Disclaimer: This section is a short description of the disease written by a patient, for fellow patients. It is not a medical text and should not be used as a substitute for diagnosis and treatment by an accredited professional.
Myopia is also called near-sightedness or short-sightedness. It is caused by an abnormal elongation of the eye, and makes objects in the distance appear blurry. Simple myopia can be corrected with glasses, contact lenses, or refractive surgery. However, when the eye becomes too stretched, and shaped like a football or rugby ball, rather than a basketball, complications can happen.
Myopia is measured in two main ways : your lens prescription (in diopters) or your eye axial length (in mm).
High myopia is often defined as an axial length greater than 26 mm, or a prescription higher than -6 D. This causes excessive stretching and thinning of the retina, not unlike the stretched fabric on a too-small shirt. The retina at the back of the eye is a complex tissue made of several types of cells, including the photoreceptors that capture visual information and send it to the brain.
When the eye is too long, and the retina is stretched, the cells receive less oxygen and fewer nutrients, and can eventually die, which leads to blank spots in a person's vision. This can be particularly troublesome if the macula, the central part of the retina responsible for high acuity vision such as reading and recognizing faces, is affected. This type of change is the dry form of Myopic Macular Degeneration (MMD), and it is also the most common type, affecting about 80-90% of MMD patients. There are currently no treatments for dry MMD. It usually causes a slow visual decline, but this varies a lot from patient to patient.
Sometimes, abnormal blood vessels can grow beneath the retina and leak, causing rapid distortion or loss of vision. This affects 10-20% of MMD patients and is known as the wet form of MMD or as CNV (choroidal neovascularization). It often causes visual distortion, such as straight lines appearing wavy, or the appearance of bright or dark spots in the patient’s vision. Fortunately, treatments are now available for this complication, and visual loss can be halted or sometimes reversed.
Symptoms of MMD
MMD symptoms are similar to other types of macular degeneration and can include:
Distorted vision (lines look wavy)
Blank spots in vision, especially central vision
Trouble distinguishing between shades of colors
Difficulty in adjusting your eyes going from brightly lit to dim spaces, and vice-versa
Dry MMD causes a gradual loss of central vision; wet MMD is like wet AMD and can cause rapid loss of central vision.
There is currently no treatment for dry MMD, which accounts for 90% of all cases.
The most common treatment for wet MMD is an injection in the eye of an anti-VEGF drug, which makes the abnormal blood vessels shrink. Some common commercial names for these medications are Avastin, Lucentis, and Eylea. Other treatments, such as laser or photodynamic therapy, are available, but they are less commonly used. Some patients need only one or a few injections to control wet MMD, while others may need more frequent treatment. Wet MMD needs to be treated quickly (ideally within a few days of the bleed) to ensure the best possible visual recovery.
High myopes can get another type of bleed that is not treated with anti-VEGF injections. They are sometimes called "simple bleeds" or "dot hemorrhages" and are caused by the stretching of the retina, resulting in small leaks of blood in the upper layers where the visual information is perceived. This can cause visual disturbances like distortions, flashes, or shadows, but they can also go unnoticed. Simple bleeds usually cause smaller visual disturbances than those resulting from the leakage of abnormal blood vessels. Simple bleeds usually do not require treatment as they often resolve on their own within a few weeks.
There are other complications to high myopia that are caused by the tension, pulling and stretching of the different layers of the retina, but these are less common than dry or wet MMD. These complications include epiretinal membrane, macular hole, foveoschisis, among others. Sometimes, surgery is required to release the tension on the retina.
A major complication is retinal detachment. It can happen to anyone but high myopes are much more at risk. Retinal detachment is a major medical emergency requiring surgical treatment as soon as possible (preferably within hours or days) to reattach the retina and recover as much vision as possible.
Some other complications your ophthalmologist might mention to you are lacquer cracks and staphyloma that may be present in patients with high and pathological myopia. Lacquer cracks are breaks in Bruch’s membrane in the posterior part of the eye, while staphyloma is a posterior outpouching (protrusion) of the wall of the eye caused by stretching.
In summary: The two main complications of MMD need to be treated very quickly by an ophthalmologist or retinal surgeon in order to preserve or restore vision : retinal detachments and CNVs. If you have doubts, please seek medical advice as soon as possible. Unfortunately, the most common, dry form of MMD currently does not have any treatments, but one of the goals of our group is to change that.
If you would like to learn more about MMD, here are some links to other websites with good information :
UK Macular Society: Description of MMD
Macular Disease Foundation Australia: Detailed MMD description along with downloadable factsheet
Stanford Research Lab, Dr. Mahajan’s research into genetic causes of MMD and potential treatments: Patient Guide to Myopic Degeneration | Mahajan Laboratories (stanford.edu)
Professor Coffey, UCL: Video conference, Myopic Macular Degeneration and how to find a cure