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THE DAMAGING EFFECT OF THE SUN ON OUR EYE.

INTRODUCTION: THE SUN

The sun is the center of our solar system. It is a giant ball of glowing gases and it gives off energy in the form of light and heat. It is about 100 times the diameter of the earth. Without the sun, the earth would just be one cold rock where no plant or animal can survive. Everything on earth needs the warmth and light of the sun to survive. But, also too much of the sun can be dangerous to our health. The sun emits energy. This energy is measured in waves, just like the waves of the ocean. Some of these waves are fast and some are slow. Some of them are short and some are long. This short-ness and long-ness of the waves is known as Wavelength. The sun radiates three types of energy, namely:

Ultraviolet Rays ( most dangerous) Visible Light Rays Infra-Red rays

Our eyes can only see a portion of the whole electromagnetic spectrum of light emitted by the sun. These portions of light from sunlight that our eyes can see are called Visual Spectrum. Visual Spectrum falls between 400nm to 700 nm. Other lights like Ultraviolet [UV] and Infra-red [IR] are imperceptible to the human eye. The eye cannot perceive them just because they fall below the visual spectrum. i.e. the wavelengths fall between 280nm to 400 nm.

DANGERS POSE BY SUNLIGHT TO OUR EYES [Light toxicity ]

Most people are aware of the risk of developing skin cancer from sun exposure but majority are less aware that sun can cause damages to the eye. Sunlight is definitely associated with the formation of cataracts. The invisible UV component of sunlight promotes free-radical damage in the lens. The brighter the sun, the greater the UV radiation dose. The effect of radiation on our eyes, are cumulative throughout life. They add up as we go along. That is why skin cancers can develop four or five decades after major sun exposure. Cataracts (i.e. cloudiness of the eye lens) are similar symptoms of over-exposure to the sunshine. Long time exposure to UV rays is also related to some eye diseases like Macular degeneration, Corneal sunburn (Photokeratitis) and even skin cancer around the eyelids. Changes in the earth's ozone layer mean that more UV radiation is now reaching the earth's surface. Therefore, the need to prevent eye problems will only increase. This is why it is advisable for everyone who is exposed to reflected UV light from snow, on beaches or tanning salon to cover their eye area with UV blocking sunglasses to prevent exposure to UV radiation. The eye is so susceptible to damage as a result from heat from Infra-Red in the range of 800nm to 13000 nm. At this range, major damage can occur to the lens and retina. Infrared in form of extended source such as blast furnace can cause the protein in the eye lens to coagulate (i.e. solidify). This coagulation of lens can cause cataract. (as in Glass-blower cataract)

SCINETIFIC EXPLANATION ON THE DAMAGING EFFECT OF SUNLIGHT ON THE EYE

The mechanisms of damage from UV exposure are photochemical and thermal (i.e. heat). UV radiations are of 3 types, namely: UV-A [380 - 315 nm], UV-B [315 -  290 nm], and UV-C [290 - 200 nm]. Photochemical damage to the eye is predominantly caused by the UV-C and UV-B wavebands. The thermal (i.e. heat) damage is caused by the UV-A. Photochemical damage is usually within the internal part (i.e. cell nucleus) of the lens. Damage results when the energy of the UV matches the receptor of the cell. Since the lens inside our eye is a protector against radiations, it must then absorb all the incident radiation of UV to be an effective protector. Thus radiation [UV] absorbed by our lens caused biological tissue damage. This is how cataracts are formed in our lens. UV-C is completely absorbed by the Ozone layer in the atmosphere (called Stratosphere} whereas UV-A and UV-B (above 288 nm) are transmitted through the Ozone layer to reach the earth. In the earth, the eye (cornea) absorbs UV-B (below 295 nm). This is what caused many people corneal burns and Pterygium. UV-A can penetrate the corneal quite well but it is significantly absorbed by the lens inside our eye. This is what caused Cataracts. Also, a small but significant amount of UV-B and UV-A (above 305 nm) that could filter through the corneal and lens is absorbed by the Retina. This cause what is known as Solar Retina Burns. Changes in environment [ozone layer depletion] pose the most serious concern for eye problems from exposure to UV radiation. Yearly loses of Ozone layer has caused an increase in the amount of UV-B reaching the earth (and our eye). Beginningombined with cold wind and snow, UVB has the potential to cause snow blindness (photokeratitis), a temporary (lasting 12 to 48 hours) but painful problem in the cornea of the eye.

SOURCES OF UV RADIATIONS

The Sun (Natural source: The sun emits the highest proportion) Electric Arcs (used by welder). This is artificial source Sunlamp (Artificial source) Furnaces (used in steelmaking and glass blowing. This is an               artificial source)

MILD EFFECT OF THE SUN ON OUR EYES

The eyes are extremely quite sensitive to UV rays. Even, a brief exposure can result in a painful, but temporary condition known as photokeratitis and conjunctivitis. Photokeratitis is a painful condition caused by the inflammation of the cornea of the eye. The eye waters and vision is blurred. Conjunctivitis is the inflammation of the conjunctiva (the membrane that covers the inside of the eyelids and the sclera, the white part of the eyeball) which becomes swollen and produces a watery discharge. It causes discomfort rather than pain and does not usually affect vision.

MAJOR EFFECT OF THE SUN ON OUR EYES

Eye damage occurs due to absorption of radiation by the anterior structures of the eye (i.e. Cornea, Conjunctiva, Iris, etc) and the posterior surface (lens and retina). The eye damage associated with UV-B and UV-A exposure include: Pterygium - An abnormal tissue growth on the eye Pinguecula A yellowish discolouration of the eyeball Corneal damage e.g in corneal burns Lens damage e.g. as in cataract Retinal damage e.g as in retina burns Ultimately, radiation damage can cause age related macular degeneration. Macular degeneration is one of the most common causes of blindness in the world.

PEOPLE WHO ARE AT RISK OF EYE PROBLEMS CAUSED BY THE SUN

People with certain retinal disorder Patient who had just had cataract operation (aphake) People with cataract People with pterygium and pinguecula People who are placed on photosensitizing drugs (e.g. 	Contraceptives, cholorothiazides, Tetracycline, 		diuretics, sulpha drugs, tranquilizers, etc). Workers on vocations rich in UV radiation like Arc 		welding, Electronic chips, Graphic arts, Watermen, 	Researchers, People on avocation rich in UV like Snow skiing, 		sunbathing at the beach, mountain climbing, etc People who spend excessive hours in sunlight: (Sun 	exposure        above 8 hours a day) E.g. Policemen, traffic warden, open market women, taxi drivers, etc. People who use sunlamps or visit solariums: Solarium sources are rich in UV-A and contain UV-B, and both have been associated with skin cancer. Children who are exposed to excessive UV in sunlight. Children are at special risk since their eyes do not have the same ability as adults to protect from UV radiation. Laboratory workers who use bactericidal lamps. Physiotherapists who use phototherapy lamp Welders (UV radiation from welding equipment) Farmers, Police, Construction workers, Taxi drivers, Traffic Warden, and other outdoor workers Lithographic and printing workers (UV from printing and        Polymerizing equipment).

TIPS ON EYE PROTECTION FROM THE SUN EXPOSURE.

1. Sunglasses offer 90-100 percent protection from both ultraviolet A (UVA) and ultraviolet B (UVB) rays. Sunglasses should cover the entire eye area, including the eyelids, and should wrap all the way around to the temples. Full coverage prevents damaging rays from entering from the side. It is especially important for those who spend hours under sun on daily basis.

2. Wearing a wide-brimmed hat along with sunglasses will further block rays from the sun. 50% of sunlight comes from directly overhead, and may slip past non-wraparound sunglasses.

3. UV coatings on contact lenses are important, but do not fully protect the eyes. Contact lens wearers should additionally wear sunglasses.

4. Certain drugs may make the eyes more sensitive to light. Be sure to read drug labels.

PROFESSIONAL ADVICE

The primary eye care practitioner is in particular good position to advise the patient or public in general, about the risk of exposure to UV radiation and the protection regime that should be used against UV radiation exposure. The wavelength range of the sunlight that reaches the earth lies between 288nm to 2600 nm and it contains almost all the sun’s total irradiance. The hours between 10.00 am and 2.00 pm are particularly important clinically, because over 50% 	of the UV radiation that reaches the earth in any 24 hours period arrives within the hours of 10.00 am to 2.00 pm. Thus a patient can limit exposure to UV radiation by simply selecting the appropriate hours for outside activities. When unavoidable, wear protective sun lenses with UV blockers. We can limit exposure to UV radiation by prudent selection of outdoor activities [like games]. For example, the beach sand reflects about 35% of solar UV radiation: whereas the green grass in the lawn tennis reflects about 3.5% of solar UV radiation. The freshly fallen snow reflects about 85- 95% of the incident UV radiation. Also, the snow skier is at risk of about 15% increase in UV radiation for each kilometer [3000 ft] of altitude above sea level. So skiers should always protect themselves when on the ski slope. People on the beach may think they are being protected from sunlight by lying under an umbrella but the umbrella itself acts as a collector of UV radiation from the sunlight being reflected from the sand and concentrate it to the area underneath the umbrella. So, when on the beach, protect your eyes by wearing sunshade with UV blocker. Wearing a hat with a 4 inches brim reduces the ocular exposure to UV radiation in sunlight by about 50%. This is important for those who spend 	long hours under the sun. Many Researches have confirmed that Antioxidants like Vitamins C, Vitamin E, Selenium and the Carotenoids help to inhibit the damaging effects of UV light on the retina. Take these supplements as	 regular as possible. They are also available in fruits. Eat them regularly. Add 6mg of Lutein to your daily supplement. Lutein 	and zeaxanthin in plants are known for their protection against UV light. Also available in some 	fruits. (Note: Before you take any drug please contact your doctor

CONCLUSION

Light is the great love the eyes can’t live with and 	can’t live without. While light allows us to see, 	excessive exposure to wrong kinds of light can severely damage our eyes [and our skin too], overtime. We live by light, we thrive by light, and we suffer from too much or too little light. We need light to reach our retina to produce sight, just as we need it to reach our skin to produce Vitamin D, an 	essential hormone. The good news is that light allows sight and can create psychological sense of well being. The bad news is that too much light, especially UV light, can damage our eyes. With the loss of the ozone layer, one would expect a dramatic increase in UV related eye problems. So protection lies in clinical intervention by advising our patients to wear the proper UV absorbing ophthalmic lenses or sun-lenses. UV absorbing contact lenses and Intra-ocular lenses [IOL] afford protection for the cornea, lens, and retina against UV radiation. There is a strong possibility that UV-related eye disorders will increase over the next decade. This is 	due to the thinning of ozone layer and growing popularity of outdoor activities. Finally, I want you to enjoy nature and your great outdoor activities, but remember that your lifestyles 	choices today may protect you for the future. and take appropriate precautions. If you are on these drugs, wear protective sunglasses when under sun. Children's eyes need to be protected, as they are more prone to sun damage because their natural lenses are clearer. Sunglasses is especially necessary for children who must spend more time under sun. It is important to never look directly at the sun, or even to look at reflections of the sun off water, as this can directly damage the retina. Intra-ocular lens implants after cataract surgery often include a substantial ultraviolet filter. Nevertheless, sunglasses will protect the parts of the eye not protected by the implants. in the early 1980's, the atmospheric ozone layer has been declining by about 3 % per year. According to researches conducted in 1993 by Fredrick, a 1% decline in ozone layer results in a 1.3% increase in biological activity. The environmental loses in stratospheric ozone results in dramatic increases in UV (especially UVB below 325 nm) that get to the earth and consequently our eye. This dramatic increase further emphasizes the need for eye and With the loss of the ozone layer, one would expect a dramatic increase in UV related eye problems. So protection lies in clinical intervention by advising our patients to wear the proper UV absorbing ophthalmic lenses or sun-lenses. UV absorbing contact lenses and Intra-ocular lenses [IOL] afford protection for the cornea, lens, and retina against UV radiation. There is a strong possibility that UV-related eye disorders will increase over the next decade. This is 	due to the thinning of ozone layer and growing popularity of outdoor activities. Finally, I want you to enjoy nature and your great outdoor activities, but remember that your lifestyles choices today may protect you for the future.

WRITTEN BY: DR. FELIX OLAFISOYE, SUPREME VISION (EYE CLINIC), ABUJA, NIGERIA. E-MAIL: felix_soye@yahoo.com