Korean J Ophthalmol.  2019 Aug;33(4):315-325. 10.3341/kjo.2019.0016.

Additive Role of Optical Coherence Tomography Angiography Vessel Density Measurements in Glaucoma Diagnoses

• Kwon HJ
• Kwon J
• Sung KR

• KMID: 2454772
• DOI: http://doi.org/10.3341/kjo.2019.0016

Abstract

PURPOSE
This study compared the glaucoma diagnostic abilities of optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). In addition, the possibility of enhancing diagnostic capability by combining the two modalities was investigated.
METHODS
A total of 131 healthy eyes and 113 glaucomatous eyes were imaged by both OCT and OCTA. In OCT, glaucoma was defined as when the color of the superior or inferior quadrant of the peripapillary retinal nerve fiber layer thickness map was yellow (borderline, <5%) or red (outside normal limits, <1%). In OCTA, glaucoma was determined using the cut-off value of the superior or inferior peripapillary vessel density, calculated after receiver operating characteristic curve analysis. Sensitivity and specificity were determined by OCT alone, by OCTA alone, or by OCT and OCTA combined.
RESULTS
The sensitivity of OCT (86.7%) was better than that of OCTA (74.3%), whereas the specificity of OCTA (87.0%) was better than that of OCT (67.9%). When these two modalities were combined, both sensitivity and specificity were enhanced (90.3% and 92.4%, respectively). Among the 131 eyes, 32 were misdiagnosed as glaucomatous by OCT but accurately diagnosed as normal by OCTA. These eyes were myopic, with a longer axial length and a thinner and temporally displaced peak of peripapillary retinal nerve fiber layer thickness, causing the false positive result in OCT.
CONCLUSIONS
When OCTA was combined with OCT, the specificity of glaucoma diagnoses were enhanced. OCTA may compensate for the shortcomings of OCT in the diagnosis of glaucoma.

Keyword

Diagnostic techniques and procedures; Glaucoma; Optical coherence tomography angiography

MeSH Terms

Angiography*
Diagnosis*
Diagnostic Techniques and Procedures
Glaucoma*
Nerve Fibers
Retinaldehyde
ROC Curve
Sensitivity and Specificity
Tomography, Optical Coherence*
Retinaldehyde

Figure

• 

  Fig. 1 Receiver operating characteristic curves for calculating the cut-off values of peripapillary vessel density in the (A) superior and (B) inferior regions. The cut-off value was (A) 55.70% for the superior region and (B) 54.85% for the inferior region. AUC = area under the curve.

• 

  Fig. 2 Receiver operating characteristic curves of optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). (A) The area under the curve (AUC) was 0.773 in OCT and 0.807 in OCTA in total. In each particular region, (B) AUC was 0.744 in OCT and 0.743 in OCTA for the superior region. (C) AUC was 0.797 in OCT and 0.782 in OCTA for the inferior region.

• 

  Fig. 3 Representative case of a normal control patient misdiagnosed by optical coherence tomography (OCT) as having glaucoma but diagnosed by optical coherence tomography angiography (OCTA) as not having glaucoma (normal). The axial length of this eye was 27.45 mm, corresponding to high myopia. In the TSNIT (temporal-superior-nasal-inferior-temporal) graph of peripapillary retinal nerve fiber layer thickness (pRNFLT), generalized thinning and temporal movement of pRNFLT peaks were noted. Therefore, the color of the inferior quadrant in the pRNFLT map was red (A). However, vessel density values calculated by OCTA, which included the radial peripapillary capillary layer, were 59.53% for the superior region and 58.66% for the inferior region, which were higher than the cut-off values (B). Circumpapillary B-scan image and macular OCT presents the absence of segmentation error or other retinal pathology (C).

• 

  Fig. 4 A glaucoma patient with a false negative result following optical coherence tomography (OCT). On the peripapillary retinal nerve fiber layer thickness (pRNFLT) map, some wedge-shaped localized RNFL defects were observed both in the superior and inferior quadrants. In the TSNIT (temporal-superior-nasal-inferior-temporal) graph, the thinned area did not reach the yellow or red area (borderline or outside normal limits). The color of the 4-quadrant pRNFLT map was green (A). However, vessel density values calculated by optical coherence tomography angiography (OCTA) were 53.77% for the superior region and 53.94% for the inferior region, which were lower than the cut-off values (B). Circumpapillary B-scan image and macular OCT presents the absence of segmentation error or other retinal pathology (C).

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