Time to Achieve Best Post-Operative Visual Acuity Following Boston Keratoprosthesis Surgery

Authors: Jonathan El-Khoury, Majd Mustafa, Roy Daoud, Mona Harissi-Dagher.

Disclosure Block: J. El-Khoury: None. M. Mustafa: None. R. Daoud: None. M. Harissi-Dagher: None.

Abstract Title: Time to Achieve Best Post-Operative Visual Acuity Following Boston Keratoprosthesis Surgery

Abstract Body:

Purpose: Since its clearance, the Boston type I keratoprosthesis (KPro) has gained wide usage for the treatment of several blinding corneal diseases. Having been long considered a last resort procedure, its use has evolved to be performed as the first surgical intervention in some cases. Patients often ask for the time required to achieve their best postoperative visual acuity. In PKP this duration is affected by surface irregularities and suture-induced astigmatism. However, since KPros have a fixed front plate with a specified optical power, these factors should not delay the time to best corrected visual acuity (BCVA). The purpose of this study is to evaluate the time to BCVA for KPro patients and all contributing factors.

Study Design: Retrospective observational case series.

Methods: One hundred and thirty-seven consecutive eyes of 118 patients who underwent KPro at the Centre Hospitalier de l’Université de Montréal (CHUM) between 2008 and 2017 were included in this study. All KPros were the same model (threadless aphakic KPro, snap-on model, with an 8.5 mm PMMA backplate and 16 fenestrations) and were performed by one surgeon (MHD). The primary outcome was time to BCVA. Pre and postoperative factors potentially influencing this time duration were addressed. These included patient demographics, ocular comorbidities and postoperative complications.

Results: Half of the 137 eyes underwent at least one previous corneal graft, and 58% had concomitant glaucoma. The mean follow-up was 5.49 years [0.39 - 9.34 years]. Median time to BCVA was 6 months [mean 1.12 years], with 47% of patients achieving their BCVA by 3 months. Patients retained their BCVA for 18 months after reaching it. The mean logMAR BCVA was 0.71 [0 - 3.30], representing a gain of 6 lines on the Snellen chart. Postoperative glaucoma, retroprosthetic membrane (RPM) and endophthalmitis prolonged the time to BCVA. We found no correlation between the following factors and time to BCVA: gender, age, indication for KPro surgery, primary versus secondary KPro, number of previous PKPs, previous retinal surgery, intraoperative anterior vitrectomy and preoperative glaucoma.

Conclusions: In our retrospective cohort, most subjects reached their BCVA between 3 and 6 months after KPro implantation. This duration was significantly prolonged by the development of postoperative glaucoma, RPM and endophthalmitis.