Keratoprosthesis yielding impressive outcomes

Dr. Belin, professor of ophthalmology and director of cornea and refractive surgery, Albany Medical College, Albany, NY, presented findings based on 147 type I keratoprostheses implanted at 19 surgical sites since January 2003. Data were collected with a standard pre-printed reporting form that contained approximately 70 parameters describing preoperative, intraoperative, and postoperative data.

With a mean follow-up of 8.5 months, the keratoprosthesis had an impressive 95.2% retention rate with only seven failures. Vision improved dramatically. While only 4% of eyes had a best-corrected visual acuity (BCVA) of 20/200 or better prior to the procedure, 20/200 or better was achieved by 57% of eyes at the last follow-up. More impressively, 18% of eyes achieved legal driving vision of 20/40 or better.

"The patients are doing extremely well. Visual recovery and rehabilitation occur almost immediately, and the very high retention rate in this high-risk population is superb. For these individuals who have no other option, this procedure has been very rewarding for the patients and physicians alike," he added.

Prior to receiving the keratoprosthesis, the eyes included in this analysis had undergone an average of 2.3 transplants (range, 0 to 8). The most common preoperative diagnoses were chemical injury and bullous keratopathy.

Comorbid glaucoma was also common, with about 60% of eyes having glaucoma, about 32% having prior tube shunts, and about 8% having undergone trabeculectomy. The pseudophakic design of the keratoprosthesis was implanted in 63% of eyes and the rest received the aphakic design.

Total operating time averaged just short of 2 hours, and the surgery often included other procedures. Vitrectomy (42%) was most common, while lens removal was performed in 20% of eyes, and tube shunts, IOL removal, IOL placement, and tarsorrhaphy were each performed at rates of 12% to 15%.

Intraoperatively, only six complications occurred, and they were varied with single events of vitreous loss, front-plate dislodgement, host corneal perforation, hyphema, very thin host rim, and difficult anesthesia.

"This is a tertiary procedure and most patients have other concomitant ocular diseases, but the keratoprosthesis implantation itself involves techniques familiar to experienced transplant surgeons and is relatively quick," Dr. Belin said.

Postoperative complications

Development of retroprosthetic membranes, elevated IOP, and vitritis were the most common postoperative complications. Consistent with those data, the most common postoperative procedures were YAG membranectomy (18%) and tube shunt placement (7.5%). There were no cases of endophthalmitis.

Analyses of vision outcomes among 62 patients who were at least 1 year postimplantation showed BCVA was 20/200 or better in 55% while almost one-third had visual acuity of 20/50 or better, 11% were able to see 20/30 or better, and BCVA was 20/20 in 1.6% of eyes.

"Published data for the intralamellar AlphaCor keratoprosthesis in a subset with a similar follow-up duration reported that 42% of eyes achieved 20/200 or better visual acuity while 20/30 was the maximum BCVA at 12 months. No direct comparisons are possible, but it appears that the outcomes achieved with the type I Boston keratoprosthesis are at least equal to other available technologies," said Dr. Belin.