Abstract
Purpose: :
To determine the association between visual function, as measured by Humphrey visual field (HVF), and structural parameters of lamina cribrosa (LC), peripapillary retinal nerve fiber layer (pRNFL) and ganglion cell complex (GCC) thickness, as measured by optical coherence tomography (OCT) at different stages of glaucoma.
Methods: :
Forty one eyes of 24 glaucoma patients were classified as pre-perimetric (glaucomatous optic neuropathy with normal HVF), early with mean deviation (MD) > -6 dB and advanced with MD ≤ -6 dB. The RTVue spectral domain OCT commercial software was used to measure GCC (RNFL + ganglion cell + inner plexiform layers) and pRNFL thickness. LC thickness was measured by 3 masked observers from 3D optic nerve OCT scan images. Significance of differences in structural parameters among groups was established using analysis of variance. Linear regression analysis determined the association between structural parameters and visual function.
Results: :
LC thickness measurements in pre-perimetric, early, and advanced glaucoma were 262 + 29, 193 + 27 and 107 + 16 microns, respectively. pRNFL thickness measurements in pre-perimetric, early, and advanced glaucoma were 98 + 14, 77 + 11 and 70 + 6 microns, respectively. GCC thickness measurements in pre-perimetric, early and advanced glaucoma were 90 + 10, 73 + 9 and 71 + 8 microns, respectively. There was a statistically significant difference in LC, pRNFL and GCC thickness among patients with pre-perimetric (MD = 0.66 + 0.8 dB; N=13), early (MD = -2.9 + 1.6 dB; N=14) and advanced (MD = -12.1 + 7.0 dB; N=14) glaucoma (p ≤ 0.001). In the pre-perimetric group, pRNFL and GCC thickness significantly correlated with MD (r=0.75, p=0.003 and r=0.84, p=0.0003, respectively). In the early group, LC and pRNFL thickness significantly correlated with MD (r=0.86, p<0.001 and r=0.75, p=0.002, respectively). In the advanced group, only LC thickness significantly correlated with MD (r=0.67, p=0.008).
Conclusions: :
An overall association between visual function and structural parameters of LC, pRNFL, and GCC thickness was found. The results suggest that LC thickness may be a better parameter for monitoring patients with advanced stage glaucoma.
Keywords: imaging/image analysis: clinical • nerve fiber layer • visual fields