Abstract
Purpose: :
To evaluate the anatomic stability of an implanted Boston Type I Keratoprosthesis (KPro)-donor cornea interface, and assess the presence or absence of a potential space (gap) between the KPro front plate and donor cornea using anterior segment optical coherence tomography (AS- OCT). The presence of a gap would raise concerns of a possible pathway for the exchange of fluid between the ocular surface and the anterior chamber.
Methods: :
Fourteen eyes implanted with a Boston Type I KPro were studied by the non-contact technique of AS-OCT (AC Cornea OCT prototype, OTI, Canada). All the KPro devices had been implanted at least 4 weeks prior to the study (range: 1 to 22 months). Seven eyes had aphakic Kpros and the other 7 had pseudophakic implants. Anesthetized eyes were imaged before and during pressure application using sterile cotton tip applicators. Pressure was applied for 10 seconds just outside the temporal limbal area. Images were analyzed for any possible changes in the KPro-donor cornea interface during the application of pressure.
Results: :
Of 14 eyes, 10 had the threaded front plate model with a T-shaped silhouette and corrugated sides, whereas 4 had the threadless type with a T-shaped silhouette and smooth sides on cross-sectional OCT. Two of the 14 eyes revealed a gap between the front plate and the surface of the donor cornea, along with pooling of fluorescein within the gap. The rest revealed no gaps. With pressure, none of the eyes, including the two with gaps, demonstrated any change in the KPro-donor cornea interface during dynamic imaging (e.g. gaping, evidence of fluid entry or escape along the KPro-donor cornea borders). In all eyes, the titanium locking ring was visualized in its proper position.
Conclusions: :
The stability of an implanted KPro-donor cornea interface has been demonstrated dynamically utilizing AS-OCT. A gap that has been documented with this imaging tool showed neither extension nor exchange of fluid between the two environments during dynamic cross sectional imaging. All 14 eyes demonstrated proper positioning of the back plate and titanium locking ring, thus confirming that the phenomenon is not due to a loose fitting, unscrewing or improperly placed locking ring. Further studies will be needed to assess the cause of these gaps and determine if they are possibly related to the hydration status of the cornea, interaction of the cornea with prolonged use of a bandage contact lens or to other factors not yet determined.
Keywords: keratoprostheses • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • wound healing