-6 fatty acids, particularly AA and its eicosanoid derivatives, are present in ocular tissues including the retina and trabecular meshwork. Clinical data indicate that consuming omega-6 fatty acids has positive effects on glaucoma. The trabecular meshwork contains omega-6-responsive receptors modulating aqueous humor drainage. Evidence in the retina is primarily structural (AA is a constituent of photoreceptor phospholipids).
- omega-7 fatty acidsScientific
Sea buckthorn oil (omega-7 source) has been shown in a registered randomized, double-blind, placebo-controlled trial (Larmo et al., J Nutr 2010, n=100) to attenuate tear film osmolarity and reduce dry eye symptoms over 3 months. A separate trial in Sjögren's syndrome patients demonstrated improvement in ocular mucosal conditions.
- palm oilScientific
Red palm oil's high β-carotene content provides provitamin A essential for maintaining retinal function, and multiple clinical trials have demonstrated it can cure night blindness and correct vitamin A deficiency-related ocular disorders in deficient populations. The β-carotene in RPO has high bioavailability and is efficiently converted to retinol required for rhodopsin synthesis.
- palmitateScientific
Vitamin A palmitate is integral to the structure and function of the visual system, from rhodopsin synthesis in photoreceptors to corneal and conjunctival epithelial maintenance. Clinical trials confirm its role in retinitis pigmentosa, dark adaptation, and dry eye.
- panthenolScientific
Dexpanthenol is clinically used in ocular formulations for dry eye disease and corneal epithelial healing. A double-blind RCT in 50 dry eye patients demonstrated significant improvement in corneal permeability and tear film parameters. A ClinicalTrials.gov-registered phase II/III trial (NCT06210373) is currently evaluating 5% dexpanthenol eye gel for moderate-to-severe DED.
- parsleyScientific
Parsley is among the richest common culinary sources of the macular carotenoids lutein and zeaxanthin, which selectively accumulate in the human retina and protect against AMD and cataracts. Vitamin A (from beta-carotene) further supports rhodopsin synthesis and visual function. These links are supported by robust clinical and epidemiological evidence.
- pineScientific
Pycnogenol has been investigated in five clinical trials (total N=1,289 patients) for diabetic retinopathy since the late 1960s. A 2009 RCT (N=46) published in the Journal of Ocular Pharmacology and Therapeutics showed significant improvement in retinal edema and visual acuity at 2 months (14/20 to 17/20) in early diabetic retinopathy. The 2024 RDP review of 39 trials confirmed eye health as a documented domain of benefit.
- pine barkScientific
Pine bark extract (rich in oligomeric proanthocyanidins, OPCs) is clinically studied for diabetic retinopathy, with RCTs demonstrating improved retinal blood flow, reduced leakage, and improved visual acuity. Its constituents protect retinal capillaries and inhibit VEGF-driven vascular complications in the eye.
- pterocarpus marsupiumScientific
P. marsupium has preclinical anti-cataract evidence in alloxan-diabetic rats and is used in Ayurvedic ophthalmic preparations. The effect is linked to blood glucose reduction and potentially direct antioxidant protection of the lens.
- pumpkinScientific
Pumpkin is a top food source of provitamin A beta-carotene, which is essential for retinal photoreceptor function and prevention of night blindness. Lutein, zeaxanthin, and vitamin E in pumpkin specifically protect the macula from oxidative degeneration. Epidemiological cohort analyses confirm carotenoid intake associations with reduced cataract and AMD risk.
- pycnogenolScientific
Pycnogenol (French maritime pine bark extract) has been evaluated in double-blind RCTs for diabetic retinopathy. Studies found it significantly improved retinal blood flow, reduced retinal leakage and edema, and improved visual acuity in early diabetic retinopathy patients. Its OPC constituents protect retinal microvascular integrity.
- quercetinScientific
Quercetin is a dietary flavonol that inhibits aldose reductase (reducing diabetic cataract formation), protects retinal ganglion cells from oxidative damage, and inhibits VEGF in retinal endothelial cells. It is an active constituent of eyebright used traditionally for eye ailments. Evidence is primarily preclinical with epidemiological support.
- resveratrolScientific
Resveratrol is a polyphenol stilbene with anti-angiogenic and neuroprotective properties relevant to AMD and diabetic retinopathy. Preclinical studies show robust protection of RPE cells and inhibition of choroidal neovascularization via Sirt1 activation and VEGF suppression. A small human pilot study in AMD showed improvements in visual acuity and OCT macular structure.
- rosmarinic acidScientific
Rosmarinic acid has been investigated for dry eye syndrome and ocular surface inflammation in preclinical studies, reducing tear fluid inflammatory markers and corneal epithelial damage. Its antioxidant and anti-inflammatory properties are mechanistically relevant to multiple ocular conditions including age-related macular degeneration and diabetic retinopathy in preclinical models.
- saffronScientific
Saffron (Crocus sativus) contains the carotenoids crocin and crocetin, which protect retinal photoreceptors and inhibit retinal neovascularization. Multiple clinical studies show 20–50 mg/day saffron or 5–15 mg/day crocin improves best-corrected visual acuity, contrast sensitivity, and retinal function in AMD patients. Reviewed by the American Academy of Optometry in 2025.
- spinachScientific
Spinach is among the richest dietary sources of lutein and zeaxanthin, which selectively accumulate in the retina and macula. These carotenoids filter harmful blue light, neutralise ROS, and protect against AMD progression. RCT and cohort data confirm their role in preserving macular pigment density and visual function.
Human tear fluid constitutively contains SPMs, which are reduced in dry eye disease. An RvE1 analog successfully completed Phase II clinical trials for dry eye, making ophthalmology the most advanced SPM clinical application. A resolvin D6 isomer reduces corneal inflammation and stimulates nerve regeneration in ocular models.
- taurineScientific
Taurine is the most abundant amino acid in the retina and all ocular tissues. It is essential for photoreceptor survival, protects retinal ganglion cells from excitotoxicity and degeneration, and its deficiency is linked to glaucoma, diabetic retinopathy, and retinal degeneration.
- triphalaScientific
Triphala has a robust body of evidence for ocular health, including a clinical study in 141 patients with computer vision syndrome showing marked improvement with Triphala eye drops, anti-cataract activity in animal models, and traditional classification as 'Chakshushya' (ocular nourishment). Preclinical evidence for cataract prevention is strong.
- vitamin AScientific
Vitamin A is essential for rhodopsin synthesis in rod photoreceptors; deficiency causes night blindness and, in severe cases, corneal ulceration and preventable blindness. As part of the AREDS formula, it contributed to a 25% reduction in AMD progression risk in a landmark RCT. Vitamin A deficiency remains the leading cause of preventable childhood blindness globally.
- vitamin B2Scientific
Riboflavin is essential for eye health via FAD-dependent glutathione recycling in the lens, protecting against oxidative damage and cataracts. Deficiency causes corneal vascularization. The FDA has approved an ophthalmic riboflavin formulation for corneal cross-linking. Dietary B2 intake is inversely associated with cataract risk in the AREDS cohort.
- vitamin B3 (niacin)Scientific
Niacinamide supports retinal ganglion cell (RGC) health by replenishing NAD+, which is critical for mitochondrial function and RGC survival. Clinical and epidemiological evidence links higher niacin intake to reduced glaucoma risk, and short-term trials show improved visual quality of life and reduced IOP in glaucoma patients. NAD+ depletion is increasingly recognized as a central mechanism in glaucomatous neurodegeneration.
- vitamin CScientific
Vitamin C is concentrated in the aqueous humor at levels far exceeding plasma, where it is the primary water-soluble antioxidant protecting the eye from oxidative stress. It was a key component of the AREDS formula shown to reduce advanced AMD risk by 25% in a landmark NEI RCT. Epidemiological studies also associate higher vitamin C intake with reduced cataract risk.
- vitamin EScientific
Vitamin E is the principal fat-soluble antioxidant in photoreceptor membranes, protecting polyunsaturated fatty acids (especially DHA) from lipid peroxidation. It was a core component of the AREDS formula that reduced AMD progression by 25% in a large RCT. Multiple epidemiological studies associate higher vitamin E with reduced cataract and AMD risk.
- watercressScientific
Watercress is a recognized dietary source of lutein and zeaxanthin—carotenoids that accumulate in the macula and retina. The Gill 2007 RCT demonstrated a 100% increase in plasma lutein after 8 weeks of watercress consumption. Lutein and zeaxanthin have robust clinical trial evidence (AREDS2) for protection against AMD progression and cataract development.
- watermelonScientific
Watermelon provides lycopene and vitamins A and C, which are associated with reduced risk of AMD and cataracts. Population studies link lycopene deficiency to macular degeneration, and in vitro evidence shows lycopene protects retinal cells from inflammatory damage.
- zeaxanthinScientific
Zeaxanthin is the dominant xanthophyll carotenoid at the center of the macula, where it acts as a blue-light filter and antioxidant. AREDS2 showed that a supplement including 2 mg zeaxanthin (with 10 mg lutein) reduced risk of progression to advanced AMD. Supplementation consistently increases macular pigment optical density in RCTs.
- zincScientific
Zinc is the most concentrated trace mineral in the retina and choroid. It is essential for vitamin A transport to the retina for rhodopsin synthesis and is a cofactor for retinal antioxidant enzymes. The AREDS trial established that 80 mg/day zinc with antioxidants reduced advanced AMD progression by 25%; zinc is a recognized component of AREDS and AREDS2 formulas.
- belleric myrobalanTraditional
Belleric myrobalan is documented across Ayurvedic, Unani, and RxList sources for ocular applications including sore eyes, myopia, hypermetropia, and stye. Triphala Ghrita (containing T. bellirica) is used in classical Ayurveda for eye disorders. Topical application of fruit paste and seed oil to the eye region is described. Multiple classical Ayurvedic formulations for eye health contain T. bellirica as a key ingredient.
- calendulaTraditional
Calendula is traditionally used as an eyewash for conjunctivitis and blepharitis, documented across Eclectic medicine and ethnobotanical traditions. Animal studies support anti-inflammatory benefits for ocular tissues. An in vitro study evaluated wound healing on conjunctival epithelium. Clinical human trials are absent.
- chickweedTraditional
Chickweed has a historical documented use for soothing irritated and inflamed eyes, mentioned by classical herbalists including Gerard. Herbal Reality notes chickweed's specific affinity for the eyes as an external remedy. No clinical evidence exists.
- dodderTraditional
Improving eye health and vision is one of the four classical indications of dodder seed in TCM, documented since the Shennong Bencao Jing. TCM texts describe it as improving eyesight through liver-kidney nourishment. It is used traditionally for eye dryness, fatigue, and visual decline. No dedicated human ophthalmic clinical trials have been published.
- dulse leafTraditional
Dulse provides vitamin A (beta-carotene precursor), lutein, zeaxanthin, and vitamin C—micronutrients nutritionally critical to retinal and ocular health. Approximately 40% of the daily vitamin A recommendation is found in 7 g of dulse. Lutein and zeaxanthin are concentrated in the macula and retina. No dulse-specific clinical ocular trial exists; the relationship is based on nutritional composition.
- eyebrightTraditional
Eyebright (Euphrasia officinalis) has been used in European folk and herbal medicine for eye disorders since at least the 14th century, documented by Dioscorides in ancient Greece and by Culpeper in the 17th century for conjunctivitis, eye strain, and vision disturbances. Its active constituents (aucubin, tannins, quercetin, luteolin) have documented anti-inflammatory and immunomodulatory properties in vitro. No robust human RCTs confirm traditional claims.
- goldensealTraditional
Goldenseal has one of its oldest traditional uses as an eyewash for conjunctivitis and eye inflammation. The USPTO patent review and PubMed critical review both cite eye ailments as a primary traditional application. Berberine's clinical use for ocular trachoma infections is historically documented.
- haliotisTraditional
Eye health is the primary documented organ-system target of Shi Jue Ming in TCM, with historical records since the 3rd–4th centuries. The herb is listed in the Chinese Pharmacopoeia in ocular formulas and is used for a broad range of eye disorders.
- morusTraditional
Morus alba leaf is a classical TCM herb targeting the eyes via the Liver channel. It is traditionally indicated for red, irritated, or dry eyes associated with Liver heat or Wind-Heat invasion. This use is documented in the Chinese Pharmacopoeia and consistent across multiple TCM sources.
- mulberryTraditional
Mulberry leaf (Sang Ye) has documented traditional use in TCM for eye conditions including red, dry, and blurry eyes, formally listed in the Chinese Pharmacopoeia. Modern research shows mulberry anthocyanins protect human retinal cells from oxidative glucose-induced injury in vitro, with Nrf2 pathway activation.
- prickly pear cactusTraditional
Traditional use of prickly pear for glaucoma and eye inflammation is documented in Mexican and Latin American folk medicine. The antioxidant betalains and vitamin C in prickly pear are relevant to ocular oxidative stress. No clinical ophthalmic trials have been conducted.
- privetTraditional
Improving vision and treating eye disorders is one of the four primary traditional TCM indications for Ligustrum lucidum, with 2,000 years of documented use. The 2020 Chinese Pharmacopoeia officially lists clearing vision as a function. Preclinical evidence shows specnuezhenide inhibits retinal angiogenesis.