## 4 Discussion  
This study evaluated a laser-activated chitosan film as a potential surgical device for sealing penetrating corneal wounds and compared the burst pressure against sutures and cyanoacrylate. From our ex-vivo bovine model, we demonstrated that the laser-activated chitosan film was able to adhere to the corneal surface and sealed full thickness corneal wounds. We tested the adhesive against penetrating corneal wounds of 2, 4 and 6 mm in length and recorded average burst pressures ranging from 239.2 mmHg to 77.4 mmHg. The burst pressure of wounds sealed using the chitosan adhesive technology had a linear relationship with wound size--see Figure 2. For each wound size, the chitosan adhesive tolerated significantly higher burst pressures than sutured or self-sealed groups. The chitosan adhesive could not, however, tolerate the higher burst pressures observed in wounds of the same size that were closed with cyanoacrylate glue. However, the cytotoxic nature of cyanoacrylate breakdown products limits its widespread use [12]. An earlier prototype of chitosan adhesive film, SurgiLux(r), was also evaluated for its capability to seal full thickness corneal wounds in an ex-vivo bovine model, and tolerated a burst pressure of 251 mmHg (SD = \(\pm\)10.4) for 2 mm wounds, 328 mmHg (SD = \(\pm\)12.9) for 3 mm wounds and 224 mmHg (SD = \(\pm\)16.1) for 6 mm wounds [18]. This result was consistent with the high burst pressure obtained from the chitosan adhesive in our present study. However, Surgilux(r) was not fabricated in a clean environment and required approximately three times more fluence for activation. Another study evaluating 1 mm trephined corneal perforations used cyanoacrylate with a 3 mm plastic surgical drap patch and found a mean burst pressure of 325.9 mmHg [23] in an ex-vivo human model. This was consistent with the high burst pressures from our Histoacryl(r) cyanoacrylate groups, which yielded an average of 698.0 mmHg and 494.3 mmHg for 2 and 4 mm wounds, respectively. Similarly, [PERSON] et al. applied three 10-0 nylon sutures to 6 mm central corneal wounds and generated a mean burst pressure of 51 mmHg (SD = \(\pm\)7) [21]. In comparison, the slightly lower burst pressure from our suture group could be attributed to differences in clinicians. The results here clearly show that the laser-activated chitosan film was capable of adhering to the ocular surface of the bovine eye and sealing full thickness corneal wounds. The adherent property of the chitosan adhesive was postulated to be due to polyanionic-polycationic interaction and hydrogen bonding between polymers of collagen and chitosan, due to transient heat expansion and subsequent cooling [20]. The tensile strength of the chitosan film was previously determined as 31.4 MPa (SD = \(\pm\)4 MPa) [24]. Previously, in a directly measured IOP study, a voluntary eyelid squeeze raised IOP to 110 mmHg [9]. Our wound that was treated by chitosan adhesive tolerated burst pressures of 239.2, 171.8 and 77.4 mmHg for 2, 4 and 6 mm wounds, respectively, which were significantly higher than our self-sealed control groups, which yielded 36.4, 4.8 and 2.7 mmHg, respectively. From our results, leakage at bursting pressures occurred beneath intact chitosan adhesive, suggesting surface-to-surface adhesion failure as the limitation to further IOP elevation. For 2 and 4 mm wounds, chitosan adhesive tolerated higher pressures than those recorded with eyelid squeezing of 110 mmHg [9]. This study also validated the previous findings by [PERSON] et al. When an earlier prototype of chitosan adhesive was compared against Tisseel(r) fibrin glue, sutures were reinforced with Tisseel(r) fibrin glue [18]. Apart from providing clinicians with another alternative for penetrating corneal wound closure, the chitosan film allowed for hermetic closure and tolerated elevated IOP, which were risk factors for post-cataract surgery wound leak [6; 8]. Whether this could translate to lower risk of post-operative endophthalmitis will require further studies.