Many eye diseases can be devastating to your vision. With most of them, vision loss or visual disturbances are not noticed by the patient. It is only when the disease process has progressed quite far and become much more difficult to treat, that patients begin to notice changes in their vision, and come see their optometrist. Sadly, by this point, irreversible damage has already been done, and all we can do is try to save what remaining vision a patient has left.
February is Age-Related Macular Degeneration Awareness Month. Macular degeneration is a devastating disease that is the leading cause of vision loss, affecting over 2 million Americans age 50 and over.
The disease is called Age-related macular degeneration (AMD), but signs and symptoms can appear in patients at a much earlier time. There is also a genetic predilection for AMD, so if a parent or grandparent has been diagnosed with AMD, it is wise to have annual eye exams that screen for AMD, so that any changes can be caught in the early stages.
As the name implies, macular degeneration affects the macula. The macula is a small, but very important area of the retina. It is responsible for all of your sharp, detailed vision. When you look at an object, you are using the macula. The rest of the retina could be described as supplying your peripheral vision.
The picture below is an example of a normal retina and normal macula circled in black. The white marks are just a sheen, or reflection off of healthy nerve fibers.
When an optometrist dilates your eyes and looks into them with their bright lights, this is the view they see. At Family Vision Care of Bountiful, we also have an instrument called OCT. OCT is described as an MRI for the eye. It allows the doctor to view a cross section of retina, as opposed to an areal view like in the previous picture. It allows an optometrist to see what's going on in the layers beneath the surface, that may not have been visible just by looking into the eye. Below is an OCT of a "normal" retina. The macula is circled in white, and corresponds to a cut-away-view of the area circled in black in the previous photo.
As you can see, the retina looks healthy, and all of the layers are regular an defined. Especially the bright white band towards the bottom of the OCT. That bright white band is called the retinal pigment epithelium or RPE. It is responsible for maintaining the retina, and keeping it functioning properly.
In AMD, this RPE layer is the first place that signs will occur. At this stage, AMD is called "dry AMD". Instead of being a crisp, regular line like the previous photos show, it becomes lumpy, and irregular because it is holding onto cellular debris, and beginning to atrophy and die. Below is a picture of a retina with dry AMD.
In the above photo, areas of pigmentation and and small white spots called drusen are visible within the macula. These are the first sign of irreversible degeneration in the macula. At this stage, the patient would notice very minor, if any visual changes.
Below is an OCT of a retina, also with dry AMD. The crisp, regular layer of the RPE is gone, replaced by an irregular, lumpy appearing RPE layer.
At this stage, the standard of care, and only treatment available, would be heavy doses of eye-specific vitamins with things like leuteine, antioxidants, omega-3, taurine, and zinc. These would serve to protect the RPE from continued damage, and help it function to maintain the retina. Cessation of smoking would be highly recommended, strict UV protection, and regular eye exams in order to monitor change.
As AMD progresses, patients may begin to see visual changes. At first they may experience a slight decrease in clarity, with some straight lines appearing wavy, or distorted.
AMD progresses into what is called "wet AMD". At this stage, blood and fluid from below the RPE, begin to break through that compromised RPE layer, and leak into the retinal layers, causing widespread damage, scarring, and death to the retina. Below is an OCT of wet AMD. The large areas of fluid buildup are visible as black spaces, and scarring is visible as well. The retinal layers are no longer regular and defined, and have separated in may areas.
At this stage, the only options available as treatment are intraocular injections of a drug that helps to stop the formation of the vascular nets that form and leak blood and fluid into the retina and cause the widespread scarring. The patient may see a slight improvement in vision, but not much. At this point, almost all central vision is gone. A simulated view of what a patient may see is shown below.
At this point, no cure for AMD exists. Efforts are being made, and research is being done to find a cure. That is why it is so important to have your eyes examined regularly by an optometrist, so that we can help to slow the progression of AMD from the very earliest stages. If a patient has progressed to the point of significant vision loss, a referral can be made to a low vision professional, who can help with devices and training to utilize what retinal tissue is left for vision.
Keep in mind, that AMD does not exclusively affect older patients, however it is much more prevalent in that population. Additional risk factors include fair skin, light colored eyes, and positive family history.
If you have any questions regarding AMD or other topics related to the eyes, please feel free to give us a call.
No comments:
Post a Comment