Automated detection of wedge-shaped defects in polarimetric images of the retinal nerve fibre layer

Abstract

Purpose Automated glaucoma detection in images obtained by scanning laser polarimetry is currently insensitive to local abnormalities, impairing its performance. The purpose of this investigation was to test and validate a recently proposed algorithm for detecting wedge-shaped defects. Methods In all, 31 eyes of healthy subjects and 37 eyes of glaucoma patients were imaged with a GDx. Each image was classified by two experts in one of four classes, depending on how clear any wedge could be identified. The detection algorithm itself aimed at detecting and combining the edges of the wedge. The performance of both the experts and the algorithm were evaluated. Results The interobserver correlation, expressed as ICC(3,1), was 0.77. For the clearest cases, the algorithm yielded a sensitivity of 80% at a specificity of 93%, with an area under the ROC of 0.95. Including less obvious cases by the experts resulted in a sensitivity of 55% at a specificity of 95%, with an area under the ROC of 0.89. Conclusions It is possible to automatically detect many wedge-shaped defects at a fairly low rate of false-positives. Any detected wedge defect is presented in a user-friendly way, which may assist the clinician in making a diagnosis.

RPE-Normalized RNFL Attenuation Coefficient Maps Derived from Volumetric OCT Imaging for Glaucoma Assessment

“…Also, algorithms for specifically detecting wedge-shaped defects may be developed, as was previously done for other imaging modalities. [21][22][23] These improvements should, however, be made and evaluated on a larger data set.…”

Wedge Defects on Optical Coherence Tomography Angiography of the Peripapillary Retina in Glaucoma: Prevalence and Associated Clinical Factors

“…Each hemisphere was qualitatively categorized by type of microvasculature defect. The term "wedge defects" has previously been used in literature both on perimetry [31][32][33][34] and RNFL anatomy 19,20,25,[35][36][37] and thus the terminology may be confusing. However, in our study of the RNFL microvasculature, we define wedge defects as focal loss of retinal microvasculature in an arcuate or wedge-shaped pattern beginning at the ONH margin and extending into the peripapillary region (see superior hemisphere of Fig.…”

Detection of retinal nerve fiber layer defects on retinal fundus images for early diagnosis of glaucoma

“…It is well known that NFLD development precedes an occurrence of morphologic change in optic nerve head and development of visual field defects in many cases, and is considered as one of the earliest glaucomatous changes. 6,7 There have been studies about the analysis of RNFL using fundus photographs, 8,9 scanning laser polarimetry, [10][11][12][13] and optical coherence tomography [13][14][15][16][17] for diagnosis of glaucoma. Although more studies were focused on new technologies, computerized detection and quantification of NFLDs in fundus photographs [18][19][20][21][22][23] can be important because of its routine use.…”