Assessment of the size spectrum of epithelial lesions of punctuate superficial keratitis during dry eye
Abstract
Purpose
Quantification of staining of the ocular surface by fluorescein and lissamine green is important for diagnosis and follow up of dry eye syndromes, especially in clinical trials. Analysis of digital pictures may help improving the reliability of this quantification but require objective data on the basic lesions constitutive of punctuate superficial keratitis (PSK) to develop adequate algorithms. Aim: to evaluate the size spectrum of epithelial lesions of PSK during dry eye to improve the existing diagnosis tools.
Methods
Fluorescein was instilled to six patients suffering from dry eye graded according to the Oxford scheme. Pictures (3008x1960px) were taken using a Topcon slit-lamp using the Cobalt blue light without barrier filter. Two magnifications (x10 and x16) were used and calibrated using a certified standard reference grating. It allowed determining the size of observed objects with the software ImageJ. The most visible and isolated PSK lesions (green dots) were selected. The size of 180 different PSK lesions (30/patient, 15/magnification) were measured by tracing the light intensity profile and manually measuring the width at half maximum.
Results
All patients combined, the mean was 21.6 ± 4.8 μm (15.2-30 μm, 10°-90° percentile). Lesion diameters ranged between 11.4 and 30.4 μm.
Conclusions
Lesions seem to be smaller than epithelial cells (approximatively 25 μm×50 μm for superficial cells) and might correspond to the beginning of cell detachment with fluorescein retained between cells. These new quantitative data will help developing automatic recognition algorithm to obtain reliable objective classification of the corneal staining.
