Factors associated with false positives in retinal nerve fiber layer color codes from spectral-domain optical coherence tomography.

PURPOSE: To determine the factors that contribute to false-positive retinal nerve fiber layer (RNFL) color code results from spectral-domain optical coherence tomography (OCT).
DESIGN: A prospective, cross-sectional study. PARTICIPANTS: This study included 149 eyes from 77 healthy participants.
METHODS: Participants, who were consecutively enrolled from June 2009 to December 2009, underwent Cirrus OCT. Recorded demographic and clinical factors included age, gender, eye side, intraocular pressure, central corneal thickness, spherical equivalent, axial length, anterior chamber depth, disc area, and the extent of retinal vasculature. MAIN OUTCOME MEASURES: An abnormal finding in RNFL color codes was defined as ≥1 yellow or red sectors by quadrant and clock-hour maps and a wedge-shaped color pattern represented by yellow or red in the deviation map. The incidence of false-positive color codes was determined. The influence of clinical and demographic factors on the incidence of false-positive RNFL color codes was assessed using generalized linear mixed model analysis.
RESULTS: The false-positive rate for ≥1 of the quadrant, clock-hour, and deviation maps was 26.2%. Longer axial length and smaller disc area were significantly associated with an increased incidence of false-positives when other factors were controlled (odds ratios, 2.422 and 0.165; P = 0.008 and 0.035, respectively).
CONCLUSIONS: The factors that significantly affected the false-positive RNFL color code results using spectral-domain OCT were axial length and disc area, which may significantly affect the specificity of spectral-domain OCT. Therefore, axial length and disc area should be considered during RNFL thickness profile analysis.