Abstract
Dear Editor,
We want to thank the authors for the review article by Posarelli et al. published in JOPT Volume 35, Number 7, 2019. 1 We agree that a topical cross-linked HA has a lot of value in protecting the ocular surface and acting as a tear film substitute. As noted by the authors in the Future Perspectives, one characteristic of dry eye disease is its potential to damage the ocular surface. Thus, a cross-linked hyaluronic acid (HA) that has been shown to accelerate closure of corneal wounds may be useful in aiding the repair of the ocular surface in dry eye disease.2,3
In Europe and Asia, topical HA eye drops are the standard of care for dry eye as well as corneal superficial epithelial injuries. Topically applied noncross-linked HA eye drops, however, are quickly degraded and cleared. A novel and proprietary high-concentration cross-linked HA eye drop was developed, as the authors call out, that withstands the forces of blinking and tear turnover on the ocular surface.2,3 Owing to the remarkable physical properties of this HA, it remains clear and nonblurring as it coats the ocular surface and helps to heal the cornea by accelerating re-epithelialization.4,5
This specific high-concentration (0.75%) cross-linked HA has been shown to provide a mechanical barrier that aids in the management of corneal epitheliopathies and accelerates re-epithelialization in animals in both traumatic corneal injuries and in cases of nonhealing persistent corneal defects. 3 By providing a thin coating on the surface of the eye, it serves as a hydrating protectant and lubricant that facilitates acceleration of corneal re-epithelialization. A study was conducted by EyeGate (Waltham, MA) to evaluate the efficacy of this novel formulation of HA (Ocular Bandage Gel [OBG]) in subjects with large corneal defects. 5
This specific cross-linked HA utilizes thiolated carboxymethyl HA (CMHA-S), as pointed out by the authors. Although the use of this version of cross-linked HA in veterinary medicine was reviewed in the article, we would like to add that it has now been used in human clinical studies as well. The initial study using the cross-linked CMHA-S liquid gel, called OBG, demonstrated a good safety profile and accelerated re-epithelialization of large corneal wounds created during photorefractive keratectomy as compared with a bandage contact lens. 5 We are now in the final stages of clinical development for demonstrating corneal wound repair (NCT03938883) based on the initial study.
The wealth of data on the use of cross-linked CMHA-S in animals for corneal wound repair and ameliorating the symptoms of keratoconjunctivitis sicca, combined with the results of these initial human clinical studies, indicates the potential for this version of cross-linked HA for aiding the repair of damage to the ocular surface in humans. Further clinical studies to examine this potential and other applications are being planned.