Classification of Retinal Ganglion Cell Defects Seen on Frequency-Domain OCT in the Macula of Patients with Glaucoma

Abstract

 

Purpose

 

To classify patterns of retinal ganglion cell (RGC) defects in glaucoma patients as seen on frequency-domain optical coherence tomography (fdOCT) volume macular scans and to compare these patterns to associated visual fields (VF).

 

Methods

 

One eye of 35 glaucoma patients or suspects (inclusion criteria: 24-2 MD of -6 or better) was prospectively tested with fdOCT and 10-2 VFs. The combined RGC and inner plexiform layers (RGC+) of the OCT scans were segmented using a computer-assisted manual segmentation technique.[1,2] RGC+ probability plots [3] (divided into an 8 by 8 grid) were generated. First, a scan was considered abnormal if at least 3 contiguous abnormal squares (at 5%, 2%, 2%) respecting the horizontal midline were present. This criterion yielded 24 abnormal OCT hemifields, similar to the number (26) of abnormal 10-2 VFs yielded by the typical 5%, 5%, 1% criterion. The 24 abnormal OCT hemifields were classified as arcuate-like, widespread, or "other." "Other" included temporal and non-continuous defects. RGC+ thinning plots were obtained by averaging the RGC+ thickness by classification and subtracting the average control thickness.[4] For each OCT group, the means of the associated 10-2 total deviation values were acquired.

 

Results

 

24 (34%) of the 70 OCT hemifields were abnormal. Of these, 10 (14%) were arcuate-like, 8 (11%) widespread, and 6 (9%) "other." Fig. 1 (field view) shows the average OCT thinning plots for the inferior retinal hemifield and Fig. 2 the averaged associated VFs. For OCTs classified as normal (Fig. 1A), the mean 10-2 VF appeared normal (Fig. 2A). OCTs classified as arcuate exhibited greater thickness loss in the nasal retina (Fig. 1B) and the mean 10-2 VF appeared arcuate (Fig. 2B). For OCTs classified as widespread (Fig. 1C), the mean 10-2 VF also appeared widespread (Fig. 2C). Finally, there was no clear correspondence between OCT (Fig. 1D) and VF (Fig. 2D) for the "other" class, although the sample size was small.

 

Conclusions

 

The pattern of RGC defects on OCT could be classified into 4 groups. Except for the "other" category, the average 10-2 VF closely resembled the pattern of OCT RGC+ thinning. 1. Yang et al. Biomed Opt Exp 2011. 2. Raza et al. AO 2011. 3. Hood & Raza. Biomed Opt Exp 2011. 4. Hood et al. TVST 2012.

 

 

Average thinning for inferior hemifield OCT classification (field view).

 

 

Average visual fields.

 

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 531 ganglion cells