Robust and Objective Evaluation of Superficial Punctate Keratopathy in a Murine Dry Eye Model

Abstract

Purpose: To establish a robust and objective method to evaluate (SPK) superficial punctate keratopathy in a murine dry eye model by developing a reliable photographic system. Design: Experimental study. Subjects: A murine dry eye model was generated by exorbital lacrimal gland excision. Sham-operated mice were used as healthy controls. For the sham operation, an incision was made without touching the gland. Methods: A photographic system was constructed, consisting of an LED lamp and a digital camera fitted with a zoom lens and sharp cut filter. SPK was detected by applying fluorescein solution. To validate the system, SPK was compared between dry eye mice and healthy control mice, and diquafosol (DIQUAS ophthalmic solution 3%; Santen Pharmaceutical Co., Ltd.) or cyclosporine (PAPILOCK Mini ophthalmic solution 0.1%; Santen Pharmaceutical Co., Ltd.) was used to dry eye mice. Main Outcome Measures: SPK was evaluated using the parameters of fluorescence score and fluorescein-stained area. Results: The photographs clearly indicated SPK in dry eye mice. A fluorescence score of 0 to 9 could be easily assessed, and the fluorescein-stained area was quantifiable. The fluorescein-stained area correlated with fluorescence score (correlation coefficient: 0.98), with good interobserver reliability (intraclass correlation coefficient: 0.999). The fluorescein-stained area increased significantly in dry eye mice compared with that of healthy controls (P < 0.0001). Both types of therapeutic eye drops decreased the fluorescein-stained area relative to saline-treated mice (P < 0.05 in diquafosol vs. saline; P < 0.01 in cyclosporine vs. saline). Conclusions: This newly developed system is a robust alternative for quantitative evaluation of SPK in a murine dry eye model. Financial Disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords

• Dry eye model
• Superficial punctate keratopathy
• Corneal fluorescein staining
• Methodology