Objective: The aim of this study was to compare the accuracy and the reproducibility of scotopic pupil measurements using 2 different methods.
Methods: Scotopic pupil diameter was measured in 56 eyes of 28 volunteers and the results were compared between the green light test at the slit lamp (Haag-Streit, Switzerland) and the automatic measurements of the wave-front analyser WASCA (Carl-Zeiss-Meditec) by 2 independent examiners. Non-parametric sign test as well as All Pairwise Multiple Comparison Procedures (Student-Newman-Keuls method) were performed for the comparison of means for each individual eye as well as the results of both eyes tested by both examiners.
Results: Mean age of the subjects was 34.9 years. The colour of iris was green or blue in 22 cases and brown in 6 cases. REPRODUCIBILITY: For the green light test we found for the first investigator in the right eye a mean pupil diameter of 6.58 mm (SD 0.68). The measurement of the second investigator for the same eye was 6.64 mm (SD 0.61). The left eye values were as follows: 6.36 mm (SD 0.68) and 6.75 mm (SD 0.68). For WASCA we found for the first investigator in the right eye 6.33 mm (SD 0.64) vs. 6.30 mm (SD 0.64) for the second investigator, in the left eye 6.39 mm (SD 0.69) vs. 6.36 mm (SD 0.60). There was a statistically significant difference between the two investigators when the green light test was used (6.47 mm vs. 6.69 mm for both eyes). No difference was found using the WASCA integrated pupillometer (6.35 mm vs. 6.33 mm). There was a significant difference between the means of combined data for both measurement methods: 6.58 mm for the green light test (SD 0.57) vs. 6.34 mm for WASCA (SD 0.62).
Conclusions: The integrated pupillometry of the WASCA analyser showed better reproducibility of measurements than the green light test. The green light test measures a slightly larger diameter (in the mean by 0.25 mm) than WASCA. Because of the fair and clinically sufficient reproducibility as well as virtually non-existing additional costs the green light test can be strongly recommended to referring ophthalmologists and low-volume refractive surgeons.