Progression in Stationary Cone Dysfunction? Clinical and Electrophysiological Evaluation in Patients With Mutations in the CNGA3–, CNGB3–, GNAT2 Genes (Rod Monochromacy) or the Red/Green Opsin Gene Cluster (Blue Cone Monochromacy)

Abstract

Abstract: : Purpose:To report on the functional findings in patients with either rod monochromacy (RM) or blue cone monochromacy (BCM) with established molecular genetic mutations. Methods: Retrospective analysis of functional evaluation (full–field electroretinography (ERG; ISCEV standard)), visual field and color vision testing) in 15 RM patients associated with mutations in the CNGA3–, CNGB3– or GNAT2 genes and 9 BCM patients associated with mutations in the red/green opsin gene cluster. Results: All 24 patients presented with severely reduced visual acuity. In the electroretinogram residual cone responses were detected only in 2 BCM patients. Dark–adapted ERG recordings were variable, however, amplitudes of rod–dependent responses were reduced in 8 RM patients and 6 BCM patients. The majority of patients (11 RM and 6 BCM) had retinal abnormalities on ophthalmoscopy. 4/5 BCM patients older than 25 years had dystrophic alterations in the macula. Four RM patients and 2 BCM patients reported subjective disease progression. In 2 RM patients disease progression was observed with either ERG or visual acuity and visual field testing. Conclusions:Functional deficits in the rod system as well as abnormalities of retinal morphology were observed in the majority of the patients with RM and BCM. Although both disorders are regarded as stationary, in some patients progression may occur. BCM patients should be cautioned that macular dystrophy may develop in adults older than 30 years.

Keywords: retinal degenerations: hereditary • electroretinography: clinical • genetics