Kamalipour and colleagues evaluated the global and regional circumpapillary capillary density and the retinal nerve fiber layer (RNFL) thickness in 80 healthy eyes, 64 preperimetric eyes, and 184 early primary open-angle glaucoma (POAG) eyes.1
They found that capillary density measurements had higher diagnostic accuracies than RNFL thickness in detecting preperimetric glaucoma and early glaucoma. Global and regional capillary density normalized relative loss values were also higher than those of RNFL thickness in preperimetric and early glaucoma eyes. At the individual eye level, greater global magnitudes of capillary density loss than RNFL thickness loss were observed in 67.2% of preperimetric glaucoma and 61.4% glaucoma eyes.
Capillary density measurements had higher diagnostic accuracies than RNFL thickness in detecting preperimetric glaucoma and early glaucoma
A subanalysis suggested that eyes with greater microvascular loss might have different characteristics in terms of ethnicity, IOP, and capillary density compared with those with greater RNFL thickness loss. This is a very important result from this study. This implies that there are a few glaucomatous eyes where the microvascular loss is greater than RNFL loss and a few eyes where RNFL loss is greater than the microvascular loss. This justifies that OCTA and OCT complement each other in the diagnosis of early glaucoma.
Their findings justify that OCTA and OCT complement each other in the diagnosis of early glaucoma
These results demonstrate the need for defining glaucoma phenotypes based both on structural (RNFL) and microvascular features. Also, when extrapolated to the situation of glaucoma progression detection, these results highlight the fact that progression is likely to be detected earlier using OCTA in a few early glaucoma eyes and using OCT RNFL measurements in a few eyes, implying that longitudinally imaging glaucoma eyes on both OCTA and OCT are important.
A similar evaluation in different ethnic groups and also in different subtypes of glaucoma like angle closure glaucoma and pseudoexfoliation glaucoma, will provide important information on the role of OCTA in glaucoma management.