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Clement C. Chow, Rohan J. Shah, Jennifer I. Lim, Felix Y. Chau, Joelle A. Hallak, Thasarat S. Vajaranant; Effect of Macular Thinning, Vessel Tortuosity, and Vessel Diameter in Peripapillary RNFL Thickness by Spectral Domain OCT in Sickle Cell Disease: Implications for Glaucoma Evaluation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):659.
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Our group has previously reported that sickle cell patients with focal macular thinning had significantly thinner retinal nerve fiber layer (RNFL) compared to those without macular thinning and controls. The aim of this study is to report the effect of temporal macular thickness, vessel tortuosity, and vessel diameter in the measurement of RNFL thicknesses by spectral domain optical coherence tomography (SD-OCT).
In this prospective study, sickle cell (SS, SC, and S-Thalassemia) patients and age-similar, race-matched controls underwent SD-OCT of the macula and optic nerve head (ONH) using the Heidelberg Spectralis. Patients with prior retinal treatments (laser or surgery), diabetes mellitus, glaucoma, or other ocular diseases were excluded. RNFL thickness measurements within each of the seven subfields of the ONH as displayed on the SD-OCT report were recorded. The sickle cell patients were grouped into those with focal macular thinning and those without. Temporal macular thickness was recorded from the macular SD-OCT. Vessel tortuosity was graded by two masked retina specialists (JIL, FYC) and vessel diameters were measured using native Heidelberg software near the disc margin.
151 eyes of 88 sickle cell patients and 57 eyes of 31 age-similar and race-matched controls were included. In the macular thinning group (n= 81), there is a positive linear relationship between temporal macular thickness and global RNFL thickness with a Person correlation coefficient of 0.60 (p<0.0001). In the no macular thinning group (n=70), those with vessel tortuosity (n=17) had significantly thicker RNFL than those without vessel tortuosity (n=53), despite similar age and macular thickness (unpaired t-test, p<0.03 in 5 of 7 subfields). On average, both arteries (80 vs. 103 um, p<0.001) and veins (109 vs. 138 um, p<0.001) at the disc margin were significantly wider in sickle cell patients compared to controls.
There are unique factors that could affect RNFL measurements in sickle cell patients on SD-OCT. Severity of macular thinning has a direct effect on RNFL thinning while vessel tortuosity and larger vessel diameter may have an inverse effect.
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