Age-Related Macular Degeneration

As the baby boomer population ages, the likelihood of having patients with age-related macular degeneration will increase. Therefore, it becomes increasingly important to understand what the patient is capable of seeing and provide answers to questions about how this condition affects vision.

AMD is a disease that destroys central vision and is associated with ageing. Specifically, the macula is what degenerates. The macula is a part of the retina that contains the most amounts of cones, a light sensitive receptor cell. As some of you may remember from anatomy, cones provide photopic vision, while rods, another type of photoreceptive cell, provide scotopic vision. Photopic vision is what we associate as clarity and color in our vision in well lit environments. Scotopic vision on the other hand is what allows us to see in dim light and is monochromatic. The macula is about 90% cones. In the center of the macula is the fovea centralis. This area contains only cones and provides us with our clearest vision.

There are 2 forms of AMD, wet (exudative) and dry (nonexudative). The dry form is noted by deposits of drusen, which are yellow-white deposits in the fundus. The deposits are found in Bruch’s membrane. Bruch’s membrane is a layer of the choroid, the vascular portion of the eye sandwiched between the sclera and the retina. Although drusen is not uncommon in patients, scientists have only found a correlation between size and number of drusen, and AMD. Typically, a patient with the dry form of AMD will complain of blurry vision.

The wet form of AMD is usually due to neovascularization or bleeding into the macula. The cause remains unknown. This type of AMD causes rapid vision loss. Patients with this form of AMD will notice abnormalities in vision such as wavy lines while looking at an amsler grid. This form of AMD may require prompt treatment.

There are several risk factors that predispose one to AMD, some of which are within our control. According to the NEI, race is a factor; Caucasians are more likely to be affected by AMD. Gender is a factor; Women are more likely to develop AMD than men. Obesity is a factor; Aside from other health issues obesity predisposes you to, there is a link that obesity may affect the rapidity in which the disease progresses. Genetics is a factor; a family history will also predispose one to AMD. Smoking may also increase the risk of developing AMD.

What one does now may help one’s vision in the future. For those of us who wish to reduce the chance of developing this disease, there are several things we can do. We can watch our weight and quit smoking. Keep blood pressure under control. Exercise, which ties in to weight management, is also recommended. Although it’s not enough to watch one’s weight, eating healthy is important. Eating dark green leafy vegetables may also help reduce the risk of developing AMD. Minimizing UV light exposure should also provide some help since UV light is damaging to the retina.

As an optician there are some things we can do. By far the most important is to be patient. There will be a lot of hand-holding on our part. Many patients will not understand why their brand new glasses do not correct their vision. Vision loss is difficult to accept. I personally like to use the analogy of a camera. Many patients will understand that the optical system of a camera is independent of the film. It should be readily apparent to an individual that if the film is damaged in a camera, changing the lens of the camera will not have any effect.

Fitting the patient in lenses that are impact resistant and block UV light, such as polycarbonate, should be the preferred choice. If one eye becomes sufficiently blind, it becomes paramount to protect the “good” eye. Blocking UV light minimizes the chance that these harmful rays ever reach the retina to cause damage of any type. Generally single vision lenses will be the preferred choice. Since the central vision is affected, the patient will use their peripheral vision. Single vision lenses provide wider fields of view compared to progressives or bifocals. The patient may not divulge their condition at first. Generally, a very high add power is a tip-off that something is amiss. Do not be afraid to ask patients about their eye related medical history.