Abstract
Purpose: :
To compare measurements of pupil sizes made under mesopic room lighting and with a HAAG-STREIT P3000 USB Pupillometer.
Methods: :
10 eyes (5 subjects) were measured by two operators for pupil size under mesopic light condition with a lab setup and with the HAAG-STREIT P3000 USB Pupillometer. With the lab setup images of the eyes were captured by an infrared video camera with telecentric optics at 7 Lux room lighting. Pupil size was evaluated by measurement horizontally and vertically and calcuation of the mean pupil size for each eye. The measurement with the P3000 was made with mesopic lighting with 7 Lux (measured). The P3000 automatically calculated the pupil size as the mean diameter of 5 measurements within 1000 milliseconds. The pupil detection was assessed by the operators and frames with poor pupil fits were excluded from the calculation.
Results: :
The mean pupil size as measured by the lab setup was 5.6mm and using the P3000 4.0mm. The mean difference of pupil size between these methods was 1.6mm ± 0.47 (SD). In all cases the measured pupil size in lab setup was larger than with the P3000 with a minimum of 0.8mm and a maximum of 2.3mm. The difference is highly significant, with P=0.006.
Conclusions: :
These results give evidence that there is a difference between pupil size measurements made using a lab setup with indirect room lighting and those made with a HAAG STREIT P3000 USB pupillometer. Further investigations are needed to identify the reason for this difference. The difference between direct and indirect lighting or the bandwidth of the lighting may be important factors. This is of high clinical relevance because mesopic room lighting is the physiological situation that is intended to be simulated with automated pupillometry.
Keywords: pupil • pupillary reflex • neuro-ophthalmology: diagnosis