Article Date: 11/1/2007

Recognizing the Ocular Dangers of UV Radiation
CALL FOR UV PROETCTION

Recognizing the Ocular Dangers of UV Radiation

Experts sound a wake-up call about the threat the sun poses to patients everywhere.

Stephen M. Cohen, OD, (moderator): In this discussion, we'll review research on the harmful effects of ultraviolet (UV) radiation on the eyes. We'll talk about best practices for protecting our patients, including the newest and least-utilized approach to prophylaxis — the use of contact lenses. Most significantly, we'll focus on a troubling question: Why is our profession not adequately meeting the needs of patients when it comes to educating them about UV protection?

Dr. Bergmanson, with your extensive background in researching this issue, please provide an overview of how UV exposure affects the eyes and what kind of damage occurs over time.

HARMFUL EFFECTS OF UV

Jan P. G. Bergmanson, OD, PhD, PhD h.c., FCOptom, FAAO (Dip): Based on existing research, we know the following:

UV rays affect all cellular layers in the cornea, including the epithelium, stroma and endothelium.1 The UV-filtering ability of the cornea decreases when it becomes thinner, increasing potential risks of UV damage in patients who have conditions associated with stromal thinning, such as keratoconus and pellucid marginal degeneration. LASIK, PRK and PTK also may raise risks, although this hasn't been proven. Even in the normal cornea, UV radiation can produce polymegethism, corneal edema and climatic droplet degeneration.2–4

"Although people in the southern hemisphere are most at risk for ocular UV damage, those in northern regions are also in harm's way. The holes in the ozone layer have been located at both poles."

Jan P.G. Bergmanson, OD, PhD

The conjunctiva is vulnerable. The most prevalent UV-related conjunctival disease is pterygium, affecting more than 10% of the population in the southern United States and more than 20% in central Mexico.5–7 This condition is generally a cosmetic issue, but pterygium can grow over the limbus and affect vision. The only treatment is surgery, which presents unacceptable risks for complications and recurrence. Researchers believe that temporally and tangentially incident rays focused by the cornea on the opposite side at the limbus, where light can be concentrated by a factor of 20 by the cornea, causes pterygia.8

The crystalline lens is the primary filter of UV rays. Because of this, the crystalline lens loses its transparency when it's exposed to excessive UV radiation, requiring cataract surgery as the patient ages.9

The retina is at risk. The retina of the average, healthy person receives very little UV exposure. But when the retina of an aphakic patient isn't protected, it can be dangerously exposed, resulting in solar retinitis and possibly age-related macular degeneration (AMD) long term. I recently saw three aphakic patients who, for different reasons, didn't have intraocular implants or any form of UV protection.

Today's environment increases the threat. The ozone is expected to continue to deplete another 20% over the next 10 to 20 years. This could lead to as many as 830,000 more cases of cataract surgery at an estimated cost of $2.8 billion.10 Although people in the southern hemisphere are most at risk for ocular UV damage, those in northern regions are also in harm's way.9,11 The holes in the ozone layer have been located at both poles, so people in northern locations are certainly not immune to UV damage, especially if they spend a lot of time outdoors. Research at the University of Houston College of Optometry showed that in 9 out of 10 days, radiation levels were unhealthy during the summertime in the southern United States.1 We probably won't see the environment improve to pre-ozone hole levels before 2050. So as long as we remain in practice, all of us must regard UV protection as an essential part of our critical mission.

Both UVB and UVA rays are harmful. UVB has long been established as a cause of ocular damage. Now we know that UVA radiation also poses a serious threat. The cornea has almost no ability to filter UVA rays, which directly stress the crystalline lens. When UVA rays hit the eye tangentially, it makes the conjunctival stem cells vulnerable, leading to pterygia. The radiation easily penetrates the cornea on one side and becomes focused on the opposite side.

UV damage is cumulative and long-term, and it affects children more than any other population. The World Health Organization estimates that up to 80% of a person's lifetime exposure to UV radiation is received before age 18. So as you can see, the eye is exceptionally vulnerable to the sun's rays, and, therefore, we must do all we can as clinicians to protect our patients.

The ABCs of UV Radiation in Children
Studies show that 90% of people understand that the sun can damage their skin. But probably only 10% understand how extensively it can damage their eyes — and not just on sunny days. Time limitations are a big challenge when explaining ultraviolet (UV) dangers to patients. We can save time by communicating a few important points succinctly, including:
■ UV radiation can cause long-term damage to your child's eyes, just as it can to their skin. Protecting your child now will decrease the potential for serious eye problems later in life.
■ The World Health Organization estimates that 80% of a person's lifetime UV light exposure occurs before age 18.
■ Adults tend to wear sunglasses, but children spend more time outdoors without wearing them.
■ Since your child will be wearing contact lenses for vision correction, I'm prescribing a contact lens that can help block UV rays.

Stephen M. Cohen, OD

IDENTIFYING HIGH-RISK PATIENTS

Dr. Cohen: This information is very helpful, although more research is needed. We know all patients are at risk, but especially children, aphakes and people with thin corneas. Are there any other patients at high risk for ocular UV damage?

Dr. Bergmanson: Those at highest risk are albinos and diabetes patients. Usually, I make UV protection mandatory for these individuals. In addition, people who take certain medications, such as antibiotic agents, and who eat citrus fruit and other types of foods have a higher sensitivity to the sun than others.12

Paula R. Newsome, OD, MS, FAAO: People who spend a lot of time outdoors, such as athletes and construction workers, are especially at risk.

Jason J. Nichols, OD, MPH, PhD, FAAO (Dip): We should ask all patients about activities in which they participate that might increase their UV radiation exposure, such as fishing, hiking, water skiing and other outdoor activities. We also have patients who are exposed to nonsolar UV radiation, such as that found in welding arcs, lasers and tanning beds, for example.

EDUCATING PATIENTS

Dr. Cohen: We understand the risks of UV exposure. How do you educate your patients about these risks?

Dr. Newsome: We try to identify high-risk patients when we confirm their appointments. If a patient has lived in a tropical climate or a foreign country, in particular, we ask them to bring in all of their eyewear, including contact lenses and sunglasses so we can evaluate how much UV-radiation protection they need. In our lifestyle survey, we ask patients how they use their eyes. We have various brochures in our office that address UV radiation, in addition to information on our computers in exam rooms. Patients can view the information on UV protection on those computers. We also show videos in our exam rooms since they're all equipped with televisions. The posters we have on the walls in exam lanes also reinforce the message.

Dr. Cohen: We often forget that our younger patients are most susceptible because of the cumulative effect of UV radiation exposure. They also have larger pupils, clear lenses and spend more time outdoors. Since the effect is cumulative and damage may not show up for decades, I feel that we have a responsibility to consistently and comprehensively educate parents and children about UV radiation and its effects on their eyes. What's your view on this, Dr. Newsome?

Dr. Newsome: When I was on the Vision Council of America's board a few years ago, we interviewed patients after their eye exams and found that, without fail, the doctor hadn't explained the deleterious effects of UV rays on the eye. Often, doctors feel like they're selling when they offer UV-protection options. But they should offer UV protection knowing that they're providing basic eye care. CLS

REFERENCES
  1. Walsh JE, Bergmanson JPG, Saldana G, Gaume A. Can UV radiation-blocking soft contact lenses attenuate UV radiation to safe levels during summer months in the southern United States? Eye Contact Lens. 2003;29:S174-S179.
  2. Ringvold A, Davanger M, Olsen EG. Changes of the cornea endothelium after ultraviolet radiation. Acta Ophthalmol. 1982;60:41-53.
  3. Pitts DG, Bergmanson JPG, Chu LWF. Ultrastructural analysis of corneal exposure to UV radiation. Acta Ophthalmol. 1987;65:263-273.
  4. Good GW, Schoessler JP. Chronic solar radiation exposure and endothelial polymegethism. Curr Eye Res. 1988;7:157-162.
  5. Cullen AP, Perera SC: Sunlight and human conjunctival action spectrum. Ultraviolet radiation hazards, Proceedings of SPIE — The International Society for Optical Engineering. 1994;2134:24-30.
  6. Taylor HR. A Historical perspective of pterygium. In Tayor HR, ed. Pterygium. The Netherlands: Kugler Publications. 2000;3-14.
  7. Horner DG, Long A, Roseland J, et al. Pterygia, cataract, and age-related macular degeneration in a Hispanic population. Optom & Vis Sci. 2006;83(Supp).
  8. Coroneo MT, Muller-Stolzenburg NW, Ho A. Peripheral light focusing by the anterior eye and the ophthalmohelioses. Ophthalmic Surg. 1991;22:705-711.
  9. Taylor HR, West SK, Rosenthal FS, et al. Effect of ultraviolet radiation on cataract formation. New Engl J Med. 1988;319:1429-1433.
  10. West SK, Longstreth JD, Munoz BE, et al. Model of risk of cortical cataract in the US population with exposure to increased ultraviolet radiation due to stratospheric ozone depletion. Am J Epidemiol. 2005;162:1080-1088.
  11. Javitt JC, Taylor, HR, Cataract and latitude, Doc Ophthalmol. 1994;88:307-325.
  12. Bergmanson JP, Sheldon TM. Ultraviolet radiation revisited. CLAO J. 1997;23:196-204.


Contact Lens Spectrum, Issue: November 2007