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Regional cone dysfunction in retinitis pigmentosa evaluated by flicker ERGs: relationship with perimetric sensitivity
Giancarlo Iarossi1, Benedetto Falsini, Marco Piccardi
1Ophthalmology Institute, Catholic University of S. Cuore, Rome, Italy.
Purpose:
To evaluate regional cone dysfunction in retinitis pigmentosa (RP) by recording focal electroretinograms (FERGs) from the central and paracentral retinal regions and to correlate the FERG with perimetric sensitivity losses.
Methods:
Twenty-three typical patients with RP (age, 18-65 years; visual acuity, 20/100 to 20/20; kinetic visual field by size II/4e, 20-40 degrees ) and eight age-matched control subjects were evaluated. FERGs were recorded in response to either a central (eccentricity, 0-2.25 degrees ) or a paracentral annular (2.25-9 degrees ) field, presented on a light-adapting background. Fields' luminances (mean: 80 cd/m(2)) were sinusoidally modulated at different temporal frequencies (TFs; 10.3, 14, 21, 32, 41, and 52 Hz). Amplitude and phase of the responses' fundamental harmonic (1F) were measured. Perimetric sensitivity was measured by a visual field perimeter. For each patient, mean sensitivity losses were calculated for both the central (0-2.25 degrees ) and paracentral (2.25-9 degrees ) regions.
Results:
On average, central and paracentral FERGs of patients with RP were reduced in amplitude (P
Conclusions:
In RP, central and paracentral FERGs are differently altered as a function of TF, indicating regional differences in the stage and/or pathophysiology of retinal cone dysfunction. FERG abnormalities may predict, to some extent, perimetric results at corresponding retinal regions. The data support the use of the present FERG method to evaluate regional cone dysfunction in different stages of RP.