Ability of Stratus OCT to detect progressive retinal nerve fiber layer atrophy in glaucoma

To evaluate the ability of Stratus optical coherence tomography (OCT version 4.0; Carl Zeiss Meditec, Inc., Dublin, CA) to detect progressive glaucomatous retinal nerve fiber layer (RNFL) atrophy observed by red-free RNFL photography.

Intersession test-retest variability of each clock hour, quadrant, and average RNFL thickness was determined in 53 control subjects. The sensitivity and specificity of OCT for identification of progressive RNFL atrophy were tested on subjects in whom this condition was clearly observed in red-free RNFL photographs (n=27) and in another control group (n=62), according to criteria derived from test-retest variability.

The sensitivity of Stratus OCT RNFL measurement ranged from 14.8% (for average RNFL thickness) to 85.2% (for clock hour thickness) when tested at the 95% confidence level. The specificity of Stratus OCT RNFL measurement was approximately 95% for average RNFL thickness, but decreased considerably with clock hour (59.7%) and quadrant thickness (77.4%). This is presumably because multiple testing was used for multiple clock hours and quadrants. When calculated based on two consecutive follow-up examinations, the specificity for the clock hour measurements increased to 86.6% and that for quadrant thickness increased to 92.5%. The OCT-measured RNFL thickness change showed excellent topographic agreement with the progressive RNFL atrophy observed using RNFL photography.

Within the limits of retest variability, Stratus OCT detects progressive RNFL atrophy with high sensitivity and moderate specificity in cases showing localized progressive loss of retinal nerve fibers in red-free photographs. The specificity can be improved by use of multiple measurements. Stratus OCT is a potentially useful technique for detection of glaucoma progression.