Reversible presence of corpuscular mature dendritic cells in Thygeson's superficial punctate keratitis

Abstract

BACKGROUND: Increased intracorneal dendritic cell (DC) density is a common, non-specific in-vivo confocal microscopic finding in keratitis of various etiology. DCs are observed as either mature or immature forms. Mature forms are capable of antigen presentation and may play a key role in the pathophysiology of immune-mediated keratitis. The present article aims to describe the intracorneal density of three morphologically distinct DC types in Thygeson's superficial punctate keratitis (TSPK) before and after treatment. MATERIAL AND METHODS: Four consecutive cases of TSPK were prospectively included into this study. The Heidelberg Retinal Tomograph II, Rostock Cornea Module (HRTII-RCM; Heidelberg Engineering, Heidelberg, Germany) was used for in-vivo confocal microscopy. All layers of central cornea of both eyes were examined. Within each corneal layer, at least five non-overlapping areas were imaged for representative analysis before and one month after treatment initiation. Dendritic cells were classified as mature or immature. Densities of both forms were calculated. Mature cells were further differentiated in predominantly corpuscular and interdigitating forms. RESULTS: Before treatment, mean overall DC density was 369.3 ± 75.6 cells/mm2, and mean ratio of mature to immature forms (MIR) was 1.09 ± 0.9. There were 58.5 % immature forms and 41.5 % mature forms (27.1 % interdigitating DCs, 14.4 % corpuscular DCs). After four weeks of topical treatment with rimexolone 1 %, an overall DC density of 106.1 ± 147.9 and a MIR of 0.53 ± 0.38 was measured. Mean overall DCs decreased by 71.3 %. Immature forms decreased by 58.2 %, mature interdigitating forms by 85.2 %, and mature corpuscular forms by 98.2 % to virtual disappearance. CONCLUSIONS: Successful topical treatment of TSPK is associated with a greater decrease of mature than immature DCs. The reversible intracorneal presence of corpuscular mature dendritic cells may point towards a key role of antigen presenting cells in the pathophysiology of TSPK and serve as an in-vivo confocal diagnostic indicator of immune-mediated keratitis.