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J. P. Garcia, Jr., J. dela Cruz, R. B. Rosen, D. F. Buxton; Imaging Implanted Keratoprostheses With Anterior Segment OCT and UBM. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3868.
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© ARVO (1962-2015); The Authors (2016-present)
To compare anterior segment OCT and UBM for evaluating the status of implanted keratoprostheses.
A retrospective study was made of patients who underwent surgery with implantation of a Boston Keratoprosthesis (KPRO Type I) and were examined with anterior segment OCT (AC Cornea OCT prototype, OTI, Canada) and UBM (OTI Scan 35-50MHz Ultrasound, OTI, Canada). Similar scans were acquired using each modality sequentially, then images were analyzed and compared.
Four eyes were included in the study. Cross-sectional OCT imaged the constructed KPRO as a T-shaped silhouette with corrugated sides (bolt screw pattern of the KPRO) at the apical center of the cornea. The KPRO-host borders were sharply demarcated. The rest of the cornea appeared thickened and hyper-reflective, producing shadows on the iris. Directly beneath the cornea, the implant’s back plate blended inconspicuously with the anterior chamber. The titanium locking ring that secures the back plate was discernible as bright horizontal lines flanking the bottom sides of the corrugated figure. These lines cast shadows that obscured the iris below. The back surface of the KPRO cylinder defined the pupillary space beneath, with the pupil becoming more apparent when a PCIOL was in place. OCT outlined a PCIOL as having a straight top line and a curved bottom line. The angles could be seen as open or closed. Coronal OCT, on the other hand, showed the "hubcap" pattern of the KPRO, and revealed the status of the central cylinder's back surface. UBM imaged the KPRO as a space at the apical center of the cornea with lines approximating the host cornea’s outer and inner surfaces. The KPRO-host borders were ill-defined, and the rest of the host cornea appeared thickened, grainy and at times vague. The back surface of the KPRO displayed two parallel linear artifacts below it. UBM imaged a PCIOL as two bright parallel lines between the back surface of the KPRO and its artifacts. The anterior chamber, angle and iris could be seen on radial scans. Unlike OCT, UBM was able to image glaucoma tubes and haptics below the iris.
Imaging of implanted keratoprostheses was superior with anterior segment OCT compared to UBM. Cross-sectional OCT allowed visualization of the angle, iris and PCIOL better than UBM. More significantly, coronal OCT showed the en face image of the KPRO including its back surface, clinically important for monitoring development of retro-keratoprosthetic membranes. UBM, on the other hand, was more effective for imaging haptics and glaucoma tubes inserted beneath the iris.
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