Abstract
Purpose: :
To compare a local functional measure, the multifocal electroretinogram (mfERG), to a local structural measure, frequency domain optical coherence tomography (fdOCT), of receptor damage in patients with retinitis pigmentosa (RP).
Methods: :
MfERGs (Veris, EDI) and fdOCT scans (Spectralis HRA+OCT, Heidelberg Engineering) were obtained from seven patients with RP (2 autosomal dominant RP (RHO or RDS mutations), 2 autosomal recessive RP, and 3 RP isolates). Patients ranged in age from 23 to 59 years (44 ± 16 yrs, mean ± SD). All had best-corrected visual acuity better than 20/32 and a visual field extending beyond 15 degrees (HFA, Carl Zeiss Meditec). The mfERG was performed with 103 scaled hexagons and procedures conforming to ISCEV standards. All patients demonstrated good signal to noise ratio within the central 8 degrees. Volume scans (pattern size 30° X 25°, 31 B-scans) were obtained with automatic real-time registration (ART, Heidelberg Engineering) with an average of 10 frames per B-scan. A computer program (IGOR Pro, WaveMetrics) aided manual segmentation and calculated OCT thickness in the scans. The average receptor thickness (the distance between the choroid/Bruch’s membrane and outer plexiform/inner nuclear borders) was calculated for the central 3-degree circle and three concentric annuli located between 3 to 8 degrees, 8 to 15 degrees, and 15 to 24 degrees. These four concentric circle/annuli matched the inner four concentric circle/annuli in the mfERG.
Results: :
Across four circle/annuli, the average receptor thicknesses correlated well with the amplitude of the mfERG. For individual patients, the correlation (Pearson r) ranged from 0.93 to 0.99. For the combined data, r was 0.76 (p < 0.001).
Conclusions: :
In patients with RP, preserved cone photoreceptor function measured by mfERG amplitude correlate well with the remaining total thickness of the photoreceptor layer.
Keywords: retinal degenerations: hereditary • imaging/image analysis: clinical • electroretinography: clinical