Enhanced imaging algorithm may better assess RNFL morphology

An enhanced form of scanning laser polarimetry may better assess the morphology of the retinal nerve fiber layer, a study found.

Nicolaas J. Reus, MD, and colleagues at Rotterdam Eye Hospital obtained retinal nerve fiber layer (RNFL) retardation images of 177 eyes of patients with glaucoma, patients with ocular hypertension and healthy controls. To obtain the images, the researchers used the Carl Zeiss Meditec GDx scanning laser polarimeter with variable corneal compensation (VCC) and enhanced corneal compensation (ECC). In ECC, the variable compositor introduces a "bias" birefringence that is removed mathematically for each individual pixel to produce the RNFL image, according to the study.

The researches found that ECC produced better RNFL images better than VCC. The typical scan score, which quantifies the amount of atypia, was higher with ECC than with VCC. Residual anterior segment birefringence was significantly lower with ECC. Measurements of peripapillary RNFL retardation showed reduced temporal and nasal values with ECC, whereas superior and inferior values were not significantly different.

The accuracy of the temporal, superior, nasal, inferior, temporal average and inferior average for detecting glaucoma was higher with ECC than with VCC, and the study authors concluded that ECC "may enhance the clinical utility of the GDx VCC in glaucoma management."

ECC may be implemented in current VCC systems via a software upgrade, according to the study.

The study is published in the September issue of Investigative Ophthalmology & Visual Science.