Diagnostic Innovations in Glaucoma Study (DIGS): Comparing the Rates of Macular Ganglion Cell layer loss in Healthy, non-progressing Glaucoma and progressing glaucoma Eyes

Abstract

Purpose : To compare the rates of ganglion cell layer (GCL) thickness, retinal ganglion cell – inner plexiform layer (GCIPL) thickness and inner plexiform layer (IPL) change over time in healthy and non-progressing glaucoma and progressing glaucoma eyes using a novel cubic thickness grid (Figure 1).

Methods : 57 eyes of 29 healthy subjects and 181 eyes of 96 glaucoma subjects from the Diagnostic Innovations in Glaucoma Study (DIGS) were included. All eyes underwent 24-2 standard automated perimetry (SAP) and spectral-domain optical coherence tomography (Spectralis SD-OCT) high-resolution volume macular scans every 3 months for 2 years. Glaucoma progression was evaluated using Glaucoma Progression Analysis (GPA). The GCL, GCIPL and IPL layer thicknesses were measured using the San Diego Automated Layer Segmentation Algorithm (SALSA). Mixed effects models were used to compare the rate of change.

Results : Mean age was 47 years (range 22.5-66) for healthy subjects and 68 years (32-90) for glaucoma subjects. 22 eyes were detected as progressing using GPA. In healthy eyes, mean rates of GCL, GCIPL and IPL change were -0.073 µm/year, -0.117 µm/year and -0.039 µm/year, respectively; In glaucoma eyes, the rates of change were -0.184 µm/year, -0.25 µm/year and -0.064 µm/year, respectively. In both healthy and glaucoma eyes all GCL, GCIPL and IPL slopes were significantly different from zero. In glaucoma eyes, only the mean rates of GCL and GCIPL change in the nasal inferior sector were significantly faster in progressing glaucoma eyes than non-progressing glaucoma eyes (-0.053 µm/year vs. -0.029 µm/year, P=0.011 and -0.11 µm/year vs. -0.064 µm/year P=0.019 respectively).

Conclusions : In this cohort with relatively short follow-up time, the mean rate of GCL, GCIPL and IPL change was significantly faster in glaucoma eyes than in healthy eyes. In glaucoma eyes, only the mean rates of the GCL and GCIPL in the nasal inferior sector was significantly faster in GPA progressing glaucoma eyes than non-progressing glaucoma eyes. Further prospective clinical cohort studies with longer follow-up are needed to confirm these results.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Figure 1: 4mm x 4mm Novel Thickness Grid with 1.5mm x 1.5mm center excluded from scan sampling (A) takes into account areas more peripheral to those encompassed by the 3.45mm Standard Thickness Grid (B).