Chromatic pupillometry for assessment functional rod and cone patterns in Usher syndrome patients

Abstract

AbstractPurpose The aim of the study was to characterize the functional rod and cone patterns using chromatic pupillometry in Usher syndrome patients.Methods Prospective case series study enrolled 45 Usher syndrome patients. All patients underwent in‐depth phenotypic examination. Functional rod and cone patterns were obtained using custom‐made chromatic pupillometer(AMTech, Dosenheim, Germany). Pupil diameter was recorded monocular in response to red (640 nm) and blue (462 nm) light stimuli for varied intensity levels (ranged from 1000 cd/m2 to 0.001cd/m2). Response amplitudes were analyzed and compared to the clinical phenotype.Results Pupil responses to rod‐ and cone‐weighted stimulation were significantly diminished in all Usher syndrome patients for all intensity levels (mean decrease 60% and 30%, respectively p<0.001). Lower rod‐weighted responses were related with decreased b‐wave amplitude in full field ERG (r=0.37,p<0.001). Decreased cone‐weighted responses were correlated with diminished photopic ERG b‐wave amplitude (r=0.43,p<0.001) and mfERG amplitudes (r=0.65,p<0.001). Higher cones‐weighted responses were associated with preserved cone mosaic in adaptive optics and presence of inner/outer segment in optical coherence tomography, although not always related with preserved visual field and visual acuity. Rod‐ and cone‐weighted responses were recordable even in a very advanced Usher syndrome cases associated with abolished ERG.Conclusion Chromatic pupillography is an objective tool to assess functional rod and cone patterns in Usher syndrome, which potentially could be used as an outcomes measure to assess safety and efficacy in therapy trials, in particularly in advanced cases.