Abstract
Abstract: :
Purpose: The accommodation response and accommodative vergence of subjects with emmetropia (EMM), stable myopia (SM) and progressive myopia (PM) were measured in this study. We compared the difference of these parameters between the three groups in order to evaluate the effect of accommodation, vergence, and their interaction on the development of myopia. Methods: 38 subjects, including 16 EMM, 13 SM, and 9 PM, participated in this study. The accommodative response (AR) was measured with an autorefractor (Grand Seiko WV–500) from the subject's right eye when the eye was fixating at a monocular target formed by a 3x3 array of 20/100 Snellen letters. The accommodative vergence (AC) was measured subjectively with a device which combined a Risley prism with Maddox rods in front of the subject's left eye while the right eye was viewing the target. The accommodative response and accommodative vergence were measured at three stimulus levels (1D, 2D, and 3D). From each subject's AR/AS slope and AC/AS slope, we were also able to estimate the subject's AC/A ratio. One–way ANOVA was used for data analysis.Results: At 1D stimulus level, there was no significant difference in accommodative response between the three groups (p>0.05). At 2D and 3D stimulus levels, the accommodative responses of PM (0.86 ± 0.28 D, 1.55 ± 0.32 D) were lower than that of EMM (1.11 ± 0.31 D, 1.91 ± 0.51 D) (p < 0.05). For the AR/AS slope, PM (0.59 ± 0.14) was lower than EMM (0.77 ± 0.18) (p < 0.05) while SM (0.72 ± 0.19) showed no significant difference from PM and EMM (p > 0.05). For the AC/AS slope (Prism diopter/D), PM (3.85 ± 0.86) was higher than EMM (3.14 ± 0.82) (p < 0.05) while EMM showed no significant difference from SM (2.62 ± 1.15). For the AC/A ratio (Prism diopter/D), PM (6.67 ± 1.95) was higher than both EMM (4.30 ± 1.65) and SM (4.09 ±2.45) (p < 0.01) while there was no significant difference between EMM and SM.Conclusions: The lower AR/AS slope and higher AC/AR ratio in PM were due to the fact that they had lower accommodative responses and higher esophorias in higher accommodative demands. This result suggests that both accommodation and accommodative vergence affect the development of myopia.
Keywords: myopia • eye movements • refractive error development