The influence of age, refractive error, visual demand and lighting conditions on accommodative ability in Malay children and adults

Purpose: Near work, accommodative inaccuracy and ambient lighting conditions have all been implicated in driving the myopic development mechanism. However, difference in accommodative responses with age and refractive error under different visual conditions remain unclear. This study explores differences in accommodative abilities and refractive error when exposed to differing ambient illumination and visual demands in Malay schoolchildren and adults. 
Methods: Sixty young adults (21-25 years) and sixty school children (8-12 years) were recruited. Accommodative lag and accommodative fluctuations at far (6 m) and near (25 cm) were measured using the Grand Seiko WAM-5500 open field autorefractor. The effect of mesopic room illumination on accommodation were also investigated. 
Results: Repeated measures ANOVA indicated that accommodative lag at far and near was significantly different in school children and young adults (F(1.219, 35.354) = 11.857, p < 0.05) with post hoc tests using the Bonferroni correction determined that at near, there was a greater lag in school children (0.486 ± 0.181 D) than young adults (0.259 ± 0.209 D, p < 0.05). Repeated measures ANOVA also determined that accommodative lag differed statistically at near demands between non-myopic group and the myopic group in young adults and school children (F(3.107, 31.431) = 12.187, p < 0.05). Post hoc tests using the Bonferroni correction showed that accommodative lag at near was significantly greater in myopic school children (0.655D ± 0.198D) compared with non-myopic school children (0.202D ± 0.141D, p < 0.05) and myopic young adults (0.316D ± 0.172D, p < 0.05), but no significant difference between myopic young adults (0.316D ± 0.172D) and non- myopic young adults (0.242D ± 0.126D, p > 0.05). Accommodative lag and fluctuations were greater in mesopic room conditions for all ages [all p < 0.05].
Conclusion: Greater accommodative lag was found in myopes compared to emmetropes, school children compared to adults and in mesopic compared to photopic conditions. Accommodative fluctuations were greatest in myopes and in mesopic conditions. These results suggest that differences exist in the amount of blur experienced by myopes and non-myopes at different ages and in different lighting conditions.