Does a simple thing such as wearing dark glasses while out in the sun require thought?
To understand this, we need to look at how our eye responds to different light conditions.
The eye regulated the amount of light entering it by adjusting the size of the pupil. The pupil is the central dark window formed in our eyes by the Iris. The color of our eye is determined by the color of the Iris. At the center, the Iris has a circular window called the Pupil. This pupil can be seen by shining a torch into another person"s eye. Normally, our pupil measures 3-4 mm in diameter.
When exposed to bright light, the pupil can constrict (becomes smaller) to just about 2 mm in diameter or lesser. This mechanism of reducing the aperture restricts the amount of light entering our eyes. When we go out in the sun, our pupils constrict so that the excess light is cut off and we do not have discomfort.
When we enter a dark room, or when the sun goes down, the reverse happens. Because the light reaching our eye is too less for us to see well, the pupil dilates (becomes larger) to about 5-6mm. This also exposes the Rod cells of our retina to the light. The Rod cells help us to see in the dark.
Now, it is easy to imagine what happens when we put on a dark glass while going out in the sun. The dark lenses cut off the light entering our eye, and our pupil dilates as a result. As a result, more light enters the eye. Since the lenses are dark, we do not feel any discomfort. But, there is a concern. The dark glasses do not block out the Ultraviolet Radiation (UV Rays) in the light.
UV Rays cause severe damage to our retina. They are known to cause macular degeneration, Macular Hole, Cataract, Pterygium (a growth on the eye), etc.
Therefore, it is imperative that the dark glasses that we use should have a UV filtering capacity. If such a UV protection is not available on the dark glasses that you wear, it is better to go out into the sun without them than to wear them.
In conclusion, it is ideal to wear a UV protective sunglass while out in the sun. A sunglass without UV protection must be avoided at all costs as that is more damaging to the eye.
What you should do:
Contact Dr. Ashley Mulamoottil, who is the Medical Director & Chief Surgeon in Mulamoottil Eye Hospital & Research Center, Kozhencherry, Kerala. You can also interact with him from his Facebook page.