Glaucoma Morphologic Damage Estimated from Functional Tests

Abstract

Purpose To compare direct morphologic measurements with the ones deduced from functional tests. Methods A total of 111 normal eyes (examined twice) and 112 consecutive eyes with suspected or confirmed glaucoma were analyzed using Spark strategy (Oculus Easyfield Perimeter) and Cirrus optical coherence tomography (OCT). The threshold values were used to deduce the thickness of the retinal nerve fiber layer (RNFL) in 25 sectors. They were also used to derive a normalized value of the neuroretinal rim area, correcting the influence of the optic disc area size, and expressing the result as a percentage of their normal average relation. Results The correlation between the deduced and the measured RNFL thicknesses were r = 0.77 (p<0.001, standard error [SE] = 15.4 μm in normal and 15.1 μm in glaucomatous eyes) in the sector to sector comparison, and r = 0.80 (p<0.000001, SE = 10.0 μm in normal and 10.4 μm in glaucomatous eyes) for the average thickness. In normal subjects, the SE of deducing a second OCT result from the previous one was 13.2 μm in the sector by sector analysis and 4.6 μm for average thickness. The correlation between the deduced and measured rim area was r = 0.87 (p<0.000001, SE = 6.7% in normal and 15.9% in glaucomatous eyes). Receiver operating characteristic analysis yielded the following areas, sensitivities, and specificities: measured thickness: 0.89, 75.5%, 91.5%; deduced thickness: 0.91, 86.5%, 93.4%; measured rim area: 0.96, 89.2%, 95.3%; deduced rim area: 0.94, 82.9%, 96.2%. Additionally, the results in a new series of 71 normal and 68 glaucomatous eyes are verified. Conclusions Spark perimetry allowed deducing glaucomatous morphologic alterations with significant accuracy.