As I stated in the beginning, one of the ways I wanted to use this blog was to educate people about pathological myopia and myopic macular degeneration, and giving a general overview of the basics seems like a good place to start.
Note: I am not a doctor, nor do I have any medical training outside some very basic biology classes in high school and college, and they were never my strong points. Please do not use this website to diagnose yourself, it is strictly me speaking about my personal experiences with the addition of a bit of research. This article published in November 2017 by the American Academy of Ophthalmology was the primary resource I used for some of the more medical information in this post and if you are interested in reading in more detail, I strongly recommend it: Myopic Choroidal Neovascularization.
What is Myopic Macular Degeneration?
Myopic Macular Degeneration is a retinal disease that impacts the macula, the part of the eye which controls detailed and central vision. It is really a shortened way of describing the condition, which medically is known as myopic choroidal neovascularization, secondary to pathological myopia. That is a quite a mouthful though, so MMD it is. Myopic macular degeneration shares a lot of similarities with age-related macular degeneration (AMD) in terms of symptoms and treatment, but rather than being a result of getting older, it’s caused by the strain put on the retina in those who have an extreme form of near-sightedness. If you’ve never heard of MMD, you’re not alone – I did not know what it was until I was diagnosed. It only impacts about .035% of the US popular, and is slightly more common in women.
If you don’t have much time and want the simplified version, this video from the pharmaceutical company Novartis does a good job at providing a succinct overview of myopic choroidal neovascularization (CNV).
Cause of Myopic Macular Degeneration
As the name indicates, this condition affects people who suffer from a severe form of myopia, or near-sightedness, which is caused by the elongation of the eye. For those of you who may be wondering if your vision puts you in the category or someone who may be at risk of developing MMD, let’s take a look at the numbers.
If you have received a glasses or contact prescription from an optometrist or ophthalmologist in the past, the power of the lens needed to correct your visual acuity to 20/20 will be measured in a unit called diopters. The larger the number, the higher the strength of your prescription.
- Mild myopia includes powers up to -3.00 diopters (D)
- Moderate myopia, values of -3.00 to -6.00D
- High myopia is myopia over -6.00D
- Severe myopia is is myopia exceeding -10.00D
When a person reaches the point of having severe myopia, they are then at risk of developing what is known as degenerative myopia or pathological myopia (leading me to sometimes refer to myself as a pathological degenerate, but I also have an odd sense of humor). When I was diagnosed, my prescription was around -18 in my right eye, -22 in my left eye.
In pathological myopia, the retina and other layers at the back for the eye become so thin that the cells in the retina can die slowly. This leads to atrophy and a slow decline in central vision and increases the likelihood of cracks or tears in the retina. About 5% of people with pathological myopia will start to develop abnormal new blood vessels underneath the macula, and if those blood vessels begin to leak, a person will be diagnosed with myopic choroidal neovascularization/myopic macular degeneration.
Symptoms of Myopic Macular Degeneration
While age-related macular degeneration and myopic macular degeneration share a lot of similarities, the one of the differences I’ve learned about with regards to symptoms is that myopes (as my doctor calls us) experience two different types of bleeds.
The strain on the retina caused by severe myopia can cause cracks in the retina, referred to as lacquer cracks due to their shape, and occur in approximately 5% of highly myopic individuals.
Occasionally small amounts of blood can get through these cracks, causing what appears in the vision to be a small shadowy area. Visually, it appears as the holes or blurring on the grids in the image at the top of this section, but rather than being in the most central part of my vision, they are typically slightly off-center. My doctor refers to these blood spots as benign or innocent bleeds because although they cause temporary disruption to my vision, they will eventually resolve themselves on their own without treatment and do not leave any lasting damage. They’re more annoying than anything, and occur in my vision quite frequently. I almost always have at least one benign bleed in my eye at a time. The farther away these shadows are from my central vision, the more confident I feel going into an appointment that it will be determined to be a benign bleed.
My doctor has termed the occurrence of choroidal neovascularization as an “active” bleed, since it occurs when the abnormal blood vessels growing under the macula have started to hemorrhage fluid into the eye. This causes large areas of distortion in my central vision, causing everything to look warped, as seen in the “curvy lines” grid in the image at the top of this section. This area of distortion will continue to grow and worsen until treatment is received, and as the fluid grows more dense, it can create a blind spot in the vision. Left untreated, the leakage from these blood vessels will continue to grow and increase the likelihood and size of scarring on the macula, leaving permanent damage to the vision.
Both active and benign bleeds are unpredictable; there are no indicators that one is oncoming until you start to notice changes in your vision, so as soon as something seems out of the ordinary, CALL YOUR DOCTOR. I have monthly appointments scheduled, and I’ll still call to have someone see me, even if I was just there a few days earlier.
The scar tissue the develops on the macula both as a result of the retinal atrophy and growth of blood vessels caused by myopic CNV is the cause of the permanent distortion in central vision that significantly deteriorates vision in those with MMD. It decreases an individual’s visual acuity, which makes things such as reading, identifying faces and anything that requires seeing in detail more difficult. As the scarring and atrophy become more and more severe, that is when a person is at risk of becoming legally blind.
One of more mild, but still impactful, symptoms of pathological myopia is photophobia, or an increased sensitivity to light. This both takes the form of being uncomfortable when confronted with bright lights and having difficulty adapting to changing light levels. Although it may not seem as significant as retinal bleeds or macular scarring, photophobia can still cause people to have to make drastic changes to their day-to-day living; in my case, I had to make the choice to no longer drive at night because of the difficulty I have with the headlights of other vehicles.
Treatment for Myopic Macular Degeneration
If you are squeamish, skip right on down to the next section, Long Term Prognosis.
Currently, the most common form of treatment for myopic macular degeneration is injecting one of three drugs directly into the eye: Lucentis, Eylea or Avastin. These drugs bind to the proteins that are responsible for the growth of abnormal blood vessels to slow and stop their growth. Depending on the severity of the bleed, injections may need to be administered several months in a row, but frequently for myopic CNV they can be cleared up after one injection. Prior to treatment, your doctor will numb your eye (mine uses a combination of drops and gels) so you will not feel anything aside from a slight amount of pressure. My doctor also uses a lot of betadine to help prevent any potential infection. In my personal experience, the stinging from the betadine is wayyy more unpleasant than the actual injection.
There is not currently any way to prevent the growth of these abnormal blood vessels or to reverse the scarring on the macula that they cause, which is why it so important to CALL YOUR DOCTOR if you notice any changes to your vision so they can treat you immediately, if necessary.
If you made it through reading about the treatment for MMD (and for anyone who made it to the end of this massively long post), congratulations! Here’s a pup-rito!
Long Term Prognosis
Unfortunately, this is the part of the post where I shrug a little bit. The injections used to treat CNV were only approved by the FDA 10-years ago. Combined with the limited number of people diagnosed with MMD and how unpredictable this condition can be, there’s no real timeline to determine “your visual acuity declines at a rate of X per year, and Y years after a diagnosis is when you may be considered legally blind.” Approximately 35% of individuals diagnosed with MMD in one eye will develop it in their other eye within an 8-year period; it took about 3.5 years for that to happen to me. I happen to have a fairly active form of myopic macular degeneration and will have an active bleed every couple months; I’ve spoken with some people who go years between occurrences. It’s true about all things in life, but this is definitely a condition where everyone is different and why I consider it to be so important to find a retina specialist that you trust is giving you the best care possible and continually informing you about the prognosis of your condition and any new forms of treatment that may be available along the way.
Currently, there are a number of clinical trials in progress to find a way to reverse the visual distortion caused by scarring on the macula, and several of them have had encouraging results. I remain hopeful that during my lifetime treatment will be available to either reverse the vision loss caused by macular scarring or to prevent active bleeds before they happen.
Leave me a note in the comments or send me an email and let me know any aspects of myopic macular degeneration or how I live with it you’d like to know more about! I have a few things in mind for future posts relating to it, but I’d love to know if there is anything specifically you want to know!