Diagnosing Persistent Hypertransmission Defects on En Face OCT Imaging of Age-Related Macular Degeneration

Abstract

Purpose: A training exercise was performed to study the ability of graders to reliably identify precursor lesions to geographic atrophy (GA), known as persistent choroidal hypertransmission defects (hyperTDs), using en face OCT images from eyes with nonexudative age-related macular degeneration (AMD).

Design: Intergrader agreement study.

Participants: Eleven graders participated in this exercise.

Methods: Formal training on how to identify persistent hyperTDs on en face OCT images was provided to the graders. A persistent hyperTD was defined as a bright lesion having a greatest linear dimension (GLD) of at least 250 μm. Training consisted of a tutorial session followed by the grading of 3 pretest exercises, each consisting of 3 cases. After all graders scored 100% on the pretest exercises, they performed a final exercise consisting of 30 en face OCT images from 29 eyes with nonexudative AMD containing 107 hyperTDs that each grader needed to evaluate. The cases contained a variety of AMD-related atrophic lesions.

Main outcome measures: The sensitivity, positive predictive value (PPV), and modified accuracy were assessed for each grader.

Results: A total of 1177 hyperTDs from 30 en face OCT images were reviewed by the graders. The mean sensitivity, PPV, and modified accuracy for all the graders were calculated to be 99.0%, 99.2%, and 98.2%, respectively. There was a 97% agreement observed between all the graders (first-order agreement coefficient [AC₁] = 0.97). Internal graders from the Bascom Palmer Eye Institute had a slightly higher agreement compared with the external graders (AC₁ = 0.98 vs. AC₁ = 0.96). The hyperTDs most often incorrectly identified included the following features: (1) hyperTDs containing hypotransmission defect cores, (2) single hyperTDs that were incorrectly graded as 2 separate lesions, and (3) hyperTDs with borderline GLDs that were close to 250 μm.

Conclusions: The accurate detection of persistent hyperTDs on en face OCT images by graders demonstrates the feasibility of using this OCT biomarker to identify disease progression in eyes with nonexudative AMD, especially when used as a clinical trial end point in studies designed to test new therapies that may slow disease progression from intermediate AMD to GA.

Keywords: Age-related macular degeneration; En face OCT; Geographic atrophy; Hypertransmission defect.