Use of a digital infrared pupillometer to assess patient suitability for refractive surgery

To assess the role of binocular infrared dynamic pupillometry in measuring and recording the pupil size in scotopic, low mesopic, and high mesopic illumination prior to refractive surgery.

The Rosen Eye Surgery Centre, Alexandra Hospital Victoria Park, Manchester, United Kingdom.

In this prospective study, the pupil sizes of 58 patients (mean age 46 years +/- 11.7 [SD]) presenting for refractive surgery assessment were evaluated using the P2000 SA pupillometer (Procyon Instruments Ltd.). Each patient was measured at 3 illumination levels: 0.02 lux (scotopic), 0.15 lux (low mesopic), and 10.6 lux (high mesopic). At each level, 10 images were acquired by the system at 5 images per second. Both eyes were imaged at the same time, with a spatial accuracy of 0.03 mm per pixel.

Pupillary unrest (PU) occurred at all levels of illumination. Some degree of PU amplitude was observed in both eyes of all patients. The median PU was 0.12 mm (95% confidence limits [CLs], 0.11, 0.14) in the scotopic range, 0.34 mm (95% CLs, 0.28, 0.38) in the low mesopic range, and 0.28 mm (95% CLs, 0.23, 0.30) in the high mesopic range. The degree of anisocoria varied among individuals. The median value was 0.28 mm (95% CLs, 0.21, 0.39) in the scotopic range, 0.32 mm (95% CLs, 0.26, 0.37) in the low mesopic range, and 0.16 mm (95% CLs, 0.12, 0.19) in the high mesopic range. Because of PU and anisocoria, single versus multiple binocular measurements demonstrated the possibility of errors greater than 1.0 mm in some patients.

Patients showed an appreciable degree of pupillary motion during measurement at all levels of illumination; the motion was largest under low mesopic illumination. The 2 pupils were rarely identical. Multiple-measurement binocular pupillometry is better than single monocular measurement to gain a precise description of pupil behavior before refractive surgery.