Evaluation of Two New Instruments measuring Retinal Nerve Fiber Layer Thickness for Glaucoma Managements

Abstract

Abstract: : Purpose: To evaluate the ability of two new instruments, scanning laser polarimeter with variable corneal compensation (GDxVCC, Laser Diagnostic Technologies) and optical coherence tomography with higher resolution (OCT–3000, Carl Zeiss Meditec AG) for managing glaucoma patients. Methods: One hundred and seven eyes of 75 patients with glaucoma or suspected glaucoma were enrolled (mean age, 55.0±14.9 years old) at Glaucoma Clinic, Kyoto Prefectural University of Medicine. Quantitative retinal nerve fiber layer (RNFL) measurements were obtained by GDxVCC and OCT–3000 on the same day, and standard automated perimetry (SAP, Humphrey Field Analyzer 24–2, Carl Zeiss Meditec AG) was performed within two months. To compare the reproducibility of each instrument, 32 eyes of 19 patients (mean age, 48.9years±15.3) were randomly selected, and coefficients of variation (SD/average*100) were calculated for each instrument. In all subjects, the correlation between mean total deviation and mean RNFL thickness from each instrument was evaluated, on both whole area and superior/ inferior quadrants. Results: Mean coefficients of variation in RFNL measurements by GDxVCC were significantly lower than those of OCT–3000 (1.90±1.42%, 2.71±1.28%, respectively, P<0.05, paired t–test). Significant differences were observed between the mean RNFL thickness by GDxVCC and by OCT–3000 (49.1±7.6µm, 87.2±17.6µm, respectively, P<0.001, paired t–test). There was a high correlation between mean total deviation and mean RNFL thickness by both GDxVCC (r=0.396 P<0.0001) and OCT–3000 (r=0.405 P<0.0001). In superior and inferior quadrants, the high correlation between mean total deviation and mean RNFL thickness by each instrument was also observed (P<0.0001). Conclusions: Although the reproducibility of OCT–3000 was less than that of GDxVCC, RNFL thickness by each instrument had a similarly good correlation with total deviation of SAP. Therefore, both instruments were considered to be useful for managing glaucoma patients.

Keywords: nerve fiber layer • visual fields • imaging/image analysis: clinical