Ability of retinal nerve fiber layer measurements of spectral domain optical coherence tomography and scanning laser polarimetry to diagnose preperimetric glaucoma

Abstract

Purpose: To compare the abilities of retinal nerve fiber layer (RNFL) parameters of spectral domain optical coherence tomograph (SDOCT) and scanning laser polarimeter (GDx enhanced corneal compensation; ECC) in detecting preperimetric glaucoma.

Methods: In an observational, cross-sectional study, 129 eyes of 106 consecutive subjects referred to a tertiary eye care center by general ophthalmologists as glaucoma suspects based on optic disc appearance and with normal visual fields (VF) underwent digital optic disc photography and RNFL imaging with SDOCT and GDx ECC. Two glaucoma experts masked to clinical and VF information independently classified the optic nerves into glaucoma and non-glaucoma groups based on optic disc photographs. Ability of RNFL parameters of SDOCT and GDx ECC to discriminate glaucoma (preperimetric) eyes from non-glaucoma (control) eyes was compared using area under receiver operating characteristic curves (AUC), sensitivities at fixed specificities and likelihood ratios (LR).

Results: Experts classified 35 eyes of 32 subjects as glaucomatous and 94 eyes of 74 subjects as non-glaucomatous (controls). Age and VF characteristics were comparable between the groups. All SDOCT RNFL parameters were significantly thinner (p<0.05) in the glaucoma while all GDx ECC parameters except the temporal and nasal quadrant RNFL measurements were significantly lesser in the glaucoma group. AUC of the average RNFL parameter of SDOCT (0.786) was significantly greater (p<0.001) than that of GDx ECC (0.627). Sensitivities at 95% specificity of the corresponding parameters were 20% and 8.6% respectively. AUCs of other RNFL parameters of SDOCT, except the nasal quadrant measurement, were also significantly (p<0.05) greater than the respective RNFL parameters of GDx ECC. LRs of outside normal limits category of SDOCT parameters ranged between 3.3 and 4.0 while the same of GDx ECC parameters ranged between 1.2 and 2.1. LRs of within normal limits category of SDOCT parameters ranged between 0.4 and 0.7 while the same of GDx ECC parameters ranged between 0.7 and 1.0.

Conclusions: Diagnostic abilities of the RNFL parameters of SDOCT were significantly better than that of GDx ECC in preperimetric glaucoma.

Keywords: 627 optic disc