Although endophthalmitis is rare (ie, a 0.2% incidence rate), the clear-corneal incision has been identified as increasing the risk for endophthalmitis following cataract surgery by as high as 7.4-fold, according to the recent European Society of Cataract and Refractive Surgeons (ESCRS) endophthalmitis study.¹ Other peer-reviewed studies have also correlated the clear corneal incision with increased rates of endophthalmitis after cataract surgery.^2,3

A new liquid ocular bandage, developed by Hyperbranch Medical Technology, (Durham, North Carolina), may help seal and protect these corneal incisions against mechanical stress and irritation in postsurgical, posttraumatic and nontraumatic conditions.⁴

This unique ocular bandage consists of a synthetic dendritic hydrogel that is easily applied—via a special applicator—directly onto the ocular surface as a liquid. The hydrogel is activated by mixing two separate components. Upon application to the cornea, it crosslinks within 30 seconds to form a low-profile, smooth, soft, and transparent protective barrier film on the ocular surface (Figures 1 and 2).

ONGOING STUDIES
A clinical trial is currently underway to evaluate the safety, tolerability and effectiveness of this ocular bandage in human patients. Currently, the interim data from treating five normal human eyes has revealed promising results: No patient discomfort, complications or adverse events were noted during the first 30 days after application, and BCVA remained at 20/20 in all eyes.

Slit-lamp examinations of all eyes performed throughout the study showed no evidence of any inflammation or other abnormal findings, and fluorescein staining of the surface helped to identify and confirm the presence of the ocular bandage (Figure 3).

In a preclinical study, the ocular bandage was applied to 18 New Zealand white rabbit eyes (ie, eight normal corneas, six abraded corneas and four scored corneas). Average duration of the bandage varied depending on the type of wound, lasting 1 day in normal eyes, 1.5 days in abraded eyes, and 6.3 days in eyes that received a linear partial-thickness incision. International Organization for Standardization (ISO) 10993 biocompatibility testing was performed in the following areas: agar diffusion (ISO reference 10993-5); systemic injection (ISO reference 10993-11); intracutaneous injection (ISO reference 10993-10); murine local lymphnode assay (ISO reference 10993-10); primary ocular irritation (ISO reference 10993-10); primary ocular irritation (ISO reference 10993-10); reverse mutation assay (ISO reference 10993-3); rodent bone marrow micronucleus assay (ISO reference 10993-3); and chromosomal aberration assay (ISO reference 10993-3).

SAFE MICROBIAL BARRIER
Laboratory studies were performed to evaluate the in-vitro microbial barrier properties of the liquid ocular bandage against common pathogens associated with endophthalmitis. The study paired 18 control samples against 300 samples with the ocular bandage and included five parts: (1) a modified strike-through test model using Dey and Engley (D/E) agar containing bromocresyl purple to determine the presence or absence of acidic bacterial metabolic byproducts, (2) applying four drops of the ocular sealant material on the surface of the D/E agar and allowing it to polymerize within a 10.4-mm test tube, (3) adding 5 µL of inoculum (with 104 organisms of either Pseudomonas aeruginosa or Staphylococcus aureus), (4) incubating the specimens at 35º C to 37º C, and (5) observing the samples at 24 hours for color change. Six of six samples in the positive control tests experienced a color change at 24 hours compared with zero of 300 samples with the ocular bandage (Table 2).

The ultrastructure of the ocular bandage may provide insight into the microbial barrier properties demonstrated with this material. Scanning electron microscopy (SEM) has revealed the pore size in the polymer network of this ocular sealant to be very small (ie, 1 µm to 3 µm) (Figure 4).

Interim results from an ongoing clinical trial have shown the liquid ocular bandage to be safe, well-tolerated, and effective in human patients. Coupled with the in vitro data, these findings support the role that the ocular bandage could play in sealing and protecting corneal incisions and other ophthalmic wounds. Given the potential risk factor of clear corneal incisions in increasing endophthalmitis rates, the ocular bandage could serve as a more attractive alternative to sutures for improving wound integrity and hopefully lowering the risk for infection.

Terry Kim, MD, is associate professor of ophthalmology at Duke University Eye Center, in Durham, North Carolina. Dr. Kim states that he is a paid consultant for Hyperbranch Medical Technology. He may be reached at terry.kim@duke.edu.

1. Barry P, Seal DV, Gettinby G, Lees F, et al. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: Preliminary report of principle results from a European multicenter study. J Cataract Refract Surg. 2006;32:407-410.
2. Cooper MA, Holekamp NM, Bohigian G, Thompson PA. Case-control study of endophthalmitis after cataract surgery comparing scleral tunnel and clear corneal wounds, Am J Ophthalmol. 2003;136: 300–305.
3. Nagaki Y, Hayasaka S, Kadoi C, et al. Bacterial endophthalmitis after small-incision cataract surgery. Effect of incision placement and intraocular lens type. J Cataract Refract Surg. 2003;29:20-26.
4. Kim T, Mah F, Lee C, Carnahan M, D'Alessio K. Novel Liquid Ocular Bandage: Human Clinical Trial and Microbial Barrier Function. Presented at the 24th Congress of the ESCRS. September 9-13, 2006. London.