Purpose: To investigate the morphology of the ciliary muscle during the act of accommodation in a population of children.
Methods: Thirty children ages 6 to 12 years were enrolled. Measurements were taken on the right eye only. Accommodative response was measured through habitual correction. Height and weight were measured as control variables. Central axial length was measured with the IOLmaster. Four images of the temporal ciliary muscle were taken with the Visante OCT at three different stimulus levels (0D, 4D, 6D) while accommodative response and pupil size were monitored concurrently with the PowerRefractor. Accommodative response monitoring was time- matched to ciliary muscle image capture, and the mean was calculated for five seconds surrounding this time point. Four cycloplegic images of the temporal ciliary muscle were also taken.
Results: Increased accommodative response was correlated with increases in the thickness of CMTmax (p=<0.001) and CMT1 (p=lt;0.001), and decreases in the thickness of CMT3 (p=<0.001). Thicker values of CMTmax under cycloplegic conditions were significantly correlated with values of CMTmax (p=<0.001) and CMT1 (p=0.001) while accommodating, and approached significance in modeling CMT3 (p=0.06). Mean axial length was correlated with the amount of thinning at CMT3 with accommodation (p=0.002). Axial length was not significantly correlated with thickness values at CMTmax (p=0.7) or CMT1 (p=0.6). No significant coefficients were found for modeling CMT2.
Conclusions: Knowledge of the accommodative response is important when analyzing ciliary muscle thickness in vivo because it is correlated with ciliary muscle thickness at CMTmax, CMT1, and CMT3. Further investigation is necessary to determine if significant factors for modeling CMT2 exist or if there is a “fulcrum” point along the length of the ciliary muscle where the net change with accommodation is always zero.