Ocular Health

Introduction

What should I know about Ocular Health?

Our eyes are the tools that we use to gather information from our environment. This information not only gives us pleasure but also guides our behavior. (1) We take our eyes for granted yet we value them so highly. Taking care of our eyes is critical and the importance of eye examinations cannot be over emphasized. Eye examinations often reveal signs of disease and ocular disorders. Regular examinations can also determine the effects of drugs that are either administered systemically or used directly in the eye itself.

The eyes are mounted in a prominent position on the head, and thus are vulnerable to a variety of disturbances. Our vision can be damaged by trauma, exposure, or infection and there are many diseases of the eye including glaucoma, cataracts, or retinal detachment. Other diseases may have ocular symptoms, as do some of the neurologic diseases affecting areas of the cortex, thalamus, and brainstem that are devoted to visual perception or to the execution of eye movements. Although it may be determined that a patient requires specialized eye care, the initial examination and assessment of visual acuity, pupils, eye movements, and visual fields, can be done by a general practitioner.

A cataract is a clouding of the lens sufficient to reduce vision. Most cataracts develop slowly as a result of the aging process, and lead to a gradual reduction in vision. The only treatment is surgical extraction of the opacified lens. Remarkable technical innovations have made it possible to remove the cataract while leaving the lens capsule intact. A plastic or silicone lens is then placed in the empty lens capsule, replacing the natural lens, and most generally leading to improved sight in most patients.

Other physical conditions also affect vision. For example if a person has a stroke that affects the right optic pathway, he/she may develop hemianopsia, or defective vision/blindness in half of the visual field. If the stroke affects the right side, the patient’s left visual field is affected since the image projected by the eye reverses the field. The term used to describe this condition is left homonymous hemianopsis. The patient would only see the right half of his environment, since the right optic tract impairment has affected his ability to see the left side of his visual field. Using visual field defects can help vastly in attempting to localize the point of a lesion.

The FDA has done a review to determine which ophthalmic conditions may occur that are self-treatable. It must be remembered, though, that each of these may potentially be serious enough to seek treatment by a physician or ophthalmologist. If patients experience eye pain, changes in vision, continued redness, or irritation in the eye, or if the condition worsens or persists, patients must discontinue use of nonprescription products and see a physician. Self-treatable conditions include:

    Dry eye Loose foreign material Redness caused by minor eye irritation Discomfort caused by minor eye irritation Corneal edema Ophthalmic allergic conjunctivitis

Dry eye refers to a syndrome resulting from many conditions that produce abnormalities of tear film flow and/or stability rather than denoting a specific disease. (2) This condition can result from a number of circumstances. Tear production is also affected by total body hydration. Aqueous secretions such as tears and saliva may be compromised as the body conserves water to provide water to the cells of more vital organs.

Vitamin A deficiency is a major cause of childhood blindness in underdeveloped countries because vitamin A deficiency results in mucin deficiency. (3) The eye undergoes a loss of mucin-secreting goblet cells, resulting in an unstable tear film that causes dry patches on the eye. If not corrected this can lead to more serious complications. (4) Impaired dark adaptation is a good test for vitamin A deficiency. Dry eye is usually the result of an abnormality in one or more tear-stability dependent factors. (5) There are six to eight different types of possible abnormal tear film conditions, but the most severe form is called keratoconjunctivitis sicca (KCS), which causes 80 to 90 percent of diagnosed cases of dry eye. (6)

Dry eye may also be caused by a long list of medications such as: certain diuretics like hydrochlorothiazide and chlorthalidone; antihistamines such as diphenhydramine, dexbrompheniramine, and chlorpheniramine; and anticholinergics like atropine and scopolamine. Phenothiazines, tricyclic antidepressants, cimetidine, indapamide, clonidine, and isotretinoin are others that may produce dry eye as a side effect.

Red or painful eyes may be the result of minor irritations that may be self-treated, or may be caused by serious conditions such as trauma to the eye, certain infectious diseases, or glaucoma. Eye pain or redness that does not resolve within 72 hours should be referred to an optometrist or ophthalmologist.

A pinguecula is a small raised conjunctival nodule that occurs commonly in adults, and is inconsequential unless it becomes inflamed (pingueculitis).

Blepharitis is the term used to describe inflammation of the eyelids and must be treated by a physician. Usual treatment includes strict eyelid hygiene, warm compresses, and an antibiotic ointment, such as erythromycin. An external hordeolum (sty) is caused by staphylococcal infection.

Conjunctivitis is the most common cause of red, painful eyes. Most frequently, pain is minimal and visual acuity affected only slightly. The most frequent viral cause is adenovirus infection, causing a watery discharge, light sensitivity, and a mild foreign body sensation. Mild cases are usually treated with topical, broad-spectrum ocular antibiotics. Allergic conjunctivitis is often mistaken for infectious conjunctivitis; however, allergic conjunctivitis is generally seasonal, and accompanied by prominent itching. The eyes are slightly red, tearing, and burning, but with little discharge. (7)

Prolonged contact wearing, corneal inflammation, glaucoma, infection, iritis, or a degeneration of cells lining the back of the cornea may cause corneal edema. Corneal edema occurs as the water content of the cornea increases causing the cornea to swell and lose transparency. Although corneal edema is one of the conditions deemed self-treatable by the FDA, the wise choice is to be treated by a physician since it may be produced by a serious underlying problem.

Statistic

Center for Global Development, 2007.

  • 45 million Indians experience visual impairment, and about 12 million are blind.
  • One quarter of the world’s blind live in India.
  • 80 percent of blind people, or more than 10 million individuals, suffered from bilateral cataract, and another 10 million individuals had a cataract in one eye.
  • An estimated 3.5 million cataract surgeries in India in 2000 saved 320,000 people from blindness.

Ministry of Science and Technology, Malaysia  National Eye Survey 1996.

  • Cataract was the leading cause of blindness (39%) followed by retinal diseases (24%).

  • Uncorrected refractive errors (48%) and cataract (36%) were the major causes of low vision.

  • 50% of 54,000 blind people and 80% of  464,000 low vision people were due to cataract and uncorrected refractive errors.

       

World Health Organization, Geneva 2006.

  • More than 161 million people were visually impaired, of whom 124 million people had low vision and 37 million were blind.
  • More than 82% of all blind persons are 50 years of age or older.
  • Cataract is responsible for 50% of blindness globally.
  • Chronic, noncommunicable diseases such as glaucoma and diabetic retinopathy cause 12% and 5 % of global blindness, respectively.
  • Globally, 75% of blindness is avoidable.
  • Vitamin A deficiency leads to blindness (xerophthalmia) in 350,000 children annually.

 

National University of Singapore, 2006.

  • In Singapore, the 2 leading causes of visual impairment are undercorrected refractive errors and cataracts.

Royal New Zealand Foundation of the Blind, 2004.

  • In New Zealand, there were 3,161 blind people and 8,132 vision impaired people.

Vision 2020 Bangladesh, 2006.

  • There are 7,500,00 blind adults in Bangladesh.
  • Cataract was identified as the major cause of bilateral blindness (79.6%) and low vision (74.2%) amongst Bangladeshi adults.
  • Refractive error was the second major cause of visual impairment (18.87%).
  • There are 40,000 blind children in Bangladesh and cataracts are the leading cause of childhood blindness.

National Center for Health Statistics (NCHS), 1999.

    Glaucoma was the principal diagnosis of 17.5 million doctor visits during 1991 and 1992, an annual estimate of 8.7 million visits. Glaucoma is the leading cause of irreversible blindness among the African American population. About three-quarters of glaucoma visits were made to ophthalmologists. Nine out of 10 glaucoma visits result in a scheduled return visit. Medication therapy was the most frequently mentioned therapeutic service at glaucoma visits.

Health Communications and Public Relations, World Health Organization, Geneva 1999.

    It has been estimated that the global number of blind in the world in 1990 was about 38 million. The number of persons with low vision was estimated to be 110 million. Cataract, trachoma, and glaucoma, together account for more than 70% of the world's blindness and visual disability. Vitamin A deficiency leads to blindness (xerophthalmia) in some 350,000 children annually. Diabetic retinopathy is the leading cause of blindness and visual disability in adults in economically developed societies. After 15 years of diabetes, approximately 2% of people become blind while about 10% develop severe visual disability.

The World Health Organization (WHO) Programme for the Prevention of Blindness, 1999.

    Trachoma is the most common cause of preventable blindness; the disease, in its active inflammatory form, affects close to 150 million people, mainly children and women. 5.8 million cases of trachoma complications and/or blindness, which corresponds to 15.5% of world blindness.

National Eye Institute, Vision Problems in the US, 2000

  • Estimated number of cases of visual impairment including blindness in those over 40 years of age: 3,406,280

  • Estimated number of cases of blindness in those over 40 years of age: 1,046,920

  • Estimated number of cases of Age-related Macular Degeneration in those over 50 years of age: 1,651,335

  • Estimated number of cases of Cataracts in those over 40 years of age: 20,476,040

  • Estimated number of cases of Diabetic Retinopathy in those over 18 years of age: 5,353,233

  • Estimated number of cases of Glaucoma in those over 40 years of age: 2,227,485

Signs and Symptoms

[span class=alert]The following list does not insure the presence of this health condition. Please see the text and your healthcare professional for more information.[/span]

There are many different conditions, which may cause one, or a combination of the symptoms. Symptoms for which patients should seek medical advice include; changes in vision, prolonged irritations or eye pain, severe redness, infections of the eyelids, eye injuries (trauma), chemical exposure, and foreign bodies that cannot be removed through tears or flushing with water or saline. A red eye with a thick mucous discharge and minor eye discomfort indicates bacterial infection. This often results in eyelids being stuck together upon awakening. Viral infections or conjunctivitis is also characterized by redness of the eye; however, the discharge is usually watery and not thick.

The human cornea has no nerve receptors for dryness or wetness and cannot interpret dry eye in this manner. However, it is thought to be perceived through stimulation of receptors for warmth, cold, and pain. There may also be some combination of receptors in the other parts of the eyes such as the eyelids that interact to produce the feeling of dryness. Symptoms of dry eye include eye discomfort, blurred vision, discharge, an awareness of the eyes, feeling of dirt or sand in the eyes, burning, and redness.

A response as a result of an allergy includes inflammation, itching, redness, swelling, sensitivity of light, and excessive tearing. Corneal edema or swelling within the cornea due to fluid build up shows up as foggy vision, haloes, or "star bursts" around lights, and blisters that cause sensitivity to light and irritation. If these blisters break, terrible pain will be experienced within the eye.

Dry eyes

  • Eye discomfort
  • Blurred vision
  • Discharge
  • An awareness of the eyes
  • Feeling of dirt or sand in the eyes
  • Burning
  • Redness

Allergic conjunctivitis

  • Itching
  • Redness
  • Swelling
  • Sensitivity to light
  • Excessive tearing

Corneal edema (swelling)

  • Foggy vision
  • Haloes or "star bursts" around lights
  • Blisters (if condition worsens) that cause sensitivity to light and irritation
  • Excruciating pain if blisters rupture or break

Conjunctivitis (infection)

  • Redness
  • Minimal pain
  • Watery discharge when caused by a virus
  • Bacterial infection usually leads to more thick, mucous like discharge, often causing eyelids to be stuck together when awakening

Treatment Options

Conventional

Mild forms of dry eye may be treated with nonprescription tear substitutes. Occasionally, surgery may be necessary. Ophthalmic redness due to minor irritations may be treated with ophthalmic vasoconstrictors such as tetrahydrozaline, oxymetazoline, or naphazoline. These products are contraindicated, however, in patients with glaucoma. Corneal edema may be treated with a 2 to 5% sterile sodium chloride solution or ointment to draw fluid from the cornea. The nonprescription remedies available for allergic conjunctivitis generally contain vasoconstrictors and antihistamines.

Bacterial or viral conjunctivitis is treated with broad-spectrum ocular antibiotics. Glaucoma is treated with cholinergic drugs to cause contraction of the pupil and constrict the ciliary muscles in order to facilitate fluid drainage from the anterior chamber.

The discussion of ocular health is a broad topic, and many ocular manifestations of systemic diseases have been omitted, as well as detailed discussions of optic neuropathies, retinal detachment, and other conditions.

Nutritional Suplementation


Antioxidant Nutrients

Antioxidant nutrients are thought to help protect the eyes against aging damage. When light enters the eye, it activates oxygen, which can initiate free radical reactions that damage the macula. Results from the Baltimore Longitudinal Study of Aging reported that vitamin E, vitamin C, and beta-carotene all provided antioxidant protection against the development of age-related macular degeneration (ARMD). (8) Epidemiological studies have also found that people with cataracts have lower serum levels of vitamins C, E, and carotenoids than control subjects. In one study, individuals who regularly took vitamin C and/or vitamin E as supplements had a more than 50 percent decrease in cataract risk compared to people that did not supplement with C and E. (9) , (10) Another study showed that long-term vitamin E reduced the progression of age-related lens opacification. (11)


Lutein, Zeaxanthin

Lutein and zeaxanthin are two carotenoids that are found in the eyes. They are concentrated in the lens and macula and have been reported to provide important protective benefits for the eyes. These compounds belong to a sub-category of carotenoids called oxycarotenoids. A review of studies on these pigments states that the concentration of dietary carotenoids in the macula is not accidental. They are antioxidants that protect the eyes by quenching oxygen free radicals and singlet oxygen, which are generated in the retina as a consequence of the simultaneous presence of light and oxygen and they protect the blood vessels that supply the macular region. (12)

Results of a study conducted at the Department of Ophthalmology, Harvard Medical School, indicated that increasing the consumption of carotenoid-containing foods lowered the risk of developing age-related macular degeneration (ARMD). Individuals with the highest carotenoid intake had a 43 percent lower risk for ARMD compared to those with the lowest. In this study, lutein and zeaxanthin were the carotenoids most strongly associated with a reduced risk for age-related macular degeneration. (13) Both pigments occur naturally in a wide variety of green leafy vegetables such as spinach, kale, broccoli, and brussels sprouts.


Vitamin A

Vitamin A is a nutrient that plays an important role in vision. In the pigment epithelial tissues of the retina, vitamin A compounds bind to proteins in the rods and cones. This produces the highly photosensitive proteins which absorb blue, green, and red wavelengths of light. These photopigments are responsible for night vision. Night blindness (nyctalopia) is the classic vision problem resulting from vitamin A deficiency. Another problem known as xerophthalmia can also develop. This condition causes a drying and hardening of the cellular membranes in the eye, which often results in blindness. Overall, vitamin A deficiency is the single most common preventable cause of blindness in the world. (14)


Zinc

Zinc is a mineral that regulates the sensory perceptions of taste, smell, and vision. It has been reported that the retina of the eye contains a higher concentration of zinc than any other organ in the human body. (15) One of zinc’s roles in vision is due to the fact that it is required for the synthesis of rhodopsin, which is also known as visual purple. (16) Zinc also regulates serum levels of vitamin A by controlling the release of stored vitamin A from the liver. Since vitamin A is essential to vision, a zinc deficiency could also affect vision by preventing the release of vitamin A.


Selenium

Selenium deficiencies may be associated with an increased risk of cataracts. In one study, it was reported that the lens tissue from individuals with cataracts had significantly less selenium that the lenses of normal controls. (17)

Herbal Suplementation


Bilberry

Bilberry is one of the most popular herbs on the market today. During World War II when British air pilots ate bilberries, they reported an improved ability to adjust to glare and an increase in their visual acuity and nighttime vision. (18) Bilberry extracts show promise in the areas of diabetic retinopathy, macular degeneration, cataracts, glaucoma, and varicose veins. (19) Bilberry is an excellent antioxidant. (20) With age, oxidative stress due to free radicals increases in some people more than in others. This damage to ocular tissues may lead to various eye problems.


Green Tea

Green tea reportedly has antioxidant properties (21) and the ability to protect against oxidative damage of red blood cells. (22) Antioxidants protect cells and tissues against oxidative damage and injury. (23) It is important to note that the addition of milk to any tea may significantly lower the antioxidant potential. (24)


Grape Seed Extract

Proanthocyanidins (PCO's), the active constituent in grape seed, is a flavonoid-rich compound which is being heavily touted as one of the most potent free radical scavengers. It has been reported to enhance the absorption of and work synergistically with vitamin C. (25)

References

  1. Horton JC. Disorders of the eye. In: Fauci AS, Braunwald E, Isselbacher KJ, et al, eds. Harrison’s Principles of Internal Medicine 14th ed. New York: McGraw-Hill; 1998:159-172.
  2. View Abstract: Khurana AK. Tear film profile in dry eye. Acta Ophthalmol. 1991;69:79.
  3. Kaden I, Mayers M. Systemic associations of the dry-eye syndrome. Int Ophthalmol Clin. 1991;31:69.
  4. Pray WS. Ophthalmic Conditions. In: Nonprescription Product therapeutics. Baltimore MD: Lippincott, Williams & Wilkins; 1999:396-411.
  5. Patel S. A Possible reason for the lack of symptoms in aged eyes with low tear stability. Optom Vis Sci. 1990;67:733.
  6. View Abstract: Fassihi AR, Naidoo NT. Irritation associated with tear-replacement ophthalmic drops. A pharmaceutical and subjective investigation. S Afr Med J. Mar1989;75(5):233-5.
  7. View Abstract: Fujishima H, et al. Allergic conjunctivitis and dry eye. Br J Ophthalmol. 1996;80:994.
  8. View Abstract: West S, et al. Are antioxidants or supplements protective for age-related macular degeneration? Arch Ophthalmol. Feb1994;112(2):222-7.
  9. View Abstract: Robertson JM, et al. A possible role for vitamins C and E in cataract prevention. Am J Clin Nutr. Jan1991;53(1 Suppl):346S-351S.
  10. View Abstract: Chylack LT, et al. The Roche European American Cataract Trial (REACT): A randomized clinical trial to investigate the efficacy of an oral antioxidant micronutrient mixture to slow progression of age-related cataract. Ophthalmic Epidemiol. Feb2002;9(1):49-80.
  11. View Abstract: Jacques PF. Long-term nutrient intake and 5-year change in nuclear lens opacities. Arch Ophthalmol. 2005 Apr;123(4):517-26.
  12. View Abstract: Schalch W. Carotenoids in the retina--a review of their possible role in preventing or limiting damage caused by light and oxygen. EXS. 1992;62:280-98.
  13. View Abstract: Seddon JM, et al. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group. JAMA. Nov1994;272(18):1413-20.
  14. Micronutrient deficiencies. Combating vitamin A deficiency. Nutrition: World Health Organization; Jul2002.
  15. Underwood EJ. Trace Elements in Human and Animal Nutrition, 4th Edition. London. Academic Press; 1977:198.
  16. View Abstract: Shuster TA, et al. Zinc causes an apparent increase in rhodopsin phosphorylation. Curr Eye Res. Oct1996;15(10):1019-24.
  17. Swanson AA, et al. Elemental analysis in normal and cataractous human lens tissue. Biochem Biophys Res Commun. Dec1971;45(6):1488-96
  18. Jayle GE, et al. Study Concerning the Action of Anthocyanoside Extracts of Vaccinium myrtillus on Night Vision. Ann Ocul. Paris. 1965;198(6):556-62.
  19. Morazonni P, et al. Vaccinium myrtillus. Fitoterapia vol. LXVII, no. 1; 1996:3-29.
  20. Morazonni P, et al. Vaccinium myrtillus. Fitoterapia vol. LXVII, no. 1; 1996:3-29.
  21. Cheng TO. Antioxidants in Chinese Green Tea. J Am Coll Cardiol. Apr1998;31(5):1214.
  22. View Abstract: Grinberg LN, et al. Protective Effects of Tea Polyphenols against Oxidative Damage to Red Blood Cells. Biochem Pharmacol. Nov1997;54(9):973-78.
  23. View Abstract: Halliwell B. How to Characterize an Antioxidant: An Update. Biochem Soc Symp. 1995;61:73-101.
  24. View Abstract: Hertog MG, et al. Antioxidant Flavonols and Ischemic Heart Disease in a Welsh Population of Men: The Caerphilly Study. Am J Clin Nutr. May1997;65(5):1489-94.
  25. Maffei Facino R, et al. Regeneration of Endogenous Antioxidants, Ascorbic Acid, Alpha Tocopherol, by the Oligomeric Procyanide Fraction of Vitus vinifera L:ESR Study. Boll Chim Farm. 1997;136(4):340-44.