Reply to Comment on: ‘Corneal confocal scanning laser microscopy in patients with dry eye disease treated with topical cyclosporine’

Sir,

We thank Dr Kumar¹ for the interest shown in our paper² and for the comment. Two points are emphasized. The first one is in relation to the importance of ensuring that the same part of the cornea is evaluated sequentially in follow-up studies for accurate demonstration of change. This is correct but in practice difficult with in vivo confocal microscopy (IVCM) as the area scanned is very small and there are no fixed landmarks that can be used for reference in subsequent imaging. This is a limitation associated with all similar IVCM studies. However, one can ensure with reasonable certainty that the same quadrant is examined at each visit. Furthermore, the Heidelberg IVCM device (used in this study) has a side camera that monitors the area of contact of the objective with the cornea and provides images that can be used to examine the same area, as closely as possible, at subsequent visit. In this study¹ we confined our examination to the center of the cornea with the patient looking straight hence is it very likely that the same area or its close vicinity was examined at each visit and that the LC and DC had not migrated to the area of examination.

The second issue that was highlighted is that the images illustrated in our paper¹ do not demonstrate Langerhan’s (LC) or dendritic cells (DC). Both LC and DC are normally concentrated in the periphery of the corneal epithelium and stroma, respectively. Their number increase nonspecifically in inflammation and they migrate to the central area of the cornea. Changes in distribution and density of LC and DC do not directly correlate with nerve and keratocyte changes. The inflammatory component of dry eye disease (DED) can be variable and consequently changes in distribution and density of DC and LC can also be variable. When these changes are present they can be documented at the outset and response to treatment can be monitored. This study shows that they are not a consistent feature of DED as we did not see them in all patients. This also reflects the fact that DED is a heterogenous group of conditions that we lump together under one diagnostic term. It is likely that DED of post-menopausal women, DED post laser refractive surgery, DED associated with collagen vascular disease and age related DED are not the ‘same’ condition and the pathological manifestation of disease is different. This could be another reason why we did not see LC or DC in this study.