A patient’s OCT images that show signs of shallow, irregular retinal pigment epithelium (RPE) elevation may indicate they are at a higher risk for nonexudative macular neovascularization (NE-MNV), a study in Ophthalmology reports.

Researchers from Australia and the Bascom Palmer Eye Institute in Florida enrolled patients with large drusen (greater than 125μm) secondary to AMD in at least one eye. Masked graders assessed the characteristic features found in patients in a “discovery cohort” who had known NE-MNV that was identified on OCT angiography (OCT-A) and the “double layer sign” on OCT.

The discovery cohort of four eyes showed the following characteristics of the “double layer sign” when NE-MNV was present: RPE elevations with greatest transverse linear dimension ≥1000μm, an irregular RPE layer with a height of predominantly <100μm and non-homogenous internal reflectivity.

The research team used the acronym “SIRE”—based on “Shallow, Irregular RPE Elevation”—to define these collective features.

In the evaluation cohort of 233 eyes, the features that were significantly associated with NE-MNV when RPE elevation was greater than 1000μm in length included: height of the RPE elevation, an overall flat or variable morphology, RPE layer irregularity and non-homogeneous reflectivity.

SIRE identified 24 eyes (10.3%) in the study. Using OCT-A imaging, the researchers found six of the 233 eyes had definite NE-MNVs, and all six graded positively for SIRE (sensitivity 100%). The absence of SIRE was identified in 209 of 227 eyes without NE-MNV (specificity 92.1%). The positive predictive value for SIRE was 25%, and the negative predictive value was 100%.

“OCT images that display a SIRE sign are at higher risk of having a subclinical NE-MNV. SIRE can be used as a screening tool on routine structural OCT imaging,” the researchers wrote in their paper.

More frequent follow-up and diligent home monitoring are recommended for patients with SIRE, they added.