Abstract
PurposeTo objectively classify the optic discs of open-angle glaucoma (OAG) patients into Nicolela's four disc types, i.e., focal ischemic (FI), myopic (MY), senile sclerotic (SS), and generalized enlargement (GE), with swept-source optical coherence tomography (SS-OCT).MethodsThis study enrolled 113 eyes of 113 OAG patients (mean age: 62.5 ± 12.6; Humphrey field analyzer-measured mean deviation: -9.4 ± 7.3 dB). Newly developed software was used to quantify a total of 20 optic disc parameters in SS-OCT (DRI OCT-1, TOPCON) images of the optic disc. The most suitable reference plane (RP) above the plane of Bruch’s membrane opening was determined by comparing, at various RP heights, the SS-OCT-measured rim parameters and spectral-domain OCT-measured circumpapillary retinal nerve fiber layer thickness (cpRNFLT), with Pearson's correlation analysis. To obtain a discriminant formula for disc type classification, a training group of 72 eyes of 72 OAG patients and a validation group of 60 eyes of 60 OAG patients were set up.ResultsCorrelation with cpRNFLT differed with disc type and RP height, but overall, a height of 120 μm minimized the influence of disc type. Six parameters were most significant for disc type discrimination: disc angle (horizontal), average cup depth, cup/disc ratio, rim-decentering ratio, average rim/disc ratio (upper and lower nasal). Classifying the validation group with these parameters returned an identification rate of 80.0% and a Cohen’s Kappa of 0.73.ConclusionOur new, objective SS-OCT-based method enabled us to classify glaucomatous optic discs with high reproducibility and accuracy.
Highlights
Correlation with circumpapillary retinal nerve fiber layer thickness (cpRNFLT) differed with disc type and reference plane (RP) height, but overall, a height of 120 μm minimized the influence of disc type
Optic disc cupping and thinning of the neuronal rim are characteristic of glaucomatous optic neuropathy (GON). [1, 2] During the past decade, several objective, quantitative methods have been introduced to assess these structural changes in the optic disc and the retinal nerve fiber layer
We found that 120 μm was the optimal reference plane height in this analysis to minimize the effect of optic disc type
Summary
Optic disc cupping and thinning of the neuronal rim are characteristic of glaucomatous optic neuropathy (GON). [1, 2] During the past decade, several objective, quantitative methods have been introduced to assess these structural changes in the optic disc and the retinal nerve fiber layer. [1, 2] During the past decade, several objective, quantitative methods have been introduced to assess these structural changes in the optic disc and the retinal nerve fiber layer. These include red-free fundus photography, [3, 4] stereo photography, [5] scanning laser polarimetry, [6] confocal scanning laser ophthalmoscopy (Heidelberg retinal tomography: HRT), and optical coherence tomography (OCT) [2, 7,8,9]. The BMO-minimal rim width (MRW) is a highly reproducible ONH measurement parameter with a strong potential to differentiate normal subjects from glaucoma patients. [19] New OCT technology promises to improve assessment of the ONH
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