David Wilkie DVM, Ohio State University
Project Summary from AKCCHF.org website:
“The study "Capsular tension ring effect on canine lens epithelial migration and post-operative lens capsule opacification" is a two-part study looking at the behavior of lens epithelial cells (LEC) and lens capsule scarring in response to capsular tension ring (CTR) placement during cataract surgery. 100% of dogs undergoing cataract surgery develop some degree of capsule scarring due to LEC proliferation and migration. There are multiple ways capsule scarring may be treated or prevented in humans, however to date, there is not an effective approved method of preventing or eliminating capsule scarring in the canine population undergoing cataract surgery. Rarely, the capsule scarring may be opaque enough to obstruct a dog’s vision completely and the goal of this study is to provide a mechanism to improve the degree of capsule scarring.
The first part of the study involved comparing the effect of CTR with synthetic lens (IOL) implantation in a "sham cataract surgery" setting in the laboratory. Lens epithelial cells were cultured on lens capsules containing CTR, IOL, and a combination of both CTR/IOL. The degree of LEC proliferation and migration (capsule scarring) was compared at different time points of cell culture. The results show that lens capsules containing both CTR and IOL showed a lesser degree of LEC proliferation and migration in a laboratory setting. This correlates with findings in human medical literature on CTR effects.
The second part of the study involves a clinical trial with CTR implantation in clinical patients. This study is currently in progress with a majority of the necessary client-owned dogs enrolled as far out as 12 months post-cataract surgery. Half of the eyes enrolled receive CTRs and half serve as control eyes. Photos are taken of the lens capsules at all recheck appointments, and the degree of capsule scarring is evaluated by a software program to eliminate subjectivity. In April 2008, preliminary statistical analysis was completed on clinical trial data at time points 2 weeks, 2 months, and 4 months. The preliminary statistics showed that eyes receiving CTRs had statistically less PCO at 2 months post-operatively and non-diabetic dogs receiving CTRs had statistically less PCO at 4 months post-operatively. In May 2009, complete statistical analysis of the findings will determine the significance of the capsular scarring difference between control eyes and eyes receiving CTRs. This data will be submitted in manuscript form for publication to Journal of Cataract and Refractive Surgery. Our clinical impression is that the CTR will statistically significantly decrease PCO by 12 months post-cataract surgery as 1) we are seeing some difference with the preliminary statistics and 2) subjectively in the clinic we are able to discern which eye has received the CTR by the smaller amount of scarring despite being blinded prior to the ophthalmic examination.
The significance of this research involves improving overall vision postoperatively in canine cataract patients. Different biomaterial types, lens implant designs, drugs, and other methods have been researched to improve the incidence of lens capsule scarring. This research has more historically been looked at in humans and rabbits. The CTR has shown statistically significant improvement in the incidence of human capsule scarring post-operatively. This research project will determine if CTRs have the same effect in canine lens capsules post-cataract surgery.”
Publication:
Wilkie DA, Colitz CM. Update on veterinary cataract surgery. 2009. Curr Opin Ophthalmol. Jan;20(1):61-8.