Comparison of retinal nerve fiber layer and optic disc imaging for diagnosing glaucoma in patients suspected of having the disease

Abstract

Purpose: To compare retinal nerve fiber layer (RNFL) and optic disc topographic imaging for detection of optic nerve damage in patients suspected of having glaucoma.

Design: Observational cohort study.

Participants: A cohort of 82 patients suspected of having glaucoma based on the appearance of the optic nerve.

Methods: All patients were imaged using the GDx VCC scanning laser polarimeter and HRT (software version 3.0) confocal scanning laser ophthalmoscope. All patients had normal standard automated perimetry visual fields at the time of imaging and were classified based on history of documented stereophotographic evidence of progressive glaucomatous change in the appearance of the optic nerve occurring before the imaging sessions.

Main outcome measures: Areas under the receiver operating characteristic (ROC) curves were used to evaluate the diagnostic accuracies of GDx VCC and the HRT.

Results: Forty eyes with progressive glaucomatous optic nerve change were included in the glaucoma group, and 42 eyes without any evidence of progressive damage to the optic nerve followed untreated for an average time of 8.97+/-3.08 years were included in the normal group. The area under the ROC curve for the best parameter from GDx VCC (nerve fiber indicator [NFI]) was significantly larger than that of the best parameter from the HRT (rim volume) (0.83 vs. 0.70; P = 0.044). The NFI parameter also had a larger ROC curve area than that of the contour line-independent parameter glaucoma probability score (0.83 vs. 0.68; P = 0.023). Assuming borderline results as normal, the Moorfields regression analysis classification had a sensitivity of 48% for specificity of 69%. For a similar specificity (70%), the parameter NFI had a significantly larger sensitivity (83%) (P = 0.003).

Conclusions: Retinal nerve fiber layer imaging with GDx VCC had a superior performance versus topographic optic disc assessment with the HRT for detecting early damage in patients suspected of having glaucoma. For glaucoma diagnosis, these results suggest that GDx VCC may offer advantage over the HRT when these tests are combined with clinical examination of the optic nerve.

Figure 1

Receiver operating characteristic (ROC) curves for the parameters with largest areas under the ROC curve for GDx VCC (nerve fiber indicator) and HRT (rim volume). The ROC curve for the contour line–independent HRT parameter glaucoma probability score is also shown.

Figure 2

Examples of typical eyes included in the study. Both eyes had an optic disc with a suspicious appearance and normal visual fields (VFs) at time of imaging. Eyes were classified based on documented history of progressive changes to the optic nerve. A, Eye from the normal group. The patient was observed untreated for approximately 18 years (August 26, 1987–November 22, 2005) without any evidence of progressive optic disc change, providing confidence that this patient had only a normal variation of optic disc morphology but no glaucomatous damage. B, Eye from the glaucoma group. The patient showed progressive optic disc change from March 17, 1992 to March 26, 2002 (superior rim thinning) but retained a normal VF. dB = decibel; GHT = glaucoma hemifield test; MD = mean deviation; PSD = pattern standard deviation.