Artifacts in OCT Retinal Nerve Fiber Layer Imaging in Patients with Boston Keratoprosthesis Type 1

Abstract

To determine the clinical utility of optical coherence tomography retinal nerve fiber layer (OCT RNFL) imaging for glaucoma evaluation in patients with Boston keratoprosthesis type 1 (KPro) by investigating imaging artifacts. Case-control study. Patients with KPro and without KPro (controls) matched for age, gender, and glaucoma diagnosis. The most recent Cirrus OCT RNFL scan from one eye was categorized as with good signal strength (SS; ≥6 out of 10) or poor SS (<6). Those with good SS were analyzed by two independent reviewers for artifacts. Images with good SS and no artifacts affecting the scanning circle were considered useful for glaucoma evaluation. The incidence of poor SS and artifacts in OCT RNFL images; patient characteristics associated with useful scans. Sixty-five patients with KPro and 75 controls were included; 89.2% of KPro patients and 89.3% of control subjects had glaucoma (p=0.98). 40.0% of KPro patients and 5.3% of controls had poor SS (p<0.001). The proportion of images with either poor SS or artifacts was similar in KPro (76.9%) versus controls (72.0%, p=0.51). The most common artifacts in both groups were missing data (43.6%, 53.2%, respectively, p=0.32) and motion artifact (25.6%, 19.7%, respectively, p=0.47). 43.1% of images in KPro patients and 69.3% in controls were useful for glaucoma evaluation (p=0.002). In the KPro group, patients with useful OCT scans, compared to those without, had better visual acuity (0.4±0.3 vs. 0.9±0.7 LogMAR, p=0.004), and did not have congenital corneal pathologies (0.0% vs. 24.3%, p=0.008). A multivariable analysis showed KPro patients with older age had higher odds of useful OCT images (odds ratio 1.05, p=0.03). Among KPro patients with useful OCT scans, RNFL thickness correlated with observed cup to disc ratio (Pearson correlation r=-0.42, p=0.03). The rate of OCT RNFL images with either poor signal strength or artifacts in the KPro and control population was comparable. In patients with KPro, where intraocular pressure measurements are difficult and glaucoma is highly prevalent and often severe, OCT RNFL imaging can be useful for glaucoma evaluation.