September 2009

 

CATARACT/ IOL

 

Wound closure alternative


by Matt Young EyeWorld Contributing Editor

   
Post-op day 1 fibrin glue for epithelial ingrowth after LASIK after RK; fibrin adhesive still has some drawbacks, and some researchers suggest a tissue-adherent hydrogel ocular bandage may be better suited for cataract surgery incisions Source: David R. Hardten, M.D.

Besides sutures or perhaps fibrin tissue, is there anything else available to protect against endophthalmitis in a clear corneal incision wound? Perhaps there is, a new study suggests. The study, undertaken by John A. Hovanesian, M.D, Jules Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, investigated wound closure with a polymerizing liquid hydrogel ocular bandage. Results showed promise. “A tissue-adherent hydrogel ocular bandage created a watertight seal in clear corneal cataract wounds,” Dr. Hovanesian reported.

New wound closer?

Dr. Hovanesian analyzed 24 clear corneal incisions in eye bank corneas, 12 of which were administered the liquid hydrogel bandage (I-ZIP Ocular Bandage, I-Therapeutix, Waltham, Mass.). The other 12 were used as controls, receiving no bandage. Incisions were made with a 2.5 mm clear corneal dual-bevel knife. They began at the limbus and tunneled about 2.0 mm centrally.

“Each eye was tested under low-pressure conditions to detect fluid ingress of India ink on the eye’s surface,” Dr. Hovanesian reported. “Eyes were tested again with external compression to distort the wound to detect fluid egress.”

Dr. Hovanesian found that India ink did not enter the hydrogel bandage group. It did, however, enter 9 (75%) of 12 incisions in the control group. Further, fluid egress with external manipulation also was not experienced by the hydrogel bandage group. Eleven eyes (92%) of the control group did experience this. The hydrogel group also performed well under wound compression conditions. “At 45 cm bottle height, simulated IOP should be 33 mm Hg,” Dr. Hovanesian reported. “The mean measured IOP was 36 mm Hg +/–4 (SD) in the control group and 34 +/–4 mm Hg in the treated group. The mean incision size was 2.6 +/–0.07 mm and 2.6 +/–0.03 mm, respectively.” Therefore, Dr. Hovanesian concluded that in these experimental conditions, the hydrogel bandage performed well. “To provide useful wound closure after ocular surgery, a technology must (1) prevent ingress and egress of fluid under low- and high-pressure conditions, (2) be resistant to external wound compression, (3) be simple to use with a short learning curve, and (4) be safe inside and outside the eye,” Dr. Hovanesian noted. “This study suggests that the hydrogel ocular bandage meets the first 2 of these criteria as it provided significantly greater wound closure than in control eyes, in which no bandage was used.”

The tool also was quite easy to use. “The PEG [polyethylene glycol] polymer requires mixing of components immediately before application to the eye and surgical technique to apply the desired quantity on the eye,” Dr. Hovanesian reported. “However, the surgeon in this study … had no experience with the ocular bandage used and was able to apply it successfully after a short practice session preceding the investigation. This suggests the material has an acceptably short learning curve.”

As determined by previous research, Dr. Hovanesian called the hydrogel “a noncytotoxic, nonsensitizing, nonirritating material with no systemic toxicity,” adding, “Histopathology found that the healing of rabbit eyes treated with this hydrogel polymer was at least equivalent to, and potentially faster than, that in untreated corneal incisions.”

The material is similar to that in bandage soft contact lenses, he noted. “This study suggests that a tissue-adherent hydrogel polymer ocular bandage may allow more secure closure of clear corneal cataract wounds than the current standard of care, which is to leave nonleaking wounds uncovered and unsutured,” Dr. Hovanesian reported. “This technology may also apply to other surgical techniques, such as closure of sutureless 25-gauge vitrectomy incisions, which has been shown to have a 12-fold greater risk for postoperative endophthalmitis than when 20-gauge instruments (with sutures) are used.”

Dr. Hovanesian also contrasted this material with fibrin adhesive, suggesting there are some advantages with hydrogel. “Other studies suggest that fibrin tissue adhesive may be a useful sealant in scleral tunnel and clear corneal cataract surgery but that fibrin adhesive carries some risks inherent in pooled donor plasma,” Dr. Hovanesian noted. Jost Jonas, M.D., department of ophthalmology, Faculty of Medicine Mannheim, University of Heidelberg, Germany, also cited risks with donor plasma as one of the reasons why he doesn’t use fibrin adhesive. “First of all it’s a blood product with potential risk of infection,” Dr. Jonas said. “Second, it is more expensive. Third, it may not be necessary.”

Dr. Jonas hasn’t used the liquid hydrogel bandage during surgery but has found his own method to put a lid on endophthalmitis outbreaks. “The more peripheral the sutureless incision, the lower the risk,” Dr. Jonas said. “This incision can be longer, and it’s closer to the ocular vessels, leading to faster rehealing.” Dr. Jonas estimated his endophthalmitis rate to be 1 in 2,000 cases.

Editors’ note: Dr. Hovanesian reported no financial interests related to this study, which was funded by a grant from I-Therapeutix (Waltham, Mass.). Dr. Jonas has no financial interests related to his comments.

Contact information

Hovanesian: drhovanesian@harvardeye.com
Jonas: +49 621 383 2652, Jost.jonas@augen.ma.uni-heidelberg.de

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