Correlations of Full-Field Stimulus Threshold With Functional and Anatomical Outcome Measurements in Advanced Retinitis Pigmentosa

Purpose: To compare full-field stimulus (FST) threshold values to conventional functional and anatomical measures commonly used in clinical practice.

Design: Cross-sectional study.

Methods: Patients with retinitis pigmentosa with nondetectable electroretinogram rod-mediated responses and light-adapted 3.0 cd·s·m² 30-Hz flicker (LA 3.0 flicker) amplitudes of 15 mV or less were included in this study. The threshold values for blue, white, and red stimuli on FST were correlated with best-corrected visual acuity, LA 3.0 flicker amplitude and implicit times, length of the ellipsoid zone (EZ) band and thickness of outer nuclear layer measurements on optical coherence tomography, and the vertical and horizontal diameters of the autofluorescent ring on autofluorescence imaging.

Results: Forty-two eyes of 21 patients were included in the study. The mean FST thresholds were -22.5 ± 15.5 dB, -17.6 ± 11.5 dB, and -12.7 ± 6.0 dB for the blue, white, and red stimuli, respectively. The threshold values for the 3 FST stimuli were significantly correlated with selected functional and anatomical outcome measures. Specifically, they were strongly correlated with LA 3.0 flicker amplitude and EZ band length measured on optical coherence tomography. Using linear regression, blue and white stimulus values on FST were found to be predictive of EZ band length (R² = 0.579 and 0.491, respectively), and the vertical (R² = 0.694 and 0.532, respectively) and horizontal (R² = 0.626 and 0.400, respectively) diameters of the hyperautofluorescent ring.

Conclusions: The significant correlations between FST and other clinical outcome measures highlight its potential as an adjunct outcome measure.