Abstract
Abstract: :
Purpose: To evaluate the relationship between electrophysiological, psychophysical and structural measurements in normal, ocular hypertension (OH) and glaucomatous eyes and to test the hypothesis that there is a continuous structure–function relationship between ganglion cell numbers and visual field sensitivity. Methods: : 120 eyes were examined with white–on–withe (Humprey 30–2) perimetry, with pattern electroretinigram (Glaid) and with Heidelberg retina tomograph (HRT II) disc analisis. Each patient underwent a complete ophthalmic evaluation. The patients were divided in 4 groups according clinical and visual field (VF) conditions: 1) normal subjects (IOP < 21 mmHg, no damage in VF) 2) subjects with ocular ipertension (IOP > 21 mmHg, no damage in visual field), 3) early open–angle glaucoma (IOP > 21 mmHg, early glaucomatous visual field loss according Hodapp classification), 4) advanced open–angle glaucoma (IOP > 21 mmHg, advanced glaucomatous visual field loss according Hodapp classification). Pattern electroretinogram amplitudes and phases were measured; morphometric optic disc parameters obtained by HRT II were determined (cup shape measure CSM, linear cup disk ratio C/D). Theese data were correlated each–other and with perimetric indices (MD and PSD). Results: in normal subjects were found significant correlation only for the PSD, the MD and the phase (r=–0.37, p=0.04 and r–0.36, p=0.04) and between PSD and CD (r=–0.37, p=0.04); in the subjects with ocular ipertension were found significant correlation between MD and PSD (r=–0.52, p=0.008), MD and CD(r=–0.43, p=0.003), MD and amplitude (r=–0.49, p=0.01), PSD and amplitude (r=–0.54, p=0.006), CSM and CD (r=–0.54, p=0.005), CD and amplitude (r=–0.42, p=0.003); in early Glaucoma patients were found significant correlation between CSM and CD (r=0.37, p=0.0002), MD and PSD (r=–0.57, p=0.001), MD and C/D (r=0.55, p=0.002); in advanced glaucoma patients were found significant correlation between MD and C/D (r=–0.60, p=0.001), MD and phase (r=–0.37, p=0.04), MD and PSD (r=–0.78, p<0.0001), CSM and PSD (r=0.41, p=0.04), CSM and CD (r=0.77, p<0.0001), PSD and CD (r=0.61, p=0.001). Conclusions: The results indicate that in OH subjects there is a significant although weak correlation between PERG amplitude, shape of the optic disc cup and the perimetric indices, suggesting a parallel invlovement of both function and morphology. In the glaucoma patients there is significant correlation between psychophysical and structural measurements only.
Keywords: electrophysiology: clinical • imaging/image analysis: clinical • optic disc