May Feature: Dr. Andrew Schimel explains the Retina, Dry AMD and Wet AMD in our language!
Our very own Dr. Andrew Schimel was recently elected President of the Miami Ophthalmology Society by his peers. When not fixing retinas in our office, he can be found touring the country giving presentations and leading discussions about the most effective treatments of retinal diseases including macular degeneration, diabetic retinopathy, epiretinal membranes and macular holes. He will be starting a blog about the retina through a link on our website. He is hoping to break down retinal disease into terms and concepts that the general public can understand.
Dr. Schimel strongly believes that his retina practice involves teamwork between himself and each patient.
The better his patients understand what is happening to their retinas, the better he can work together with his patients to make optimal decisions in their care. He will start with a background about what the retina is and does and discuss each of the many diseases as well as common concerns and problems that arise as he moves forward. More information on how to find his retina blog coming soon.
This is the first post!
The Retina – Basics
If you imagine the eye as a camera (film cameras, not digital cameras), the retina is the equivalent of the film in the camera. It lines the back of the eye like the film lines the inside back of the camera. Like a camera, even if the entire camera is in perfect working order, if the film is damaged, the picture will not turn out correctly. This is the same for the retina. Even if the eye is otherwise in perfect working order, if the retina is damaged, it will prevent the eye from seeing clearly.
Similar to a camera, the images from the outside world are focused onto the retina by the lens of the eye. The reason people need glasses or contact lenses is because the focusing system in their eye is not perfect and needs to be adjusted. Using the same camera analogy, sometimes the camera is not focusing on the right object and needs to be corrected. We optimize the focus in the eye by placing glasses or lenses in front of the eye.
If there is a retina problem, glasses or contact lenses will NOT be able to fix the problem because it is not an issue of focusing the light. If the film in the camera is broken, changing the focus of that camera’s lens will NOT make the picture come out any clearer.
So, we have the light coming through the front of the eye and being focused by the lens onto the retina which lines the back of the eye. The retina is an extremely thin but incredible piece of tissue. The retina’s function is to convert the light images from the world into electrical signals that can be sent to the brain via the optic nerve for processing.
Thus, the visual system, from eye to brain is similar to a desktop computer. On a desktop computer, there is the main component (the tower), the cord running from the main part of the computer to the monitor, and the computer screen. So, there are 3 things that might be broken if you don’t see an image properly on your computer screen. The screen itself may be broken, the cord running from the screen to the main tower may be broken, or the main tower may be broken.
In this comparison, the cord acts like the optic nerve running from your eye to your brain and the main tower is similar to your brain. When you come to the eye doctor for a vision problem, the problem could be with your eye itself, your optic nerve which carries the images from the eye to the brain or your brain which processes the images.
Dry Age-related Macular Degeneration (Dry AMD) – The Basics
There are 2 forms of AMD, wet (exudative) and dry (non-exudative). In the dry form of AMD, small deposits called drusen build up underneath the retina over time. These drusen are typically made up of toxic byproducts created by the retina. These drusen often accumulate in the central and most important part of the retina called the macula.
Dry macular degeneration will typically cause a very slow loss of central vision over time. This is why we call it dry age-related macular degeneration, because there is a slow degeneration of the center of the retina (macula) without the presence of fluid (dry). This loss of vision usually occurs over the course of several years. People with dry macular degeneration that experience vision loss will notice loss of central details. For example, if they are looking at a book, they will often lose the central few letters or if they are looking at a face, they may not be able to recognize the details of the eyes, nose and mouth, but will be able to tell that they are looking at a face.
The good news for patients with dry AMD is that the progression of the disease is typically slow and they shouldn’t lose their peripheral vision unless there are other problems in addition to the dry AMD. The unfortunate news is that there is no cure at this time for dry AMD; although there are many people working to find one.
Three major risk factors significantly increase the risk of developing dry AMD. These risk factors include age, genetics and smoking. All smokers with signs of AMD should try to quit as soon as possible in order to prevent worsening.
The best thing we have to slow the progression of dry AMD is a particular combination of vitamins and minerals including vitamin C, vitamin E, copper, zinc, lutein and zeaxanthin that is sold over the counter under several brand names.
The most important study regarding this set of vitamins was called the Age Related Eye Disease Study (AREDS) and the best proven formula is the AREDS or AREDS 2 formula (sold as Preservision ®, Ocuvite®, etc.) Patients who do not smoke can take either the AREDS or AREDS 2 formula, but smokers should only take the AREDS 2 formula as they may have an elevated risk of lung cancer if smoking while taking high doses of vitamin A.
Other suggestions to slow the progression of dry AMD include eating green leafy vegetables, fish as well as blueberries and other colorful fruits and vegetables. A major concern for patients with dry AMD is that they also have an approximately 15% chance of progression to wet AMD (see below about wet AMD). For this reason, patients with dry AMD are given an amsler grid to monitor themselves at home. If they note changes or distortion on their amsler grid, they should see their physician quickly to ensure they have not progressed to wet AMD requiring urgent treatment.
Wet Age-related Macular Degeneration (Wet AMD) – The Basics
As discussed above, patients with dry AMD have an approximately 15% risk of progression to wet AMD. This risk is increased or decreased based on the presence of certain retinal findings that can be discussed with Dr. Schimel.
To simplify wet AMD, there is a layer in your eye below the retina called the choroid that contains blood vessels that supply the retina with oxygen. In dry AMD, the barrier between the retina and the choroid becomes brittle and a blood vessel can break through that barrier and begin to leak and bleed into the retina. This vessel leaking and bleeding into the retina is what defines wet AMD and is the reason we call it wet.
The fluid and blood leaking from the vessel into the retina will usually cause significant scarring and damage that leads to rapid and complete loss of central vision if left untreated. If you consider the retina to be like the film in a camera, the presence of fluid or warping of the film would lead to distortion of the final image. Fluid in the retina results in the same distortion. Straight lines suddenly appear wavy when the retina gets swollen with fluid or blood. This is why we have patients with dry AMD check their vision regularly with an amsler grid because if they develop fluid or blood in the retina, the straight lines in the grid will suddenly appear wavy or distorted or be blocked out completely.
The treatment of wet AMD was originally with a hot laser that burned and cauterized the bad blood vessel. Unfortunately, using a hot laser on the blood vessel caused significant scarring and damage to the retina and often left patients with very poor vision. Retina specialists then developed a special cold laser that didn’t cause as much damage and helped slow the damage caused by wet AMD, but most patients still lost a majority of their vision. Doctors also came up with the idea of removing the bad blood vessel with surgery, but unfortunately, the removal of the blood vessel caused significant scarring and loss of vision as well.
In the last 10 years, there was a revolutionary discovery that the eye was actually producing a signal that made the bad blood vessels grow, leak and bleed into the retina. This signal was called vascular endothelial growth factor or VEGF.
Fortunately, retina specialists soon figured out how to block that signal and shrink the bad blood vessels to slow wet AMD and prevent loss of vision. Unfortunately, the only way to get the medicine to the retina for treatment was by injection of the medication directly into the eye.
While it may sound terrible to have to get an injection into the eye, it is really not too bad. The eye is numbed very well and usually patients just feel a small pinch from the injection itself. The current medications used for wet AMD last for a different amount in different patients. Patients are typically given one injection every month for three months straight and then the interval is optimized for each patient over time.
The medication shrinks the bad vessel for a specific amount of time before the vessel starts to grow and cause trouble again. Therefore, the injection needs to be repeated on a regular basis to prevent permanent loss of vision from the bad blood vessel recurring. Most patients require injections as often as every 4 weeks or as little as every 12 weeks on a recurring basis to prevent loss of vision.
The good news is that with regular injections, vision can be maintained in 90% of patients with wet AMD that would have otherwise completely lost their central vision without treatment. Impressively, 30-40% of patients who receive injections will even see a significant improvement in their original vision.
If you or anyone you know has been diagnosed with a retinal condition, call us at 305-598-2020 today to get an appointment with Dr. Schimel!