Myopia Regulation: Myth or Megatrend?
Many methods purportedly slow the progression of myopia. But, do they really work?
Release Date: August 2009
Expiration Date: August 31, 2012
Efforts to better understand myopic genesis are escalating. By isolating the stimulus and response factors behind myopia, researchers are learning how to regulate myopic progression. A thorough discussion of the causal factors of myopia, as well as past, present and developing strategies for myopia regulation, will prepare practitioners to utilize successful strategies, clinical findings and new technologies and therapies when diagnosing and managing their myopic patients.
Jerome A. Legerton, O.D., M.S., M.B.A., and Brian Chou, O.D.
COPE approval for 2 hours of CE credit is pending for this course. Check with your local state licensing board to see if this counts toward your CE requirement for relicensure.
This continuing education course is joint-sponsored by the Pennsylvania College of Optometry.
Dr. Legerton is a consultant to Paragon Vision Sciences and the founder of Synergeyes, Inc. Dr. Chou has no relationships to disclose.
In 1990, the financial cost of
myopia in the United States was
estimated at $4.8 billion.1 And,
in addition to this societal burden, myopia carries an increased risk
of associated pathology, including
cataract, retinal degeneration, retinal
holes and choroidal neovascularization.2 Although it is just the seventh
most frequent cause of legal blindness in the U.S., myopia has a significant public health impact because
resultant vision loss tends to extend
over a longer period of life.3 Patients
with myopic retinopathy are legally
blind for an average of 17 lifetime
years, vs. five lifetime years of blindness due to diabetes or age-related
Efforts to better understand
myopic genesis are escalating. By
isolating the stimulus and response
factors behind myopia, researchers
are beginning to understand how to
regulate myopic progression. Given
the significant worldwide prevalence
of myopia, interest in regulating
myopic development runs high.5-7
What Causes Myopia to
The question of nature vs. nurture persists. Most researchers agree
that environmental and genetic factors contribute to myopia, yet the
specific factors involved, as well as
their relative contributions, remain
elusive.8 Environment and genetics
may interact together to determine
One recent review of familial
studies indicates a definite genetic
basis for high myopia, and a strong
genetic basis for low myopia.9 Also,
twin studies provide compelling evidence that myopia is inherited.10
Meanwhile, the concept of environmental influence on myopia
was bolstered by a 2008 study that
found higher levels of outdoor activity are associated with a reduced
prevalence of childhood myopia-even after adjusting for near work,
parental myopia and ethnicity.11 Perhaps outdoor light releases a retinal
neurotransmitter that inhibits eye
A leading model for myopic progression incorporates important
roles by optical stimuli, neurotransmitters, and choroidal and scleral
growth factors. Data show that
hyperopic defocus in the retinal
periphery, even in the absence of
visual signals from the fovea, can
stimulate myopic progression.12
Hyperopic peripheral defocus is also
implicated as a stimulus for myopic
progression, according to research in which central refraction was compared to peripheral refraction.13 This
study found that hyperopic peripheral defocus is present in eyes of
myopic children. In his discussion of
aberrations and myopia, William N.
Charman, Ph.D., concluded, “There
is stronger evidence in favour of
differences in patterns of peripheral
refraction in both potential and
existing myopes, with myopes tending to show relative hyperopia in the
periphery. These differences appear
to be related to a more prolate eyeball shape.”14
Peripheral hyperopic defocus
appears to further increase with
accommodation due to induced
negative spherical aberration. One
study found that spherical aberration decreased and became negative
as the accommodative response
increased in those patients under the
age of 40.15
Peripheral hyperopic defocus may
cause the release of neurotransmitters that in turn lead to the release
of growth factors that elongate
the eye. In examining the role of
growth modulators in elongating
the eye, study researchers concluded, “Changes in scleral glycosaminoglycan synthesis accompany
lens-induced changes in the length
of the eye. Furthermore, changes
in the thickness of the choroid are
also associated with changes in the
synthesis of glycosaminoglycans.
These results are consistent with the
regulation of the growth of the eye
being bidirectional, and with the
retina being able to sense the sign of
Strategies to Regulate Myopia
Although regulating myopia is
desirable, the development of viable
treatment demands emphasis on
both safety and efficacy because
these treatments target children,
before significant myopic progression takes place. For example, a
study of 11,178 children in Taiwan
demonstrated that a 12% myopic
rate at age six jumped to 84% for
the age range of 16 to 18 years.17 So,
the regulation of myopia requires
intervention in children as young as
six years of age, and it may be effective in patients through the late teen
The established metric for determining effective myopia regulation
is the axial length of the eye—or,
more specifically, the change in vitreous chamber depth as measured
by ultrasonography. Refractive
stability alone is a poor indicator
of successful myopia regulation,
because temporary changes in cor-neal curvature or crystalline lens
thickness can overshadow increased
vitreous chamber depth. Unfortunately, early myopia research often
did not measure vitreous chamber
Researchers have evaluated
several purported treatments for
regulating myopia in children. These
include spherical rigid and soft
contact lenses, undercorrection of
myopia, drug therapy, vision training and corneal reshaping. Thus
far, the cumulative evidence has not
supported any single intervention.
Rather, it leans heavily toward the
potential for optical intervention.
Spherical Contact Lenses
As early as 1956, anecdotal
reports suggested that spherical,
rigid contact lenses could slow
myopic progression. Several study
results investigating this theory were
confounded by flaws, such as inadequate control of important variables,
incomplete follow-up and poor
selection of study participants.18
More recently, the National Eye
Institute funded the Contact Lens
and Myopia Progression (CLAMP)
study, the results of which were
published in 2004.19 CLAMP
evaluated myopia progression over a
three-year period in more than 100
eight- to 11-year-old patients. Rigid contact lens wearers experienced
less myopic progression than soft
lens wearers. However, the reduced
progression appeared temporary and
was not due to stabilization in vitreous chamber depth.19 The growth in
axial length between rigid and soft
lens wearers was similar.
Because CLAMP found that
rigid lenses do not slow myopic eye
growth, the study authors concluded
that their findings “do not indicate
that [rigid gas-permeable lenses]
should be prescribed primarily for
myopia control.” CLAMP results
were corroborated by findings from
a randomized clinical trial in Singapore, which also demonstrated that
rigid lenses do not slow axial growth
in myopia children.20 A related study, the Adolescent
and Child Health Initiative to
Encourage Vision Empowerment
study (ACHIEVE), investigated if
wearing spherical soft contact lenses
affected myopic progression in children.21 Children between the ages of
eight and 11 with -1.00D to -6.00D
myopia and less than 1.00D of astigmatism were randomly assigned to
wear soft contact lenses (n = 247) or
spectacles (n = 237) for three years.
Researchers found an average rate
of myopic change of 0.06D per year
more for contact lens wearers than
spectacle wearers. After three years,
the adjusted difference between contact lens wearers and spectacle wearers was not statistically significant,
and there was no difference between
the two groups regarding change in
axial length or steepest corneal curvature.
Study authors concluded, “These
data provide reassurance to eye
care practitioners concerned with
the phenomenon of ‘myopic creep.’
Soft contact lens wear by children
does not cause a clinically relevant
increase in axial length, corneal
curvature or myopia relative to spectacle lens wear.” But, while spherical
soft lenses prescribed for distance
correction do not cause nor inhibit
myopic progression, they are frequently an excellent form of vision
For years, a handful of practitioners have advocated undercorrecting
myopia in order to slow its progression. But, one study found no significant difference between groups that
received full correction vs. undercorrection.22 Two recent studies even
found that undercorrecting myopia
actually increases myopic progression.23,24
Despite the questionable value
of undercorrection, a pilot study to
evaluate Neural Vision Correction
(NVC, NeuroVision) is underway.25 NeuroVision has developed patient-specific computerized visual stimulation for the purpose of facilitating
the neural connections responsible
for vision. This NVC technology has
received FDA 510(k) market clearance for the treatment of amblyopia
in patients over the age of nine. The
pilot study now seeks to evaluate
the improvement of visual acuity
in undercorrected children and to
evaluate any reduction of myopia
An alternate method of undercorrection involves prescribing bifocal
or progressive addition spectacle
lenses, reducing the accommodation
required for near work and reducing
the accommodative lag associated
with a high accomodative convergen/ROExams/accomodation (AC/A) ratio or
near point over-convergence.
The National Eye Institute funded
a randomized clinical trial called the
Correction of Myopia Evaluation
Trial (COMET). This ongoing study
has found that progressive addition
lenses, compared to single vision
lenses, slowed the progression of
myopia in children by a small but
statistically significant amount during the first year. But, the treatment
effect did not significantly change
over the next two years. The authors
concluded that the “small magnitude of the effect does not warrant
a change in clinical practice.”26 In response to these COMET findings, the NEI released a statement
that doctors should not routinely
prescribe progressive eyeglasses for
Despite undercorrection’s seeming
inefficacy, another study reported
the value of multifocal contact lenses
for controlling myopia in patients
with accommodative lag, high AC/A
and near point esophoria. This study
of identical twins documented the
reduction in myopic progression in
the twin wearing multifocal contact
lenses vs. the twin wearing single-vision soft lenses.28 Researchers suggest that this is caused by the control
of accommodative lag, but it could
also be due to peripheral myopic
defocus similar to that provided by
corneal reshaping for myopia.
Drug studies, including use of
atropine, have concentrated on the
role of accommodation in myopia progression. Perhaps the most
convincing information was documented in the recent Atropine in
the Treatment of Myopia (ATOM)
study, which was the largest randomized controlled trial of its kind
to date.29 The ATOM study followed 400 eligible children between the ages of six and
12 for two years.
After two years,
in the placebo-treated eyes, the
of myopia was
axial elongation of
with an axial length essentially
Despite the efficacy of atropine
in reducing childhood myopia progression, atropine therapy is not
accepted as a standard treatment.
Although no serious adverse events
related to atropine were reported
in the ATOM study, side effects
include increased light sensitivity
due to mydriasis and cycloplegia,
which together can impair a child’s
ability to perform well in school
and athletics. The cosmetic issues
of pupil dilation caused by atropine
can be awkward for children during
a critical period of social development, when they seek the acceptance
of their peers. It is unknown whether the myopia control derived from
atropine therapy is due to cycloplegia, increase in pupil-dependent
aberrations, or other effects.
While atropine therapy is not
appropriate for most children,
ATOM results suggest that pharmaceutical management has potential.
Indeed, other atropine-like drugs,
including pirenzepine and cyclopentolate, are under investigation.
One study found that 2% pirenzepine gel slowed childhood myopia
progression by almost half after a
year of treatment; however, 11% of
subjects withdrew from the study
due to adverse effects.30,31 Further safety and efficacy data is expected.
Currently, pirenzepine is not FDA
approved or available in the U.S.
Other pharmacologic research
as well as scleral
One such study
examined the effect
of a nitric oxide
synthase inhibitor, NG-nitro-Larginine methyl ester (L-NAME),
on modulating choroidal thickness
in conjunction with myopic defocus. Results showed that L-NAME
inhibited choroidal thickening.32 Thus, nitric oxide may play a role in
modulating choroidal thickness.
Another study examined the effect
of 7-methylxanthine, a metabolite
of caffeine, on the collagen fibrils
in the sclera in rabbits.33 Researchers found that 7-methylxanthine
increased collagen density and the
diameter of collagen fibrils in the
posterior sclera, which may prevent
axial myopia. This study’s sponsor,
Trier Research Laboratories, has
registered a Phase II trial for the oral
administration of 400mg of 7-methylxanthine per day vs. placebo
to a study population of children
between the ages of eight and 13.
New technology that measures
corneal hysteresis, a viscoeleastic
property of the cornea thought to
reflect its biomechanical integrity,
may offer a method to evaluate
efficacy of pharmacologic intervention in myopic progression and
diagnosing eyes at risk for myopic
progression.34,35 In a study of corneal
hysteresis measured with the Ocular
Response Analyzer (Reichert Ophthalmic Instruments) high corneal
viscoelasticity correlated with high
scleral viscoelasticity.36 Patients with
high scleral viscoelasticity may have
greater risk for myopic progression.
Vision training has also been
investigated as a regulator of myopic
progression. But to date, efforts to
control accommodation have failed
to alter progression.37 Even so, there
is evidence of the role of accommodative lag and its relationship to
measured AC/A ratios in children
who are developing myopia.
Donald O. Mutti, O.D., Ph.D.,
and colleagues concluded that, “An
elevated AC/A ratio was associated
with myopia and was an important
risk factor for its rapid onset.”38 In another recent study, Jane Gwiazda,
Ph.D., and colleagues found that
myopic children with esophoria
under-accommodate at near and
noted that, “This [finding] suggests
that a child who is esophoric must
relax accommodation to reduce
accommodative convergence and
maintain single binocular vision.
The reduction in accommodation
could produce blur during near
work, which could induce myopia as
in animal models.”39
A related study examined the
AC/A ratios before and at the onset
of myopia in children and found
that myopes, when compared to
emmetropes, had elevated AC/A
ratios at one to two years before the
onset and at all times later.40 “These
findings suggest that the abnormal
oculomotor factors found before the
onset of myopia may contribute to
myopigenesis by producing hyper-opic retinal defocus when a child is
engaged in near-viewing tasks,” the
Another study modeled AC/A
and convergence accommodation/
convergence (CA/C) interactions
and their influence on accommodative lag. “Adaptable tonic
accommodation and tonic vergence could potentially reduce the
progression of myopia by reducing
the lag of accommodation, ” found
Currently, the Cambridge Anti-Myopia Trial: Accommodation
Training and Aberration Control in
Myopia Development is investigating the role of contact lenses along
with vision training in the regulation
of myopic progression. Multifocal
contact lenses worn in conjunction
with vision training for modulating
the AC/A ratio may hold promise.
The aforementioned treat-ments—spherical contact lenses,
undercorrection, drug therapy and
vision training—are not accepted as
standard treatments for regulating
myopia progression. However, significant interest exists in controlling
progression with non-surgical cor-neal reshaping, or corneal refractive
therapy (CRT), in which the patient
wears special therapeutic lenses
In 2002, strong anecdotal evidence of myopia control came from
investigators in the first FDA pre-market approval overnight corneal
shaping study conducted by Paragon
Vision Sciences, Inc. In the study,
adolescent myopes were followed
for 12 months. Investigators found
that many subjects did not require
changes in their lens parameters
at the two and three year anniversaries from the initial fitting. This
change would have been expected
if the axial lengths of the eyes were
increasing due to anticipated myopia
Corneal reshaping is hypothesized
to inhibit myopia progression by
inducing peripheral retinal myopic defocus. Spherical aberration
increases following CRT as a result
of the oblate corneal shape induced
by the central flattening in CRT.43,44 Spherical aberration allows the
central image to focus on the fovea,
while the peripheral image field is
focused in a significantly shorter
Peripheral refractions out to 34º
of eccentricity in four subjects undergoing corneal reshaping resulted in a
central decrease in myopia with little
change in their myopic peripheral
refraction.45 Researchers concluded
that if converting peripheral hyperopia to peripheral myopia limits axial
elongation, then corneal reshaping is
an excellent option for the achievement of peripheral myopia.
The first controlled trial of cor-neal reshaping for myopia control
was published in 2005: Longitudinal
Orthokeratology Research in Children (LORIC).46 The authors of the
two-year pilot study concluded that
corneal reshaping could both correct
and control childhood myopia. They
also noted that substantial variations exist in changes in axial length
among children and that there is no
way to predict the effect for individual subjects.
An additional two-year study,
Corneal Reshaping and Yearly Observation of Myopia (CRAYON),
was recently completed.47 The results
of CRAYON confirmed that cor-neal reshaping slowed eye growth
in children at one and two years of
treatment. The authors concluded,
“Corneal reshaping contact lenses
hold promise for myopia control. It
has now been shown by two separate controlled trials to slow axial
growth of the eye.”
Interim data from the Stabilization of Myopia via Accelerated
Reshaping Technologies (SMART)
study were reported at the Global
Specialty Contact Lens Symposium
in January 2009. This five-year
study, funded by Bausch & Lomb,
seeks to compare changes in vitreous chamber depth in a test group
wearing lenses for myopic corneal
reshaping against a control group
wearing soft contact lenses. At one
year, data demonstrated less progression in myopia in the test group;
however, there was no significant
difference in vitreous chamber depth
growth between the test and control
Other studies are underway to
determine the optimum peripheral myopic defocus to make such
treatment more predictable and
consistent. Prototype instruments now exist that conduct a peripheral
refraction in order to ameliorate the
problem of the variance in equatorial diameter in eyes that have the
same refractive error. In order to
properly focus a peripheral field on
or in front of the peripheral retina,
one must know the peripheral
refraction circumferentially. With
these data, it is possible to design a
contact lens that optimally defocuses
the peripheral image field.
A ‘Farsighted’ Perspective on
The prevalence of myopia, its
impact on quality of life, and the
related economic cost collectively
underscore the value of preventing
myopia. Corneal reshaping, multifocal contact lenses with a peripheral
near add, and modulating accommodative convergence may each play a
role in reducing myopic progression.
As more research comes forth, eye
care professionals may find diagnostic instruments, such as peripheral
refractors, A-scan ultrasonographers, wavefront aberrometers and
scleral rigidity analyzers, valuable
for assessing myopic progression
and treatment efficacy. Further,
pharmacologic treatment to control
neurotransmission and choroidal
and scleral growth may complement
the armament for regulating myopia.
Accumulating evidence tells us
that the regulation of myopia is
plausible. The next few years may
bring a critical mass in understanding myopic progression. Viable treatment will require a robust dioptric
effect and intervention at the first
sign of childhood myopia.
Dr. Legerton was in private
practice in San Diego for 26 years,
followed by 14 years in product
development with Pilkington Barnes
Hind, VISX, Paragon Vision Sciences and SynergEyes. He holds 20 patents for aberration-blocking contact
lenses, presbyopic laser refractive
surgery, corneal refractive therapy,
hybrid contact lenses and myopia
Dr. Chou is an industry consultant and private practitioner in San
Diego. He is a frequent contributor
to eye care publications and is the
co-developer of the online contact
lens reference, www.EyeDock.com.
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