Contrast-to-noise Ratios to Evaluate the Added Value of the Ganglion Cell Complex Thickness for the Detection of Progression in Glaucoma.

PRCIS: This study shows that GCC thickness is most sensitive for detecting progression at the onset of glaucoma, but less sensitive than cpRNFL thickness. These findings suggest no clear additional value of GCC thickness over cpRNFL overall, although further evaluation in larger cohorts with advanced glaucoma is warranted. PURPOSE: To compare the sensitivity of ganglion cell complex (GCC) thickness in the macula to circumpapillary retinal nerve fiber layer (cpRNFL) thickness from OCT, and Mean Deviation (MD) and Visual Field Index (VFI) from Standard Automated Perimetry (SAP), for detecting glaucomatous progression across glaucoma stages. METHODS: Using longitudinal data from 205 eyes (125 participants), contrast-to-noise ratios (CNRs) were calculated for GCC, cpRNFL, MD and VFI. Glaucoma stage was defined by MD. Contrast was the parameter difference between two stages; noise was the variability from linear regression residuals from five consecutive OCT scans and HFA 24-2 tests per eye. Higher CNR indicates greater sensitive for detecting progression between stages. RESULTS: CNRs ranged from 3.7 to 13.2. In the transition from suspect to mild glaucoma, cpRNFL (13.2) and GCC (8.7) had significantly higher CNRs than MD (4.5) and VFI CNR (4.8); cpRNFL was also significantly higher than GCC. No significant CNR differences were found between structural and functional measures in later stages. CONCLUSIONS: GCC thickness is more sensitive than functional measures, but less than cpRNFL thickness, for detecting progression at glaucoma onset. In later stages, structural and functional parameters showed comparable sensitivity within the limits of the available data.