GDX-VCC VS GDX-ECC IN GLAUCOMA DIAGNOSIS

Background: To compare results provided by scanning laser polarimetry variable corneal compensation (VCC) vs enhanced corneal compensation (ECC) and evaluate correlation of visual field results in glaucoma patients. Methods: Study included 339 eyes of 182 patients screened by the glaucoma unit of the University Eye Clinic of Pavia (Italy). Patients were submitted to complete ophthalmic examination, standard automated perimetry (SAP), scanning laser polarimetry with GDx-VCC and Gdx-ECC. We evaluated for each exam quality image Q, typical scan score (TSS), nerve fibers index (NFI), nerve fibers layer average thickness (TSNIT average), upper sector (TSNIT sup) and lower sector (TSNIT inf). Q, TSS and morphometric parameters VCC and ECC were compared using Wilcoxon signed-rank test and Lin correlation coefficient. Correlation between GDx and perimetric indexes MD and PSD were evaluated with Pearson correlation index “r”. Results: With VCC only 204 images on 339 images (60%) were good quality (Q > 7) meanwhile with ECC 325 on 339 (96%). With VCC 140 scanning on 339 (41%) had TSS < 80 meanwhile with ECC were atypical 20 scanning on 339 (6%). ECC vs VCC displays constantly lower TSNIT thickness and higher NFI. All comparison between ECC and VCC showed statistically significant differences. GDx parameters and perimetric indexes were compared with statistic significance. The correlation was better for ECC parameters and first of all NFI. Conclusion: ECC provides better quality images vs VCC. High quality exam is the first condition to reproduce the real RNFL structure (more reliably). ECC notes nerve fibers layers significantly lower vs VCC and reveal a better correlation with perimetric indexes, is plausible GDx-ECC could improve early glaucoma diagnosis.