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Chronic hypotony may be significant complication of keratoprosthesis implantation
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Implantation of the Boston type 1 keratoprosthesis may cause a high incident rate of chronic hypotony that appears to be associated with retroprosthetic membranes, according to a retrospective case series.
“Chronic hypotony has not been reported in the literature all that well. It is mostly glaucoma that has been reported as an adverse event following implantation,” corresponding author Esen K. Akpek, MD, director of the Ocular Surface Disease and Dry Eye Clinic at the Wilmer Eye Institute, said in an interview with Ocular Surgery News.
Meanwhile, retroprosthetic membranes have been reported to occur in 30% to 40% of cases but are mostly regarded as a benign and trivial complication after surgery, she said.
Chronic hypotony
Akpek, who performed all the surgeries in the series, noted that during follow-up, patients were generally not developing glaucoma.
“We were ecstatic because glaucoma is the No. 1 complication that causes permanent vision loss after keratoprosthesis,” she said. “However, we eventually detected lower than normal blood pressure.”
Esen K. Akpek
Akpek and colleagues were expecting to find vision loss from glaucoma in their series but instead found chronic hypotony.
“We believe that if you follow patients long enough, retroprosthetic membranes can potentially damage the eye from this complication,” Akpek said. “After a time, these membranes extend onto the ciliary body, thereby causing compromised production of aqueous humor.”
The authors also speculated that retroprosthetic membranes might lead to retinal detachment.
The study
In the case series, the 1-year predictive incidence of chronic hypotony after Boston keratoprosthesis (KPro) implantation was 4.7%. But at 3 years, the rate jumped to 18.7%. The longer the follow-up, the higher the incidence, Akpek said.
The study, which was published in the American Journal of Ophthalmology, reported that six of 68 eyes developed chronic hypotony at a median 18.5 months after KPro implantation.
Five of the six eyes had already undergone multiple intraocular surgeries before implantation, and three of the six eyes had glaucoma tube shunts inserted previously.
Additionally, none of the six eyes had ocular surface pathologies, and all of them were fairly healthy.
The authors were unable to identify any preoperative risk factors for developing chronic hypotony; postoperatively, a retroprosthetic membrane was the only risk factor found. There was no increase in risk for older patients or those with a history of multiple donor corneal transplants. About one-third of study patients developed retroprosthetic membranes.
Four of the six patients successfully underwent a pars plana vitrectomy 3 to 6 months after onset of chronic hypotony. The fifth patient declined surgery and the eye was eventually enucleated, and the sixth patient did not need surgery.
Updated version of device
Akpek called herself “a big fan” of the KPro and has performed more than 100 procedures to date.
“It provides hopeless patients with such good vision as long as there is good potential in the eye,” she said. Some patients achieve 20/20 the day after surgery, and 80% have some vision improvement.
A newer version of the KPro, which is in the investigative stage, features a back plate made of titanium instead of PMMA, which is used in the current device.
“The titanium plate has been shown to decrease the incidence of retroprosthetic membranes,” Akpek said.
Newer antifibroproliferative agents to address anterior fibrotic membranes could also potentially reduce the occurrence of hypotony in patients. – by Bob Kronemyer
Reference:
- Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus id dolor est.Dokey A, Ramulu PY, Utine CA, et al. Chronic hypotony associated with the Boston type 1 keratoprosthesis. Am J Ophthalmol. 2012;154(2):266-271.
For more information:
- Esen K. Akpek, MD, can be reached at Ocular Surface Disease and Dry Eye Clinic, Wilmer Eye Institute, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Maumenee No. 317, Baltimore, MD 21287-9238; 410-955-5214; email: esakpek@jhmi.edu.
- Disclosure: Akpek has no relevant financial disclosures.