When you visit your eye doctor yearly, one of the main things they are monitoring for is a disease called macular degeneration. You have probably heard of this, and it sounds very scary! What exactly is it, and what can we do for it?
To understand macular degeneration, it is best to have a basic understanding of eye anatomy.
The macula is the part of the eye responsible for your best central vision. It is part of the retina—the back most structure of the eye that detects light and transfers it to the brain for processing.
The macula is a structure near the center of the retina consisting of a total space of 5 millimeters. It contains the densest area of photoreceptors—the cells that detect and transmit light signals.
If you were to see a picture of the back of the eye, the macula would be the small, almost bullseye-like, red dot in the center of the picture.
You would also notice that the blood vessels curve around the macula to leave it clear. This is because there are so many light-detecting cells within the macula that we want to keep it as void of obstacles (like major blood vessels) as possible!
The information gathered by the macula also takes up almost half of the total area dedicated for vision in the brain. This should show you how important the macula region is—with the macula being so small in comparison to the rest of the retina, the brain prioritizes its’ input as #1!
Macular degeneration is a progressive disease in which the macula is destroyed from the inside out.
The eye is a very fine-tuned organ with several parts to keep it protected against damage. One such protective agent is called the blood-retinal-barrier.
Blood, and other bodily fluids, is toxic to the retina. This makes sense as we need our eyes to be clear and void of structures to permit unaltered input of light to the brain for processing.
When blood, or other fluids, enter the retina outside of designated blood vessels—we perceive the area as absence of light—or vision loss. When blood and fluids accumulate in the retina for prolonged periods of time, the retinal cells start to die off, and this loss of vision becomes permanent.
The retina still needs some blood for nutrition and oxygen—hence why you will see some large blood vessels in images of the retina. These blood vessels however are unique and extra strong to prevent blood and fluids from leaking out.
The retinal blood vessels get their blood supply from an ocular structure called the choroid. The choroid sits behind the retina and consists of large, fenestrated (leaky) blood vessels that provide blood access to the retinal vessels.
The outermost layer of the choroid is called Bruch’s Membrane. It borders the outermost layer of the retina called the Retinal Pigmented Epithelium (RPE). The RPE cells contain a special connector piece called a “tight junction”.
Basically, tight junctions keep fluids and unwanted debris out, almost like a waterproof seal. Therefore, the choroid can leak as much as it wants and only the nutrients the retina wants will pass through into the eye. The unwanted material is then reabsorbed by the choroid and flows back to the rest of the body.
In macular degeneration, however, the unwanted debris builds up within Bruch’s membrane. This debris is often referred to as Drusen and appear as yellowish clumps.
A few small drusen over time is normal and usually does not cause problems. The number one risk factor with drusen accumulation is age. (Hence the name age-related macular degeneration).
Most people will have a drusen or two build up as we have more birthdays—this is not typically an issue. It is the accumulation of excess drusen that creates macular degeneration.
Since drusen is the “stuff” the eye does not want, it often is made of things like lipids, cholesterol, normal cellular debris, etc., these materials are sticky and water impermeable. As it builds up, it not only causes structural damage to Bruch’s membrane (and thus the RPE), but it also creates a blockage making it more difficult for nutrients and blood to get into the retina.
If enough drusen accumulates, it can increase the pressure on Bruch’s membrane resulting in Bruch’s membrane ripping, creating a pocket in between Bruch’s and the RPE in which fluids can accumulate and new blood vessels begin to grow. This is called a choroidal neovascular membrane (CNVM).
These new blood vessels can sneak their way through the RPE and thus into the retina. They do this because nutrients are not reaching the retina (due to the accumulation of drusen blocking healthy nutrient passage) and they think they are helping the retina. However, these new blood vessels are significantly weaker than the blood vessels made for the retina, and therefore leak blood and debris into the retina.
The blood and debris blocks incoming light and thus decreases vision. As these vessels continue to leak and build up in the retina, the retina begins to die.
There are two major types of age related macular degeneration (ARMD)—Dry and wet.
Dry macular degeneration refers to macular degeneration in which there is no break in Bruch’s membrane. There can be large amounts of drusen accumulation in Bruch’s that block passage of wanted nutrients into the retina—essentially starving the retina and ultimately resulting in retinal death and vision loss (i.e. macular degeneration).
Dry macular degeneration is typically less symptomatic and severe than wet. It starts as minor vision loss, but can also progress into severe vision loss depending upon how much of the macula is involved. It is also the more common type of the two.
Dry macular degeneration can progress into wet macular degeneration—this is one of the many reasons why yearly eye exams are so important. If dry macular degeneration is caught early enough, treatments can be used to try and prevent the disease from further progression.
Wet macular degeneration refers to macular degeneration in which there is a break in Bruch’s membrane and choroidal neovascular membrane formation (i.e. blood is now leaking into the retina).
The accumulation of blood within the macular region of the retina leads to severe vision loss and cell death (i.e. macular degeneration).
The short answer to this question is that we really do not know. We know that there are many changes that occur with the vascular system with age—this could simply just be one of them.
There seems to be some hereditary connection with macular degeneration, however just because someone in your family has AMD does not necessarily mean you will develop it as well. It is an increased risk factor, nonetheless, and therefore annual eye exams to monitor for this disease are of the upmost importance.
Other risk factors include smoking, obesity, and diets high in fats and cholesterol.
If you or someone you know has been diagnosed with macular degeneration, it can be hard news to hear.
The good news is that just because you have macular degeneration does not necessarily mean you will go blind. Macular degeneration vision loss can vary from mild impairment to severe. Some cases progress, and others do not.
In fact, the majority of cases stay in the “mild” range!
The best thing you can do if you have macular degeneration is talk with your optometrist and ophthalmologist to see what treatment plan is best for you.
Often in early stages, doctors recommend an over-the-counter vitamin called the AREDs 2 formula. This vitamin is made specifically for the eyes and helps to provide the eyes with the nutrition it may not be getting due to the accumulation of drusen. This can help to prevent the macula from further damage and thus vision loss.
In many caseshealthy diet, exercise, cessation of smoking, and AREDs vitamins can keep the degeneration at bay and the disease will not progress much further.
Other treatments for more severe macular degeneration include laser treatments to inhibit new blood vessel growth and low vision rehabilitation to help you learn how to better utilize your remaining “good” vision.
Whatever the case, your eye doctor is here to help with treatment plans, concerns, and rehabilitation!