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Robert Fargione, Wen-Jeng (Melissa) Yao; Relationship Between Asymmetric Central Corneal Thickness and Retinal Nerve Fiber Layer Thickness in Patients with Primary Open Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4573. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Central corneal thickness (CCT) has been identified as an independent risk factor for the development and progression of primary open angle glaucoma. No studies to date have evaluated the difference in retinal nerve fiber layer (RNFL) thickness between eyes in patients with asymmetric CCTs. The aim of our study is to evaluate the difference in glaucomatous nerve damage between eyes in patients with asymmetric CCTs.
This study is a retrospective cohort study that included all patients seen by a single surgeon from July 1 to September 30, 2014 with a diagnosis of primary open angle glaucoma. Subjects with a history of keratoplasty, refractive surgery, or corneal pathology or surgery affecting CCT were excluded. Average retinal nerve fiber layer measurements were obtained with the Spectralis© Ocular Coherence Tomography (OCT).
143 patients met the inclusion criteria, of whom 60 (41%) were male. The mean age was 67.2 years. Among patients with RNFL difference of more than 5 microns between eyes, the mean CCT in eyes with the thicker RNFL was 535.10 microns, compared with 525.70 microns in eyes with the thinner RNFL (p=0.05). Among patients with a CCT asymmetry of 30 or more microns, the average RNFL in the eyes with thicker CCT was 80.07 microns and that in the thinner eyes was 65.15 microns (p=0.02). Patients with a CCT difference of 30 microns or more showed an average RNFL difference of 14.92 microns, a statistically significant difference compared to that of patients with a CCT difference of less than 30 microns, with an average RNFL difference of 0.90 microns (p=0.01). Spearman’s correlation coefficient was calculated to assess the relationship between CCT asymmetry and RNFL asymmetry, showing a positive correlation at 0.13, although not statistically significant (p=0.12).
Our results demonstrate that primary open angle glaucoma patients with asymmetric central corneal thickness between eyes, especially those with a high degree of asymmetry, are at risk for more advanced nerve fiber layer loss in the eye with the thinner CCT. Because OCT RNFL is an objective measure that can frequently used in identifying pre-perimetric nerve damage, this has clinical implications for the treatment and monitoring of such patients.
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