Intraobserver Reproducibility of Retinal Nerve Fiber Layer Measurements Using Scanning Laser Polarimetry with Variable Corneal Compensation in Glaucoma Suspect Patients

To quantify the intraobserver reproducibility of retinal nerve fiber layer (RNFL) measurements using scanning laser polarimetry with variable corneal compensation in glaucoma suspect patients.

Twenty-six eyes of 26 glaucoma suspect patients were included. Complete ophthalmologic examination and standard automated perimetry were performed for all of them. RNFL measurements were done using GDx-VCC (Laser Diagnostic Technologies, San Diego, CA) by an experienced operator. The test repeated immediately by the same operator.

Patients were 24 to 70 years old (55.9±11.5 years). Twenty patients were female and 6 patients were male. Eighteen patients were ocular hypertensive and 8 patients had large cup to disk ratios. None of them had glaucomatous field defect in standard perimetry. The mean coefficient of variation for measurements of TSNIT average (Avg), superior Avg, inferior Avg, TSNIT-SD and nerve fiber indicator (NFI) were 0.77, 0.95, 0.91, 0.81, and 0.98 respectively. The mean coefficient of variation of GDx-VCC was 88.4 for the 5 main parameters (TSNIT Avg, superior Avg, inferior Avg, TSNIT-SD, and NFI).

GDx-VCC showed a good test-retest correlation and acceptable intraobserver reproducibility. NFI may be the most reproducible major GDx-VCC parameter in glaucoma suspect patients.