To investigate the effect of over-correction for myopia on the accommodative function of the human eyes.

16 patients (30 eyes) with over-corrected myopia in optometry clinic of Beijing Tongren Eye Center from Jan. 2010 to Jun. 2014 were selected and analyzed retrospectively, including 10 males (19 eyes) and 6 females (11 eyes). The average ages were (23.7±7.2) years-old with a range from 14 to 38 years. All the patients accepted examination of visual acuity, objective refraction, cycloplegic refraction, spectacle lenses test and subjective accommodative amplitude (AA) test, the over-corrected myopic patients were divided into groups according to the reduction in subjective AA test, the objective insufficiency of accommodation, the abnormality of objective accommodative measurement and the increase in HFC of accommodative micro-fluctuations. The distribution of age was described by mean± standard deviate. The number and distribution in different groups were described by the number of eyes and percentage. McNemar paired Chi-square test was used to compare the proportion of patients with over-correction of myopia differences among the group of reduction in subjective AA test, objective insufficiency of accommodation, abnormality of objective accommodative measurement and the group of increase in high frequency component (HFC) of accommodative micro-fluctuations. The Kappa coefficient of agreement was analyzed for the consistency of the group of reduction in subjective AA test, abnormality of objective accommodative measurement and increase in HFC of accommodative micro-fluctuations.

Among the 16 patients (30 eyes) with over-corrected myopia, 8 cases (11 eyes) accounting for 36.7% (11/30) were normal in the subjective AA test, and 11 cases (19 eyes) accounting for 63.3% (19/30) were reduced in the subjective AA test. In the objective accommodative function test, 6 cases (7 eyes) accounting for 23.3% (7/30) were normal, and 13 cases (23 eyes) accounting for 76.7% (23/30) were abnormal, in which 3 cases (3 eyes) accounting for 10.0% (3/30) with single objective accommodative insufficiency, 1 case (2 eyes) accounting for 6.7% (2/30) with single objective accommodative excess, 4 cases (7 eyes) accounting for 23.3% (7/30) with single objective accommodative strain and 1 case (2 eyes) accounting for 6.7% (2/30) with single objective accommodative spasm, 4 cases (7 eyes) accounting for 23.3% (7/30) with objective accommodative insufficiency and accommodative strain and 1 case (2 eyes) accounting for 6.7% (2/30) with objective accommodative insufficiency and accommodative spasm. The sum of all the objective accommodative strain was 7 cases (14 eyes) accounting for 46.7% (14/30). The sum of all the objective accommodative insufficiency was 8 cases (12 eyes) accounting for 40.0% (12/30). The sum of all the increase in HFC of accommodative micro-fluctuations was 8 cases (18 eyes) accounting for 60.0% (18/30). The comparison between the group of subjective AA test and the group of objective insufficiency of accommodation by McNemar paired Chi-square test showed statistically significant difference (χ²=5.143, P<0.05). The comparisons between the group of subjective AA test for abnormality of objective accommodative measurement and increase in HFC of accommodative micro-fluctuations by McNemar paired Chi-square test did not show statistically significant differences, respectively (χ²=2.250, 0.000; P>0.05). After using Kappa analysis, the agreement between the group of subjective AA test and increase in HFC of accommodative micro-fluctuations was weak (κ=0.366, P<0.05). The agreement between the group of subjective AA test and abnormality of objective accommodative measurement was significant (κ=0.689, P<0.05).

This small sample retrospective clinical case series showed that patients of over-corrected myopia had accommodative dysfunction, in which accommodative insufficiency and accommodative strain were the most common types. The objective accommodative analyzer can objectively and quantitatively evaluate the cases of over-corrected myopic asthenopia. According to the significant agreement between the group subjective AA test and objective accommodative function measurement, the subjective AA test might be regard as a practical screening indicator for the following detailed objective accommodative functional measurement in the cases of asthenopia with over-corrected myopia.