Two cases of unilateral cone-rod dysfunction presenting in adult females

To describe cases of unilateral cone-rod dysfunction presenting in two middle-aged females.

This case series highlights two middle-aged female patients with progressive visual decline in one eye. Fundus photography, fundus autofluorescence (FAF), spectral-domain optical coherence tomography (SD-OCT), multi-focal electroretinogram (mfERG), full-field electroretinogram(ffERG), and genetic testing were obtained.

In the first patient, mfERG showed an extinguished response and ffERG demonstrated markedly reduced a-wave and b-wave amplitudes (more pronounced under photopic conditions) in the right eye. SD-OCT showed attenuation of the ellipsoid zone of the right eye. Similar findings were appreciated in the second patient. Genetic testing in the first patient identified three heterozygous variants in PRPH2, RCBTB1, and USH2A. The second patient was found to have heterozygous variants in BBS1 and ABCA4.

These two cases add to the literature of case reports of unilateral cone-rod and rod-cone dystrophies. However, the underlying etiology of the unilateral pattern of cone-rod dysfunction and the significance of the heterozygous mutations found in both cases remains uncertain.