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Chunwei Zhang, Carolina Pelegrini Gracitelli, Alberto Diniz-Filho, Ricardo Yuji Abe, Linda M Zangwill, Robert N Weinreb, Felipe A Medeiros; The Retinal Ganglion Cell Index and Longitudinal Changes in Quality of Life ofPatients with Glaucoma.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):348. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The Retinal Ganglion Cell (RGC) index is a combined index of structure and function designed to provide estimates of RGC counts based on results of standard automated perimetry (SAP) and optical coherence tomography (OCT) in glaucoma. The index has been shown to improve diagnosis, staging and detection of progression. In this investigation, we provide further validation of its relevance to glaucoma management by studying its longitudinal association with changes in patient-report quality of life (QoL) outcomes over time.
This was an observational cohort study involving 130patients with glaucoma followed for an average of 3.4 ± 0.9 years. All patients had SAP and spectral-domain OCTtesting during follow-up. The RGC index was calculated by combining estimates of RGC counts from SAP and OCT using a previously described method (Medeiros et al. AJO 2012; 154:814-824). In addition, change in vision-related QoL over time was investigated by annual administration of the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25). Rasch analysis was performed to obtain a summary score representing vision-related QoL. A joint multivariate linear mixed model was used to investigate the association between change in NEI VFQ-25 Rasch-calibrated scores and changes in the RGC index, adjusting for confounding socioeconomic and clinical variables.
Rates of change in the RGC index were significantly associated with change in NEI VFQ-25 scores over time. On average, a loss of 50,000 in estimated RGC counts was associated with a change of 2.3 units in the NEI VFQ-25 score (P<0.001). Baseline estimated RGC counts, indicating severity of glaucomatous damage, were also associated with change in NEI VFQ-25 (P<0.001). For individuals with lower estimated RGC counts at baseline, neural losses led to greater loss in QoL compared to those with higher counts. A multivariable model containing baseline and slope of change in the RGC index performed similarly (R2 =59%; P<0.001) to a multivariable model containing slopes of SAP, slopes of OCT and baseline disease severity (R2 =59%; P<0.001).
Progressive changes in the RGC index are associated with changes in vision-related QoL in patients with glaucoma. These results suggest that the RGC index is a relevant biomarker for the degree of neural loss in glaucoma with significant relationship to glaucoma-associated disability.
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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