Defining corneal chemical burns: A novel exact and adjustable ocular model

INTRODUCTION: Live-animal-free ocular toxicity models and tests are a necessity in multiple branches of medicine, industry and science. Corneal models with adjustable ranges of injury severities do not exist. In this work, a novel and precise and dose - response method to induce and observe ex vivo corneal chemical burns has been established. METHODS: The EVEIT (Ex Vivo Eye Irritation Test) is based on an ex vivo corneal organ model for rabbit corneas from food industry. Further, a highly precise three – axis workstation has been employed to apply liquid corrosive, sodium hydroxide (NaOH), droplets in a nanolitre (nL) range onto the corneal surface. Optical Coherence Tomography (OCT) has been used to observe and quantify the elicited changes in the corneal layers. RESULTS: The speed and intervals of single nanodroplet application played a crucial role in the extent of the corneal changes. Similar total volumes applied at low frequencies elicited deep and extensive changes in the corneal layers whereas high application frequencies elicited comparatively superficial changes. Increasing NaOH concentrations effected measurably increasing corneal changes. Increasing the volume of applied NaOH also showed an increase in corneal changes. CONCLUSIONS: OCT imaging proved to be effective in observing, documenting and quantifying the changes in the corneal layers. The ex vivo model, in conjunction with the novel application method was able to induce and display distinctive and consistent correlations between NaOH volume, concentration and elicited corneal changes. This ex vivo ocular chemical burn model provides a consistent in vitro basis for pharmaceutical and toxicological experiments and investigations into corneal chemical burn mechanisms and treatment.