Findings from a recent study published in the Journal of Glaucoma assessed peripapillary and macular vessel density (VD) in unilateral early pseudoexfoliation glaucoma (PXG) and unaffected fellow eyes compared to healthy controls.
Give me some background.
Pseudoexfoliation syndrome (PXS) is characterized by the production and accumulation of white dandruff-like exfoliative material on anterior segment structures—and is also a major risk factor for developing glaucoma.
- How: The accumulation of pseudoexfoliative material in the trabecular meshwork results in increased aqueous humor outflow resistance and elevated intraocular pressure (IOP).
Of note: PXS and PXG are associated with ocular and systemic vascular disease and abnormalities.
Bring it back to this study.
Optical coherence tomography angiography (OCT-A) has allowed for comprehensive analyses of VD in the optic nerve head and macular regions.
Consequently: The research team sought to understand whether vascular dysfunction can be detected at the preclinical stage of PXG using OCT-A and how it may be involved in the pathogenesis of glaucoma.
Now talk about the study.
In this cross-sectional study, investigators included a total of 56 patients:
- 28 eyes with PXG and 28 nonglaucomatous pseudoexfoliation-free fellow eyes of 28 patients as well as 28 eyes of 28 healthy participants
All subjects underwent OCT-A imaging and were evaluated for:
- Radial peripapillary capillary VD (RPC-VD)
- Macular VD
- Retinal nerve fiber layer (RNFL) thickness
- Ganglion cell complex (GCC) thickness
Findings?
The average RPC-VD and RNFL thickness were significantly reduced in PXG eyes compared to both fellow eyes and the control group (p < 0.001-0.002).
- Neither RNFL thickness or RPC-VD parameters differed from controls in fellow eyes
Using sector-based analysis, researchers determined that RPC-VD loss in the PXG eyes was significant in specific regions (p = 0.005-0.031):
- Nasal-superior
- Nasal-inferior
- Superonasal
- Inferonasal sectors
Conversely: RNFL thinning extended from the nasal sectors toward the supertemporal and temporal-superior sectors (p < 0.001-0.014).
Tell me more.
RPC-VD was strongly correlated with average and all-sector RNFL thicknesses (r = 0.402-0.759, p < 0.001-0.034).
Although perifoveal GCC differed from both fellow and control eyes (p < 0.001), there was no significant difference in macular VD parameters among the groups.
RPC-VD and RNFL had comparable area under receiver operating curve (AUROC) values in the average and nasal sectors, while RPC-VD had no ability to distinguish PXG from controls in the superotemporal and inferotemporal sectors.
Expert opinion?
The study authors noted that “the duration of PXS may increase the likelihood of subclinical PXG in the fellow eyes, and the stage of PXS might be a marker for the severity of RPC-VD and RNFL changes in fellow eyes.”
They added that these findings do not support the hypothesis that vascular deterioration may be a precursor to structural loss.
- Instead: In early PXG, structural damage appears to be more pronounced than VD changes.
Limitations?
These included:
- The relatively small study group
- The eyes in the PXG group consisted of eyes with preperimetric glaucoma (PPG) and early glaucoma
- Patients with type 2 diabetes mellitus were included in the study, which is negatively associated with VD parameters
- They did not account for the impact of systemic and topical medications on VD parameters
Take home.
These findings suggest that during the early stages of PXG, RPC-VD was reduced nasally, while the RNFL thinned from the nasal to temporal sectors.
Based on these results, RNFL parameters mostly appear to have better diagnostic ability than RPC-VD parameters.
Further, fellow eyes in the preclinical stage may not exhibit any RPC-VD and RNFL loss detectable by current OCT-A technology.