Ultraviolet Awareness

After this abnormally tedious Boise winter, we are all ready to get outside and play in the sun! Hold on though, before you rush outside, have you taken the necessary precautions to protect yourself for ultraviolet rays? There are three types of ultraviolet rays, these wavelengths are not visible to the human eye and are shorter than violet wavelengths of light.
 

Shorter wavelengths of light actually have a higher energy, which can cause more damage. One ultraviolet wavelength, UV-C, is absorbed by the Earth's atmosphere. The two remaining wavelengths that reach us, UV-A and UV-B, can cause damage to body tissue.

Everyone is aware that wearing sunscreen is important (especially at these higher elevations) but what can be done to protect the eyes? The sun can cause damage to multiple ocular structures they are as follows:

• Eyelids – just like any other epithelial tissue on our body, the eyelids are susceptible to skin cancer. The skin around the eye is very thin and sensitive.

• Cornea – the cornea is the transparent, dome-shaped structure, that arches over the iris and helps refract light rays through the pupil. While it is a clear structure, the cornea is highly innervated (lots of nerves), meaning it is very sensitive to even mild irritants. When the cornea is irritated it is generally called a keratitis. A keratitis is classified depending on the insulting agent, for example, if it is caused by a bacterial infection it is called a bacterial keratitis, or if it is caused by the herpes virus it is called a herpetic keratitis. There is a keratitis classified as a photokeratitis, meaning it is caused from light rays (photons make up light rays). Think of a photo keratitis like a painful sunburn...but on the eye. If you cringed a little bit that is an appropriate response. A photokeratitis is very uncomfortable and can have symptoms of pain, light sensitivity, watering, redness, etc.

• Conjunctiva – the conjunctiva is a soft clear tissue that covers the sclera, the white part of the eye, and the inside of the eye lid. It forms a protective barrier that prevents foreign bodies from getting behind the eye. So if you ever thought you lost your contact in your brain, no worries, it is mostly likely folded up under one of your eye lids. The conjunctiva is also prone to injury associated with UV light. Similar to the cornea, the conjunctiva can experience a “sunburn.” Generally if the cornea is being damaged the conjunctiva is too. The conjunctiva is also susceptible to developing a pinguecula, which is an elevation of conjunctival tissue that develops a yellowish hue. Generally a pinguecula is cosmetically unappealing but it can also affect the way tears adhere to the eye causing an increase in dryness. A pinguecula can expand in size and can encroach onto the cornea which is called a pterygium. A pterygium can eventually impeded vision.

• Lens – the crystalline lens is a clear structure that is behind the iris and is responsible for refracting light to the retina to form clear images. The lens is a pretty remarkable structure because it is able to change shape depending on the viewing distance of an object for increased clarity. The lens also has some protective qualities. The lens absorbs some of the UV wavelengths that are penetrating the eye. This is protective to the retina. Unfortunately when the lens absorbs UV rays it causes biochemical changes to the proteins inside the lens that causes cataracts. Cataracts can cause decreased vision and increased glare. Cataract surgery is a common procedure that occurs within industrialized countries but cataracts are a major cause of blindness around the world. Interestingly enough following cataract surgery an intra-ocular lens is implanted where the crystalline lens was prior to surgery. It was found that following cataract surgery the likelihood of developing age-related macular degneration (ARMD) increases 200%. This means that appropriate precautions to prevent UV exposure need to be considered. Luckily intra-ocular lens manufacturers have developed lenses with chromatophores that block UV light.

• Retina/Macula – the retina is the neurologic structure inside the eye that is responsible for transmitting the signal that forms images. The macula is the center of best vision and is responsible for seeing fine detail and color. When the retina is exposed to UV light, it increases the likelihood of developing ARMD (please see our blog on Low Vision and Macular Degeneration). An interesting fact is that the retina gets the majority of its UV exposure before the age of fifteen. Talk about a good reason to get sunglasses on kids!
   

Ultraviolet exposure doesn't just occur in the sunlight. Certain things can produce UV radiation such as tanning beds, welding equipment, and lasers (yes even laser pointers). So what are the best ways to protect the eyes from UV exposure? The following things can be done to lessen UV exposure:

• Wear a hat – if a brimmed hat is worn appropriately with the brim above the eyes it can lessen UV exposure 22-95%.

• Wear sunglasses – not all sunglasses are created equally. Sunglasses should always have lenses that state they are 100% UV-A/UV-B protective. If the UV protection is not noted on the lenses they can actually increase ocular damage because the tinted lenses cause the pupil to dilate more leading to increased UV rays penetrating the eye. The most appropriate sunglasses should be UV protective and have a blue-blocking anti-reflective coating.

• Have appropriately fitting sunglasses – if sunglasses are not fitting appropriately UV light can penetrate. It is important to work with an experienced optician to find the best pair of sunglasses and the best lenses to protect the eyes.
   

Ultraviolet rays can damage many ocular structures. Before you rush outside this spring, stop in to work with our opticians to find the best sunglasses to protect your eyes!