Ask the Low Vision Specialist: Vision Loss Causes Explained

Q: How do common eye diseases turn into vision loss?

A: There may come a time, as age or injury or disease steals your vision, when your eye doctor shares the unpleasant news that changing your glasses will not provide the improvement you may have come to expect. There can be many reasons for this to be true. Try to imagine your visual system as a camera requiring three things to give you a good picture. First, you need lenses to focus the image, next you need film to capture the image and finally you need some kind of development and printing to get the quality photograph you want.

The “lenses” in your own visual system are the cornea, the crystalline lens inside your eye and the clear fluids that fill your eye. Anything that makes these components cloudy will blur your vision. Of course, a cataract is just such a cloud. Removing the cataracts usually works, however, in some cases they cannot or should not be removed.

The “film” in your biological camera, is the retina and its closely associated layers of blood supply and pigment. Retinal disorders, like macular degeneration, diabetic retinopathy or retinitis pigmentosa interfere with the proper capture of the image. If the light that falls on this “film” fails to be captured and turned into nerve impulses to be sent to your brain, then the picture is lost– even if it is in perfect focus. There are several treatments and surgeries that can be helpful but most of the time a retinal problem is not correctable to perfection and often not at all.

The “development and printing” that I refer to in the camera analogy would correlate to the nerve pathways to your brain and the brain’s processing of that information into something we understand as a “picture” or vision. Any interruption in these pathways will result in a permanent loss of at least part of the “picture.”

Dr. Robert McClenathan provides Low Vision Services at VisionCorps. To make an appointment or submit a question, please call 717-291-5951 or 1-866-876-6550. This column is not an alternative to your physician’s medical opinion, and questions should be directed to your personal doctor.