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WGC-2021

Editors Selection IGR 19-1

Clinical Examination Methods: Blood Flow: Macular OCT-A in Glaucoma

Zia Pradhan
Harsha Rao

Comment by Zia Pradhan & Harsha Rao on:

74446 Quantitative optical coherence tomography angiography of macular vascular structure and foveal avascular zone in glaucoma, Choi J; Kwon J; Shin JW et al., PLoS ONE, 2017; 12: e0184948


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There is a rapidly growing body of knowledge examining the diagnostic value of optical coherence tomography angiography (OCTA) in glaucoma. Vessel density, the percentage area occupied by the large vessels and microvasculature in a particular region, is the most common parameter quantified on the OCTA scans. While most studies reported good diagnostic value of peripapillary vessel density in glaucoma,1,2 the same for macular vessel density was poor.3,4 In a recent study, Choi et al5 determined a few new parameters of the foveal avascular zone (FAZ) on OCTA, namely the FAZ size, perimeter, and circularity index, and evaluated their diagnostic ability in glaucoma.

While most studies reported good diagnostic value of peripapillary vessel density in glaucoma,the same for macular vessel density was poor
The FAZ circularity index, which is a measure of the compactness of shape relative to a circle, graded as 1.0 for a perfect circle and a value closer to 0 for an irregular shape, was found to have an area under the receiver operating characteristic curve (AUC) of 0.905; this was similar to the AUC of peripapillary retinal nerve fiber layer (RNFL) thickness (0.969) and macular ganglion cell-inner plexiform layer thickness (0.948). In addition to this study, a few others have reported that the diagnostic value of macular vessel density measured beyond the central 3 mm zone was greater than that measured within the central 3 mm zone (as done in most previous studies).6,7 These results highlight that a lot remains to be explored in the field of macular imaging with OCTA in glaucoma.
The clinical usefulness of imaging the macular vasculature in glaucoma is likely to be limited since the geriatric macula is affected by several other diseases (age-related macular degeneration, diabetic retinopathy, etc)
Despite these interesting findings, the clinical usefulness of imaging the macular vasculature in glaucoma is likely to be limited since the geriatric macula is affected by several other diseases (age-related macular degeneration, diabetic retinopathy, etc). Additionally, systemic diseases, such as diabetes mellitus and hypertension, are known to affect the macular vessels on OCTA in the absence of any clinically detectable retinal changes.8 Therefore, currently RNFL thickness remains the most useful parameter in glaucoma imaging. However, these new findings with OCTA will help us better understand the pathogenesis of glaucomatous macular damage.

References

  1. Liu L, Jia Y, Takusagawa HL, et al. Optical Coherence Tomography Angiography of the Peripapillary Retina in Glaucoma. JAMA Ophthalmol 2015;133:1045-52.
  2. Yarmohammadi A, Zangwill LM, Diniz-Filho A, et al. Optical Coherence Tomography Angiography Vessel Density in Healthy, Glaucoma Suspect, and Glaucoma Eyes. Invest Ophthalmol Vis Sci 2016;57:OCT451-9.
  3. Rao HL, Pradhan ZS, Weinreb RN, et al. Regional Comparisons of Optical Coherence Tomography Angiography Vessel Density in Primary Open-Angle Glaucoma. Am J Ophthalmol 2016;171:75-83.
  4. Chen HS, Liu CH, Wu WC, et al. Optical Coherence Tomography Angiography of the Superficial Microvasculature in the Macular and Peripapillary Areas in Glaucomatous and Healthy Eyes. Invest Ophthalmol Vis Sci 2017;58:3637-45.
  5. Choi J, Kwon J, Shin JW, et al. Quantitative optical coherence tomography angiography of macular vascular structure and foveal avascular zone in glaucoma. PLoS One 2017;12:e0184948.
  6. Takusagawa HL, Liu L, Ma KN, et al. Projection-Resolved Optical Coherence Tomography Angiography of Macular Retinal Circulation in Glaucoma. Ophthalmology 2017;124:1589-99.
  7. Rao HL, Riyazuddin M, Dasari S, et al. Diagnostic Abilities of the Optical Microangiography Parameters of the 3x3 mm and 6x6 mm Macular Scans in Glaucoma. J Glaucoma 2018 (In Press).
  8. Rao HL, Pradhan ZS, Weinreb RN, et al. Determinants of Peripapillary and Macular Vessel Densities Measured by Optical Coherence Tomography Angiography in Normal Eyes. J Glaucoma 2017;26:491-7.


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