Prevention of Myopia: Are Ophthalmologists Seeing Clearly?

It is impossible to listen to AM radio or surf the Internet without coming across advertisements from companies promising to prevent or even reverse the progression of myopia. This is because the prevalence of myopia is increasing throughout the world, and myopia is occurring at earlier ages and progressing at rates faster than seen in previous generations. In many countries, for example, pathologic myopia is a leading cause of blindness; and in many Asian countries the prevalence of myopia is as high as 80% among college-age students (Epidemiol Rev. 1996;18:175-187). Although refractive errors are for the most part genetically determined, and myopia can be “treated” by spectacles or contact lenses and “cured” by refractive surgery, these therapies fail to prevent the development of vision-threatening ocular conditions associated with moderate and high myopia. Because axial myopia greater than -7 diopters (D) places the individual at risk for retinal detachment and myopic macular degeneration, any treatment that slows the progression of myopia, even by as little as 25%, may significantly reduce the risk of related, vision threatening complications. Therefore, ophthalmologists should pay more attention to modalities that might slow the progression of this common ocular disorder.

Optical Intervention

There is no conclusive evidence that purposeful undercorrection of myopia will prevent myopic progression. In fact, evidence exists that this practice may actually result in worsening myopia (Vision Res. 2002;42:2555-2559). The Correction of Myopia Evaluation Trial (COMET) investigated the use of progressive bifocals versus single vision distance correction. While statistical significance was not achieved, some myopes with near point esophoria did benefit from using bifocals, as this group of myopes progressed at a slower rate (Invest Ophthalmol Vis Sci. 2003; 44:1492-1500).

Soft contact lenses do nothing to prevent myopia, and daily wear, rigid, gas permeable lenses (RGP) can slow progressive myopia, but it is unclear if the effect is long lived. Orthokeratology, the use of RPG lenses to progressively flatten (or steepen) the cornea when worn at night, provides patients with a false belief that their myopia is “cured.” There is no evidence that this therapy retards axial elongation, and there have been several cases of bacterial keratitis and ulceration associated with use of these types of lenses (Cornea. 2005;24(7):783-788).

Furthermore, most studies investigating the incidence, prevalence, progression, and prevention of myopia have been limited by design flaws of selection bias, lack of randomization and control, questionable treatment compliance, and limited duration of follow-up. In the past decade there have been few well designed, controlled, and implemented studies which meet adequate evidence based criteria. While there have been several National Eye Institute (NEI) sponsored trials investigating myopia prevention, but ophthalmic involvement has been limited, reflecting the ophthalmic community’s apparent disinterest in the topic.

Pharmacologic Treatments

Atropine used daily does slows the rate of myopic progression from an average of -1.0 D per year to -0.50 D per year (on average a 50% reduction in rate of progression), but such side effects as photophobia and blur necessitate the use of bifocals and make long term compliance difficult. Whether the reduction of myopic progression is a lasting or temporary effect has not been well studied, but a few long-term studies show a 1-2 D reduction in final degree of myopia in patients who used atropine for an extended period of time. Side effects of long-term use include decreased accommodative amplitude and potentially unknown effects on the retina from increased light exposure.

Meanwhile, pirenzepine 1% ophthalmic gel is a selective muscarinic antagonist which, like atropine, has been shown to reduce myopic progression by about 50% in short-term trials (Arch Ophthalmol. 2004;122:1667-1674). It also has fewer side effects than atropine and produceds less cyloplegia and photophobia. Long-term studies are currently being performed in Asia, but this agent is unavailable in the United States.

Recommendations

Besides the effect of ethnic heritage and genetic background, refractive error development is also affected by visual tasks. Children who spend more time reading and performing near work (e.g., handheld video games) have a tendency to develop higher degrees of myopia earlier in life than those who do not engage in extensive near activities of this type (Optom Vis Sci. 2000;77:549-554). The pathogenesis of near work related myopia involves either the mechanical effect of accommodation (old theory) or optically induced retinal blur from near work, which causes local, neuromodulated, scleral growth and axial elongation (new theory).

When ophthalmologists are asked to provide care for children with progressive myopia and a worrisome family history of myopic retinal detachment or myopic maculopathy, physicians should perform a cycloplegic refraction and repeat the refraction in 6 months. If the myopia is progressing rapidly (greater than 1 D year), progressive lenses with + 3.00 adds may help. These progressive lenses are stronger than those used in the COMET study and may have some benefit in myopes who have poorer facility of accommodation compared to emmetropes.

Patients desiring contact lenses may be prescribed RGPs. With pediatric patients, it is very difficult to later convert a young child into RGPs once they have used soft contact lenses. Therefore, it is better to start with contact lenses that some studies have shown to be effective, despite the findings of the Contact Lens and Myopia Progression (CLAMP) study, which failed to show RGPs preventative effect on progression. Finally, in some children who continue to progress rapidly despite these modalities, the ophthalmologist may want to consider offering atropine with photochromic progressive bifocal lenses after a having an informed discussion of the potential long and short-term side effects of atropine with the child’s parents.

While correction of refractive error may seem mundane compared to the treatment of cataracts and glaucoma, ophthalmologists should not abdicate their role as researchers in the prevention of eye disease and as practitioners in the prevention of infirmity. There is not a large body of evidence on which to base therapeutic decisions regarding myopia prevention; thus, there is still a place for carefully considered medical and optical interventions which respect the fully informed desires and fears of patients. Surgical bias against myopia should not obscure the ophthalmic community’s role in investigating this significant and increasingly prevalent condition.

References

Author Disclosure

The author states that he has no financial relationship with the manufacturer or provider of any product or service discussed in this article or with the manufacturer or provider of any competing product or service.