Protecting your eyes from UV rays
Written by Seamus Flynn, Optometrist.
The sun emits Infrared, visible and UV rays.
The UV rays are high energy wavelengths and the high energy can cause damage to the eye if it is overexposed to it.
95% of the UV rays that reach us are UVA rays whereas the remaining 5% are UVB rays, The UVB rays are higher energy wavelengths and cause more damage to our eyes than UVA.
The Ozone layer provides a certain level of protection from UV light but as we all know this layer is continuously being depleted leaving us more vulnerable to its harmful effects.
Short term damage
If our eyes are exposed to UV in the short term it can cause photokeratitis which is like a sunburn of the eye. This is a painful eye condition caused by exposure to either intense sunlight or can also occur with exposure to artificial UV light such as welders arc.
It results in a burn of the cornea and conjunctiva which are the front layers of the eye and causes intense tears, eyelid twitching, discomfort from bright light, and constricted pupils.
Long term damage
In the longer term UV light can damage not just the front surface of the eye but every layer from the front to the macula at the back of the eye.
Cataracts – UV exposure can cause cataracts in the crystalline lens (1)
This is where the normally clear lens becomes cloudy and affects the clarity of vision for everyday tasks.
Macular degeneration – Exposure to UV rays can cause ARMD (age related macular degeneration) (2)
The macula in the back of the eye is the area that we use for sharp focus of images. UV rays cause wear and tear to the macula which results in loss of central vision over time. This condition cannot be treated but can be slowed down by taking supplements contain lutein and zeaxanthin.
Pterygium and Pinguecula – UV exposure can cause pterygiums and pinguecula in the conjunctiva. A pinguecula presents as a small yellow lump at the nasal side of the eye. It can vary from barely noticeable to a prominent yellow lump. It is made up of fat and protein molecules and does not cause any problems. A pterygium is similar to a pinguecula but can grow across the eye and even over the pupil in more severe cases. If this occurs it can affect the vision as it prevent as much light entering the eye that would otherwise occur and physically blocks the vision.
The best way to prevent UV damage is to wear sunglasses that block UVA and UVB rays. It is important to ensure that the lenses fully protect against these wavelengths as not all sunglasses do. Sunglasses tint vary in darkness from a very light tint up to 90% tint which is a very dark lens. The darkness of the lens does not relate to the amount of UV protection. You can have a lightly tinted lens that offers full UV protection and a dark tinted lens that does not. Another common misconception is that all polarised lenses provide UV protection and this is not necessarily the case either so its important to check what level of protection your lenses have.