In vivo corneal confocal microscopic analysis in patients with keratoconus

AIM: To quantify corneal ultrastructure using laser scanning in vivo confocal microscopy(IVCM) in patients with keratoconus and control subjects. METHODS: Unscarred corneas of 78 keratoconic subjects without a history of contact lens use and 36age-matched control subjects were evaluated with slit-lamp examination(SLE), corneal topography and laser scanning IVCM. One eye was randomly chosen for analysis. Anterior and posterior stromal keratocyte,endothelial cell and basal epithelial cell densities and sub-basal nerve structure were evaluated.RESULTS: IVCM qualitatively demonstrated enlarged basal epithelial cells, structural changes in sub-basal and stromal nerve fibers, abnormal stromal keratocytes and keratocyte nuclei, and pleomorphism and enlargement of endothelial cells. Compared with control subjects, significant reductions in basal epithelial cell density( 5817 ± 306 cells / mm2 vs 4802 ±508 cells/mm2,P < 0. 001), anterior stromal keratocyte density(800 ±111 cells/mm2 vs 555 ±115 cells/mm2, P <0.001),posterior stromal keratocyte density(333±34 cells/mm2vs270 ±47 cells/mm2, P <0.001), endothelial cell density(2875 ±223 cells/mm2 vs 2686 ±265 cells/mm2, P <0.001),sub-basal nerve fiber density(31.2 ±8.4 nerves/mm2vs18.1 ±9.2 nerves/mm2, P <0.001), sub-basal nerve fiber length(21.4±3.4 mm/mm2 vs 16.1±5.1 mm/mm2, P <0.001),and sub-basal nerve branch density(median 50.0(first quartile 31.2- third quartile 68.7) nerve branches/mm2 vs median 25.0(first quartile 6.2- third quartile 45.3) nerve branches/mm2, P <0.001) were observed in patients with keratoconus.CONCLUSION: Significant microstructural abnormalities were identified in all corneal layers in the eyes of subjects with keratoconus using IVCM. This non-invasive in vivo technique provides an important means to define and follow progress of microstructural changes in patients with keratoconus.