Highly Reflective Cells in the Corneal Stroma Visualized by in vivo Confocal Microscopy

Abstract

Abstract: : Purpose: To study the highly reflective cells with a tail (HRC) in more detail in the corneal stroma of diabetic and control patients with in vivo confocal microscopy (IVCM). Methods: We analyzed eight type 2 diabetic patients, four with level 20 ETDRS (age 53y to 69y) and four with level 35 (age 59y to 64y) and eight healthy controls (age 35y to 74y). The number of HRC found in the stroma was counted using registered images obtained by IVCM (Tomey Confoscan P4). Length and width of HRC and keratocyte nuclei was measured. Results: Structures consisting of a highly reflective head and a vague tail (straight or undulated) were found mainly in anterior and mid–stroma of patients and controls. They were often observed near the stromal nerves and were rare in posterior stroma. The average number of HRC was 52.5±9.3 and 40.0±14.0 in level 20 and 35 diabetic patients, respectively. There were significantly less present in healthy controls, 6.8±2.1 (p<0.001). In level 35 patients more HRC were found in the posterior stroma, usually associated with a higher tortuosity of the adjacent nerves. In general, stromal nerves are not located in the posterior stroma of the central cornea. The average length and width of a HRC is 19.5±5.7 µm and 10.4±4.4 µm, respectively, and those of a keratocyte nucleus are 27.2±2.5 µm and 9.5±3.5 µm, respectively. There is a significant difference in length (p<0.001) but not in width (p=0.16). Undulated structures with dimensions similar to large stromal nerves (width: 8 to 11 µm) were also observed in the diabetic patients. Conclusions: HRC is a new kind of structure found in high densities in the corneal stroma of diabetic patients but their identity and their origin are yet unknown. The undulated large stromal structures in diabetic patients might represent altered straight stromal nerves as observed in controls.

Keywords: microscopy: confocal/tunneling • cornea: stroma and keratocytes • diabetes