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Navid Amini, Farideh Sharifipour, Pablo Romero, Sharon Henry, Simon K Law, Joseph Caprioli, Kouros Nouri-Mahdavi; Structure-Function Relationships in Glaucoma after Normalization of Minimum Rim Width and Comparison to Retinal Nerve Fiber Layer. Invest. Ophthalmol. Vis. Sci. 2016;57(12):372.
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© ARVO (1962-2015); The Authors (2016-present)
To estimate changes in global and regional structure-function relationships between SD-OCT minimum rim width (MRW) and visual field sensitivity after normalization for Bruch’s membrane opening (BMO) circumference and to compare findings to those for retinal nerve fiber layer (RNFL).
110 eyes of 70 glaucoma patients with RNFL and optic nerve head images (24 radial scans, 768 scans/6 mm) with Spectralis SD-OCT were prospectively recruited. BMO locations were delineated automatically on each radial B-scan, manually corrected when necessary by an experienced observer, and MRW measurements exported. The latter were normalized with the Patel and Harwerth approach based on the average BMO ellipse circumference from a separate normal database. Nonparametric correlations were explored between global and 6 sectoral MRW (raw and normalized) and RNFL thickness measures, and both of these parameters vs. global or cluster-based (Garway-Heath) visual field mean deviation.
The average change in global MRW after normalization was 14 (±12μm). The Spearman’s correlation coefficients between raw MRW and RNFL thickness varied between 0.54 and 0.77 (highest at TI sector) and improved to 0.56-0.80 after normalization for BMO circumference (p>0.053 for all the differences). The correlation coefficients between raw MRW and VF clusters varied between 0.35 (T sector and central cluster) to 0.65 (TI sector and superior midperipheral cluster)(p<0.001 for all), whereas normalized MRW demonstrated slightly stronger relationships (rho=0.40-0.67; p>0.06 for all differences, lowest p value in TS sector). RNFL thickness demonstrated stronger relationships with VF sensitivities compared to MRW. The differences were statistically significant globally (0.70 vs. 0.51, p=0.004), and in the NI sector (0.58 vs. 0.46, p=0.04), the TS sector (0.79 vs. 0.53, p=0.003), and the T sector (0.65 vs. 0.40, p=0.002). The dynamic range for normalized MRWs was larger than that for RNFL (344 vs. 119 um).
MRW measurements have slightly better correlations with RNFL and VFs after normalization for BMO circumference. The dynamic range of MRW is greater than RNFL, even after accounting for the lateral resolution of OCT. Compared to MRW, RNFL thickness is more closely related to VF measurements.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Difference between raw and normalized MRW as a function of BMO area
RNFL and MRW dynamic range
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