Reductions in the 300 μm band around the outer border of foveal avascular zone (FAZ), the foveal vessel density (FD300), can be used as an objective sign of poor 24-2 and 10-2 visual fields, according to study findings published in the British Journal of Ophthalmology. While the FAZ itself is not correlated with central visual field changes, it can be correlated with intraocular pressure (IOP), the research shows.
The cross-sectional study included a total of 188 participants (248 eyes), consisting of 24 healthy patients (38 eyes), 37 glaucoma suspects (42 eyes) and 127 patients with primary open angle glaucoma (POAG) (168 eyes). The mean age among the healthy group was significantly lower than both glaucoma and glaucoma suspect groups.
Participants underwent imaging using optical coherence tomography angiography (OCT-A) and standard automated perimetry (SAP) utilizing the 24-2 and 10-2 Swedish Interactive Thresholding Algorithm (SITA). The researchers measured OCT-A-based and OCT-based FAZ parameters (superficial FAZ area, FAZ circumference), FD300, and foveal thickness. Linear mixed model was used to evaluate the correlation between FAZ parameters and visual field parameters.
The researchers found that axial length adjusted-FAZ area did not differ among the 3 groups (mean [95% CI]): in healthy 0.31 (0.27 to 0.36) mm2, glaucoma suspect 0.29 (0.26 to 0.31) mm2 and eyes with POAG 0.28 (0.27 to 0.30) mm2 (P =.578). They noted that the FD300 was lower in glaucoma suspects and eyes with POAG than healthy eyes, although the difference was not statistically significant (P =.071).
In multivariable linear mixed models, low FD300 was associated with worse 24-2 and 10-2 visual field mean deviation and foveal threshold (all P <.05). Researchers also found that a smaller FAZ area was associated with reductions in IOP (P =.026).
Study limitations included that only the superficial FAZ area was investigated, certain characteristics such as age, ocular hypotensive eye-drops and treatment status differed in the healthy group compared with the other groups, and possibility of insufficient detection of microcirculation around the FAZ.
“Further longitudinal studies are needed to clarify the relationship between OCT-A-derived FAZ metrics and VF parameters or IOP in glaucoma,” according to the researchers.
Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. This research was supported by multiple sources. Please see the original reference for a full list of disclosures.
Nishida T, Oh WH, Moghimi S, et al. Central macular OCTA parameters in glaucoma. Br J Ophthalmol. Published online August 23, 2021. doi:10.1136/bjophthalmol-2021-319574