CONTROL OF MYOPIA

Contributor: Deepika Nehuray, BOVS (2^nd year), NAMS

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Individuals with myopia are more prone to early myopic macular degeneration, glaucoma, posterior sub-capsular cataract, glaucoma, retinal detachments and retinal tears and holes. As half of the world is predicted to be myopic by 2050, with nearly one fifth at the risk for blindness, myopia progression has been posed as a threat. Several studies have shown to effectively control the progression of myopia which can be achieved through following techniques;

1. Atropine drops

The environmental theories suggested that near work and mechanisms related to accommodation as the cause of myopia. Several researches were published later which proved that a non-accommodative mechanism was involved in experimental myopia onset and progression. Although atropine’s exact mechanism of action has not been determined, compelling evidences from researches have concluded that atropine can effectively slow progression of myopia. The 0.5% of atropine drop is found to be the most effective in slowing the progression of myopia but due to its high dropout rate, its efficacy was reduced and low dosage atropine of 0.01% to 0.25% is found to be well tolerated. The high dropout rate in high dose atropine use is because of the symptoms like photophobia and glare (due to enlarged pupil), reading difficulties (due to reduced focusing mechanism and depth of focus), and headache. The cessation of atropine often resulted in myopic rebound effect which was more pronounced in eyes that received high dose (1.0%, 0.5% and 0.1%) atropine than those who received low dose (0.01%) atropine. The advantage of the low dose atropine is tolerance due to less side effects but is ineffective relatively as myopia may still progress during its use. A once or twice a week application could be an alternative treatment option for the use of high-dose concentration atropine (0.5% or 1.0%). Although some concerns regarding long term safety has not been resolved, the general consensus of the clinical studies is that the treatment is safe.

2. Multi-focal contact lens

Animal studies have shown that the peripheral retina regulates the eye growth. When single-vision lens is used to correct myopia, the central macula although in focus, the peripheral retina has a hyperopic defocus. Peripheral hyperopic defocus is also found to have a role in myopic progression. The multifocal soft contact lens design has two basic portions; central portion that corrects the nearsightedness and the peripheral portion which adds focusing power to bring the peripheral light rays to focus in front of the retina. The peripheral light rays meeting in front of the retina give cue to slow growth of the eye which results in the decrease in lengthening of the axial length of the eye. MiSight 1 Day disposable contact lens marketed by Cooper Vision is one of many that needs to be mentioned.

Courtesy: nih.gov

3. Orthokeratology

Courtesy: Carillon Vision Care

Orthokeratology (ortho-k) refers to the overnight use of gas permeable contact lens to create a temporary change in shape of the cornea for low-to-moderate myopia and astigmatism correction. The ortho-k lenses have much flatter central base curve than the secondary curve. It creates positive pushing pressure against the central cornea and negative pulling pressure against the mid-peripheral cornea which redistributes the epithelial cells towards the mid-periphery. Due to this plateau shaped cornea, the eye has a peripheral myopic defocus which slows the axial elongation of the eyeball. The control effects of myopia progression with orthokeratology is shown upto 8 years.

3. Myopic control glass

Courtesy: bjo.bmj.com

A spectacle les design especially for myopic control is designed recently. This is probably the most comfortable solution for myopia management. Defocus Incorporated Multiple Segments (DIMS) lens consists of a central optical zone (9mm in diameter) for correcting distance refractive errors and an annular multiple focal zone with multiple segments (33mm in diameter) having a relatively positive power that supports peripheral myopic defocus. No statistical difference is observed which influences accommodation and visual acuity. Through several studies, it has been found that the myopic progression can be effectively reduced by the use of myopic control glasses.

REFERENCES

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5347209/

2. https://www.aaojournal.org/article/S0161-6420(18)30285-9/fulltext

3. https://www.aoa.org/news/clinical-eye-care/diseases-and-conditions/atropine-in-myopia-control?sso=y

4. https://modernod.com/articles/2020-may-june/myopia-control-with-multifocal-contact-lenses

5. https://modernod.com/articles/2020-may-june/myopia-control-with-multifocal-contact-lenses

6. https://www.nih.gov/news-events/news-releases/multifocal-contact-lenses-slow-myopia-progression-children

7. https://pubmed.ncbi.nlm.nih.gov/24061152/

8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5721542/

9. https://bjo.bmj.com/content/104/3/363.long#DC1

10. https://www.zeiss.com/vision-care/int/spectacle-lenses-from-zeiss/myopia-management-lens-solutions.html#:~:text=Special%20myopia%20management%20spectacle%20lenses,solution%20for%20a%20young%20patient.