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 poorThe 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.