This study showed that RPE-BM distance may contribute to GA growth. Photo: Jessica Haynes, OD.
This study showed that RPE-BM distance may contribute to GA growth. Photo: Jessica Haynes, OD. Click image to enlarge.

In a recent study, researchers introduced a new approach for visualizing and documenting geographic atrophy (GA) using the optical attenuation coefficients derived from OCT data to determine if this measurement could serve as a clinical biomarker to predict the annual square root enlargement rate (ER) of GA.

Retinal pigment epithelium (RPE)-Bruch’s membrane (BM) distance was measured in 38 eyes, with thicker RPE-BM distances having a positive correlation with faster GA annual square root ERs. A multiple regression model using both RPE-BM distance and choriocapillaris (CC) flow deficit percentage was able to predict GA annual square root ERs.

“In our analysis, thicker RPE-BM distances resulted in a significant positive correlation with GA annual square root ER in all sub-regions except for R3. This result strongly suggests that the thickened RPE-BM complex around the GA margin contributes to faster GA growth, and this thickening is a local effect along the margins of GA,” the study authors explained.

“In the datasets, we observed two major sources of RPE-BM separation that included drusen-associated RPE elevations and a more homogeneously shallower RPE elevation that was not associated with typical drusen,” they continued.

One of the possible sources of this low-lying RPE elevation could be BLamDs, as previous studies have identified this as a major contributing factor for thickened RPE-BM complexes around the margins of GA.

“Our results are consistent with previous findings, as we measured RPE-BM distance from the en face view and found that eyes with a thicker RPE-BM complex around the GA tended to progress faster,” the investigators confirmed.

No significant correlations were found between RPE-BM distance and CC flow impairment, which likely indicates that CC abnormalities and RPE-BM abnormalities are two independent contributing factors for GA growth.

Chu Z, Shi Y, Zhou X, et al. OCT measurements of the retinal pigment epithelium to Bruch’s membrane thickness around geographic atrophy correlate with growth. Am J Ophthalmol. October 30, 2021. [Epub ahead of print].