Correlation between Transient Pupillary Light Reflex and Retinal Function Impairment in Patients with Retinitis Pigmentosa

Purpose. To investigate the relationship between transient pupillary light reflex (PLR) and visual function in patients with retinitis pigmentosa (RP). Methods. A retrospective study was performed with 137 eyes of 73 patients with RP. Transient pupillary light reflex was measured by the vision monitor system (MonColor; Metrovision, France). Dark-adapted transient PLRs were elicited by four specific levels of stimulus luminance (-5, -3, -1, and 0 logcd/m(2), blue or white light). Best-corrected visual acuity (BCVA) was recorded based on Early Treatment Diabetic Retinopathy Study (ETDRS) acuity charts. Fixation stability and retinal sensitivity of radial 10 degrees areas were measured with microperimetry. The retinal sensitivity (RS) was divided into central RS (fovea and radial 1 degrees areas) and peripheral RS (radial 3 degrees and 5 degrees areas from the fovea). The patients were further classified into 2 groups (P1 > 75% and P1 < 75%) according to fixation stability. Spearman's correlation was performed to identify significant associations between BCVA, fixation stability, RS, and PLR. Results. Under the stimuli of the same color light, relative pupillary constriction (RPC), latency, or velocity of constriction in the same patients was statistically different in multiple luminance, respectively. Under the same luminance, blue light induced greater RPC and velocity (except for -3 logcd/m(2)) than white light. Most patients showed varying degrees of threshold elevation and visual function deficiency. Besides, there was a statistically significant difference in the distribution of BCVA, MRS, or fixation stability under different thresholds. The correlation between pupillary constrictive area (PCA) and retinal sensitivity was mainly determined by the peripheral region. Moreover, patients with stable fixation showed a greater correlation between PCA and RS. Conclusion. PLR induced by specific colors and luminance may serve as a promising clinical approach for assessing and monitoring rod function in advanced RP patients.