Dynamics of accommodative facility in myopes

PURPOSE: To evaluate the dynamic changes in refraction during the accommodative facility test in myopes and emmetropes. METHODS: Ten myopes and 10 emmetropes participated in the study. All were young adults, and refractive error in the myopes was corrected with soft contact lenses. Monocular accommodative facility measurements were taken for a 40-cm and a 6-m working distance with +2.00/–2.00-D and Plano/–2.00-D flippers, respectively. Subjective facility was recorded with automated flippers and objective measurements of dynamic accommodation response were simultaneously taken with a photorefractor. RESULTS: Subjective and objective facility measurements showed a significantly lower facility rate in myopes when compared with emmetropes at distance (P < 0.05) but not at near (P > 0.05). The response amplitude of accommodation during facility tasks was found to be similar in the two refractive groups. However, the velocity of accommodation was found to be lower in myopes than in emmetropes for distance facility (P < 0.05) but not for near facility (P > 0.05). Velocity of disaccommodation was lower in myopes than in emmetropes at both distance and near (P < 0.05). CONCLUSIONS: During distance accommodative facility testing, myopes exhibited a lower velocity of accommodation and disaccommodation, which led to a lower distance accommodative facility rate. For near facility measurements, however, although velocity of disaccommodation was lower in myopes, velocity of accommodation was found to be similar in the two refractive groups. A variety of factors that contribute to these differences are discussed.