Background: Glaucoma is an optic neuropathy characterized by retinal ganglion cells (RGC) loss and retinal nerve\nfiber layer (RNFL) injury: this results in functional and morphological changes. The first can be observed by Standard\nAutomated Perimetry (SAP), the second by Optic Coherence Tomography (OCT) that measures the RNFL and\nganglion cell complex (GCC) thicknesses. Nevertheless, diagnosis of early glaucoma may be difficult. Recently,\nMedeiros et al. derived an empirical formula combining the measurement of structural and functional tests to\nprovide an estimate of RGC. The aim of the current study is to analyse the correlation between RGC count,\nestimated by Medeirosââ?¬â?¢ formula, and the structural and functional parameters in patients examined for glaucoma\nand to evaluate SAP, OCT and RGC counts capability to discriminate the weight of the disease itself.\nMethods: Ninety four eyes of 50 consecutive patients clinically referring to glaucoma service of the Universitary Eye\nClinic were submitted to a complete ophthalmic evaluation including SAP and Spectral Domain OCT (SD-OCT) of\nRNFL and macular GCC. Average thickness of RNFL and macular GCC, parameters Global Loss Volume (GLV) and\nFocal Loss Volume (FLV) over the entire GCC map were taken into account. Estimates of RGC were obtained with\nthe help of a model already published by Medeiros et al. combining light sensitivities from SAP and retinal\nthickness from OCT. The RGC count was estimated in the entire visual field (central 24Ã?°) and in the GCC macular\narea and then compared with functional and morphological parameters applying Pearsonââ?¬â?¢s correlation coefficient.\nResults: After the classification of the patients by the Glaucoma Staging System 2 of Brusini, we noticed a good\ncorrelation among the functional parameters considered, even if the Visual Field Index is unable to identify early\nglaucoma. An analogous result can be observed for structural data (RNFL and GCC). The correlation detected\nbetween functional and structural parameters was moderate. Great differences in RGC counts were found between\ngroups at various stages of glaucoma. GLV showed highest level of correlation (r > âË?â??0.8) with RCG counts.\nConclusions: Estimate circumpapillary and macular RGC counts can discriminate various stages of the disease and\nthere is also a good/very good correlation with both functional and structural parameters. GLV could be used\ninstead of RGC counts in clinical practice
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