Bilateral Symmetry of Visual Function Loss in Cone–Rod Dystrophies

Abstract

PURPOSE.To investigate bilateral symmetry of visual impairment in cone-rod dystrophy (CRD) patients and understand the feasibility of clinical trial designs treating one eye and using the untreated eye as an internal control.METHODS. This was a retrospective study of visual function loss measures in 436 CRD patients followed at the Ophthalmology Department of the Catholic University in Rome. Clinical measures considered were best-corrected visual acuity, focal macular cone electroretinogram (fERG), and Ganzfeld cone-mediated and rod-mediated electroretinograms. Interocular agreement in each of these clinical indexes was assessed by t-and Wilcoxon tests for paired samples, structural (Deming) regression analysis, and intraclass correlation. Baseline and follow-up measures were analyzed. A separate analysis was performed on the subset of 61 CRD patients carrying likely disease-causing mutations in the ABCA4 gene. RESULTS.Statistical tests show a very high degree of bilateral symmetry in the extent and progression of visual impairment in the fellow eyes of CRD patients.CONCLUSIONS. These data contribute to a better understanding of CRDs and support the feasibility of clinical trial designs involving unilateral eye treatment with the use of fellow eye as internal control.

Central Retina Functional Damage in Usher Syndrome Type 2: 22 Years of Focal Macular ERG Analysis in a Patient Population From Central and Southern Italy

“…[23][24][25] The present retrospective analysis of fERG responses in USH2 patients showed that fERG amplitude is already significantly (40%) reduced with respect to control subjects at the beginning of the second decade of life, when visual acuity and Goldmann visual field are still normal. Moreover, fERG rapidly declines, reaching 25% of that of control subjects by approximately 25 years of age.…”

“…19 In previous studies, we used fERG to estimate the rate of central cone function decay in different subtypes of RP, 23 and in patients with cone dystrophy. 24,25 Here, in a retrospective study, we present the evaluation of central cone function by f ERG in a cohort of 47 patients with USH2. Rather than focusing on the relative decay rate, as we did in the past, 23 we evaluated the absolute values of fERG measures and their decrease with age, comparing such decrease with changes in visual acuity and Goldmann kinetic perimetry V4e.…”

Early impairment of the full‐field photopic negative response in patients with Stargardt disease and pathogenic variants of the ABCA4 gene

“…BCVA was determined for each eye using Snellen chart. In agreement with previous studies was used, the logarithm of the Minimal Angle of Resolution (logMAR) for visual acuity fractions to minimize non‐normality …”

“…The baseline to peak rod B‐wave amplitude was measured. The amplitude of the A‐ and B‐ waves were measured as described …”

“…All measures were obtained monocularly on each eye for each patient. Only data from the left eye of both ABCA4 ‐RD patients and controls were used for the analysis to avoid data redundancy, as measures in the two eyes are known to be highly correlated . Correlation analysis between PhNR amplitude and other test outcomes was performed only when these latter measures were obtained within a maximum of 6 months from the PhNR recordings.…”