Fluorescein dye is commonly used to highlight the tarsal conjunctiva in man to facilitate diagnosis of papillary conjunctivitis. A quantitative analysis of the fluorescein-highlighted features could be useful in both assignment of severity grades as well as for objective comparisons but no data is available on the distributions of sizes (areas) of these features. An exploratory, range-finding study was undertaken to provide data on feature areas that might be encountered. After application of fluorescein, 35 mm photographs were taken at a fixed distance with zone 1/zone 2 (Allansmith) of the tarsal plate aligned perpendicular to the camera. The photographs were projected, an overlay of 150 to 180 contiguous features outlined by fluorescein made and planimetry used to assess the areas and area distributions of the features on tarsal plates clinically graded with stages 1 to 4 papillary hypertrophy. For zone 1 of the tarsal plate in asymptomatic subjects, a fluorescein solution highlights the limits of features that enclose an area averaging 30,000 microns2 (range 8000 to 120,000; median area of close to 35,000 microns2). The areas of these features were generally normally distributed and there was little variation in feature areas across the zone. At different stages of clinical papillary conjunctivitis, the areas of the negative staining patterns are larger. Averages of 60,000 to 90,000 microns2, median values of close to 70,000 microns2 and individual feature areas up to 350,000 microns2 were seen in mildly symptomatic patients. These distributions were generally heterogeneous and showed a skewed distribution. Areas averaging up to 0.755 mm2 (range 0.6 to 3.2 mm2) were measured in moderate to severe papillary hypertrophy.