Full-thickness Corneal Wounds Research Articles

Photocurable and Temperature-Sensitive Bioadhesive Hydrogels for Sutureless Sealing of Full-Thickness Corneal Wounds.

Penetrating corneal wounds can cause severe vision impairment and require prompt intervention to restore globe integrity and minimize the risk of infection. Tissue adhesives have emerged as a promising alternative to suturing for mitigating postoperative complications. However, conventional water-soluble adhesives suffer formidable challenges in sealing penetrating corneal wounds due to dilution or loss in a moist environment. Inspired by the robust adhesion of mussels in aquatic conditions, an injectable photocurable bioadhesive hydrogel (referred to as F20HD5) composed of polyether F127 diacrylate and dopamine-modified hyaluronic acid methacrylate is developed for sutureless closure of corneal full-thickness wounds. F20HD5 exhibits high transparency, wound-sealing ability, proper viscosity, biodegradability, and excellent biocompatibility. It allows in situ cross-linking via visible light, thereby providing sufficient mechanical strength and adhesiveness. In vivo, the adhesive hydrogel effectively closed penetrating linear corneal incisions and corneal injuries with minimal tissue loss in rabbits. During the 56-day follow-up, the hydrogel facilitates the repair of the injured corneas, resulting in more symmetrical curvatures and less scarring in distinction to the untreated control. Thus, bioinspired hydrogel holds promise as an effective adhesive for sealing full-thickness corneal wounds.

Full- versus partial-thickness sutures: experimental models of corneal injury repair.

To evaluate the performance of full-thickness (FT) versus partial-thickness (PT) sutures in a full-thickness corneal wound in an animal model. This is a prospective, experimental, comparative, longitudinal study. A 6-mm linear, full-thickness corneal incision was performed on the right eye of eight domestic pigs. Eyes were randomly assigned for repair with interrupted PT (80-90% depth) sutures or FT 10-0 nylon sutures. Anterior segment OCT, corneal pachymetry and clinical photographs were obtained 1, 4 and 8weeks postoperatively. Corneal thickness, depth of suture placement, perilesional edema, coaptation of wound edges and complications were noted. Histopathologic examination was performed at 8weeks. 100% of the eyes with FT sutures developed a linear, less opaque scar. 100% of the eyes with PT developed a dense, opaque stromal scar (p = 0.02). Vascularization of the cornea was present in 75% of PT group and 25% in the FT group (p = 0.50). As the corneas healed, there was a marked trend toward thicker corneas in the PT group versus FT group with a median difference of - 63µm at week 1 [median 788µm vs. 725µm, (p = 0.11)], - 38µm at week 4, (724µm vs. 686µm, (p = 0.63)) and - 47µm median difference at week 8 with (670µm vs. 623µm, (p = 0.06)). Histopathology showed disorganization of the collagen fibers and the formation of a retrocorneal fibrous membrane in the PT group. The FT group presented less corneal edema at week 8 with a more linear and less opaque scar. Histopathology showed a better-organized scar and endothelialization without the formation of a fibrous membrane.

Use of therapeutic non-refractive contact lenses to improve visual outcome after repair of traumatic corneal wounds.

BackgroundThe purpose of this study was to evaluate the effect of use of contact lenses to improve visual outcome after repair of traumatic corneal wounds.MethodsTwo groups of patients (n=30 each) with traumatic full thickness corneal wounds were entered into this study. All cases were caused by sharp objects such as a knife or piece of glass that produced a corneal full thickness wound without any other associated ocular injuries. One group was repaired and received medical treatment (non-contact lens group) and the other group was repaired and a soft contact lens was fitted over the cornea, then medically treated (contact lens group). Each patient was followed up until complete healing, the sutures were removed after about 6 weeks, and the patients were followed up for a further 6 weeks, for a complete follow-up period of 3 months, after which postoperative refraction, manifest refractive spherical equivalent, uncorrected visual acuity, and best-corrected visual acuity were measured and compared between the two groups.ResultsAfter repair and follow-up, uncorrected visual acuity ≥0.3 (decimal system) was achieved in 19 cases (63%) in the contact lens group and in only 14 cases (47%) in the non-contact lens group (P=0.018). Best-corrected visual acuity ≥0.6 was achieved in 26 cases (87%) in the contact lens group and in only 17 cases (57%) in the control group (P=0.012).ConclusionSoft contact lenses can be used after repair of traumatic corneal wounds to improve visual outcome.

Comparison of Sutures and Cyanoacrylate Tissue Adhesives for Wound Repair in a Rat Model of Corneal Laceration

Aims: The aim of the present study was to evaluate the cicatricial repair of a corneal artificial perforation in rats with 10-0 nylon suture, N-butyl-2-cyanoacrylate (NBCA) adhesive, or NBCA + methacryloxysulfolane (NBCA-MS) adhesive through microscopic and histological assays. Methods: Twenty Wistar rats were randomly divided into 4 groups each containing 5 rats: (1) control group (corneal trauma without suturing and tissue adhesives), (2) suture group, (3) NBCA group and (4) NBCA-MS group. A central full-thickness 2-mm laceration was performed in the left eyes of the studied rats in all 4 groups. The presence of corneal edema, corneal neovascularization and tissue adhesive/suture were evaluated. On the 21st day, the rats were sacrificed and histological examination was performed to determine irregularity of corneal layers, superficial epithelization, polymorphonuclear leucocytes and neovascularization. Results: Tissue adhesives were as effective as suturing in closing full-thickness corneal wounds and no difference in postoperative healing was observed clinically. As for the histological results, suture-treated eyes had persistent corneal irregularity that can limit visual acuity and may also lead to astigmatism. Conclusions: The use of tissue adhesives constitutes a viable alternative clinical procedure to conventional sutures. Possible influences on astigmatism are hypothetical, as no objective measure of astigmatism was performed in the test animals.

Decreased Vision Following Eye Trauma

A52-YEAR-OLD MAN PRESENTED TO THE EMERGENCY DEPARTMENT (ED) FOR evaluation after several days of increasingly blurred vision in the right eye. Nine days earlier, while he was operating an asphalt reclamation machine, the patient reported the sensation of an object striking his right eye, but he had no acute pain or change in vision. He was not wearing eye protection at the time. One day after the trauma occurred, the patient visited his primary care physician and was prescribed topical antibiotics. His past medical and ophthalmological histories were unremarkable. On examination in the emergency department, the best corrected visual acuities were 20/100 in the right eye and 20/20 in the left eye. Dilated, slit-lamp examination of the right eye revealed a selfsealing, full-thickness corneal wound and an area of iris irregularity (iris synechiae formation) (FIGURE 1A), minimal anterior chamber inflammation, and early cataract formation. On adduction of the eye, a large, glistening, variegated intraocular foreign body was seen encased entirely in the crystalline lens (Figure 1B). There were no additional findings in the vitreous or retina on dilated examination, including no signs of endophthalmitis. Examination results of the left eye were unremarkable. What Would You Do Next?

Feasibility of telerobotic microsurgical repair of corneal lacerations in an animal eye model

We evaluated the feasibility of telerobotic microsurgical repair of corneal lacerations. The telerobotic microsurgical device consisted of a Robotic Slave Micromanipulator Unit (RSMU) coupled to a Telepresence Surgical System (TeSS). Five mm central full-thickness corneal wounds were fashioned in five enucleated rabbit eyes and repaired remotely using the telerobotic system. Five additional eyes were also repaired by hand using a standard technique. The primary outcome measure was creation of a watertight seal. All eyes in both groups maintained an intraocular pressure (IOP) of 25 mm Hg without leak. The mean repair time was 80 min (range 50-130) with telerobotic surgery compared to 8 min (range 7-9) by hand. Histological evaluation showed that suture placement was similar in robotically assisted repair and manual repair. Subjectively, the telerobotic system provided adequate three-dimensional visualization of the surgical field. The study showed that a surgeon could close standardized corneal wounds using the telerobotic system. The potential benefits of remote eye surgery include improved access, surgical teleconsultation and telementoring.

The use of porcine small intestinal submucosa for the repair of full‐thickness corneal defects in dogs, cats and horses

To evaluate the efficacy of using a porcine small intestinal submucosa (SIS) graft covered by a conjunctival flap for the surgical repair of full-thickness corneal wounds in dogs, cats and horses. All records dating from August 1999 to February 2003 from Purdue University Veterinary Teaching Hospital of patients that had undergone ophthalmic surgical procedures and received a SIS corneal graft for a full-thickness lesion were reviewed. Fifteen cases were identified including six dogs, two cats and seven horses. Requirements for inclusion in this study were that SIS was used as a corneal graft in a full-thickness corneal defect and that the graft was completely covered with a conjunctival flap. Of the 15 cases, one canine patient had received SIS following removal of an epibulbar melanocytoma. The remaining five canine patients had undergone this surgical procedure for the repair of corneal perforation. The two feline patients had been presented for corneal perforation following chronic ulceration. One equine patient had been presented for a deep melting ulcer, three for stromal corneal abscesses, and three for corneal perforations. Complications encountered postoperatively included aqueous leakage, conjunctival flap dehiscence, synechia, cataract and fibrin in the anterior chamber. Fourteen out of 15 patients were visual at the final re-evaluation. SIS is an inexpensive, easy-to-handle biomaterial that appears to be suitable for the repair of full-thickness corneal wounds in dogs, cats and horses. Results of our study support the conclusion that this relatively new product is an effective alternative to traditional implantation materials utilized in veterinary ophthalmology.

Structure of corneal scar tissue: an X-ray diffraction study

Full-thickness corneal wounds (2 mm diameter) were produced in rabbits at the Schepens Eye Research Institute, Boston. These wounds were allowed to heal for periods ranging from 3 weeks to 21 months. The scar tissue was examined using low- and wide-angle x-ray diffraction from which average values were calculated for 1) the center-to-center collagen fibril spacing, 2) the fibril diameter, 3) the collagen axial periodicity D, and 4) the intermolecular spacing within the collagen fibrils. Selected samples were processed for transmission electron microscopy. The results showed that the average spacing between collagen fibrils within the healing tissue remained slightly elevated after 21 months and there was a small increase in the fibril diameter. The collagen D-periodicity was unchanged. There was a significant drop in the intermolecular spacing in the scar tissues up to 6 weeks, but thereafter the spacing returned to normal. The first-order equatorial reflection in the low-angle pattern was visible after 3 weeks and became sharper and more intense with time, suggesting that, as healing progressed, the number of nearest neighbor fibrils increased and the distribution of nearest neighbor spacings reduced. This corresponded to the fibrils becoming more ordered although, even after 21 months, normal packing was not achieved. Ultrastructural changes in collagen fibril density measured from electron micrographs were consistent with the increased order of fibril packing measured by x-ray diffraction. The results suggest that collagen molecules have a normal axial and lateral arrangement within the fibrils of scar tissue. The gradual reduction in the spread of interfibrillar spacings may be related to the progressive decrease in the light scattered from the tissue as the wound heals.

Correlation of Full-Thickness Corneal Wound Length With Endothelial Cell Loss

We studied 12 patients who had sustained penetrating corneal lacerations with corneal wound lengths ranging from 1 to 9 mm to determine whether wound size was directly proportional to endothelial cell loss 3 or more months after injury. Endothelial cell counts in the uninjured eye averaged 2973 +/- 330 cells/mm2 (range, 2500 to 3700). In the injured eye, near the wound (less than 2 mm from the wound), the cell counts averaged 1260 +/- 590 cells/mm2 (range, 575 to 2500); away from the wound, where cells appeared healthiest, counts averaged 1619 +/- 544 cells/mm2 (range, 850 to 2750). The average total cell loss near the wound was 1713 +/- 622 cells/mm2 (range, 500 to 2575), vs 1354 +/- 582 cells/mm2 (range, 250 to 2150) away from the wound, compared with the uninjured eye. Cell loss near the wound was not significantly different from that away from the wound. There was a positive correlation between wound length and total cell loss measured both near the wound (r = 0.830) and away from the wound (r = 0.755). Pars plana lensectomy was not associated with detectable additional cell loss. Our results suggest that patients with corneal lacerations sustain significant endothelial cell loss, which correlates closely with wound length, and that patients with larger wounds may be at greater risk for developing corneal decompensation with additional procedures or trauma.

Effect of Topically Administered Epidermal Growth Factor on Corneal Wound Strength

A 9-mm perforating corneal wound was created in one eye of New Zealand albino rabbits, sutured, and treated with mouse-derived epidermal growth factor (1 mg/L), human-derived epidermal growth factor (1.0 mg/L to 100 mg/L), or buffered saline, instilled once, twice, or four times daily. Both mouse-derived epidermal growth factor and human-derived epidermal growth factor significantly increased the tensile strength of full-thickness corneal wounds after 9 days of topical therapy. For human-derived epidermal growth factor, a concentration of 10 mg/L administered twice daily produced the maximal effect. An increase in either the concentration of epidermal growth factor or its frequency of administration failed to induce a further increase in wound strength. Indeed, at a concentration of 100 mg/L, human-derived epidermal growth factor appeared to lose its ability to accelerate healing of full-thickness corneal wounds.

Type VI Collagen in Healing Rabbit Corneal Wounds

A type-specific monoclonal antibody was used to examine the localization of type VI collagen in healing full-thickness corneal wounds (3 mm in diameter) in rabbits. By immunofluorescence, in 1-week-old wounds, type VI collagen was found only at the wound periphery. Subsequently, type VI collagen showed a rapid increase throughout the wounded area. In 3-week-old wounds, type VI collagen immunofluorescence had a laminar pattern as seen in normal corneal stroma, although it was irregular in arrangement. By electron-microscopic immunohistochemistry, type VI collagen was found in the pericellular region of fibroblastic cells possibly derived from keratocytes. These results suggest that type VI collagen might originate from the fibroblastic cells and play an important role in the regeneration of the corneal lamellar structure.

Keratoplasty Wound Separations

Forty cases of partial or full-thickness corneal wound separtions after penetrating keratoplasty comprised three groups. One group of separations occurred before suture removal, due to technical problems encountered at surgery or increased intraocular pressure, or both. Most separations occurred immediately after suture removal and may be the most preventable. The third group of separations occurred long after suture-removal and may not be associated with obvious trauma. About 50% of all wound separations caused graft failure, but patients with fullthickness wound separations had a worse prognosis for visual acuity recovery. Of those grafts that failed after wound separation and were retransplanted, there is a good chance of visual recovery. In our series, fullthickness wound separations or partial wound gape occurred in about 5.7% of our transplant cases. With delay of suture removal associated with a more adequate clinical means of evaluating wound healing, this number may be decreased.