Myopia, or nearsightedness, is the result is an inability to see objects clearly if they are at a distance. It happens when the eyeball elongates making a clear focus of objects at a distance impossible. Degenerative myopia, on the other hand, is a condition where the eyeball continues to elongate getting thinner and thinner over time.
The condition affects 40% of individuals in the US, 84% of Asian youth, twice as many women as men and Caucasians more than Blacks. Worldwide, about 22% of people, or 1.5 billion 100 million of which are children, suffer from the condition. In fact, children 7-16 suffer from the greatest progression of the disease with a mean rate of 0.35-0.60 Diopters with the fastest progression seen with early myopia.
The condition has significantly increased over the past couple of decades especially with cases of HIGH myopia. Of those affected, 6.3-26.1% of those with myopic macular degeneration will become totally blind during their lifetime. It is the 6th leading cause of blindness in the US and Europe and the #1 cause of blindness in Japan.
What Is Degenerative Myopia?
The main difference between myopia and degenerative myopia is that with the latter condition the eye does not quit elongating until the individual reaches adulthood. It is more common than glaucoma and cataracts combined and is currently incurable. The condition results as the walls in the whites of the eyes, or sclera, continue to stretch and thin over time causing pressure to build.
Eventually retinal tears, deterioration and scarring negatively affect the choroid, retina, space between the retina and vitreous gel, viterous and optic nerve. When there’s damage to the macula, loss of vision is occurs. The macula controls focus and is the most sensitive area of the eye. It collects images and places them in the vision’s center field then forwards that information to the optic nerve and eventually the brain. When macula cells deteriorate, vision in the central section of the eye becomes blurry or wavy. Eventually, there will be a complete loss of vision, even though peripheral vision still works.
When the condition fully evolves, individuals qualify as legally blind. Fortunately, animal research as well as human trials are proving very promising in discovering effective treatment options. As a result, it is giving new hope to those that once knew the black spot in the center of their vision would grow to the point where their world was visually limited to outer areas of the circle.
Symptoms of Degenerative Myopia
Most often individuals initially become aware that they are suffering from some kind of visual impairment when they see a gray spot in the middle of their visual field that darkens and expands over time. They also report seeing straight lines that are distorted or bent, an altered perception of color and experience a reduction of sensitivity to contrast. Headaches and sensitivity to light are also common. Eventually they find it difficult to drive, watch TV, have difficulty reading and even have trouble recognizing faces. In time, degenerative myopia can lead to functional blindness.
The most typical characteristics of the condition include:
- The gelatinous consistency of the vitreous becomes liquefied.
- Detachment of the posterior vitreous.
- Hemorrhages around the head of the optic nerve.
- Atrophy or thinning of the retina at its margins that may indicate a retinal detachment.
- Tilting of the optic disc.
- Retinal pigment epithelium thinning.
- Atrophy of the back of the eye.
- Dilation of the back of the sclera.
- Breaks in the membrane separating the capillaries and pigment layer of the retina resulting in what looks like lesions.
- The development of holes in the peripheral retina.
- A circular spot on the retina.
Causes and Types of Degenerative Myopia
The epidemiology of ocular conditions have various causal factors as well as mechanisms that encompass different systemic ocular disorders and genetics. They can include:
- Marfan’s syndrome.
- Stickler’s syndrome.
- Interrupted light that passes through the ocular media.
- Prematurity retinopathy.
- Ehler’s-Danlos syndrome.
- The front surface of the eye is overly curved and too powerful.
The stretching and thinning of the tissues within the eye, retina and macula can result in various disorders. Treatment varies based on many factors, including those listed above. Complications resulting from the condition include macular edema, choroid neovascularization, retinal detachment and glaucoma. Fortunately, we can treat all of them.
Myopic Macular Degeneration
This is a condition where stretching occurs at the back wall of the eye. It is usually less severe than macular degeneration and is age-related. It can be treated with photodynamic or laser photocoagulation therapies.
This condition occurs when stretching takes place along the equator of the eye. The possibility of developing retinal detachment and retinal tears is more likely in myopic individuals with the likelihood increasing over time.
Dry and Wet Macular Degeneration
Approximately 85-90% of individuals with macular degeneration will develop a “dry” or atrophic type. The rest will have an exudative or “wet” type.
Degenerative Myopia Diagnosis and Treatment
Degenerative myopia is the most severe form of the myopes. It is associated with changes in the retina to the extent that severe vision loss results. It progresses rapidly and the visual outcome depends in a large part on the extent of lenticular and fundus changes. The diagnosis of the condition is also accompanied by chorioretinal degenerations. Individuals with degenerative (also called pathologic) myopia, especially those that suffer from high refractive errors, are the highest risk group for macular changes and retinal detachment.
Until recently, laser photocoagulation which uses a thermal laser to eradicate abnormal blood vessels was one of the few treatment options. The downside was that the extreme heat also damaged healthy cells in the retina as well as light-sensitive cells. The result was some permanent vision loss. Today, however, newer treatment options are proving much safer and effective.
For children aged 8-13, a product called 7-methylxanthine has been shown to normalize abnormal growth patterns in eyes by up to 22% in the stratification layers. Myopia progression has also been slowed by 50% with the use of soft multifocal contact lenses in children. In Singapore, the result of trials utilizing low doses of atropine eye drops in children have yet to be published. Nonetheless, they are showing promising results.
The first clinically proven therapy treatment is Visudyne, a light-activated drug used in photodynamic therapy. And finally, scleral buckling that allows surgeons to reinforce thinned areas at the back of the macula in adults is common.
Although degenerative myopia may be preventable in the future, today the treatments are limited. Specialists frequently use optical correction, treating complications such as anti-angiogenic drug treatment for hemorrhaging blood vessels and intra-ocular pressure control. New research seeks to find a permanent answer. Ultimately, the corrective lens must be stabilized and extended growth must be stopped.
Degenerative myopia is a type of nearsightedness where the eye continues to grow until adulthood. As a result, it becomes longer than it should. Specialists often associate it with other conditions such as blood vessels that develop in the back of the eye. Individuals become aware they have degenerative myopia when they experience the distinctive characteristics associated with the condition. Fortunately, today there are more treatment options than ever before. As with any eye condition, however, contacting a qualified medical specialist who can detect the condition early and begin a treatment regime immediately are essential in slowing the progression of the disease.