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Karun Arora, Michael Boland, David Friedman, Joan Jefferys, Sheila West, Pradeep Ramulu, Wilmer Eye Institute, Johns Hopkins University School of Medicine; Comparing Better-eye and Integrated Visual Field Mean Deviation as Metrics for Capturing Visual Disability. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5311.
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© ARVO (1962-2015); The Authors (2016-present)
To determine 1) extent of difference between better-eye visual field (VF) mean deviation (MD) and integrated VF (IVF) MD and 2) whether better-eye or IVF MD better relates to disability measures obtained in the Salisbury Eye Evaluation (SEE)
VF testing was performed in each eye and used to calculate the amount of integrated VF loss (IVF MD) using binocular summation in both 1,098 SEE subjects and 13,955 Wilmer Eye Institute glaucoma patients. Differences between better-eye and IVF MD were calculated for the 490 SEE patients and the 7053 Wilmer glaucoma patients with VF MD ≤ -3 in at least one eye. In SEE subjects with VF loss, models were constructed to compare the relative impact of better-eye and IVF MD on driving habits, mobility, self-reported vision-related function and reading speed.
The median difference between the better-eye and the IVF MD (defined as better-eye MD minus IVF MD) was 0.41 dB (Interquartile range [IQR] = -0.21 to 1.04 dB) and 0.72 dB (IQR = 0.04 to 1.45 dB) for the SEE and Wilmer glaucoma subjects with VF loss, respectively, with differences of ≥ 2 dB between the two MDs observed in 9% and 18% of the groups. Amongst SEE subjects with VF loss, better-eye and IVF MD had similar associations with multiple disability metrics as judged by the presence/absence of statistically significant association between MD and the metric, the magnitude of observed associations (i.e. odds ratios, rate ratios or regression coefficients associated with 5 dB decrements in MD) and the extent of variability in the metric explained by the model (R^2 values). For example, a 5 dB decrement in better-eye and IVF MD slowed subjects' reading speed by -19.7 and -19.1 words per minute (p<0.0001 for both), respectively, with associated R^2 values of 0.12 and 0.10. Similar findings were noted in the subgroup of glaucoma subjects and the subgroup of persons in whom better-eye and IVF MD differed by ≥ 2 dB.
IVF MD rarely differs from, and does not predict measures of disability better than, better-eye MD. Unlike better-eye MD, IVF measurements require extra software or calculation. Furthermore, information from studies using better-eye VF MD can be more easily integrated into clinical decision-making and therefore provide a robust and meaningful method for reporting VF loss severity. Evidence supporting the use of IVF preferentially to better-eye VF is lacking.
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