Multimodal retina examination of patients with CNGA1 retinitis pigmentosa

Abstract

Purpose : Mutations in CNGA1 result in autosomal recessive retinitis pigmentosa (arRP), a rare progressive degenerative disease, leading to blindness.
A detailed clinical observation of the phenotype correlated with the genotype is necessary for the future development of potential treatments.

Methods : Six patients with arRP and mutations in CNGA1 were examined at the University Eye Hospital in Tübingen. This included BCVA, visual field, photopic and scotopic pupil campimetry (CPC), dark adapted chromatic perimetry (DAC), full-field stimulus threshold test (FST) as well as imaging with funduscopy, optical coherence tomography (OCT) and fundus autofluorescence (FA). All six patients were examined at baseline and five patients at follow-up one year later.

Results : The median age of the patients was 46 years (range 38-67 years). The BCVA varied between 20/80 and 20/20 with stable findings at follow up. The kinetic perimetry showed concentric restriction of the visual field in all patients. Scotopic and photopic CPC showed loss of rod function in all patients with good cone function in the morphologically preserved central retinal area. The FST measurements showed increased thresholds for blue and red color, indicating loss of rod function, whereas dark-adapted cone thresholds were unaffected. DAC with blue and red stimuli showed a small central island with preserved rod function in three patients. OCT and widefield FA underlined peripheral degeneration and preserved central retina. OCT findings showed perifoveal loss of outer retinal cells. One patient had macular edema.

Conclusions : CNGA1-linked arRP presents with late-onset, slowly progressive rod-cone degeneration with pronounced loss of rods but well-preserved cone-function into late adulthood. Clinical examination showed stable results within an expected range of variation during a one-year follow up period. Carefully chosen multimodal diagnostics can detect residual rod function in small, morphologically preserved retinal areas of CNGA1-RP patients.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Multimodal retinal examination of a patient with CNGA1-RP showing a tunnel vision with peripheral islands (A, E) corresponding to morphologically preserved central retina (B). Inside the central island a very good cone function with photopic CPC (C) is visible, as well as some preserved rod functionality, as shown with scotopic CPC (D) and dark adapted perimetry (F, showing the threshold differences of red and cyan stimuli).