Pupillometric quantification of residual rod and cone activity in patients with visual loss due to Leber congenital amaurosis

Abstract

AbstractPurpose Leber congenital amaurosis (LCA) is a group of genetically heterogeneous retinal dystrophies in which severe visual impairment occurs at infancy or during early childhood. We describe the threshold response function of rods and cones, as determined from pupil responses to colored light stimulation over a range of intensities, in 4 patients with LCA with different gene mutations who each had very poor visual function and non‐recordable ERG.Methods Four subjects with LCA and 10 control subjects underwent computerized pupillography under conditions of dark adaptation. The pupil response to a 1 second red (640 ± 10nm) and blue (467 ± 17nm) Ganzfeld light from ‐4.0 to 2.0 log cd/m2 was recorded continuously. Pupil responses to low light intensities were used to define the response curve of rods and the rod threshold for blue and red light. When rod‐related pupil responses were absent, those obtained from red light stimulation at brighter intensities could be used to estimate cone activity.Results A rod‐related pupil response curve was still preserved and defined in only one patient (RDH mutation) using blue light and the repsonse threshold was ‐3.1 log cd/m2 . This was almost 2 log‐units greater than the mean value in normal eyes (‐4.9 log cd/m2 blue light). Residual cone activity in all 4 LCA patients yielded response thresholds of ‐2.3, ‐0.9, ‐0.8 and ‐2.1 log cd/m2.Conclusion Pupillometry can estimate residual function and threshold responses of rods and cones in advanced stages of LCA. As such, pupillometry expands the dynamic range of photoreceptor activity that can be objectively monitored, either to follow natural progression or to assess effects of intervention. Commercial interest