TOPIC 4: MYOPIA

Question 1

Why does refractive error develop?

Answer 1

before age 6 :
due to a failure of emmetropisation possibly because:
-Initial refractive error too great to be corrected by emmetropisation
-Initial refraction within normal range but deficient emmetropisation
Or both
E.g. High refractive error associated with genetic disorders

At / after age 6:
Myopia is believed to be due to a failure of mechanisms to maintain emmetropia / low hyperopia

Hyperopia: most cases are due to persistence of infantile hyperopia
Genetics also play a part in both

Question 2

What are the complications of myopia? (You should be able to explain what they are in 1 sentence, no need to remember statistics)

Answer 2

Myopia is Potentially Blinding, myopia is associated with diseases such as posterior staphyloma, myopic maculopathy, Macular hole +/- RD, retinal holes/detachment, dome shaped macula, Lacquer cracks, Myopic CNV, Myopic Traction Maculopathy, Lattice Degeneration, Rhegmatogenous Retinal Detachment, glaucoma, Peripapillary intrachoroidal cavitation (ICC), Structural Abnormalities on and around the optic nerve in pathologic myopia

Question 3

What are the myopia management options? How would you decide how to recommend one over another for a myopic patient?

Answer 3

1. Spectacle lenses
   a. MiyoSmart – ring of defocus to provide myopic defocus (Hoya)
   b. Stellest – rings of lenslets that provide myopic defocus (Essilor)
   c. Myopilux Max – bifocal design (Essilor)
   d. Myopilux Plus – PAL design (Essilor)
   e. Myovision Pro – peripheral myopic defocus design (Zeiss)
   f. Myokids – PAL design (Zeiss)
2. Contact lenses
   a. Orthokeratology (OK) – peripheral myopic defocus (various brands and designs),
   a. some brands of OK lenses are recommended only for moderate myopia and/or
   minimal astigmatism, some can correct higher myopia with astigmatism.
   b. Soft contact lenses – rings of peripheral myopic defocus (Coopervision MiSight)
   significant risk factor for progressive VF loss. Chihara et al. (Chihara andSawada, 1990) also
   investigated the parameters that were associated with multiple defects in the retinal nerve fiber
   layer (RNFL) in eyes with glaucoma. Multivariate analysis showed that refractive error was a
   high-ranking risk factor for multiple RNFL defects. Eyes with multiple defects tended to have
   moderate myopia, focal nerve fiber layer defects, and small optic discs and were less likely to
   have a diuse defect in the nerve fiber layer, emmetropia or hyperopia,and a normal discs. The
   multiple defects in the RNFL in glaucomatous eyes were frequently focal and correlated with the
   degree of myopia and a small optic disc.
   3
   c. Soft contact lenses – centre distance multifocal design +2.50D addition (Coopervision
   Biofinity multifocal)
   d. Soft contact lenses – extended depth of focus, centre distance multifocal design
   (SEED 1-dayPure EDOF soft contact lens)
   e. Soft contact lenses - extended depth of focus, centre distance multifocal design
   (NaturalVue multifocal)
3. Atropine eye drops (various concentrations from 0.01% up to 1%. Unclear mechanism(s) of
   action)
4. Combination therapy (Orthokeratology + Atropine)
   a. There is evidence that combination therapy may work better than atropine or OK
   alone. It is believed that the slightly larger pupil size (even with low dose atropine)
   caused by atropine enhances the peripheral myopic defocus induced by the OK lenses.
5. Behavioural / Environmental
   a. Outdoor activity – 90 mins/day to delay onset of myopia
   b. Visual breaks - closer working distance (<20cm) and longer near work duration
   (c>45 minutes) have been linked to myopia

Question 4

How to manage a myopic child?

Answer 4

Managing a Myopic Child
If the child is already myopic (at least –0.50D)

Educate about the risk of myopia progression
Younger age, parental myopia, ethnicity, near work and binocular vision status
(esophoria, accommodative lag and intermittent exotropia) are risk factors for
progression
Studies have shown better ecacy of myopia control with younger children. Young
children tend to progress faster and benefit more from myopia control compared to older
children
The younger the age, the more likely for the child to become highly myopic by adulthood
(much greater risk of disease)
Educate about the risk of ocular diseases with myopia
Many people think refractive surgery e.g. LASIK is a cure for whatever problems are
associated with myopia
Educate about the myopia management products/strategies available
Ecacy, safety, advantages, side eects / disadvantages
Monitor refractive error 6 monthly
Ideally with axial length measurements, not just refraction