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Courtney Ondeck, Linda M Zangwill, Robert N Weinreb, Alberto Diniz-Filho, Felipe A Medeiros; Detection of Glaucoma Progression with the RGC Index in High- versus Low-Risk Eyes. Invest. Ophthalmol. Vis. Sci. 2016;57(12):349. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate rates of progression with an index combining structure and function (RGC index) in glaucoma eyes deemed at high- versus low-risk of progression.
This was a prospective longitudinal observational study involving 397 eyes of 274 patients followed for an average of 3.8 ± 1.1 years. All eyes had glaucomatous visual field loss at baseline. Subjects had an average of 7.3 ± 3.7 spectral domain optical coherence tomography (SDOCT) and standard automated perimetry (SAP) visual field tests during follow-up. Glaucoma eyes were classified as high- versus low-risk of progression based on intraocular pressure measurements and central corneal thickness during follow-up. Low-risk eyes were required to have maximum IOP below 18 mmHg at all visits during follow-up with mean IOP below 15 mmHg. CCT in these eyes had also to be greater than 520 μm. High-risk eyes had maximum IOP higher than 22 mmHg during follow-up, with mean IOP higher than 15 mmHg. CCT in high-risk eyes had to be lower than 580 μm. Estimated retinal ganglion cell counts (RGC index) were obtained from SDOCT and SAP data using a previously described method (Medeiros et al. Am J Ophthalmol. 2012; 154:814-824). Linear mixed effects models were used to compare rates of progression in high- versus low-risk eyes using the RGC index as well as average retinal nerve fiber layer (RNFL) thickness and SAP mean deviation (MD).
78 eyes were classified as high-risk and 101 eyes as low-risk. Average mean IOP was 19.8 ± 3.3 vs. 11.1 ± 3.1mmHg, respectively (P<0.001). Average maximum IOP was 26.8 ± 4.7 vs. 14.2 ± 2.9 mmHg, respectively (P<0.001). Mean age was not significantly different between the groups (66.3 vs. 67.7 years; P=0.422). Rates of change in the RGC index were over 3 times faster in the high-risk versus low-risk group (-15,719 vs. -4,507 cells/year; P=0.001). Corresponding rates for average RNFL thickness were -0.79 ± 0.72 vs. -0.37 ± 0.48 μm/year, respectively (P=0.047) and, for SAP MD, -0.20 ± 0.42 vs. 0.01 ± 0.32 dB/year (P=0.043).
Eyes at high risk for progression showed significantly faster slopes of change on estimated RGC counts as obtained with the RGC index compared to low-risk eyes.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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