gms | German Medical Science

Purpose: The purpose of this study was to evaluate the average pupil diameter (PD) in a large population of 1000 eyes of refractive surgery candidates and the change of PD from scotopic to low and high mesopic illumination. Moreover, we assessed the effect of age, Spherical Equivalent (SE), Mean Keratometry (MK), horizontal corneal diameter (white-to-white, WTW), anterior chamber depth (ACD) and axial length (AL) on PD respectively.

Methods: Pupillometry was performed using a P2000 SA pupillometer (Procyon Instruments Ltd.) All measurements were performed at approximately the same time of day and after 10 minutes of physical and emotional relaxation. Before each measurement, patients waited for 15 minutes in a dimly lit room with dark sunglasses (6706A, Dioptics Medical Products), after which they were seated for another 5 minutes in the testing room with 1 lux ambient illumination before pupil size was assessed. The pupillometry was performed at three illumination levels of 0.04 lx (scotopic), 0.4 lx (low mesopic) and 4.0 lx (high mesopic).

Results: A significant direct correlation between MK and ACD and PD at all illumination levels (p <0.05) was measured and as expected, there was a reverse correlation between age and PD at all levels (p <0.05). At scotopic illumination level, the PD decreased by a mean of 0.027 mm per year with age increase, decreased 0.074 mm per 1 dioptric value with increase of MK and increased significantly by a mean of 0.918 mm per 1 mm increase of ACD. These correlations could be detected at all illumination levels with a mean deviation of (± 8.91%).

Conclusions: In summary, pupil diameter is highly correlated with mean keratometry and anterior chamber depth in a direct manner and indirectly with age. Meanwhile, it was not correlated to gender, spherical eEquivalent (SE), horizontal corneal diameter (white-to-white, WTW) and axial length (AL)