What is Degenerative Myopia (Nearsightedness)?
Myopia, commonly known as shortsightedness or nearsightedness, is one of the most frequently occurring eye conditions worldwide. It happens when the eye’s focusing power is too strong for its size, causing faraway objects to seem blurry because the image is focused in front of the retina instead of directly on it. Glasses, contact lenses, or eye surgery can typically correct myopia.
However, there’s something called pathologic myopia (PM), which is linked with severe nearsightedness. Professionals have not firmly settled on how exactly to define PM. Some suggest it’s characterized by a certain degree of refractive power (between -6 to -8 D) or eye length (26.5 mm), while others think it is associated with a condition called myopic maculopathy, a severe eye problem caused by extreme nearsightedness.
What Causes Degenerative Myopia (Nearsightedness)?
Myopia, or nearsightedness, is usually caused by a mix of genetic factors and environment. The fact that myopia often occurs in families is backed up by studies on twins and siblings. Numerous gene changes have been linked to the start of myopia.
Particular genetic disorders like Marfan and Stickler syndrome, which involve changes in the protective outer layer of the white part of our eyes, can result in this kind of abnormal vision. Specific regions on 25 distinct genes are related to myopia not connected to these syndromes, although understanding how these gene changes contribute to the disorder is complex due to differing gene activity and interaction.
Various studies suggest that spending more time outside could help prevent myopia. At the same time, a move towards city living and higher education seems to be a key reason behind the increasing number of kids getting myopia in school. It’s thought that the excessive time spent focusing on nearby items due to reading encourages eye growth.
Animal research has further found that placing positive and negative lenses that blur images on the light-sensitive layer at the back of the eye can either provoke or limit eye development. Whilst there is some understanding, the exact cause of myopia and its increase in society is complex and multifaceted.
Risk Factors and Frequency for Degenerative Myopia (Nearsightedness)
Myopia, also known as nearsightedness, is more common in some parts of the world and in different ethnic groups. The condition is most common in East Asia (47% of the population) and Southeast Asia (39% of the population), compared to Central Europe (27% of the population) and Central Africa (7% of the population). Additionally, myopia is more prevalent in cities than in the countryside, which is thought to be due to differences in education and socioeconomic systems. Finally, serious cases of myopia, known as “pathologic myopia”, impact between 0.9% to 3.1% of the population.
- Myopia is most prevalent in East Asia (47% of the population).
- Next most common is Southeast Asia with a prevalence of 39%.
- Central Europe sees a prevalence of 27%.
- Central Africa has the lowest at 7%.
- Urban areas tend to see higher rates of myopia than rural areas.
- Severe myopia, or “pathologic myopia”, affects 0.9% to 3.1% of people.
Signs and Symptoms of Degenerative Myopia (Nearsightedness)
When diagnosing high myopia, a doctor will examine your eyes and ask about your general health, such as joint, hearing, or heart problems, as these can indicate a related tissue disorder. They will also want to know about any family history of eye problems or procedures you may have undergone, like corrective lens wear or refractive surgery, especially if you had previous retinal detachments. If you’ve been experiencing symptoms like shifts in your field of vision (metamorphopsia), dark patches (scotoma), flashers, or seeing new floaters, these could indicate an issue with your retina.
In examining your eyes, your doctor will measure your visual acuity and intraocular pressure and examine your eye’s reaction to light. After dilating your eyes, they will further examine the back of your eye, focusing on the macula, optic disc, and peripheral retina. In some cases, if glaucoma is a suspected issue, your doctor might also check your visual fields.
In 2015, researchers came up with a universal classification system for severe myopia, which goes as follows:
- Category 0: No macular lesions
- Category 1: Tessellated fundus – Visible choroidal vessels
- Category 2: Diffuse chorioretinal atrophy – Yellowish-white appearance to the posterior pole
- Category 3: Patchy chorioretinal atrophy – Discrete atrophic areas in the macula and peripapillary region
- Category 4: Macular atrophy – Atrophy in the foveal region
- Plus Lesions: Lacquer cracks, Choroidal neovascularisation, Fuchs spots
Symptoms of pathological myopia can include a bulging eye, irregular yellow lines in the macula area (known as lacquer cracks), and the development of a condition that causes the loss of central vision, referred to as myopic choroidal neovascular membrane (myopic CNV). Around 10% of patients with severe myopia develop it, but that number can go up to 35% if the second eye was already affected. Myopic CNV is generally seen as a grey, slightly elevated area beneath or near the fovea, and it may be associated with a buildup of fluid or bleeding. As the condition progresses, it can result in pigmented grey scars (Fuchs spots), pulling or traction on the retina leading to a split in the layers (retinoschisis), lifting off the back of the eye (retinal detachment), or formation of a hole in the macula. Additionally, an inward bulge around the foveal region (dome-shaped macula) can be seen in 20% of high myopia cases.
Impaired vision can also occur due to structural abnormalities and shrinking around the optic nerve fibers and optic disk pits or if there are any holes or breaks in the peripheral retina.
Testing for Degenerative Myopia (Nearsightedness)
Spectral-domain optical coherence tomography (OCT) is a non-invasive, quick, and easily accessible test. It’s used for diagnosing and keeping an eye on conditions like retinal pigment epithelium atrophy, myopic CNV, and myopic tractional maculopathy. In other words, it’s a helpful tool to measure how thick your retina and choroid are, and to spot any fluid buildup within or underneath the retina. It also helps identify conditions like macular holes, separations of the retinas or retinoschisis. When it comes to dome-shaped maculopathy, a condition affecting the macula, OCT can create detailed images especially when it takes radial or vertical slices.
Fluorescein angiography is another test that gives in-depth information about the type and activity of myopic CNV – a condition that can cause vision loss, and it helps in planning the treatment process. In this test, myopic CNV looks similar to type 2 or classic CNV. The images show early signs of hyperfluorescence – a bright glow that grows in size and intensity as the test progresses. This kind of test is also useful in distinguishing between a hemorrhage from myopic CNV and a lacquer crack, the latter is characterized by blocked fluorescence rather than increasing brightness.
There are other tests like OCT angiography, ultrasonography, magnetic resonance imaging, and Indocyanine Green Angiography, that can be used to study the shape and blood flow in the retina and choroid. However, these kinds of tests are not commonly used in regular clinical settings.
Treatment Options for Degenerative Myopia (Nearsightedness)
Simple myopia, also known as nearsightedness, can be corrected with eyeglasses, contact lenses, or eye surgery. Encouraging kids to spend time outdoors could help prevent it from getting worse. Other ways to manage myopia include special contact lenses and eye drops with low-dose atropine. But, there are no proven ways to stop or reverse the eye damage often linked with severe myopia.
When myopia leads to abnormal blood vessels growing under the retina (a condition known as myopic CNV), the best treatment is anti-VEGF injections into the eye. These shots have been shown in large, controlled studies to improve both vision and the physical structure of the eye, compared to other treatments such as photodynamic therapy. With anti-VEGF therapy, fewer treatments are needed to control the disease than with other forms of abnormal blood vessel growth, like age-related macular degeneration.
As for another consequence of myopia, called myopic tractional maculopathy, treatment decisions depend on the specific findings from an eye scan (known as OCT). Some doctors prefer a conservative approach, as some cases do not worsen or may improve on their own, especially after the natural release of tension on the retina. But, in cases with a lot of retinal splitting, the disease might worsen and need intervention. Surgical options include removing the gel-like substance from the inside of the eye (pars plana vitrectomy), peeling off the inner layer of the retina, or adding support for the retina with a macular buckle procedure.
What else can Degenerative Myopia (Nearsightedness) be?
When trying to diagnose degenerative myopia, doctors must consider several other conditions that can have similar symptoms:
- Age-related macular degeneration
- Choroidal rupture or angioid streaks that could be confused with lacquer cracks
- Changes in the retinal pigment epithelium due to prior central serous chorioretinopathy
- Ocular histoplasmosis
- Conditions affecting the pattern of the retina, like reticular dystrophy or Doyne honeycomb retinal dystrophy
In addition, degenerative myopia can occur alongside several different health disorders:
- Developmental delays
- Prematurity (being born early)
- Marfan syndrome
- Stickler syndrome
- Ehlers-Danlos syndrome
- Homocystinuria
- Down syndrome
- Noonan syndrome
To establish an accurate diagnosis, the doctor needs to consider these possibilities and carry out appropriate tests.
What to expect with Degenerative Myopia (Nearsightedness)
Pathologic myopia, or extreme nearsightedness, is a major reason for vision loss globally. Studies show that this condition is responsible for visual impairment in up to 0.5% of people in Europe and 1.4% in Asia.
Long-term follow-up studies have shown that patients diagnosed with a specific condition related to pathologic myopia called myopic CNV, tend to experience a decrease in visual acuity or sharpness, even when the disease appears to be under control with the use of certain therapies like anti-VEGF.
Possible Complications When Diagnosed with Degenerative Myopia (Nearsightedness)
People with a condition called pathological myopia can face a significant decrease in their ability to see clearly. This may be because of bleeding beneath the retina or a condition specific to myopia, which affects the blood vessels in the layer of the eye called the choroid. Regardless of immediate treatment, they might develop scars and a wearing away of the macula – a part of the eye that provides sharp, central vision. This could ultimately lead to a permanent blind spot in the center of their field of vision.
Additionally, these individuals also have a higher chance of developing cataracts at an earlier age, experience a condition called glaucoma, and have retinal detachments which can also impair vision.
- Significant drop in visual clarity
- Bleeding beneath the retina
- Myopic choroidal neovascular membrane – a condition that affects the blood vessels in the layer of the eye
- Development of scars and degeneration of the macula, leading to a permanent central blind spot
- Increased chance of early development of cataracts
- Higher risk of developing glaucoma – a condition that damages the optic nerve
- Potential for retinal detachments, which could further impair vision
Preventing Degenerative Myopia (Nearsightedness)
Patients must keep up with their routine eye check-ups to make sure their condition stays well-managed with the treatments available. If they experience sudden changes in vision, like distortion, blind spots, flashes, seeing spots or blurred vision, they should immediately see an eye care expert. It’s also recommended for patients to regularly use an Amsler grid to check each eye.
