Long-term retinal imaging of a case of suspected congenital rubella infection

Many retinal disorders present with pigmentary retinopathy, most of which are progressive conditions. Here we present over nine years of follow up on a case of stable pigmentary retinopathy that is suspected to stem from a congenital rubella infection. Parafoveal cone photoreceptors were tracked through this period to gain insight into photoreceptor disruption in this pigmentary retinopathy.

The patient was examined at 8 visits spanning a total of 111 months. Examination at baseline included clinical fundus examination, full-field electroretinography (ERG), kinetic visual field assessment (Goldmann), and best corrected visual acuity; all of these except ERG were repeated at follow up visits. Imaging was performed with fundus photography, spectral-domain optical coherence tomography (SD-OCT) and confocal adaptive optics scanning light ophthalmoscopy (AOSLO). For the latter four time points AOSLO imaging also included split-detector imaging.

There were no defects in hearing or cardiac health found in this patient. There were minimal visual deficits found at baseline, with mild rod suppression on ERG; best corrected visual acuity was 20/25 OD and 20/20 OS at baseline, which was stable throughout the follow-up period. Retinal thickness as measured by OCT was within the normal range, though foveal hypoplasia was present and outer nuclear layer thickness was slightly below the normal range at all time points. Cone density was relatively stable throughout the follow-up period. A number of cones were non-reflective when observed with confocal AOSLO imaging and density was markedly lower than expected values (foveal cone density was 43,782 cones/mm² on average). Genetic analysis revealed no causative variations explaining the phenotype.

This patient appears to have a stable pigmentary retinopathy. This case is likely due to a congenital insult, rather than progressive retinal disease. This finding of stability agrees with other reports of rubella pigmentary retinopathy. Imaging with AOSLO enabled observation of two notable phenotypic features. First is the observation of dark cones, which are seen in many retinal disorders including color vision defects and degenerative retinal disease. Second, the cone density is well below what is expected - this is especially interesting as this patient has near-normal visual acuity despite this greatly decreased number of normally-waveguiding cones in the fovea.