The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by optical coherence tomography

Abstract

Abstract Background Astigmatism is a worldwide common ocular disorder. Total astigmatism is mainly driven by corneal astigmatism (CA), which occurs due to an irregular shape of the cornea. In eyes with astigmatism, retinal images can be distorted, and the image size could vary according to the axis of astigmatism assessed with computer-based methodology in astigmatic eyes. Objective to evaluate the influence of corneal astigmatism on the RNFL thickness and ONH parameters obtained by spectral-domain OCT. Patients and Methods 40 patient chosen from outpatient ophthalmology of Ain Shams University Hospitals and Om El¬_Massrein General Hospital and classified in two groups, the study group (high astigmatic patients ≥ 3 diopter) and control group (normal astigmatism< 3 diopter) with no significant change in the age and sex. All cases were free of any ocular diseases with no past history of medical importance (DM, HTN or any neurological diseases), all this cases never had any previous refractive surgery or any retinal lesion. Results In this study all cases had average IOP > 21 mmhg, and randomly selected from the outpatient clinic. The study group had thinner retinal nerve fiber layer in temporal quadrant and larger disc area than the control group. These study support the concept that corneal astigmatism has an effect on retinal nerve fiber layer thickness and optic nerve head parameters. Conclusion In our study, we compare between the OCT pattern of retinal nerve fiber layer thickness (total, superior, nasal and inferior quadrants) and the optic nerve head parameters (cup area, disc area, vertical and horizontal C/D ratio) in the high astigmatic patients (≥ 3 diopter) and normal astigmatism < 3 diopter.