A Region-of-Interest Approach for Detecting Progression of Glaucomatous Damage With Optical Coherence Tomography

Abstract

Importance: Detecting progression of glaucomatous damage is often challenging.

Objective: To test the feasibility of using frequency-domain optical coherence tomography (FD-OCT) and a region-of-interest (ROI) approach to measure progressive changes in glaucomatous damage.

Design, setting, and participants: Among a group of patients in an institutional glaucoma practice who were likely to show glaucoma progression, eyes with a history of an optic disc hemorrhage (DH) confirmed by stereophotography were followed up with FD-OCT cube scans of the optic disc. All patients underwent FD-OCT scans on at least 2 occasions separated by at least 1 year (mean, 3.45 years; range, 1.42-6.39 years). Because we were not studying the effects of an optic DH, no constraint was placed on the time between the documentation of an optic DH and the first scan used in the analysis.

Main outcomes and measures: After en face images of the FD-OCT scan were aligned based on the blood vessels, circumpapillary images were derived for an annulus 100 µm in width, and the retinal nerve fiber layer (RNFL) thickness profiles were plotted for the first and last visits. The ROI width associated with the optic DH was defined as the region of the RNFL profile below the 1% CI based on healthy norms. The change in the ROI width was compared with the change in the global RNFL thickness, which was obtained by averaging the circumpapillary RNFL thickness.

Results: The change in the ROI width (mean [SD], 8.0° [6.4°]; 95% CI, 4.9° to 11.1°; range, -0.7° to 19.3°) was significant (P < .001, 2-tailed t test) while the change in the global thickness (mean [SD], 2.40 [5.87] μm; 95% CI, -0.48 to 5.28 μm) was not significant (P > .12, 2-tailed t test). Although 15 of the 16 ROIs increased in width between visits, only 11 showed a decrease in the global RNFL thickness.

Conclusions and relevance: For detecting progression of local RNFL damage in patients with glaucoma, an OCT ROI approach appears superior to the OCT global RNFL thickness measure typically used.

Figure 1. Region-of-Interest Method

A, Shown is a derived circumpapillary scan after the alignment from the first and last visits for patient 2 in the Table. B, The circumpapillary retinal nerve fiber layer (RNFL) thickness is shown for the first (August 15, 2008) and last (May 26, 2011) visits. Where 0° corresponds to the 9-o’clock and 3-o’clock positions in the right and left eyes, respectively. See the ROI Approach subsection of the Methods section for an explanation of the regions of interest.

Figure 2. Region-of-Interest Width at the First and Last Visits

A, Shown is the region-of-interest at the first (blue horizontal bars) and last (red horizontal bars) visits as a function of the distance around the optic disc for the patients in the Table. B, The circumpapillary retinal nerve fiber layer (RNFL) thickness is shown for the first (August 15, 2008) and last (May 26, 2011) visits. Where 0° corresponds to the 9-o’clock and 3-o’clock positions in the right and left eyes, respectively. See the ROI Approach subsection of the Methods section for an explanation of the regions of interest.

Figure 3. An Example of Progression Seen on En Face Slab Images

A, The circumpapillary retinal nerve fiber layer (RNFL) thickness is shown for patient 4 in the Table for the first (December 17, 2012) and last (May 20, 2014) visits. An en face slab image is shown. C and D, Shown is an enlargement of the region within the red square in B. The white arrowheads in C point to the same location and provide a reference to assess the progression of damage. The green arrowheads point to the same location in all panels.