Data from a study on epithelial lesion size in superficial punctate keratitis (SPK) could help with the development of automated algorithms to obtain more objective and reliable classifications for corneal staining, report researchers from France in the journal Cornea.¹

The isolated lesions that so often characterize SPK are small fluorescent dots of differing size and incandescent intensity that are scattered across the corneal surface. In some cases, they can become confluent, creating fluorescent areas in which the individual lesions are no longer distinguishable. Because the number and specific locations of these dots is an important clinical criterion directly connected to the level of surface integrity, differentiating between them is critical—especially during clinical trials. The new algorithms could help ease this issue.

In this study, the team from Jean Monnet University, the University Hospital of Saint-Etienne and the Institut Universitaire de France instilled fluorescein into 10 patients with dry eye graded using the Oxford Scheme. Pictures were taken using a standard slit lamp with cobalt blue light and no barrier filter to simulate the most common conditions of image acquisition. Two magnification settings (i.e., x10 and x16) were used to focus on the corneal objects in question that measured 14.40μm and 7.81μm under each setting, respectively. SPK size did not differ between the five Oxford Scheme grades of dry eye, but did appear to be slightly smaller than typical superficial epithelial cells, which measure approximately 25x50μm.

“Our data on the size of SPK staining lesions in this study is not directly relevant to clinicians,” the researchers acknowledged. “However, it will prove useful for researchers developing new devices and image analysis algorithms to improve SPK severity grading. Indeed, if the size of isolated epithelial lesions characterizing SPK is known, it will be possible to optimize device resolution to detect individual lesions using the appropriate filters or thresholds and ultimately to precisely quantify corneal staining.”  

1. Courrier E, Lepine T, Hor G, et al. Size of the lesions of superficial punctate keratitis in dry eye syndrome observed with a slit lamp. Cornea. 2016. [Epub ahead of print.]