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Benedetto Falsini, Marco Piccardi, Lucia Ziccardi, Antonello Fadda, Angelo Minnella, Dario Marangoni, Silvia Bisti, Giovanni Resta, Lucia Galli Resta; Long-Term Decay of Central Cone Function in Cone-Rod Dystrophy Evaluated by Focal Electroretinogram. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5110.
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To describe the natural history of cone-rod dystrophy (CRD) as determined by longitudinal focal ERG (fERG) recording, and determine the usefulness of fERG in monitoring and anticipating CRD progression.
A cohort of 35 CRD patients (17 males, 18 females, age range at baseline: 9-59 years, 22 autosomal recessive, eight sporadic, two X-linked, and three dominant) was followed from 2.5 to 12.6 years (average follow-up 6.4 years) by clinical examination and by recording the fERG response to a (41 Hz) flickering uniform red field overlying the central 18 degrees of visual field (average of 1 clinical-fERG examination/patient/year, all patients had at least 3 visits). Short-term repeatability and long-term changes in fERG amplitudes were determined for each patient.
The repeatability range for fERG amplitude was -54% to 67% (95th percentile). Based on these cut-off criteria, patients in our cohort resulted either stationary (STAT, n=18) or declining (DEC, n=17). Of the STAT patients, eight had high (≥ 1 µV) and 10 low amplitude (0.5-1 µV) fERG. Of the DEC patients, 11 had a slow (9%/year) and six a fast (33%/year) fERG amplitude decay (between-group difference, p < 0.01). All STAT patients also had stable visual acuity. Fifteen out of the 17 DEC patients (88%) also had a visual acuity loss (≥ 2 lines) during follow-up. All acuity losses were preceded and/or accompanied by fERG losses.
fERG represents a direct and sensitive assay to follow the progression of central retinal dysfunction in CRD. This approach might help to anticipate for an individual patient the clinical rate and timing of disease progression
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