An objective study of negative accommodation

Abstract

Purpose: to study the dynamic refraction of myopic eyes at the time when the object is fixed in an open field at a distance of 5 m and determine habitual accommodation tone (HAT) in an open field. Material and methods. 130 patients (260 eyes) aged 6 to 23 years (ave. 11.26 ± 0.2 years) with an average refraction spherical equivalent of -4.16 ± 0.13 D were divided into 4 groups, depending on the degree of myopia. The HAT was measured by an automatic binocular open field (OP) autorefkeratometer Grand Seiko WR-5100K (Japan), while the HAT according to Yuri Rosenblum was determined by a conventional autorefractometer Nidek. Results. Comparing noncycloplegic and cycloplegic refraction using the two devices, we obtained different results. In the first case, we found the maximal difference of -0.15 D (-4.38 – (-4.23)), and in the second case, the minimal difference of -0.09 D (-4.16 – (-4.07)). Over the whole group, HAT according to Yuri Rosenblum averaged -0.21 ± 0.02 D. In patients with low myopia HAT was the highest and averaged -0.33 ± 0.03 D. In patients with moderate myopia an average HAT level was -0.23 ± 0.03, and in high myopia it was -0.19 ± 0.04 D. Patients with anisomyopia showed a significant difference of the tone between the fellow eyes: the eyes with lower refraction showed a HAT of -0.21 ± 0.03 D, while for the worse eye it was 0.06 ± 0,11 D (p < 0.05) (i.e. a negative accommodation tone). Over the whole contingent HAT OP averaged -0.17 ± 0.02 D: in patients with low myopia it averaged -0.22 ± 0.04 D, in those with moderate myopia, -0.27 ± 0.02 D, in high myopia — -0.09 ± 0.04 D. PTA OP patients with anisomyopia averaged -0.07 ± 0.03 D and demonstrated a significant difference between the eyes (-0.26 ± 0.03 D for the better eyes and 0.12±0.06 D — for the worse eyes, p < 0.01). A negative tone of accommodation of HAT OP in myopia occurs, on average, in 30% of patients; the frequency was maximal in high myopia (50 %) and minimal in moderate myopia (13.8 %). Conclusions. Objectively determined the weakening of the far dynamic refraction as compared with the static refraction (in terms of cycloplegia) was objectively determined. Thus, the existence of negative accommodation was confirmed.