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Melissa D Bailey, Chiu-Yen Kao, Nidhi Satiani, Loraine T Sinnott; Two patterns of ciliary muscle growth in myopia. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3643.
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To test the hypothesis that more than one ciliary muscle growth pattern is present in human myopia and to determine if each pattern is different from emmetropic ciliary muscle growth.
Children with emmetropia (N = 55, 9.3 ± 1.2 years), myopia (N = 84, 9.2 ± 1.1 years), and hyperopia (N = 46, 8.4 ± 1.4 years) from a longitudinal study were included in analyses. Cycloplegic autorefraction was used to determine spherical equivalent refractive error. Cycloplegic images of the ciliary muscle were obtained with the Visante Anterior Segment OCT and processed with a semi-automatic algorithm to obtain thickness measurements. The thickness of the ciliary muscle at 2 mm posterior to the scleral spur (CMT2) was used to create multilevel growth models of ciliary muscle development for each refractive error group. A cluster analysis, Ward’s method, was used to group the growth curves of myopes into two groups (Myopia 1 and Myopia 2).
The CMT2 growth curve for one myopia group identified by the cluster analysis (Myopia 2) had significantly larger intercept when compared to all other groups (all p ≤ .0001) and a significantly steeper slope when compared to all other groups: emmetropia (β = −12.5, p = 0.03), myopia 1 (β = −16.7, p = 0.002), and hyperopia (β = −23.8, p ≤ 0.0001).
There appear to be at least two different ciliary muscle growth patterns present among children who develop myopia: one that is more similar to the patterns observed in emmetropia or hyperopia and another pattern that is characterized by a larger muscle that increases in thickness at a greater rate than what was observed in all other children. Our future studies will determine if differences in ciliary muscle thickness indicate that human myopia has more than one underlying cause.
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