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Ou Tan, David S Greenfield, Brian Francis, Rohit Varma, Joel S Schuman, Richard Parrish, David Huang; Harmonizing OCT and VF parameters in the assessment of glaucoma progression speed. Invest. Ophthalmol. Vis. Sci. 2021;62(8):3354.
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© ARVO (1962-2015); The Authors (2016-present)
Compare the speed of glaucoma progression as measured by global visual field (VF) and optical coherence tomography (OCT) metrics.
Glaucoma suspect, pre-perimetric glaucoma (PPG) and perimetric glaucoma (PG) participants of Advanced Imaging for Glaucoma study,1 who had at least 7 visits with visual field (VF) and OCT ONH scan, were analyzed. Severity was staged by the modified Hodapp-Parrish-Anderson Criteria. Eyes with significant cataract progression were excluded. Spectral-domain OCT (RTVue, Optovue) and VF testing were performed every 6 months. The nerve fiber layer (NFL) thickness was measured from ONH scan. The NFL mean deviation (MD) were VF-equivalent dB-scale quantities based on sectorwise nonlinear regression of NFL thickness with VF deviation using cross-sectional data over a wide range of glaucoma severity.2 Linear regression was used to estimate the glaucoma progression speed.
Seventy-five glaucoma suspect eyes (VF MD -0.1±1.2dB), 160 PPG eyes (0.2±1.3 dB), 77 early PG eyes (-0.9±1.6dB) and 20 moderate+severe PG (-10.8±3.2dB) eyes were analyzed. The follow-up duration was 54 months ± 8 months (mean ± SD). For both VF MD and NFL MD, the speed of progression increased monotonically with glaucoma severity (Table 1). For overall NFL thickness, the progression speed was greatest in the PPG and early PG stages, but slowed down at the moderate+severe stages. The ratios of progression speed for NFL thickness relative to VF were significantly different between stages (p<0.006, one-way ANOVA). The ratios of progression speed for NFL MD relative to VF MD was generally slower (0.58-0.72), but not significantly different across disease stages (p=0.08). The progression speed of both NFL-MD and VF-MD were associated with baseline parameters (faster progression in eyes with more severe disease at baseline), while progression speed of NFL thickness was not (Table 2).
Compared to VF MD, NFL thickness tends to overestimate the progression speed in the early stages of glaucoma and underestimate it in the later stages. Clinicians should be aware of the discrepancy in the apparent speed of disease progression as measured by structural and functional metrics, which strongly depend on the stage of disease severity. Converting the NFL thickness profile to NFL MD may provide a progression metric more consistent with VF MD over a wider range of glaucoma severity.
This is a 2021 ARVO Annual Meeting abstract.
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