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Clinical Assessment of Mirror Artifacts in Spectral Domain Optical Coherence Tomography

¹Ophthalmology, Tufts Medical Center, Boston, United States ²Ophthalmology, Tufts Medical Center, Boston, United States ³Ophthalmology, Tufts Medical Center, Boston, United States ⁴Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, United States ⁵Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, United States ⁶Ophthalmology, Tufts Medical Center, Boston, United States ⁷Ophthalmology, Tufts Medical Center, Boston, United States ⁸Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, United States ⁹Eye and Ear Institute, University of Pittsburgh Medical Center Eye Center, Pittsburgh, United States ¹⁰Ophthalmology, Tufts Medical Center, Boston, United States

Correspondence: Jay Duker, Email: jduker{at}tuftsmedicalcenter.org

Abstract

Purpose: To investigate the characteristics of a spectral domain Optical Coherence Tomography (SD OCT) image artifact known as the "mirror artifact", calculate its prevalence, analyze potential risk factors, measure severity, and correlate it to spherical equivalent and central visual acuity (VA).

Methods: Cirrus HD-OCT Macular Cube 512x128 scans taken between January 2008 and February 2009 at the New England Eye Center were analyzed for the presence of mirror artifacts. Artifact severity was analyzed by the degree of segmentation breakdown that it causes on the macular map. A retrospective medical records review was conducted for patients with artifacts and for a random control group without artifacts.

Results: Out of the scans from 1,592 patients, 9.3% of the patient scanned (148 patients, 200 eyes) contained mirror artifacts. Significantly more myopic spherical equivalent (p< 0.001), worse VA (p< 0.001), longer axial lengths (p= 0.004), and higher proportions of moderate to high myopia (p< 0.001) was found for patient with mirror artifacts compared to patients without artifacts. Worse VA is associated with increased artifacts severity (p= 0.04).

Conclusions: Out of all scans analyzed, a high prevalence of mirror artifacts was found. This image artifact was highly associated with moderate to high myopic patients. Improvements in instrumentation may be necessary to resolve this problem in moderate and high myopic eyes. Operators should be advised to properly position the retina when scanning patients. In cases where peripheral abnormalities in topographic measurements of retinal thickness are found, corresponding OCT scans should be examined for the presence of mirror artifacts.

Key Words: optical coherence tomography • myopia • image analysis