Consistency of Structure-Function Correlation Between Spatially Scaled Visual Field Stimuli and In Vivo OCT Ganglion Cell Counts.

PURPOSE: To investigate the effect of stimulus size and disease status on the structure-function relationship within the central retina, we correlated the differential light sensitivity (DLS) with Goldmann stimulus size I to V (GI-V) and optical coherence tomography (OCT) derived in vivo ganglion cell count per stimulus area (GCc) within the macular area in normal subjects and patients with early glaucoma.

METHODS: Humphrey Field Analyzer 10-2 visual field data with GI through V and Spectralis OCT macular ganglion cell layer (GCL) thickness measurements were collected from normal and early glaucoma cohorts including 25 subjects each. GCc was calculated from GCL thickness data and correlated with DLSs for different stimulus sizes.

RESULTS: Correlation coefficients attained with smaller stimulus size were higher compared to larger stimulus sizes in both normal (GI-GII: R2 = 0.41-0.43, GIII-GV: R2 = 0.16-0.41) and diseased cohorts (GI-GII: R2 = 0.33-0.41, GIII-GV: R2 = 0.19-0.36). Quadratic regression curves for combined GI to V data demonstrated high correlation (R2= 0.82-0.90) and differed less than 1 dB of visual sensitivity within the GCc range between cohorts. The established structure-function relationship was compatible with a histologically derived model correlation spanning the range predicted by stimulus sizes GI to GIII.

CONCLUSIONS: Stimulus sizes within critical spatial summation area (GI-II) improved structure-function correlations in the central visual field. The structure-function relationship was identical in both normal and diseased cohort when GI to GV data were combined. Congruency of GI and GII structure-function correlation with those previously derived with GIII from more peripheral locations further suggests that the structure-function relationship is governed by the number of ganglion cell per stimulus area.