Myopia is considered to be a leading cause of visual impairment. Furthermore, the prevalence of myopia young adolescents has increased substantially over the past few decades. Although myopia was identified more than two thousands years ago, a consistently effective approach to myopia control for all patients still eludes clinicians

1. Review Article
Myopia: Can Its Progression Be Controlled?
Yi Pang, PhD, OD1
Dominick M. Maino, OD, MEd, FAAO1
Guoming Zhang, MD, PhD2
Fan Lu, MD, OD3
1. Illinois College of Optometry, Chicago, IL
2. Shenzhen Eye Hospital, Guangdong, P.R. China
3. School of Optometry & Ophthalmology, Wenzhou Medical College, P.R. China
ABSTRACT Myopia is considered to be a leading cause of visual
Myopia is considered to be a leading cause of visual impairment with those having a high magnitude of
impairment. Furthermore, the prevalence of myopia in myopia being susceptible to a range of potentially serious
young adolescents has increased substantially over the ocular pathologies.1 The prevalence of myopia in young
past few decades. Although myopia was identified more adolescence has increased substantially over the past few
than two thousands years ago, a consistently effective decades affecting 25% of the adult population in the
approach to myopia control for all patients still eludes United States and 70-90% in various Asian countries.1,2
clinicians. The mechanism of development and the treatment of
Among all the treatments mentioned in this review, myopia has been a major research topic for decades.
the most promising ones are muscarinic receptor Despite the heritability of high magnitude myopia,
antagonists, including atropine and pirenzipine. Bifocal environmental factors including the level of education,
and progressive lenses can be effective in the control of urbanization, and intensity of near work play an
myopia and have greater effectiveness for subjects with important role in the development of mild and moderate
nearpoint esophoria and a high lag of accommodation. myopia. 3 There are several theories about the
The treatment outcomes of gas permeable contact lenses mechanisms of myopia development. Given the clear
have been confirmed to be effective but with association between myopia and near work, excessive
questionable overall clinical effect. Other treatments accommodation has been proposed to be the cause of
including the under correction of myopia have been myopia.4 Recent animal studies suggest myopia can be
shown to be ineffective while traditional Chinese caused by hyperopic and myopic retinal defocus,5,6 high
interventions for myopia prevention need further study lag of accommodation,7 and near-work induced transient
to access their efficacy. myopia.8,9 Chemicals such as dopamine, various growth
KEY WORDS factors, and muscarinic antagonists are proposed to be
myopia, near work, esophoria, accommodation, involved in the local retinal effects and resultant scleral
muscarinic receptor antagonists, progressive lenses growth.10-12
Although myopia was identified by Aristotle more
Correspondence regarding this article can be e-mailed to than 2300 years ago, an effective therapy for all patients
ypang@ico.edu or sent to Dr. Yi Pang, Illinois College of Optometry
3241 S. Michigan Ave., Chicago, Il. 60616. All statements are the still eludes clinicians. Several treatments towards
authors’ personal opinion and may not reflect the opinions of the slowing myopia progression have been suggested by
College of Optometrists in Vision Development, Optometry and recent animal studies. The outcomes from research with
Vision Development or any institution or organization to which they humans are not quite as straightforward because of the
may be affiliated.
difficulties associated with isolating specific
Pang Yi, Maino D, Zhang G, Lu F. Myopia: Can Its Progression Be
environmental variables. This review summarized the
Controlled? Optom Vis Dev 2006:37(2):75-79.
Volume 37/Number 2/2006 75

2. efficacy and potential adverse side effects of current found that mean three-year increases in myopia were
treatments aimed at slowing down myopia progression. -1.28 D in the PAL group and -1.48 in the SVL group,
Bifocal and progressive addition spectacle lenses which was statistically significant.18 The mean myopic
The rationale for using positive lens additions in progression in the PAL group with nearpoint esophoria
myopia control is to optimize accommodative accuracy was -1.18 D compared to -1.39 D in SVL group. Children
for near tasks and minimize the retinal blur. Despite the with nearpoint exophoria had a myopia increase of -1.43
clear effect of positive lens additions in animal studies,13 D in PAL group and -1.38 D in SVL group, which was
the results of clinical trials are inconsistent.14-18 Goss consistent with other similar studies. In summary,
examined longitudinal records from three optometry clinical trials indicate that bifocal and progressive lenses
practices, comparing 52 subjects with single vision can be effective in control of myopia and show greater
lenses (SVL) to 60 subjects with bifocal lenses.14 He effectiveness for subjects with nearpoint esophoria.
reported that esophores wearing bifocals had lower Muscarinic receptor antagonists: atropine and
progression rates than those wearing SVL (-0.32 diopters pirenzipine eye drops
(D) vs. -0.54 D), and exophores wearing bifocals had The use of muscarinic antagonists has been based on
similar progression rates as those wearing SVL (-0.45 vs. the hypothesis that excessive accommodation leads to
-0.43). No effect on myopic progression was noted in increases in myopia.24 Other mechanisms have been
other randomized clinical trials where the nearpoint reported, including retardation of axial length elongation
phoria was not taken into consideration.19,20 Another by affecting release of dopamine neurotransmitter and
study by Goss confirmed that bifocal wearers with synthesis of glycosaminoglycan in the sclera.25,26 The
nearpoint esophoria had progression rates of only -0.33 slowing of myopia progression has been observed with
D/year compared with -0.59 D/year for those of atropine instillation27-30 even in high myopes (-10 to
age-matched children who wore single vision lenses.21 -12D);31 however, some of the studies were retrospective
Fulk studied 82 myopic children with esophoria at near and/or had an insufficient sample size. Recently, Shih
and reported that myopia progression averaged -0.99 D and Lin conducted a double-masked randomized clinical
for bifocals and -1.24 D for SVL over 30 months.15 Those trial involving 227 Chinese children aged 6 to 13 years.29
studies suggest that the effectiveness of bifocals in The mean progression of myopia in the atropine with
slowing myopia progression may depend on the PAL group (-0.41 D) was significantly less than the PAL
nearpoint phoria. Bifocals seem to slow the myopia only group (-1.19 D) and SVL only group (-1.40 D) at the
progression in children with nearpoint esophoia, but not end of the 18 months follow-up period. No progression
necessarily in children with exophoria. of myopia (less than 0.25 D/year) was shown in 57.6% of
Progressive addition lenses (PAL) are often more the children receiving 0.5% atropine vs. 4.9% in SVL
cosmetically acceptable than bifocal lenses. group. The elongation of axial length was 0.22 mm in
Furthermore, children may not always use the lower atropine group and 0.59 mm in SVL group.
segment of the bifocal for reading. Thus, several clinical The side effects of atropine have been frequently
trials with PALs have been conducted. Leung and Brown reported and include: mydriasis, photophobia, blurred
examined 32 Chinese children (9 to 12 years old) with vision, and allergic dermatitis, as well as other significant
SVL and 36 children with PAL.22 They reported that the systemic effects. Thus an M1 specific muscarinic
rates of myopia progression over 2 years in PAL and SVL antagonist, pirenzepine, was tested both in the United
groups were -0.76 D and -1.23 D respectively with States and several Asian countries. The Asian
statistical significance. Another masked and randomized Pirenzepine Study with 353 myopic children aged 6 to 12
study with 254 Chinese myopic children (7 to 9 years years showed that the rate of myopia progression was
old) by Edwards and Lam noted less of a difference -0.47 D/year with pirenzepine (2% Gel twice a day) and
between PAL and SVL groups (-1.12 D vs. -1.26 D over 2 -0.84 D/year in the control group.32 The increase in axial
year) (not statistically significant).23 They found that length was 0.20 mm/year in pirenzepine vs. 0.33
PALs had a greater preventative effect on those with mm/year in control group. The United States Pirenzepine
myopia and esophoria at near (-0.89 D in PAL vs. -1.26 D Study with 174 children, aged from 8 to 12 years (mixed
in SVL) (not statistically significant). Edwards ethnicity/73% were Caucasian), found that the mean
suggested that age differences in myopic children may increase in myopia was -0.26 D/year in the pirenzepine
partially explain the different findings between the two group vs. -0.53 D/year in the control group.33 There was a
studies. The Correction of Myopia Evaluation Trial mean increase in axial length of 0.19 mm /year in the
(COMET) was a multi-center randomized clinical trial, pirenzepine group and 0.23 mm /year in the control
involving 469 ethnically diversified subjects. This study group with no statistical significance. Both studies
76 Optometry and Vision Development

3. reported that pirenzepine had innocuous side effects suggested that myopia correction by minus lenses
compared to atropine. The efficacy of pirenzepine was requires subjects to accommodate for the near demand
greater than that reported by the use of PALs,18,33 but less and leads to hyperopic retinal defocus. This would then
than the use of atropine. This may be due to the fact that stimulate the compensative ocular elongation. This
subjects in these studies were not allowed to wear theory is supported by animal studies which show that
bifocals or progressive lenses. A continuing second year the increase in axial length can be inhibited by plus
controlled evaluation of pirenzepine now being lens.40,41 In a human study, Tokoro found that the mean
conducted by the US Pirenzepine Study Group will change in myopia is significantly reduced in the under
provide further evidence of the efficacy of pirenzepine in corrected group as compared to the fully corrected
myopia prevention. group.42 However, this study did not match subjects for
Contact lenses age and had a very small sample size. Recently Chung
Soft contact lenses do not appear to affect myopia and O’Leary carried out a single masked randomized
progression compared to spectacle correction.34,35 The clinical trial with 94 myopes aged 9-14 years.43 Forty
treatment outcomes of using gas permeable (GP) contact seven myopes were under corrected by +0.75 D while 47
lens are somewhat mixed.36-38 Perrigin reported that the subjects were fully corrected. At the end of the 24 month
mean increase in myopia for 56 GP-wearing myopes period, the mean progression in the under corrected
from 8 to 13 years of age was -0.48 D as compared with group was -1.00 D versus -0.77 D in fully corrected
-1.53 D for spectacle wearers after three years of group. A greater axial length elongation was also found
follow-up.38 Although the age and initial refractive error in the under corrected group. This study indicated that
in the two groups were matched, this study had problems under correction of distance spectacles enhances rather
of high rates of loss to follow-up and was not a than prevents myopia progression. Hung and Ciuffreda
randomized design. Since myopia progression slows explained this new finding using their proposed
down as age increases, the high loss rate in young Incremental Retinal-Defocus theory.44 They stated that
children from the GP group but not the spectacle group, with myopia under correction focusing from far-to-near
may lead to the false impression that GPs significantly results in reduction of retinal image defocus, which
slow the myopic progression. A recent randomized decreases the rate of retinal neuromadulator release. This
clinical trial with 428 Chinese children by Katz and in turn decreases the rate of proteoglycan synthesis and
Chew show that there was no significant difference in adversely affects scleral structural integrity, resulting in
myopia progression between GP wearers and spectacle axial elongation.
wearers.36 The mean increase of myopia was -1.33 D and Traditional Chinese interventions
-1.28 D, and axial length increased by 0.84 and 0.79 mm China, one of several countries with high rates of
over 2 years in GP and spectacles wearers, respectively. myopia, has a myopia prevalence of 20.23% in primary
This trial however had a low retention rate (only 37.5% school, 48.18% in middle school, 71.29% in high school,
of the GP wearers and 67.8 % of the spectacle wearers and 73.01% of college students (reported by the Chinese
remained at the end of 2 year study). The latest National Teaching Institute).45 A great deal of time and
randomized study (Contact Lens and Myopia effort has been utilized to study myopic progression.
Progression Study; CLAMP) with 84.5% Causation Many traditional Chinese interventions have been tried
subjects used a better design to reduce the drawbacks of in China and other countries. These include Chinese eye
previous studies.39 The mean myopic increase was -1.56 excises, acupuncture, Qi-gong ocular exercises,
D for 59 GP wearers and -2.19 D for 57 soft contact electrophotomagnitostimulation, and eye massage.
lenses wearers after a 3 year follow-up (statistically Those interventions are based on the theory of Jing-Luo.
significant). The axial growth of the eyes was not Jing represents channels which connect the interior and
significantly different between the two groups, the exterior as well as the upper and lower parts of the
indicating that the decreased myopia progression by GPs human body. Luo represents the collaterals which
was likely due to corneal flattening instead of the slowing connect these channels and are distributed all over the
axial growth. Based on results from recent randomized body surface. Acupuncture, as well as several other
clinical trials, the effects of GPs on myopia prevention interventions, have claimed to influence circulation of
are small and may have no significant clinical blood and Qi, reduce eyestrain, and improve the neural
implications. nutrition of the eyes leading to prevention of myopia.
Undercorrection of distance spectacles Although the Chinese believe these therapies are
Myopia is proposed as an adaptive response to the effective, there has been little scientific support. 46
accommodative demand during near work. It has been
Volume 37/Number 2/2006 77

4. Chinese eye excises originally created by the that in order to slow myopic progression, clinicians
Jing-Luo school of acupuncture approximately 4000 should consider the following:
years ago are a part of the school routine and are regularly 1. Fully correct all myopia present.
performed by Chinese children 5 to 15 years of age. It is a 2. Consider using pharmacological intervention (atro-
massage and pressure exercise on selected acupuncture pine and pirenzepine) in conjunction with progres-
pressure points around the eye. A pilot study with 10 sive multifocal lenses.
subjects found that the Chinese eye excises did not have 3. Use progressive multifocal lenses for those individ-
any effect on accommodation or critical flicker fusion.47 uals with esophoria/and or a high lag of accommo-
Shih reported that Qi-Qong ocular exercise, another dation at near.
popular Chinese myopia intervention, improved It is time for optometrists to use all the resources
accommodative amplitude and accelerated the available to decrease myopic progression by using those
accommodative response;48 however, this study had only mechanisms most suitable for the individual patients we
1 7 su b j ect s. S hakola used acupunct ure a nd diagnose and treat. All too often eye and vision care
electrophotomagnitostimulation to treat 98 patients, 5 to professionals do not use these appropriate therapies
45 years, and reported a decreased myopic progression either because they choose to ignore their existence or
for 91.5% of the subjects.49 Since this was an abstract and have not kept up to date on the very latest approaches to
there was no further report, the details of the study were vision care in this area 59 We can reduce the impact
unavailable. In summary, although traditional Chinese myopia has on the child and later the adult, if we treat it
methods of intervention have been available for now.
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