Combined Probability Test for Sectoral Progression of the Circumpapillary Retinal Nerve Fiber Layer Thickness.

Abstract

Purpose: Optical coherence tomography has become a widely used tool to assess structural changes at the optic nerve head and the peripapillary retina. Often, global analyses are supplemented with sectoral analyses, but it is unclear how to control specificity as trend analyses are conducted on a larger number of sectors. We introduce a random permutation analysis for a combined probability test of progression in circumpapillary retinal nerve fiber layer (cpRNFL) thickness applied to different number of sectors.

Methods: A series of seven cpRNFL scans were extracted for 428 eyes of 255 patients with glaucoma from the DIGS/ADAGES dataset. The combined probability test was run for 2k sectors, where k = 0, ⋯, 8 in addition to the maximum possible number of pixels, 768. Positive rates were derived for specificity ranging from 100% to 85%.

Results: At 95% specificity, the positive rate for 768 pixels was 41% [37%, 46%]. The positive rates for global thickness, and for 12 sectors, were statistically significantly smaller (28% and 35%, respectively). Positive rates remained at the observed maximum until the number of sectors fell below 128.

Conclusions: The permutation of cpRNFL thickness profiles makes it possible to detect highly localized change in cpRNFL profiles from optical coherence tomography.

Translational relevance: Glaucoma-related changes in the optic nerve fiber layer are often localized rather than global. Permutation analysis provides a framework to detect such changes without sacrificing specificity.