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

PURPOSE

To evaluate the correlation of pattern electroretinogram (PERG), an index of inner retinal function, with confocal scanning laser (CSLO) optic 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 CSLO disc analysis. Two groups of normal subjects (n = 38 and 18, for PERG and CSLO, respectively) and a group of 12 patients with early open-angle glaucoma (EOAG) were also tested. Pattern electroretinogram amplitudes were measured 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 steepness of the cup walls, was determined.

RESULTS

In individual OHT patients, PERG amplitudes at 2.6 cycles/degree were negatively correlated with cup shape measures (r = -0.43, P < 0.01) obtained from analysis of the inferotemporal (IT) sector. No significant correlations were found for the other parameters. On average, the cup shape measures 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 predicting PERG abnormalities in individual OHT patients.

CONCLUSIONS

The results indicate that in OHT there is a significant although weak correlation between PERG amplitude and the shape of the optic disc cup, suggesting a parallel involvement of both function and morphology. Combined PERG and optic disc cup structural analysis is of potential diagnostic value to detect early damage to optic nerve head in individual OHT patients.