"What's my vision?"
I get asked this question daily. Most of the time, the patient is curious to know how well they are seeing, and that's where 20/20 vision comes into play. But do you really know what it means? I'll dive into this today.
20/20 vision is used to express what is seen as normal visual acuity, or normal clarity of vision at 20 feet. It essentially means that you can see clearly at 20 feet what should normally be able to be seen at that distance. For example, if you have 20/100 vision, you must be standing at 20 feet to be able to see something that a person with 20/20 vision can see at 100 feet. Put more simply, you must be five times closer to that object in order to see it clearly.
Although we usually think of 20/20 vision as being "perfect vision", it does not necessarily mean that vision is totally perfect. Many things affect how the visual system performs, including peripheral vision (or side vision), depth perception (our ability to see in 3D), focusing ability, eye coordination, and color vision. Some patients are able to see the 20/20 line on our chart, yet they have defects in their peripheral vision or their color vision is not optimal.
Many conditions can affect visual acuity, including nearsightedness and farsightedness. We know that these conditions can usually be corrected with contact lenses and glasses, but there are other conditions that affect visual clarity to the point that glasses and contact lenses do not improve it. Cataracts, for example, can affect vision so that it seems as if you are constantly looking through a dirty windshield. How annoying! Macular Degeneration affects our central vision and can make pinpointing certain letters or objects difficult. Glaucoma is a relatively common condition that messes with peripheral vision.
As you can see, "What's my vision?" is a loaded question. There are so, so many things that come into play and although you may be able to read the bottom line on our chart, it does not mean that your vision is perfect. The best way to know how your eyes are performing is to come in for a comprehensive eye exam. What are you waiting for?
Until next time!