Correlation of pattern electroretinogram with optic disc cup shape in ocular hypertension

PURPOSE. TO evaluate the correlation of pattern electroretinogram (PERG), a n index of inner retinal function, with confocal scanning laser (CSLO) opti c disc structural parameters in ocular hypertension (OHT). METHODS. Thirty-four patients with OHT, normal white-on-white (Humphrey 30- 2) perimetry, and normal clinical optic discs were examined with PERG and C SLO disc analysis. Two groups of normal subjects (n = 38 and 18, for PERG a nd CSLO, respectively) and a group of 12 patients with early open-angle gla ucoma (EOAG) were also tested. Pattern electroretinogram amplitudes were me asured in response to sinusoidal gratings of variable spatial frequency (0. 58 -5.8 cycles/degree), modulated in counter-phase at 7.5 Hz. Morphometric optic disc parameters were obtained by the Heidelberg Retina Tomograph (HRT ), either globally or from predefined disc sectors. In addition to standard parameters, the cup shape measure, an index of depth variation and steepne ss of the cup walls, was determined. RESULTS. In individual OHT patients, PERG amplitudes at 2.6 cycles/degree w ere negatively correlated with cup shape measures (r = -0.43, P < 0.01) obt ained from analysis of the inferotemporal (IT) sector. No significant corre lations were found for the other parameters. On average, the cup shape meas ures derived from IT sector or global analysis were significantly (P < 0.01 ) worse, and closer to the measures of EOAG patients, in OHT patients with abnormal PERG compared with those with normal PERGs. The cup shape measure displayed a low sensitivity (20%) and a high specificity (100%) in predicti ng PERG abnormalities in individual OHT patients. CONCLUSIONS. The results indicate that in OHT there is a significant althou gh weak correlation between PERG amplitude and the shape of the optic disc cup, suggesting a parallel involvement of both function and morphology. Com bined PERG and optic disc cup structural analysis is of potential diagnosti c value to detect early damage to optic nerve head in individual OHT patien ts.