Why Glasses Won't Help You See

31 Mar Why Glasses Won't Help You See

“Will glasses help?”  We often wonder if “correction” will help decreased vision in the presence of retinal disease such as macular degeneration and diabetic retinopathy.  Spectacles can only help so much yet won’t “reverse” the loss of vision from the disease.  This is opposite to those people who claim they are “blind,” yet with glasses see quite well.

How do Glasses Work?

The goal of corrective lenses is to focus an image, sharply, on the surface of your retina (technically the macula).  If you are nearsighted (myopic), the image of what you see falls short, or in front, of the macula.

Nearsighted Image is "TOO SHORT" and Falls in Front of Retina

Glasses are used to refocus the image on the retina.  This is exactly like a projector focusing on a movie screen.

If you are farsighted (hyperopic), the image actually is focused behind, or past, the macular surface and glasses are used to move the image forward onto the retina.

Farsighted Image is "TOO FAR" and Falls Behind the Macula

What is the Macula?

The macula is the functional center of the retina.  It measures only about 1.5 mm X 1.5 mm, yet it gives us all of the attributes of our “sight.”  It provides us our best color vision, central sight for reading and watching TV and is the only part of the retina sensitive enough to “see” 20/20.

"JUST RIGHT" - Image Falls ON the Retina

Will Glasses Work?

If there is macular disease, such as diabetic retinopathy or macular degeneration, even properly measured glasses won’t work.

The vision is decreased due to the macular disease.  It simply isn’t capable of “seeing” 20/20.  The disease is preventing the retina from working to its full potential.

When glasses are working, the image is properly focused on the retina, but the retina is not working well.

Low Vision Aids

It may now make sense why “low vision” aids don’t simply correct for the disease.  Low vision aids may be useful by enlarging the image focused on the retina.  It may make the image easier to “see,” but the disease is still present.  Sometimes, images can be focused to the side of the diseased macula, but these “para-macular” areas are not as sensitive as the macula itself.

In all cases, vision is compromised.

What Does This Mean?

When we speak of decreased vision, implicit in our discussion is the assumption that the proper glasses, or contacts, are being used.  The eye is a pretty remarkable optical system, and in most cases, it is pretty routine to find the right lens to help correct myopia, hyperopia and astigmatism.

The optical system can’t correct for disease.  while the unit may be functioning properly, that is, focusing an image precisely on the retina, the disease will always win.

This is true of macular disease, glaucoma and some cataract.