Myopia: attempts to arrest progression

Acupuncture for slowing the progression of myopia in children and adolescents

BACKGROUND

Myopia (near-sightedness or short-sightedness) is one of the three commonly detected refractive (focusing) errors. Acupuncture is the stimulation of acupuncture points by various methods including needle insertion and acupressure. It is often used by traditional Chinese medicine practitioners to treat myopia in children.

OBJECTIVES

To assess the effectiveness and safety of acupuncture in slowing the progression of myopia in children and adolescents.

SEARCH STRATEGY

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 7), MEDLINE (January 1950 to July 2011), EMBASE (January 1980 to July 2011), the Allied and Complementary Medicine Database (AMED) (January 1985 to July 2011), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to July 2011), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrial.gov), the National Center for Complementary and Alternative Medicine (NCCAM) (The first issue to August 2010), the Chinese Biological Medicine Database (CBM) (1978 to April 2011), China National Knowledge Infrastructure (CNKI) (1994 to April 2011) and VIP (1989 to April 2011). There were no date or language restrictions in the electronic searches for trials. CENTRAL, MEDLINE, EMBASE, AMED, LILACS, mRCT and ClinicalTrials.gov were last searched on 9 July 2011. NCCAM was searched up to August 2010 and CBM, CNKI, and VIP were last searched on 6 April 2011.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that included any type of acupuncture treatment for myopia in children and adolescents.

DATA COLLECTION AND ANALYSIS

Two authors independently evaluated the search results according to the inclusion and exclusion criteria. Two authors extracted and assessed data independently. We contacted the study investigator for missing data.

MAIN RESULTS

We included two RCTs conducted in Taiwan with a total of 131 participants. We did not perform a meta-analysis as the trials were assessing different outcomes. Neither trial met our pre-defined primary outcome criteria of myopia progression defined as one diopter mean change. Only one trial reported the changes of axial length without non-significant difference among groups and both trials reported that several children experienced mild pain during acupuncture stimulation.

AUTHORS' CONCLUSIONS

Two trials are included in this review but no conclusions can be drawn for the benefit of co-acupressure for slowing progress of myopia in children. Further evidence in the form of RCTs are needed before any recommendations can be made for the use of acupuncture treatment in clinical use. These trials should compare acupuncture to placebo and have large sample sizes. Other types of acupuncture (such as auricular acupuncture) should be explored further as well as compliance with treatment for at least six months or longer. Axial length elongation of the eye should be investigated for at least one year. The potential to reduce/eliminate pain from acupuncture experienced by children should also be reviewed.

The long-term results of using low-concentration atropine eye drops for controlling myopia progression in schoolchildren

PURPOSE

The purpose of this article was to evaluate the long-term efficacy of a low-concentration (LC) atropine eye drop regimen (0.05%-0.1%) for controlling myopia progression in schoolchildren.

METHODS

This retrospective, case-control study enrolled myopic schoolchildren who had been followed-up for at least 3 years from 1999 to 2007. Children who received LC doses of atropine eye drops [initial prescription 0.05%, if progression over -0.5 diopter (D) during a 6-month follow-up then changed to 0.1% atropine] every night at bedtime were included in the LC atropine group, and untreated children served as controls.

RESULTS

A total of 117 children were included in this study. The mean age was 8.4 years. There were 97 children in the LC atropine group and 20 children in the control group. The mean follow-up duration was 4.5 years. In a mixed model analysis, the adjusted myopia progression in the LC atropine group was -0.23 D/year, significantly lower than that of the control group, which was -0.86 D/year (P<0.001). About 80% of the treatment group had slow myopia progression (less than -0.5 D progression per year). In a multivariate analysis, factors such as initial spherical refraction with less myopia and treatment with LC atropine were significantly associated with less myopia progression, but age, sex, and initial astigmatism were not significantly associated (P<0.001, P<0.001, P=0.442, 0.494, and 0.547, respectively).

CONCLUSION

The results of this study demonstrate that long-term and regular instillation of LC atropine eye drops is effective for controlling myopia progression and provides a possible strategy for an initial myopia regimen.

Multifocal versus single vision lenses intervention to slow progression of myopia in school-age children: a meta-analysis

Myopia in school-aged children is a major public health problem in Asians that has been extensively studied. Multifocal lenses (MLs) are advocated as a substitute for single vision lenses (SVLs) to slow myopia progression in children, but results vary greatly across studies. We systematically searched currently available randomized controlled trials that compared the effects of MLs and SVLs in children. A meta-analysis of nine of these trials showed that MLs with powers ranging from +1.50 to +2.00D were associated with a statistically significantly decrease in myopia progression in school-aged children compared with SVLs. The benefit was greater in children with a higher level of myopia at baseline and sustained for a minimum of 24 months. Asian children appeared to have greater benefit from intervention with MLs than white children.

Molecular mechanisms of muscarinic receptors in mouse scleral fibroblasts: Prior to and after induction of experimental myopia with atropine treatment

PURPOSE

To investigate the effect of atropine on the development of spectacle lens induced myopia in the mouse and to determine if the level of mRNAs for the muscarinic receptor subtypes (M(1) - M(5)) is affected by atropine treatment.

METHODS

Experimental myopia was developed in Balb/CJ (BJ) mice by placing -10 diopter spectacle lens on post-natal day 10 over the right eyes of 150 mice (n=10 in each group, 5 repetitions) for six weeks. After 2 weeks of lens wearing, the atropine group received a daily sub-conjunctival injection (10 µl) of 1% atropine sulfate and the saline group received daily 10 µl of 0.9% normal saline for 4 weeks. In addition, myopia was developed in C57BL/6 (B6) mice by placing -10 D spectacle lens on post-natal day 10 over the right eyes of 60 mice (n=10 in each group, 2 repetitions) for six weeks with and without atropine treatment. Refraction and axial length was measured at 2, 4, and 6 weeks after treatments. RT-PCR and northern blots were performed using specific primers for M(1)-M(5), and products sequenced. Real-time PCR was used to quantify message levels.

RESULTS

Axial length of myopic eyes was 111% of their controls without atropine treatment and 103% of controls after atropine (p<0.01). Refraction shifted from myopic to emmetropic after atropine was administered in both pigmented and non-pigmented eyes. Corneal thickness, anterior chamber depth, corneal curvature and retinal thickness were not significantly different with and without atropine treatment (p=0.14). The lens thickness and vitreous chamber depth were significantly reduced after receiving atropine (p<0.05). Real-time PCR showed that message levels for M(1), M(3), and M(4) were upregulated in myopic sclera after atropine treatment, but M(2) and M(5) showed little change.

CONCLUSIONS

The present study shows that 1% atropine reduces myopia progression in both pigmented and non-pigmented mice eyes. Axial length and vitreous chamber depth appear to be the main morphological parameters related to myopia. The results suggest that atropine may act on one or more muscarinic receptors to differentially regulate expression levels of specific receptors.

Bifocal lens control of myopic progression in children

Bifocal spectacle lenses have been used as a strategy to slow myopic progression in children since the 1950s and perhaps earlier. The reported success of this strategy varies greatly, as does the design of studies reporting the outcomes of their use-from earlier retrospective analysis of records to later prospective clinical trials. Collectively, published data support the suggestion that bifocal lenses inhibit myopic development in children but only by a small amount and only in a subset of children. Possible reasons for the greatly varying outcomes include a lack of individualism of the treatment and failure to take the vergence system into account. This review summarises the results of bifocal and multifocal studies, describes how accommodation, convergence and their interaction are linked to myopic development and details how a bifocal treatment that takes this into account may be devised. Also discussed is whether alterations to peripheral retinal blur contribute to bifocal lens effects.

Factors Associated with High Myopia After 7 Years of Follow-up in the Correction of Myopia Evaluation Trial (COMET) Cohort

PURPOSE

To evaluate factors associated with the development of high myopia (worse than -6.00 D) over 7 years of follow-up in the COMET cohort.

METHODS

COMET enrolled 469 ethnically diverse children (6-11 years) with myopia between -1.25 and -4.50 D. They were randomized to either progressive addition lenses (PALs) or single vision lenses (SVLs), and followed for 5 years in their original lens assignment and 2 additional years wearing either spectacles (PALs or SVLs) or contact lenses. Refractive error was measured annually by cycloplegic autorefraction and axial length by A-Scan ultrasonography. Myopia for each child was defined as the mean spherical equivalent refractive error (SER) of the 2 eyes. Analyses were based on 7 years of follow-up. Time to high myopia was analyzed by Cox proportional hazard models and linear regression. Parental refraction data were available from 240 COMET subjects.

RESULTS

Younger (6-7 years) versus older (11 years) age at baseline was a significant risk factor (adjusted hazard ratio (HR) = 6.6, 95% CI = 3.4, 12.7) for having high myopia within 7 years. More (SER from -2.26 to -4.50 D) vs. less (SER from -1.25 to -2.25 D) baseline myopia was also a significant risk factor for high myopia at 7 years (adjusted HR = 7.4, 95% CI = 4.4, 12.4). Gender, ethnicity, and treatment assignment were not associated with the risk of high myopia within 7 years. Increased number of myopic parents was associated with a significant risk of high myopia in the children (p = 0.008).

CONCLUSIONS

Children who developed high myopia during 7 years of follow-up were younger and had more myopia at baseline. They also were more likely to have two myopic parents. These children may be at greater risk for sight-threatening conditions later in life.

Expression of muscarinic receptors in human and mouse sclera and their role in the regulation of scleral fibroblasts proliferation

PURPOSE

To determine the expression of muscarinic receptor subtypes (mAChRs) in human and mouse scleral fibroblasts (SFs), to investigate the mechanism that mediate the role mAChRs play in cell proliferation, and to explore the underlying intracellular signaling pathways involved in mouse SFs with treatment of muscarinic agents.

METHODS

Reverse transcription polymerase chain reaction (RT-PCR) was used to detect mRNA expression of mAChRs in the human and mouse sclera. Western blot analysis and immunocytochemistry were used to detect proteins of mAChRs in the cultured SFs. An immunohistochemical study was used to further detect the presence of mAChR proteins in frozen scleral sections. BrdU (5-bromo-2-deoxyuridine ) cell proliferation assay was performed to measure DNA synthesis. Enzyme linked immunosorbent assay (ELISA) was used to measure in vitro kinase activity for epidermal growth factor receptor (EGF-R), fibroblast growth factor (FGF-2), transforming growth factor (TGF)-beta1, and extracellular signal-regulated kinase (ERK)1/2. Expressions of epidermal growth factor-receptor (EGF-R); protein kinase C (PKC); Proline-rich tyrosine kinase 2 (Pyk-2), v-raf murine sarcoma viral oncogene homolog B1 (B-Raf), Rat Sarcoma (Ras), c-Jun N-terminal kinases (JNK1/2), and ERK1/2 were detected by immunoblot.

RESULTS

mAChR for subtypes M(1)-M(5) were detected in both mouse and human SFs by protein, cellular, and mRNA analysis. EGF-R, PKC, Pyk-2, B-Raf, Ras, JNK1/2, and ERK1/2 were activated after treatment by agonists and antagonists, indicated by changes in phosphorylation of these proteins. Atropine abolished the carbachol-induced activation of SF cell proliferation in a concentration-dependent manner. Carbachol also activated p42/44 mitogen-activated protein kinase (MAPK) and Ras in a time-dependent manner. Muscarinic agents also modulated fibroblast growth factor expression in these cells.

CONCLUSIONS

This study confirms the presence and functional role of all five mAChRs in human and mouse SFs. These results show that proliferative responses of SFs to muscarinic receptor stimulation are mediated via the activation of the classical MEK-ERK-MAPK cascade.

Long-term biomechanical properties of rabbit sclera after collagen crosslinking using riboflavin and ultraviolet A (UVA)

PURPOSE

Scleral crosslinking by the photosensitizer riboflavin and ultraviolet A (UVA) has been shown to increase significantly the scleral biomechanical rigidity and might therefore become a possible sclera-based treatment modality for progressive myopia. In the present study, the long-term effect of the new crosslinking method on biomechanical properties was investigated in the rabbit sclera.

METHODS

A 10 x 10 mm sector of the equatorial sclera of nine Chinchilla rabbit eyes was treated in vivo using a UVA double diode of 370 nm with a surface irradiance of 3 mW/cm(2) and application of 0.1% riboflavin-5-phosphate drops as photosensitizer for 30 min. Three days, 4 months and 8 months postoperatively, biomechanical stress-strain measurements of the treated scleral strips were performed and compared to contralateral control sclera using a microcomputer-controlled biomaterial tester. In addition, routine histological controls were performed.

RESULTS

Following the crosslinking treatment, Young's modulus was increased by 320% after 3 days, 277% after 4 months and 502% after 8 months, and ultimate stress by 341% after 3 days, 131% after 4 months and 213.8% after 8 months versus the controls. The decrease in ultimate strain was between 24% and 44.8%. On histology, no tissue damage was detected.

CONCLUSION

Our new method of scleral collagen crosslinking proved very effective and constant over a time interval of up to 8 months in increasing the scleral biomechanical strength. Therefore, the new treatment might become an option for strengthening scleral tissue in progressive myopia and other conditions associated with weakened sclera. There were no side-effects on the retina or retinal pigment epithelium. The new crosslinking treatment could now be tested in a suitable myopia model (like the tree shrew) and finally in human eyes.

Effects of unilateral topical atropine on binocular pupil responses and eye growth in mice

PURPOSE

Studies on drugs selected to target myopia development often use the vehicle-treated fellow eye as a control. However, it is not clear how much of the drug reaches the fellow eye, rendering it a potentially invalid control. Therefore, in this study, pupil responses were used to probe the effects of atropine in both eyes in mice, after unilateral topical application. In a second experiment, interocular differences in refractive development and axial eye growth were studied while atropine was applied daily to one eye.

METHODS

In 20 C57BL/6 (B6) wildtype mice, a single drop of 1% atropine solution was instilled into one eye. Mice were gently restrained by holding their necks while video image processing software detected the pupil and measured its diameter at a sampling rate of 30 Hz. A bright green LED, attached to the photoretinoscope of the video camera, was flashed. Pupil responses were quantified daily over a period of 2 weeks. In another group of 24 mice, one drop of 1% atropine was applied daily for 28 days. Axial length was measured pre- and post-treatment, using low coherence interferometry (the Zeiss AC-Master). Refractive development was measured by infrared photorefraction.

RESULTS

Similar to previous findings with the same device, untreated eyes displayed a pupil constriction of 24.84+/-1.73% upon stimulation with the green LED. A single drop of 1% atropine caused complete suppression with no significant recovery over the whole observation period of two weeks. The responses in the fellow eye were temporarily reduced to about 75% and then recovered towards baseline. After daily atropine application, there was significant reduction in axial length of the eyes, relative to the saline-treated fellow eyes (3.234+/-0.186 versus 3.378+/-0.176 mm, n=24, p<0.01, paired t-test) and the refractions became more hyperopic/less myopic (+13.46+/-2.15 D versus +10.06+/-2.02 D, n=24, p<0.01).

CONCLUSIONS

In line with previous findings, one drop of atropine solution caused a long lasting suppression of pupil responses in the mouse eye. New data show that the transfer to the fellow eye was limited, making interocular comparisons feasible. It is also new that topical atropine reduced axial eye growth even when mice had largely normal vision.

Spectacle lens compensation in the pigmented guinea pig

When a young growing eye wears a negative or positive spectacle lens, the eye compensates for the imposed defocus by accelerating or slowing its elongation rate so that the eye becomes emmetropic with the lens in place. Such spectacle lens compensation has been shown in chicks, tree-shrews, marmosets and rhesus monkeys. We have developed a model of emmetropisation using the guinea pig in order to establish a rapid and easy mammalian model. Guinea pigs were raised with a +4D, +2D, 0D (plano), -2D or -4D lens worn in front of one eye for 10 days or a +4D on one eye and a 0D on the fellow eye for 5 days or no lens on either eye (littermate controls). Refractive error and ocular distances were measured at the end of these periods. The difference in refractive error between the eyes was linearly related to the lens-power worn. A significant compensatory response to a +4D lens occurred after only 5 days and near full compensation occurred after 10 days when the effective imposed refractive error was between 0D and 8D of hyperopia. Eyes wearing plano lenses were slightly more myopic than their fellow eyes (-1.7D) but showed no difference in ocular length. Relative to the plano group, plus and minus lenses induced relative hyperopic or myopic differences between the two eyes, inhibited or accelerated their ocular growth, and expanded or decreased the relative thickness of the choroid, respectively. In individual animals, the difference between the eyes in vitreous chamber depth and choroid thickness reached +/-100 and +/-40microm, respectively, and was significantly correlated with the induced refractive differences. Although eyes responded differentially to plus and minus lenses, the plus lenses generally corrected the hyperopia present in these young animals. The effective refractive error induced by the lenses ranged between -2D of myopic defocus to +10D of hyperopic defocus with the lens in place, and compensation was highly linear between 0D and 8D of effective hyperopic defocus, beyond which the compensation was reduced. We conclude that in the guinea pig, ocular growth and refractive error are visually regulated in a bidirectional manner to plus and minus lenses, but that the eye responds in a graded manner to imposed effective hyperopic defocus.

Long-term biomechanical properties after collagen crosslinking of sclera using glyceraldehyde

PURPOSE

Chemical crosslinking by glyceraldehyde has been shown to increase significantly the biomechanical rigidity of sclera. It might therefore become an option for a sclera-based treatment of progressive myopia. The present pilot study was designed to test the long-term biomechanical efficiency of the new crosslinking method.

METHODS

Six Chinchilla rabbits were treated with sequential sub-Tenon's injections of 0.15 ml 0.5 m glyceraldehyde, which were given in the supero-nasal quadrant of the right eye (OD) five times over 14 days. The rabbits were killed 4 months and 8 months after crosslinking treatment, respectively. Biomechanical stress-strain measurements of scleral strips from the treatment area were performed and compared to non-treated contralateral control sclera using a microcomputer-controlled biomaterial testing device. In addition, the eyes were examined histologically by light microscopy to evaluate possible side-effects.

RESULTS

Following the crosslinking treatment, the ultimate stress was 10.2 +/- 2.3 MPa after 4 months and 8.5 +/- 2.2 MPa after 8 months versus 2.4 +/- 0.3 MPa in the controls (increases of 325% and 254.17%, respectively); Young's modulus was 104.6 +/- 13.7 MPa after 4 months and 53.2 +/- 5.2 MPa after 8 months versus 9.6 +/- 1.3 MPa in the controls (increases of 989.6% and 554.17%, respectively); and ultimate strain was 15.8 +/- 1.5% after 4 months and 24.1 +/- 0.7% after 8 months versus 38.4 +/- 4.6% in the controls (decreases of 58.84% and 37.24%, respectively). Histologically, no side-effects were found.

CONCLUSION

Our new method of scleral collagen crosslinking proved very efficient in increasing scleral biomechanical strength over a period of up to 8 months. Glyceraldehyde can be applied easily by sequential parabulbar injections. Before clinical application in myopic patients, a study in an animal myopia model is recommended.

Systemic 7-methylxanthine in retarding axial eye growth and myopia progression: a 36-month pilot study

The adenosine antagonist 7-methylxanthine (7-mx) works against myopia in animal models. In a clinical trial, 68 myopic children (mean age 11.3 years) received either placebo or 7-mx tablets for 12 months. All participants subsequently received 7-mx for another 12 months, after which treatment was stopped. Axial length was measured with Zeiss IOL-Master and cycloplegic refraction with Nikon Retinomax at -6, 0, 12, 24, and 36 months. Axial growth was reduced among children treated with 7-mx for 24 months compared with those only treated for the last 12 months. Myopia progression and axial eye growth slowed down in periods with 7-mx treatment, but when the treatment was stopped, both myopia progression and axial eye growth continued with invariable speed. The results indicate that 7-mx reduces eye elongation and myopia progression in childhood myopia. The treatment is safe and without side effects and may be continued until 18-20 years of age when myopia progression normally stops.

Features of the multifocal electroretinogram may predict the rate of myopia progression in children

OBJECTIVE

To investigate the multifocal electroretinogram (mfERG) in myopic children in relation to the rate of myopia progression.

DESIGN

Observational study.

PARTICIPANTS

Eighty-one school children with myopia.

METHODS

Cycloplegic refraction, ocular biometry, and mfERG recordings were performed in myopic children aged 9 to 11 years in 2002. The refraction and ocular biometry assessments were repeated 2 years later in 2004. The 2-year myopia progression rate was calculated for a randomly selected eye of each individual. The mfERG parameters recorded at the initial visit in 2002 were compared with subsequent progression rates.

MAIN OUTCOME MEASURES

First-order kernel mfERG responses.

RESULTS

Of the 81 eyes, 12 eyes had a high progression rate (defined as a progression rate of >1 diopter [D]/2 years), 44 eyes had a moderate progression rate (progression rate of >0.25 D but < or =1 D/2 years), and 25 eyes showed no progression or a low progression rate (progression rate of < or =0.25 D/2 years). The P1 amplitude of the mfERG in the high progression group was significantly smaller than that in the moderate (P = 0.023) and non/low-progression groups (P = 0.030) but only within the central 5 degrees (ring 1). None of the other mfERG parameters of the central ring were significantly different among the groups. The mfERG parameters of the outer rings were similar in all groups.

CONCLUSIONS

Decreased foveal function as determined by the mfERG is associated with a high rate of myopia progression. Electrophysiologic examination of central retinal function may predict the progression and severity of myopia in school children.

Topical Atropine in Retarding Myopic Progression and Axial Length Growth in Children with Moderate to Severe Myopia: A Pilot Study

PURPOSE

To study the safety and efficacy of topical 1% atropine eye ointment in retarding myopic progression in children with moderate to severe myopia.

METHODS

This was an interventional control study. Children (aged 5-10 years) with myopia of -3.00 diopters (D) or more were treated with 1% atropine ointment once daily for 1 year. Baseline and regular assessments of refractive errors by cycloplegic autorefraction and of axial length were done by ultrasound biometry, and the results were compared with data of control subjects.

RESULTS

Twenty-three children (mean age: 7.4 +/- 1.6 years) with moderate to severe myopia, being treated in the Hong Kong Eye Hospital of the Chinese University of Hong Kong, were recruited into the atropine group, and 23 children from the same eye clinic were matched with the study subjects with respect to age, sex, and initial spherical equivalent refraction, as controls. The initial refractive errors were -5.18 +/- 2.05 D and -5.12 +/- 2.33 D in the atropine and the control groups, respectively (P = 0.934). Myopic progression was significantly less (P = 0.005) in the atropine group (+0.06 +/- 0.79 D) than in the control group (-1.19 +/- 2.48 D). Axial length increase was also significantly smaller in the atropine group (0.09 +/- 0.19 mm) than in the control group (0.70 +/- 0.63 mm) (P = 0.004). One child (4.3%) developed an allergic reaction. No other major adverse effects related to the treatment were noted.

CONCLUSION

Topical 1% atropine ointment is a safe and effective treatment for retarding myopic progression in moderate to severe myopia. Further large-scale randomised controlled study with longer follow-up seems warranted.

Multifocal electroretinogram in children on atropine treatment for myopia

AIM

To assess retinal function by multifocal electroretinogram (mfERG) in children on atropine eye drops for the treatment of myopia.

METHODS

mfERGs were recorded in children receiving atropine eye drops (n = 48) once daily for 2 years and in those receiving placebo eye drops (n = 57) for a similar time. All recordings were performed between the second and third month of cessation of atropine/placebo treatment by a masked investigator. The amplitude and implicit time of the first order kernel (k1) and first slice of the second order kernel (k21) of mfERG responses were used to study the outer and inner retinal function, respectively.

RESULTS

There was no significant reduction in k1 response amplitudes of the atropine group compared to that of the placebo group (N1, p = 0.181; P1, p = 0.150). No significant difference in the k1 response implicit times between the groups was found (N1, p = 0.767; P1, p = 0.849). The differences in the k21 amplitudes and implicit times between the groups were not statistically significant (k21 amplitude, p = 0.058; k21 implicit time, p = 0.156).

CONCLUSIONS

Daily atropine usage over 2 years for the treatment of myopia has no significant effect on retinal function as demonstrated by recordings of mfERG.

The autonomic control of accommodation and implications for human myopia development: a review

Prolonged nearwork has long been associated with myopia development, however, there is no well described linking mechanism. One theory suggests that if accommodation accuracy during nearwork is not maintained, the defocused retinal image leads to myopia development. Here we review the findings of research aimed at determining whether the autonomic inputs to the ciliary smooth muscle are involved in this type of environmental myopia. We examine whether an autonomic imbalance could be a precursor to axial elongation and the resulting myopia. Accommodation responses, such as tonic accommodation and nearwork-induced accommodative adaptation, as a function of refractive error, are described in relation to an autonomic imbalance model. The collective results of this research point to anomalous accommodation responses, possibly as a result of underlying anomalous autonomic input to the ciliary muscle, being involved in myopia development and progression.