Measurement of pupillary unrest in eyestrain

Using a computer-assisted infrared optometer with a pupillometer, we studied pupillary unrest in 20 eyes of 20 patients suffering from eyestrain, and 20 eyes of normal controls. The eyestrain patient group had smaller mean pupil area than the control group (29 mm2 vs 38 mm2; P < 0.01); showed prominent pupillary unrest, and had an increased mean coefficient of variation (CV) of the pupil area (9.2% vs 3.4%; P < 0.001). Long-duration waves of pupillary unrest (> 1 second) were frequently recorded in this group, but not in the control group. The patient group also had a significantly higher dark focus of accommodation than the control group (1.1 D vs 0.4 D; P < 0.01). These findings suggest that abnormal parasympathetic excitation of the iris and/or ciliary muscle may be a factor in the etiology of eyestrain.