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Dario Marangoni, Marco Piccardi, Angelo Minnella, Matteo Bertelli, Dario Degiorgio, Monia Zuntini, Silvia Bisti, Benedetto Falsini; Interocular Difference and Interocular Correlation in Visual Acuity and Focal Macular Electroretinogram in Stargardt Disease Patients with an ABCA4 Genotype. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1367.
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To determine, in Stargardt disease (STDG) patients with an ABCA4 genotype, the interocular difference (ID) and interocular correlation (IC) in visual acuity (VA) and macular focal electroretinogram (fERG).
Forty STDG patients (age 10 - 78 years) with an established ABCA4 genotype were enrolled in the study. VA (log10) was assessed with a calibrated, retro-illuminated Snellen chart. FERGs were recorded in response to a 18 deg flickering (41 Hz) field presented to the central retina over a light adapted Ganzfeld background. Amplitude (log10) of the Fourier-isolated fERG fundamental harmonic was measured. ABCA4 allele severity was graded according to Cidecyian et al.1
Patients’ VA ranged (-2) - (0). Mean ID in VA was -0.003 (± 0.57 SD). VA ID tended to be largest when the best eye VA ranged (-0.3) - (0). There was a positive IC in VA (r = 0.45, p < 0.01). Patients’ fERG amplitude ranged (-1.2) - (0.4). Mean ID in fERG amplitude was 0.008 (± 0.24 SD). fERG amplitude ID tended to be largest when best eye amplitude ranged (-0.8) - (0). There was a positive IC in fERG amplitude (r = 0.7, p < 0.001). ID and IC for both VA and fERG amplitude were independent of ABCA4 allele severity.
VA and macular fERG of STDG patients with an VA and macular fERG of STDG patients with an ABCA4 genotype display large IDs. IC could account for only a limited part of uniocular measurement variances. Knowledge of ID and IC in macular function parameters may be important to select STDG patients with similar macular function in both eyes, for clinical trials based on uniocular therapeutic interventions. 1Cideciyan AV et al. ABCA4 disease progression and a proposed strategy for gene therapy. Hum Mol Genet. 2009 Mar 1;18: 931-941.
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