In their recent article, Li and associates evaluate the long-term complications associated with glaucoma drainage devices (GDD) in patients who have undergone Boston type 1 keratoprosthesis (KPro) surgery. The authors speculate an association between the presence of soft contact lenses (SCL) and GDD erosion in this particular population.

In a retrospective, interventional case series that aimed to determine prevalence, progression, treatment, and impact of glaucoma on visual acuity, we reviewed 38 consecutive eyes (38 patients) that have undergone KPro surgeries between 2008 and 2009 at our center. Of these patients, 21% (n = 8) had, along with their glaucoma, an implanted GDD. Among them, 4 presented with the implanted tube before KPro surgery, and 4 had their tube implanted postoperatively. An SCL was placed after KPro surgery in all our patients. In fact, SCL has been proven beneficial in efficaciously protecting the ocular surface, adequately maintaining its hydration, and decreasing the risk of corneal melts. Among patients who underwent KPro surgeries, had an SCL placed, and had an old or new implanted GDD, no tube erosion was recorded over a mean follow-up (FU) period of 24 months since KPro surgery. For the tubes placed postoperatively, the mean FU duration between the placement of the tube and patient’s last visit is 10 months. Regarding the old tubes, placed from 1 year to 14 years before KPro surgery, the mean FU period between the surgery (and therefore SCL placement) and the last FU visit is 22 months, which is greater than the mean duration between KPro surgery and GDD erosion of 16.5 to 18.3 months reported by Li and associates.

Our population is comparable to that of Li and associates with regard to the initial ophthalmologic diagnosis, which was mostly previous failed corneal grafts (n = 4) and chemical burn (n = 2). However, one difference between both groups of patients is the fact that we do not use vancomycin but rather vigamox only as a preventive measure to post-KPro infections. Vancomycin, which was reported to be toxic to the ocular surface, may predispose to GDD erosion in these patients, as stated by the authors. Based on this review, we are confident to state that, to us, SCL is not a cause leading to GDD erosion in KPro patients. KPro is the last hope for patients suffering from corneal blindness and for whom traditional penetrating keratoplasty has a low probability of success. Advances continue to be made in KPro devices and techniques—such as the placement of SCL as adjunct to KPro— in order to increase successful outcomes and reduce long-term complications.

From October 2009 to date, another 62 KPro surgeries have been performed at our site. Although no statistics are available on these patients with regard to their glaucoma, we can assertively affirm that no issues related to GDD, whether implanted preoperatively or postoperatively, have been documented. Therefore, no conclusions can be drawn with regard to an association between SCL and GDD erosion in patients with KPro implantation. Larger studies are needed to confirm or disprove this hypothesis, and to investigate what factors are associated with erosion of GDD in patients with KPro implantation.