Anterior Segment Optical Coherence Tomography in Patients with Boston Type I Keratoprosthesis Allows Early Detection and Monitoring of Corneal and Scleral Melts

Abstract

Purpose: To quantify corneal/scleral thickness in Boston type I keratoprosthesis (KPro) patients using spectral domain anterior segment optical coherence tomography (AS-OCT) for early detection and monitoring of corneal and scleral melting.

Methods: This retrospective study included 10 eyes of 10 patients who underwent implantation of Boston type I KPros at the Massachusetts Eye and Ear Infirmary, Boston, MA. Corneal thickness in the four cardinal quadrants around the KPro optic stem as well as potential spaces (gaps) and areas of melting were measured serially using non-contact AS-OCT (RTVue OCT, Optovue Inc., Fremont, CA). The findings were correlated with findings documented by slit-lamp examination. The Mann-Whitney test was used to compare data.

Results: Ten patients (5 men; 5 women) with a mean age 65.7 ± 13.6 years were included. Four eyes had polymethylmethacrylate (PMMA) back plates, 5 had titanium, and 1 had consecutive PMMA and Titanium back plates. Six eyes had gaps between the KPro stem and the donor cornea with an average size of 117 ± 86 μm. Three eyes were noted to have early corneal melting with an residual stromal bed of 461 ± 84 μm, and 1 was noted to have scleral melting with average residual sclera of 200 ± 163 μm. The size of the gaps according to type of back plate was similar (PMMA, 88 ± 65 μm vs. Titanium, 110 ± 71 μm; p-value 0.11), but the average distance between optic and residual cornea in patients with early corneal melting was larger with PMMA back plates (346 ± 125 μm vs. 204 ± 44 μm; p-value<0.001). The average thickness of donor cornea was 564.2 ± 86.5 μm nasally, 577.2 ± 114.9 μm temporally, 554.7 ± 107.0 μm superiorly and 539.6 ± 101.4 μm inferiorly. Five of 6 eyes with gaps by AS-OCT (83.3%) were not noted to have gaps by slit-lamp examination. Of 3 eyes with corneal melting, AS-OCT recognized melting earlier and pointed to a greater extent. Slit-lamp examination also failed to detect progressive scleral melting where AS-OCT showed decreased scleral thicknesses from 75 to 36 μm and from 365 to 301 μm.

Conclusions: AS-OCT allows evaluation of the KPro-donor cornea interface for clinically non-apparent corneal/scleral thinning and melting. Early identification of corneal/scleral thinning and melting in Boston type I KPro patients allows for early intervention and may lead to improved outcomes.

Keywords: 575 keratoprostheses • 550 imaging/image analysis: clinical