A team of researchers from the Department of Ophthalmology and Visual Sciences at Dalhousie University, Nova Scotia, Canada, have tackled the question: is macular ganglion cell layer (GCL) thinning a more accurate marker for detecting early glaucoma than macular perfusion density (PD) loss?
Examining optical coherence tomography angiography (OCTA) and OCT images of healthy subjects and early open-angle glaucoma patients taken with Heidelberg’s Spectralis, the researchers checked images taken every four months to establish which measurement might more accurately determine early glaucoma signs.
The prospective longitudinal cohort study evaluated macular PD and GCL thickness in 16 tiles of the macula (only using tiles in OCT that completely overlapped with OCTA images). In half of the tested regions (8 tiles), patients who showed worsening vision over time already had more GCL thinning at the start, suggesting that structural damage happened before functional loss. In 94 percent of regions (15 tiles), the more GCL thinning observed at the beginning, the faster the vision declined over time. In 75 percent of these regions (12 tiles), more patients showed significant GCL thinning than those who had vision worsening, meaning structural changes were more common than functional changes.
The study concluded that a decrease in GCL thickness precedes a measurable decrease in macular PD, with early glaucomatous progression more frequently detectable with changes in GCL thickness compared to macular PD.
