Effect of fixation distance, luminance and target on accommodative response in children with early stage myopia

Objective To study the effects of fixation distance luminance and target stimnulus on the accommodative response (AR); to explore the latent effect of these visual environmental factors on the onset and development of myopia.Methods This was a cross-sectional comparative study.The AR of myopic children wearing their best-corrected trial lenses was measured under different fixation conditions that included various distances luminance and word/picture targets.An SRW-50001K infrared autorefractor was used for measurements and AR was then calculated.Results One hundred sixty-eight myopic children were measured successfully and showed an accommodative lag (AL) under all conditions.The ALs of the fixation points of 6 m,1/2 m,1/3 m,1/5 m were -0.19±0.44 D,0.67±0.41 D,0.75±0.55 D,0.93±0.57 D,respectively (F=13.53,P＜0.01).The ALs for a 1/3 m fixation point on word targets under luminances of 173 lx and 5 lx were 0.79±0.35 D and 0.90±0.33 D (t=-2.87,P＜0.01),respectively.The ALs for a 1/3 m fixation point on the target of pictures and words were 0.71±0.37 D and 0.78±0.29 D (t=46.00,P＜0.05),respectively.Conclusion A lower luminance or shorter distance can both increase accommodative lag and words can induce greater accommodative lag than pictures.This study implies that improving these visual environmental factors may slow the onset and progression of myopia. Key words: Fixation distance; Luminance;  Target;  Accommodation response;  Accommodation Lag;  Myopia