Ocular Bandage
Directly applied to the ocular tissue,
this bandage protects
against mechanical irritation.
BY TERRY KIM, MD
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.
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.
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 (Figure 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. |
