Atypical retardation patterns adversely affect ability of GDx VCC to detect progressive RNFL loss

This study's researchers evaluated the impact of atypical retardation patterns (ARPs) on the detection of progressive retinal nerve fiber layer (RNFL) loss using scanning laser polarimetry with variable corneal compensation (VCC) in 221 patients (377 eyes) diagnosed with glaucoma or glaucoma suspects. They found that ARPs significantly affected the detection of progressive RNFL loss measured with the GDx VCC (Carl Zeiss Meditec, Inc.).

The investigators obtained images annually for a median of four years with the GDx VCC, as well as optic disc stereophotographs and standard automated perimetry visual fields. They used the typical scan score (TSS) to quantify the presence of ARPs on GDx VCC images.

Changes from baseline in the TSS were significantly associated with RNFL thickness changes in progressing and nonprogressing eyes. The investigators concluded that eyes with large amounts of atypical patterns, great fluctuations in these patterns over time or both may show changes in GDx VCC measurements that can falsely appear as glaucomatous progression in eyes that are stable or mask true RNFL changes in eyes with progressive disease.

Financial Disclosures
Dr. Vold receives grant support from Alcon Laboratories, Inc., Allergan., Inc., and Ista Pharmaceuticals, as well as lecture fees from Allergan and consulting fees from Ista.