Evaluation of pupil responses to local stimuli in Patients with retinitis pigmentosa caused by USH2A mutations

Abstract

Purpose : This study is intended to explore progression and current status of patients suffering from retinitis pigmentosa caused by bi-allelic USH2A mutations. The existing FFB CRI RUSH2A protocol was amended by local ethics committee and expanded with pupil campimetry in order to establish functional read out parameters regarding local rod and cone function in the central 30 degrees visual field.

Methods : Nine patients, 6 females and 3 males in the age of 16 to 45, with USH2A mutations underwent gaze-controlled pupil-campimetry. Two campimetry protocols were used, one for the detection of rod responses and one for the cone responses. The first uses 5 degree stimulus with 0.01cd/sm and 2,1x10^-8W/sm, wavelength peak at 460nm with half-width of 30nm and 100ms stimulus duration. In the cone protocol stimuli size was 3 degree with 60 cd/m2 1,7x10^-5W/sm, wavelength peak 620 with half-width 30nm and 1sec duration. Both protocols presented the stimuli in the central 30 degrees visual field at 33 and 41 different positions respectively.

Results : The rod evaluation showed a residual activity in 8 subjects with a maximum relative amplitude of 7% in the 16 years old subject. There was a statistically significant correlation of relative maximum amplitude with age (p=0.049 and r= -0.67).
Cone activity was preserved in all patients within the macula region. To quantify the functional output the volume of responses as a summarized function over all 41 stimuli was calculated. The volume correlated statistically significant with age (p=0.037, r= -0.69). The size of peripheral scotoma was correlated with age, except in one young patient.

Conclusions : Pupillographic campimetry as a diagnostic tool is able to provide information about rod and cone function objectively.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.