Ability of cirrus high-definition spectral-domain optical coherence tomography clock-hour, deviation, and thickness maps in detecting photographic retinal nerve fiber layer abnormalities

Abstract

Purpose: To investigate the ability of clock-hour, deviation, and thickness maps of Cirrus high-definition spectral-domain optical coherence tomography (HD-OCT) in detecting retinal nerve fiber layer (RNFL) defects identified in red-free fundus photographs in eyes with early glaucoma (mean deviation >-6.0 dB).

Design: Cross-sectional study.

Participants: Two hundred ninety-five eyes with glaucomatous RNFL defects with clear margins observed in red-free fundus photographs and 200 age-, sex-, and refractive error-matched healthy eyes were enrolled.

Methods: The width and location of RNFL defects were evaluated by using the red-free fundus photograph. When a RNFL defect detected by red-free fundus photograph did not present as (1) yellow/red codes in the clock-hour map, (2) yellow/red pixels in the deviation map, or (3) blue/black areas in the thickness map, the event was classified as a misidentification of a photographic RNFL defect by Cirrus HD-OCT. In healthy eyes, the presence of false-positive RNFL color codes of Cirrus HD-OCT maps was investigated.

Main outcome measures: The prevalence of and factors associated with the (1) misidentification of photographic RNFL defects by Cirrus HD-OCT in eyes with glaucoma and (2) false-positive RNFL color codes of Cirrus HD-OCT maps in healthy eyes were assessed.

Results: Among the 295 red-free fundus photographic RNFL defects from 295 eyes with glaucoma, 83 (28.1%), 27 (9.2%), and 0 (0%) defects were misidentified in the clock-hour, deviation, and thickness maps of Cirrus HD-OCT, respectively. Fifty-six defects (19.0%) were misidentified only in the clock-hour map and 27 (9.2%) in both the clock-hour and deviation maps. The misidentification of photographic RNFL defects by Cirrus HD-OCT was associated with a narrower width and a temporal location of RNFL defects (P<0.05). Among the 200 healthy eyes, 25 (12.5%), 30 (15.0%), and 12 (6.0%) eyes had false-positive RNFL color codes in clock-hour, deviation, and thickness maps of Cirrus HD-OCT, respectively.

Conclusions: Among the clock-hour, deviation, and thickness maps obtained with Cirrus HD-OCT, the thickness map showed the best diagnostic ability in detecting photographic RNFL defects. The RNFL thickness map may be a useful tool for the detection of RNFL defects in eyes with early glaucoma.