Concordance of Objectively Detected Retinal Nerve Fiber Bundle Defects in En Face OCT Images with Conventional Structural and Functional Changes in Glaucoma

Predicting perimetric defects from en face maps of retinal nerve fibre layer reflectance

“…Further research is needed to determine the best regions to use, or whether it is better to use approaches which correct for variation in the shape of the eye before comparing with normative values. 21 In prior studies from another 21 laboratory and ours, 39 an internal reference value was obtained by imaging a large region and having an operator identify the temporal raphe so that the reference value was gathered slightly below the RNFL in healthy eyes. Locations where the attenuation coefficient was at least a criterion amount above this reference value were considered to indicate a healthy RNFL.…”

“…At the deepest depth used, 48 μm, in some healthy eyes there were locations at the edges of the region where RNFL thickness was less than 48 μm, while several control eyes in Group 3 gave false positives with both criteria. Further research is needed to determine the best regions to use, or whether it is better to use approaches which correct for variation in the shape of the eye before comparing with normative values 21 …”

“…[7][8][9] RNFL reflectance near the inner limiting membrane (ILM), which is less affected by the location of the arcades than RNFL thickness, has been found to have good sensitivity to glaucoma [10][11][12][13][14][15][16][17] and reasonable ability to predict the locations of glaucomatous perimetric defects. 5,[18][19][20][21] It has been proposed that RNFL reflectance may be at least as good as RNFL thickness in diagnostic efficiency for glaucoma, 22 and a recent study proposed that quantification of RNFL reflectance near the optic disc may make population-based screening for glaucoma feasible. 17 In clinical practice, false positive rates can be reduced by requiring the defect be detected by both imaging and perimetry.…”

“…To date, en face images of RNFL reflectance have been found to reflect the spatial extent and pattern of perimetric defect, but not the depth of defect. 5,[19][20][21] If RNFL reflectance is to be useful for screening for those at greatest risk of visual impairment, then criteria with high specificity should have high sensitivity for identifying patients with deep perimetric defects. 23 The purpose of this study was to develop criteria with high sensitivity to these defects, with less emphasis on sensitivity to milder glaucomatous defects.…”

“…RNFL thickness has substantial topographic variation, which means that en face probability maps for RNFL thickness become inaccurate when the arcades fall either closer to or farther from the fovea than on average 7–9 . RNFL reflectance near the inner limiting membrane (ILM), which is less affected by the location of the arcades than RNFL thickness, has been found to have good sensitivity to glaucoma 10–17 and reasonable ability to predict the locations of glaucomatous perimetric defects 5,18–21 . It has been proposed that RNFL reflectance may be at least as good as RNFL thickness in diagnostic efficiency for glaucoma, 22 and a recent study proposed that quantification of RNFL reflectance near the optic disc may make population‐based screening for glaucoma feasible 17 …”