Photorefractive keratectomy
Photorefractive keratectomy (PRK) is an efficacious alternative to patients seeking surgical correction of refractive errors who are not suitable candidates for laser in situ keratomileusis (LASIK) due to inadequate corneal thickness, larger pupil size, history of keratoconjunctivitis sicca (KCS), or anterior basement membrane disease.
PRK involves controlled mechanical removal of corneal epithelium with subsequent excimer laser photoablation of the underlying Bowman’s layer and anterior stroma, including the subepithelial nerve plexus. The military prefers PRK as a refractive surgery due to the stability of the PRK incision and the absence of risk for flap dislocation during military active duty. Although this procedure yields desirable visual acuity results, common complications of the procedure include post-operative pain secondary to the epithelial defects, risk of corneal infection prior to re-epithelization of the large epithelial defect, corneal haze formation, decreased contrast sensitivity, and slower visual recovery (Alio et al. 1998, Ben-Sira et al. 1997, Lohmann et al. 1991, Loewenstein et al. 1997).
Corneal wounds created while performing PRK are an excellent model for other epithelial defects, as these patients undergo the creation of large 8 to 9 mm epithelial defects following a standardized protocol to perform refractive laser surgery. The corneal wounds are expected, based on historical data, to heal within 3-5 days, although in some cases these defects can take longer. Pain is a significant side effect, as is a risk of infection, while the defects have not healed, thus creating a need for a device that can accelerate time to wound closure. Furthermore, given the pain and risk of corneal haze from delayed healing, a product that can help accelerate corneal re-epithelization could also improve time to best visual acuity outcomes. In preclinical models using a PRK wound created in healthy rabbits, these large epithelial defects were observed to have accelerated corneal wound closure by at least one day after treatment with CMHA-S applied QID versus PBS (Yang et al. 2010). This amount of accelerated closure is clinically significant and fulfills an unmet need as discussed above.
The EyeGate Ocular Bandage has been shown to provide a mechanical barrier that aids in the management of corneal epithelial defects and accelerates re-epithelization in both preclinical studies and in clinical ophthalmic veterinary use (Chen and Abatangelo 1999, Wirostko et al. 2014, Yang et al. 2010).