Repeatability and clinical use of pupillary light reflex measurement using RAPDx® pupillometer

To evaluate the repeatability of pupillary light reflex metrics measured by the RAPDx® dynamic pupillometer in healthy subjects and clinical application in patients with unilateral optic neuritis (ON).

Sixty eyes of 30 healthy volunteers were measured three times consecutively by the same technician. The amplitude of constriction (AC), the latency of constriction (LOC), the velocity of peak constriction (VC) of light-evoked pupillary constriction, RAPD score for amplitude and latency were measured using RAPDx® dynamic pupillometer. The repeatability of above metrics was assessed by the intraclass correlation coefficient (ICC) and coefficient of variation (Cov). Furthermore, pupillary light reflex measurements were performed in 48 eyes of 24 patients diagnosed with unilateral optic neuritis (ON). Interocular symmetry was evaluated both in the healthy subjects and the ON-involved patients.

High repeatability of AC, LOC, and VC in healthy subjects was displayed, presenting with the ICC value over 0.80 and the Cov less than 8.00%. But the RAPD score for amplitude (ICC: 0.67) and RAPD score for latency (ICC: 0.65) showed only moderate repeatability. Furthermore, a slight declining trend was found in amplitude and peak velocity when continuous and multiple measurements in the healthy subjects. Good symmetry of the AC, LOC, and VC of pupillary light constriction between the two eyes was displayed in the healthy subjects (P > 0.05). By contrast, there was a distinct decrease of AC and VC (P < 0.01), and a mild increase of LOC (P < 0.01) in the ON-involved eye in direct pupillary light reflex.

Pupillary light reflex measured by the RAPDx® pupillometer achieved overall good repeatability and interocular symmetry in healthy subjects. The device also presented decent preliminary results in patients with unilateral ON, suggesting its potential value to be developed as a tool in optic nerve diseases.