Myopia or near-sightness means that either the eye is too long or the optics are too strong. In either case the light from a distance object focuses in front of the retina. Minus or concave lenses are used to move the image back on the retina when viewing distance objects. Vision may be corrected with glasses, contact lenses or refractive surgery.
Myopia effects 40% of US population, in 1970 that number was 20%. There has been an 11% increase from 1975-1995 and 100% increase since 1970. The increase is way too large to be explained genitically. In Asia the incidence of myopia is over 80%. There are more women who are myopic as compared to men and it is more commonly found in Caucasian vs African-Americans. Click this link to obtain an in-depth review of myopia with scientific citations.
This is a controversial area. Clearly if your parents are nearsighted you have a better chance of becoming nearsighted. Identical twins have similar refractive errors as compared to fraternal twins. Myopia studies show that heredity is clearly a very strong indicator of the development of myopia. Myopia is more common in different societies such as Jewish and Chinese populations and less common among the American Indians and Eskimos.
Myopia is much more common in people with a higher education. There are those who claim that since people with myopia can't see clearly at a distance, they become more interested in things up close where they can see clearly, e.g. reading, computers.
The fallacy of this argument is that once myopic patients are corrected with glasses or contact lenses, distance vision is clear. Most importantly recent research shows that myopic kids spend as much time participating in outside sports as non-myopic kids. Lastly, intellectual gains tends to occur prior to the development of myopia. Zylbermann et al in 1993 studied the incidence of myopia in a Jewish cohort aged 14-18 and found that myopia was greatest in males vs females and greatest in the Orthodox population which studied 8 hours or more. Most myopia develops during periods of accelerated growth (8-19). Previously myopia stopped by the early twenties. Today, we see more myopia progressing in the late twenties or thirties in those patients who spend a preponderous amount of time reading and computer use.
When we read both our eye aiming muscles and focusing muscles stay fixated to a flat surface approximately 16 inches from the eyes. After sustaining at this distance for hours, it gets stuck there. It doesn't release to back to distance or if it does it takes time, thus, the complaint of blur after sustained reading or computer work.
There are numerous studies which show that after sustained near work the focusing system in a darkened room changes position (it moves inwards). In addition, monkeys which are hooded (constrained near environment) and not allowed to look at a distance become myopic. (Click here for more animal studies) The Naval Academy in Annapolis used have an entrance requirement that the cadets had to have 20/20 unaided visual acuity. However, upon graduation 50% of the cadets became myopic. People on submarines become myopic. Lastly, Alaska before becoming a state which required that they had mandated education had little near-sightness. Now 50% of the Eskimo children are myopic. These, studies are compelling. If you take the right genetic child and put them in an environment in which they focus up close for long times they will become more myopic. If you are a lawyer, or accountant look around most of your colleagues are myopic.
People who spend a lot of time on computers or microscopists show increased amounts of myopia. Sixty-six percent of the microscopists showed either the development or progression of their myopia. Others argue, that it might not be sustained near work that induces myopia but the amount of time spent outdoors. Myopia aslo seems to be inversely related to the time spent out-doors. Another words, out-door exposure protects against the development of myopia and this protection is not related to activity like sports.
We can use reading glasses to decrease the focusing demand and hope that the progression of near-sightness works. Previous experiments have shown them to be somewhat successful. The National Eye Institute is now studying the effects of bifocals to slow the progression of myopia. Preliminary results suggest that bifocals may or may not slow the progression of near-sightness (myopia). Two new research paper have just been published which demonstrates the positive effect of bifocals in slowing down the progression of myopia. However, the most recent study suggests that bifocals initially slow down the progression of myopia but this is short lived. There are no downsides to wearing the bifocals. If my child was at risk of developing progressive myopia, I would suggest the use of an invisible bifocal while monitoring his/her visual acuity. Click here to view the interactive acuity tester which can be used at home to monitor visual acuity. If the visual acuity in either eye decreases then make an appointment.
Drops, specifically Atropine, which dilate the eyes and paralyze the focusing mechanism have, also, been shown to slow myopia. Recently, there have a sleuth of studies demonstrating that Atropine 1% drops with bifocals have a real effect in slowing down the progression of myopia. Myopia progression dropped from .25 diopters per year to .05 diopters per year on the average. Unfortunately, treatment with drops may be worse than the disease. The drops dilate the pupils for 14 days and might result in light sensitivity. There are no known long term effects from the drops. This medication has been around for almost 100 years with a low risk of complications in children and adults. We have been using this treatment for 4 years and find it to be very successful just have to pick the right patient. Recently, there have been a number of studies using lower concentrations of Atropine (.25% to .01%) in an attempt to eliminate the temporary side of effects of pupil dilation which causes sensitivity in sunlight and loss of focusing (accommodation) which results in blur when reading. These studies are encouraging. Though not quite as effective as Atropine 1% they are effective with almost total elimination of the side effects. We are currently using Atropine .02% once a day which eliminates most side effects. The only problem with these lower concentrations is that they are not commercially available and need to formulated (sterile dilution of Atropine 1%). This takes a cheap drug and makes it expensive.
There is an experimental drug, which is in the same family as atropine but doesn't have its side effects. It is 50% as effective as atropine in stopping the progression of myopia in animal studies and patient studies. This new drug pirenzipine has been used in Japan and Europe for years to treat stomach problems. It has a long safety profile and has passed phase I and II of the FDA. The FDA has been oeverly cautious about this drug since it will be used mostly in children and thus has eliminated its future in the USA. So we are stuck with non-commercially available Atropine .02%.
Lastly, LASIK can eliminate the refractive error from myopia. It should be remembered even after LASIK, previously myopic patients with greater risks for retinal problems do not eliminate that risk. CLICK HERE FOR AN IN-DEPTH REVIEW OF MYOPIA TREATMENT
A recent study at the Anglia Polytechnic University in Cambridge, England, has shown that under-correcting for myopia may increase one's near-sightness. Daniel O'Leary, O.D., stopped his research after he discovered that under-correcting myopia actually increased the myopia. When Dr. O'Leary fully corrected some children and under-corrected others, he found that the eyeball elongated faster (became more myopic) when vision wasn't completely corrected. Thus, under-correcting may actually stimulate more myopia. This study has been repeated. In summary, your doctor should not under-correct your glasses to slow down the progression of myopia. If anything under-correction increases the progression.
Ortho Keratology or CRT (corneal reshaping therapy) is a FDA approved method for temporarily molding the shape of the cornea using semi-flexible gas permeable contact lenses. By changing the shape of the cornea myopia can be temporarily eliminated. The contact lenses are worn while sleeping and removed upon waking. The altering of the shape of the cornea is temporary and must be maintained with a "retainer" lens. There is strong evidence that this procedure when performed in your children controls or prevents myopia from increasing, i.e. reduce or permanently eliminate myopia. This is an exciting way to control myopia. It is a win-win. No glasses or contacts during the day while controlling for the progression of myopia. Since the lenses are worn at night there is a small but real increase of corneal infection. All of our doctors are certified in this technique.
The graph below uses projected progression information. Remember this is mean data, and any individual can vary from these projections with any treatment. Not all myopes progress!
It is evident from the above graph thatt undercorrection results in the greatest amount of myopia over time and Atropine 1% the least amount of myopia. However, Atropine 1% may not be practical, thus Ortho-K is the most viable treatment in physically active children
Ortho K generally works in patients with 1-6 diopters of Myopia. Learn more by clicking on the above link. If interested call for a free evaluation.