Abstract
PurposeTo evaluate the ability of normative database classification (color-coded maps) of spectral domain optical coherence tomograph (SDOCT) in detecting wedge shaped retinal nerve fiber layer (RNFL) defects identified on photographs and the factors affecting the ability of SDOCT in detecting these RNFL defects.MethodsIn a cross-sectional study, 238 eyes (476 RNFL quadrants) of 172 normal subjects and 85 eyes (103 RNFL quadrants with wedge shaped RNFL defects) of 66 glaucoma patients underwent RNFL imaging with SDOCT. Logistic regression models were used to evaluate the factors associated with false positive and false negative RNFL classifications of the color-coded maps of SDOCT.ResultsFalse positive classification at a p value of <5% was seen in 108 of 476 quadrants (22.8%). False negative classification at a p value of <5% was seen in 16 of 103 quadrants (15.5%). Of the 103 quadrants with RNFL defects, 64 showed a corresponding VF defect in the opposite hemisphere and 39 were preperimetric. Higher signal strength index (SSI) of the scan was less likely to have a false positive classification (odds ratio: 0.97, p = 0.01). Presence of an associated visual field defect (odds ratio: 0.17, p = 0.01) and inferior quadrant RNFL defects as compared to superior (odds ratio: 0.24, p = 0.04) were less likely to show false negative classifications.ConclusionsScans with lower signal strengths were more likely to show false positive RNFL classifications, and preperimetric and superior quadrant RNFL defects were more likely to show false negative classifications on color-coded maps of SDOCT.
Highlights
Glaucoma is a progressive optic neuropathy characterized by typical optic disc and retinal nerve fiber layer (RNFL) changes, with or without visual field (VF) defects
RNFL loss is a very early clinical sign of glaucoma, which is reported to be present in majority of glaucoma patients much before any detectable VF defects. [1, 2] Red free fundus photography is currently considered the gold standard for RNFL examination and loss of RNFL is seen as a wedge shaped defect in arcuate pattern, the width of which is larger than the major blood vessel, and reaching the edge of the disc margin
Spectral domain optical coherence tomography (OCT) (SDOCT) identified the RNFL defect better when the RNFL defect was associated with a corresponding VF defect (p50.004, Chi square test)
Summary
Glaucoma is a progressive optic neuropathy characterized by typical optic disc and retinal nerve fiber layer (RNFL) changes, with or without visual field (VF) defects. [4,5,6,7,8] the ability of SDOCT to detect RNFL defects is influenced by multiple factors These factors can in general be disease-related, subject- or eye-related and test- or technology-related. [4,5,6,7,8] Eye-related factors reported to influence the ability of SDOCT to detect RNFL defects are the optic disc size and axial length of the eye. [8, 9] One of the technology-related factors evaluated, but found not to influence the ability of SDOCT to detect RNFL defects is the signal strength of the scan [8] Ability of SDOCT is shown to be better in detecting wider compared to narrower RNFL defects. [4,5,6,7,8] Eye-related factors reported to influence the ability of SDOCT to detect RNFL defects are the optic disc size and axial length of the eye. [8, 9] One of the technology-related factors evaluated, but found not to influence the ability of SDOCT to detect RNFL defects is the signal strength of the scan [8]
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