A quasi-static study of accommodation in amblyopia.

A method named quasi-static recording of accommodation is introduced. While accommodative stimulus (AS) is slowly changed over a wide range with a constant velocity (0.2 D s-1), accommodative response (AR) is continuously measured. AS and AR, respectively, are recorded on the abscissa and the ordinate of an x-y recorder to produce a "quasi-static" response/stimulus curve. This method was applied to 28 monocular amblyopic and formerly amblyopic subjects, and the findings were compared with those from their sound eyes. The recordings and subsequent analysis show reduced accommodative amplitude and reduced accommodative accuracy in amblyopic eyes, similar to those reported in previous static measurements of accommodation. In about a half of the amblyopic eyes, the recordings reveal that the fluctuations of accommodation are greater as the target becomes closer. Increased microfluctuation associated with a loss of sensitivity to change of contrast is discussed. This phenomenon suggests that increased microfluctuation is directly associated with reduced performance. In three recovered amblyopes, the accommodative functions were considerably reduced, while the other 10 subjects showed improved functions. It is suggested that, in some cases, the abnormal accommodation is the cause of the amblyopia.