Comparison of a monocular pupillometer and the pupillometry function of a binocular free-viewing autorefractor.

PURPOSE

To compare a binocular free-viewing autorefractor pupillometer (WAM 5500 Binocular Accommodation Instrument) and a monocular occlusion pupillometer (Neuroptics pupillometer).

SETTING

Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, Texas, USA.

DESIGN

Evaluation of diagnostic test or technology.

METHODS

Normal subjects were tested under 1 lux and 7 lux ambient illumination with controlled distance fixation. The monocular occlusion pupillometer and free-viewing autorefractor pupillometer test order and eye test order were randomized. Devices were compared using Bland-Altman plots. Effects of eye test order and device test order were analyzed. The number of outliers (ie, difference ≥ 0.5 mm between devices) was tabulated.

RESULTS

The mean device difference (monocular pupillometer minus binocular pupillometer) was +0.51 mm ± 0.36 (SD) (range -0.20 to +1.50 mm) in right eyes and +0.27 ± 0.31 mm (SD) (range -0.30 to +1.00 mm) in left eyes at 1 lux and +0.26 ± 0.28 mm (range -0.30 to +0.90 mm) and +0.21 ± 0.24 mm (range -0.80 to +0.40 mm), respectively, at 7 lux. The outlier frequency (N = 49) at 1 lux was 23 (47%) in right eyes and 7 (14%) in left eyes and at 7 lux, 11 (22%) and 10 (20%), respectively. At all age decades, the free-viewing autorefractor underestimated dark-adapted pupil diameter. Eye test order and device order did not cause unidirectional bias.

CONCLUSIONS

The free-viewing pupillometer frequently disagreed with the monocular occlusion pupillometer by more than 0.5 mm. Testing the first eye with the monocular pupillometer did not induce sustained pupillary constriction that might bias results in the second eye.