Correlation Between Focal Macular Electroretinograms and Optical Coherence Tomography in Retinitis Pigmentosa

Abstract

Purpose: : To investigate the clinical correlation between focal macular electroretinograms (fmERGs) and optical coherence tomography (OCT) on the different layers of the macula in patients with retinitis pigmentosa.

Methods: : Sixty two eyes of 62 patients (44.8 ± 17.0 years [±SD]) with retinitis pigmentosa were studied fmERGs and OCT. FmERGs were elicited by a 15 degrees stimulus centered on the fovea and monitored by an infrared fundus camera. Spectral-domain optical coherence tomography (RTVue-100) was used to measure outer and inner retinal volume in the macula. The mean deviation (MD) of the visual field was obtained by static visual field analyses. The amplitudes of the a- and b-waves and oscillatory potentials (OPs) and the value of MD were compared with the retinal volume of inner and outer layer in the macula, respectively.

Results: : We recorded a- and b-waves and OPs in 62 eyes of all 62 patients. 23 eyes were nonrecordable fmERGs. The mean amplitudes (±SD), respectively, were: a-wave, 0.6 ± 0.7 µV; b-wave, 1.3 ± 1.3 µV and OPs, 1.0 ± 1.2 µV. The mean macular volume (±SD) were 5.4 ± 0.6 mm³, 2.0 ± 0.3 mm³; 3.4 ± 0.4 mm³ in total, inner layer and outer layer, respectively. The mean value of MD (±SD) was -15.3 ± 9.7 dB. The amplitudes of the a- and b-waves and OPs and the MD values were significantly correlated with the total macular volume. And those amplitudes of fmERGs and MD values showed a significant correlation with the inner retinal volume rather than the outer retinal volume (a-wave: r = 0.50, P < 0.001 and r = 0.24, P = 0.059; b-wave: r = 0.54, P < 0.001 and r = 0.26, P = 0.043; OPs: r = 0.50, P < 0.001 and r = 0.25, P = 0.047; MD: r = 0.52, P < 0.001 and r = 0.22, P = 0.084; inner and outer retinal volume, respectively).

Conclusions: : Although fmERGs reflect the cone function, it showed strong correlations morphologically with the inner retina rather than the outer retina in the macula of patients with retinitis pigmentosa.

Keywords: electroretinography: clinical • imaging/image analysis: clinical • retina