It can be scary for one to have degenerative myopia, and even worse when you don’t really know what it is. Read this article so you can get informed.
Prevalence of myopia has been on the rise since studies noticed a trend in the early 1970s. In Americans, studies project that 50% will have myopia in comparison to the 22.9% global figure.
These numbers provide a certain shock and awe. Properly presented, they have a less dire meaning. Myopia, overall, doesn’t have to concern an individual or a populace as treatments are plentiful and effective.
This statement isn’t true of degenerative myopia. This progressive condition related to myopia warrants concern.
This review will provide you with information on understanding myopia. We’ll also cover the state of treatments for degeneration.
Myopia Explained
The medical term for nearsightedness is myopia. This is a vision condition which causes far objects to be perceived as blurry or out of focus. Nearer objects appear with clarity.
Hence the name.
Myopia has two structural causes. The first comes from the length of the eyeball.
When your eye forces light to travel too far to reach the retina, the focal point of the light terminates too soon.
The other structural cause is over-curvature of the cornea. This, again, moves the focal point of the light to a position in front of the retina.
The best way to determine if a person has myopia is with an eye exam. When doctors catch myopia early, more treatment options exist.
The onset of myopia has genetic ties but also arises from stressors. Spending time starting at fixed points, such as screens or pages strain the eye. Diabetes represents another factor that can cause myopia.
In the United States, myopia is the most common eye disorder, affecting 30% of people.
Some people end up with pseudo versions of myopia caused by environmental factors. Night myopia reflects how darker conditions create problems for the eye to focus. The pupil size, larger to let more light in, may result in a lack of focus.
Working with objects too close to the eye create strain. This second pseudo myopia occurs from straining the focus mechanism of the eye. It often goes away after rest.
Myopia Diagnosis
To diagnose myopia, an optometrist uses a distance chart and/or a phoropter.
With a distance chart, the measurement is done with a fraction of visual acuity. This is where ideas such as 20/20 vision come from. The testing distance is 20 feet and the letters are of a size that a person with a ‘normal’ eye could identify them at 20 feet.
The further away a ‘normal’ eye can read a letter the bigger the denominator.
When a phoropter is used, different lenses adjust the focus of light into the eye. When the range of optimal light focal points is found, the test is complete.
Degenerative Myopia
Unlike the more common myopia, the degenerative variety worsens significantly over time.
Combined hereditary factors lead to degenerative myopia. Worldwide it is the most commonly attributed cause of legal blindness.
We’ll break down the causes and explain how each contributes to the problem. We’ll examine the risk factors that contribute to the acceleration of the condition. Finally, we’ll review some treatments and their efficacy.
Degenerative myopia treatments slow the process and sometimes reverse damage for periods of time. However, the underlying condition has no complete cure.
Causes
The first two categories — genetic and injury — explain how degenerative myopia begins. The next two — cornea curve and eyeball length — explain the main structural causes.
Genetic
Though it is the greatest cause of legal blindness, only 2% of the US population is affected by the condition. The hereditary markers or the diseases are found most often in Middle Eastern and East Asian peoples.
Sadly, the specific genetic markers that cause the issue aren’t well understood. This is because several different processes can go awry to produce the degeneration.
The condition may be noticed at birth. Typically, though, it is in the pre-teen puberty years that it is diagnosed.
The onset doesn’t correspond with hormonal or other puberty changes. The timing is likely due to increased awareness of sight problems.
The brain compensates for some of the damage and adjusts the muscles around the eye called ciliary fibers. The area of the macula at the center of the retina also strains to compensate.
As these components wear out and break the degeneration becomes more apparent.
Injury
Direct injury to the eye can set off a degenerative reaction. Hereditary conditions create problems for the cornea and eyeball shape. Injury reshapes the eye or breaks areas such as the ciliary fibers or even fully detaches the retina.
Structural damage to the eye socket or pressure in the sinus from a broken nose can reshape the eye.
A catastrophic injury isn’t the only problem. Strain from reading and viewing habits contribute to eventual degeneration. Squinting or glaring and reading in sub-optimal light conditions cause strain.
Though it is rare for strain leading to myopia to progress into degenerative myopia, it does happen.
Cornea Curve
The cornea works like the F-stop of a camera, it regulates the amount of light that gets into the eye and the position of focus. Not unlike a magnifying glass being used on an ant, the too powerful focal point causes damage.
The increased curvature of the cornea also puts the focal point in the wrong place. These combinations of problems create a narrow field of vision. Just like the colloquial saying, a narrow view is a myopic definition.
Depending on the cause of the corneal curve, the curve can intensify over time. This creates a worsening field of vision that can fracture the cornea altogether.
Eyeball Length
You don’t think of spherical objects, like the eye, as having cube dimensions. The width, height, and length of the eye sound as if they must be the same by definition.
The length of the eye is defined as the distance between the cornea and the retina. The longer this space, the more the cornea has to bend light to get it into the macula.
The length of the eye can change shape from intracranial pressure or genetic makeup.
Combinations
It’s rare for one factor to occur in degenerative myopia. Complications with the cornea create opportunities for damage to the retina and eyeball length. Issues with the eyeball length create strain for the cornea.
Degeneration progresses more rapidly when both conditions have external factors pushing them.
Why it Continues
Which takes us to the degenerative part of degeneration. As the underlying producers of the condition progress, they do more damage. The damage they do starts to hit adjoining systems and issues feed each other.
Treatment for the condition becomes a moving target. What helps one component of the problem does nothing for another part and makes a third part worse.
Fundus and Lenticular Changes
The changing pressure from compensation within the cornea and the macula to fix vision strains other systems.
The cornea pushes into the lens, which causes it to flatten. The flattened lens further distorts the focal point of vision. This, in turn, forces the cornea to change shape and the cycle continues.
The fundus, the interior surface, contains the photoreceptors of the eye. It also moves blood around. The more work it has to do, the more fluids it needs to move. The more fluids that need to move the greater the pressure.
Both of these changes create downward spirals.
Chorioretinal Degeneration
Blood flow to the retina needs to remain healthy and stable for the retina to function. Like any other body part, you restrict the blood flow and it will get numb. As the retina doesn’t have nerves to cause pain this numbness results in damage.
You can think of it like the pixels going out on a monitor. As the blood flow breaks down fibrosis occur and forms scar tissue. The retina stops being able to pick up light in areas.
The result makes blind spots in the vision. Unlike the fuzziness found in myopia from light hitting in front of the retina, these areas stop ‘seeing’ altogether.
Even if the area remains semi-functional, color hues get disrupted. Vision develops artifacts and halos of color rather than complete images.
Risks and Complications
The brain attempts to compensate for the degeneration and leads to headaches and eye pain. These conditions make concentrating difficult and lower life satisfaction on top of the vision loss.
The most common forerunner to major risk factors is blurred vision. Consistent blurring in vision indicates deeper underlying risks for permanent and sudden damage.
Retinal Detachment
The most violent complication to degeneration detaches the retina from the fundus. Cut off from the supply line of blood, the retina can die. Even if the retina stays connected but unseated it will focus sporadically as it floats in the space.
Macular Changes
The macula area can break down without becoming detached. Here, scar tissue or tissue thinning occur to interrupt function.
Macular changes and retinal detachment chances increase as eye length changes.
Cataract Formation
Lenticular changes and cornea curvature can lead to cataracts. These growths and discolorations in the lens are produced by clumped proteins. The lends darkness with clouds which interrupt light.
As cataracts form, they obscure light in pieces rather than a general overall darkening. This creates blurry spots and increased strain.
Treatments
Treatments for degenerative myopia start with general treatments for myopic vision. The more the eye can rest and the less strain the slower complications arise.
Therapeutic treatments prove most effective. They deal with the continuing damage and ongoing problems.
Glasses
Nearsighted glasses, prescription single lenses or bi and trifocals compensate for focal issues.
Bifocals work best to allow the eye to work at two different focal ranges. Set ranges of near and far can be seen without significant focal change.
Glasses ease eye strain and provide better vision function. Corrective lenses can work to reverse some corneal curvature when used early.
Contacts
Contacts for myopia offer a greater field of view. The constant need to change prescription poses problems. Potential damage to the eye from incorrectly worn contacts produce risk factors.
LASIK and PRK
Both of these laser procedures reshape the cornea. They do so by removing and reforming tissue.
The cornea can only safely have so much material removed. This factor limits the treatment possibilities for degenerative myopia.
Atropine
Recent studies show atropine to improve scleral and retinal function. The mechanism behind atropine effectiveness is not well understood.
One notable downside is that damage and rebound effects after disuse are severe.
7-Methylxanthine
This systemic chemical treatment introduces a growth factor into the eye. This increases proteoglycans and collagen in the area. by bulking up the connective tissue in the sclera damage from strain is reduced.
This treatment works to prevent eye lengthening and to limit the damage.
Sunshine
Early exposure to UV and sun rays before the teen years lower the risk of myopia. The cornea and sclera show improvement in shape and structure from UV exposure.
Overexposure to light creates damage. The natural light of the sun makes the best illumination when diffused and not directly engaged.
Surgery
Surgical treatments for degeneration work to lower the pressure of the sclera and fundus. The process of posterior-pole buckling looks to remove connective tissue within the sclera. This allows the eye to stay in shape without elongating.
Like other treatments, this surgical method attempts to correct the mechanisms which lead to damage. Like other treatments it’s effectiveness depends on the underlying cause of the degeneration.
As such, it does not work for all types of myopia.
Rehabilitation
The final treatment for degenerative myopia targets the corneal shape change.
Ortho-k and CRT
Orthokeratology uses rigid lenses to reshape the cornea. This reduces pressure on the lens and limits some risks.
New lenses are gradually introduced over time to reshape the cornea without strain.
A major advantage of this treatment is that the lenses need not be worn constantly. Overnight use can limit degeneration without active involvement.
Get Help
Facing a problem like degenerative myopia comes with a lot of struggle. One must overcome the fear of the diagnosis before they can seek treatment. Not knowing, like in many places, limits your options awhile the problem grows.
Learn more about the ongoing search for treatment options and find out if you have the condition by booking an appointment.
