myopia control in brief

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Myopia Control
Submitted by: Submitted to:
Bipin Koirala Sanjeev Kumar Mishra
Bachelor of Optometry Programme Coordinator
Student ID no: 122
Maharajgunj Medical Campus
Institute of Medicine

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Myopia Control
Myopia results from an eye having excessive refractive power for
its axial length. This may be due to the eye having a relatively
long axial length or to increased dioptric power of one or more
of the refractive elements.
In the review of the etiology of refractive error, 3 major theories of myopic development has
been suggested:
1. The biological-Statistical theory
2. The use-abuse theory
3. The theory of emmetropization.
Myopia is a significant global public health & socioeconomic problem. Pathologic myopia has
become a major cause of blindness or visual impairment in both Asian & western populations.
According to a summary of 145 studies regarding the global prevalence of myopia & high
myopia, there are approximately 28.3% of the global population & 4.0% of the global population
cases & are predicted to increase to 49.8% & 9.8% respectively by 2050.
Prevalence of myopia in children
Many population based studies on children have proved that the prevalence of myopia is higher
in urbanized East Asian countries with prevalence of 16.5% in Nepal (2008).
In 4282 Nepalese secondary school children aged 10-15 years the myopia prevalence was
ranged from 10.0% in 10year old to 27.3% in 15year old .

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A recent meta-analysis found a 2.6times
higher risk of developing myopia in children of
urban residence compared with those who
lived in rural areas. These differences in the
myopia prevalence among children may be
caused by a rigorous education system which
children especially living in urbanized are
exposed to. Esp.in Eastern Asian countries,
academic success is important, and most
children are enrolled in competitive,
academically oriented schooling at very early age. It is influenced by enduring patterns of
behavior & cultural attitudes that may result in the myopic environmental factors such as higher
level of more intense near work & lower level of outdoor activity. Myopes, especially high
myopes, tend to have reduced quality of life due to adverse influences from psychological,
cosmetic, practical & financial factors. Hence, affecting productivity, mobility & activities of daily
living.
Ocular biometric changes in human myopia
Cornea: Longitudinal studies indicate that changes in corneal curvature during childhood and
early adulthood are minimal & not associated with the magnitude of myopia progression.
However since the correlation between spherical equivalent refraction and axial length to
corneal radius ratio is typically stronger than that of axial length alone by 15-20%, corneal
curvature does appear to make a modest contribution to the magnitude of myopia.
Crystalline lens & Anterior chamber depth: Mutti et al observed that within 1 year of
myopia onset, compensatory crystalline lens thickening & flattening abruptly halted compared
to children who remained emmetropic, suggesting that childhood myopia is not purely axial in
nature, but involves a decoupling of highly correlated anterior & posterior segment eye growth.

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Vitreous chamber & Axial length : Axial length or more precisely , the vitreous chamber
depth is the primary individual biometric , contributor to refractive error in children , young
adults & elderly with VCD accounting for over 50% of the observed variation in SER , followed
by cornea & crystalline lens .
Choroid: The choroid is typically thinner in myopic compared to non-myopic eyes & thins with
increasing myopia & AL in both adults & children.
Sclera: Scleral thinning A/W axial myopia is primarily restricted to the posterior pole due to
scleral tissue redistribution, scleral thinning may alter the tissue strength surrounding the ONH,
rendering myopic eyes more susceptible to glaucomatous damage.
Effects of key environmental factors on myopia:
1. Near work and education
Numerous studies conducted across a range of different population have consistently found
that higher levels of education are Associated with higher prevalence of myopia.
Population studies examining the link between near work activities and myopia have been
conflicting, with some studies suggesting an Association between near work and myopia and
others indicating no significant effects
2. Urbanisation
Higher prevalence of myopia in children living in urban regions, Compared to children living in
rural regions.
A number of recent studies indicate that a higher population density is significantly associated
with increased myopia prevalence in children, independent of near work and outdoor activities.
Studies shows children living in smaller homes to have significantly higher prevalence of myopia;
it has been hypothesized that a constricted living space may result in an increased exposure to
hyperopic blur, thus promoting myopia.

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3. Light exposure
A number of recent studies a report that the time children spend engaged in outdoor activities
is negatively associated with risk of myopia.
Both cross sectional and longitudinal studies indicate that greater time spent outdoor is
associated with significantly lower myopia Prevalence and reduced risk of myopia onset in
childhood.
A recent meta-analysis of studies examining the relationship between outdoor time and myopia
indicated that there was 2% reduction in the odds of having myopia for each additional hour
what week spent outdoor.
Animal studies indicate that the intensity of daily light exposure can influence refractive
development.
A recent RCT in Taiwan suggest that increased light exposure is associated with slower axial eye
growth in the human eye.
A recent study compare the habitual Ambient light exposure (Captured with wearable light
sensors) of children living in Singapore with children living in Australia and found substantially
lower level of outdoor light exposure in children living in Singapore.
Findings From human studies suggest that children who are exposed to less than 60 minute a
day of bright outdoor light are at increased risk of more rapid eye growth and myopia
development and that approximately 2 hour or more of outdoor exposure each day is required
to provide protection against myopia development in human eye.
The main risk factors for school myopia is Education and time spent outdoor.
Other possible risk factors for Myopia:
 Digital screen time
 Sex
 Ethnicity
 Parental myopia
 Intelligence
 Urban/rural Differences
 Pollution

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 Housing
 Height
 Diet
 Sleep
 Smoking
 birth order
 season of birth
 Allergic conjunctivitis
Clinical management and control of myopia in children
A.Optical interventions
I. Spectacles
 Single vision under correction
 Bifocal and progressive Addition lenses
II. Contact lens
 Multi focal contact lens
 Orthokeratology
Pharmacological intervention
I. Atropine (low dose)
C. Lifestyle factor (Time spent outdoor)

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1. Single vision under correction
Under correction of myopia reduces the accommodative demand for near work and the
accommodative lag associated with development of myopia. Evidence from animal studies
supports under correction as a means of arresting myopia progression, however on human the
results are equivocal.
Other studies have reported that under correction of myopia in children can exaggerate myopia
in children.
Data from monocular under correction of myopia has yielded promising results with under
corrected eyes showing an average of 0.36 D per year less progression in myopia compared to
the fellow fully corrected eye.
2. Bifocal and progressive addition lenses
RCT showed that executive bifocal lenses slowed myopia progression by 39% and up to 51%
with base in prism Incorporated. It is possible that the large near segment made it more likely
for children to use the near add during near work and may also induce more peripheral myopic
defocus.
The largest RCT reported that children wearing multi focal spectacles progressed 0.20+/-0.08D
Less than children wearing single vision spectacles (p=0.004). But a difference of less than 0.25
D over three years is not clinically meaningful.
3. Soft bifocal contact lens
It is thought to work on the similar notion that myopic progression can be slowed by inducing a
peripheral myopic defocus which slows the rate of axial elongation.
Only center distance contact lens have been investigated for myopia control.
On average, this contact lens slow myopia progression by 46%.

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4. Orthokeratology
These contact lens work by temporarily reshaping the corneal surface when worn at night
mainly through central epithelial thinning.
They have also been shown to be effective in reducing axial elongation and are thought to work
similarly to bifocal soft contact lens in achieving a relative peripheral myopia which is thought
to reduce myopia progression.
A recent meta-analysis done in 2015 of seven studies by sun et al , the combined results showed
that the mean AL Of 218 subjects in ortho-K Group was 0.27mm Less than that of 217 subjects
in the control group after two years corresponding to nearly 45% decrease in myopic
progression.
But the risk of infective keratitis in children using ortho K lenses overnight is 13.9 for 10,000
wearers
5. Antimuscarinic agents (Atropine and pirenzepine)
Although the specific mechanism of treatment effect of antimuscarinics agent is unknown, it is
known that their effective myopia control is not a result of required accommodation.
From animal model it is thought to work either via on neuro chemical cascade which begins with
M1/4 Receptors at retina level or directly on scleral fibroblast by inhibiting the synthesis of
glycosaminoglycan via non muscarinic mechanism.
Schwann et al (2000) Also found that at atropine stimulated an Increasing the amount of
dopamine released from RPE Cells, which in turn might cancel out Retinal signal that control eye
growth.
The atropine for the treatment of childhood myopia (ATOM) study
1. ATOM 1
2. ATOM 2

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1. ATOM 1 STUDY
 Parallel group, placebo-controlled, Randomised, double masked study conducted in
Singapore
 Included 400 children 6-12 year (9.2yr)
 With moderate myopia (-1.00 to - 6.00) (3.50D)
 For 3 years (Two year treatment and one year washout)
 The treatment group received atropine 1% at bedtime in one eye and no treatment in
the other eye.
 Result: Over 2 year, there was 77% reduction in the mean progression of
myopia(progression of -1.20+/- 0.69 in placebo group & -0.28+/-0.92 in atropine
group)
 There was also a strong correlation with reduction in axial length in the atropine
group.
 At three year, A significant rebound was seen for both myopia progression and
axial length elongation after cessation of atropine 1% for 1 year
2. ATOM 2 STUDY
 Aim was to compare the safety and efficacy of three lower doses of atropine (0.5%, 0.1%,
and 0.01%)
 Double masked, randomised control trial
 Included 400 children(6-12year)
 Myopia > -2.00D
 Children were randomised to receive either 0.5% atropine (n=161) 0.1%(n=155) or
0.01%(n=84)
 Both eyes were treated
 Five year study that included two years of treatment, one year of washout and Two year
where treatment was restarted in children who continued to progress.

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Consolidating data from ATOM 1 & 2
 0.01% atropine Had similar efficacy compared to higher concentration of 0.1% and 0.5%
 Side effects were minimal with 0.01%
 Negligible amount of accommodation( mean Residual accommodation was 11.8 Din
0.01% group, compared to 6.8 D and 4D In 0.1% and 0.5% group respectively
 Pupil size(0.8mm & 1.2mm ) Difference from baseline in Mesopic and photophic
conditions respectively in 0.01% group compared to 2.8mm in 0.1% group & 3.1mm &
3.6mm in 0.5% group (p<0.01)
 No effect on near visual acuity in 0.01% group
 During washout period , Children in 0.01% group had minimal rebound
 No rebound seen for axial length in 0.01% group
Summary
 Environmental factors such as reduced time is spent outdoor and increased near work
activities have been shown to play a role in myopia progression.
 Of approaches that have been discussed all have shown to slow myopia progression; in
particular, Atropine, ortho-K, Soft bifocal contact lens have been shown to be most
effective.
 Each of these therapies is limited in variable extent by: Treatment compliance, potential
side effect and lack of long term data. They are likely to improve with further validation
and longer term studies. In addition, it would be interesting to evaluate the potential
additive effect of combination of therapies on the progression of myopia in further
studies.
References:
1. ATOM 1 AND 2 study
2. Previous presentation and online classes