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Gustavo De Moraes, Rafael Furlanetto, Jeffrey Liebmann, Robert Ritch; A New Index to Monitor Central Field Progression in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2633.
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The visual field index (VFI) summarizes global visual field (VF) data and was developed to monitor glaucoma progression using 24-2 SITA fields. We applied the same principles and statistical procedures to develop a new parameter, the central field index (CFI), to monitor 10-2 VF progression.
The CFI was developed by calculating age-corrected defect depth at test points obtained during 10-2 examinations. The sensitivities at these points were scored as percentages similar to the method described for the VFI: 100 - [(│total deviation│÷ age-corrected normal threshold) x 100]. Based on a published estimate of the spatial magnification present in the occipital cortex, a weighting procedure was performed in which the 4 central-most points were allotted a greater weight (x3.5) than the remaining 64 points (x1.5). Therefore, the CFI is the mean of all weighted scores in percent. To validate this, we performed mixed linear model testing for the association between the CFI and various known risk factors for glaucoma progression in a sample of 176 eyes (142 patients) with established glaucoma and at least 5 10-2 VFs. To determine whether the CFI was affected by cataract - as is known to occur with mean deviation (MD) - we conducted a pilot evaluation comparing rates of CFI change (%/yr) in 3 groups of patients: 1) eyes with cataract, 2) pseudophakic eyes, and 3) eyes in which cataract surgery was performed in the middle of the series.
We were able to generate CFI values for the entire sample based on the description above. The mean rate of CFI change of the entire sample was -1.35%/yr (95% CI, -1.66 to -1.05 %/yr). Risk factors for faster CFI progression were worse baseline CFI (P<0.001), older age (P=0.014), and higher peak IOP (P=0.050). There was no significant difference in slopes of CFI progression among the 3 groups (P=0.98) whereas MD slopes differed significantly (P=0.001).
We have developed and validated a new index to monitor central field progression that is minimally affected by the presence or removal of cataract and which correlates significantly with known risk factors for glaucoma progression. This has important implications for glaucoma management. 1. Bengtsson B, Heijl A. Am J Ophthalmol. 2008. 2. Levi DM, Klein SA, Aitsebaomo AP. Vision Res 1985.
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