In vivo laser scanning confocal microscopy confirms that the human corneal sub-basal nerve plexus is a highly dynamic structure

PURPOSE. To add to findings in a prior study on the two-dimensional arrangement of the living human sub-basal corneal nerve plexus and determine whether it is a dynamic structure. METHODS. Laser scanning in vivo confocal microscopy was performed on the left cornea of a healthy subject who had been examined with the same methodology 2 years earlier. Examinations were performed once a week for 6 weeks with the purpose of producing a two-dimensional reconstruction map of the living human sub-basal corneal nerve plexus at each session. A two-dimensional graphics program was used to arrange and map images obtained at each session into confluent montages. RESULTS. The mean dimensions of the corneal areas mapped were 4.80 +/- 0.45 mm horizontally and 4.60 +/- 0.52 mm vertically. The nerve branching patterns observed 2 years earlier did not correspond with those in any recent maps. Over the 6-week period, the sub-basal nerve pattern appeared to migrate centripetally from the corneal periphery toward an inferocentral whorl. In the region of the whorl the nerves altered their generally centripetal direction of migration, undergoing clockwise rotation. The centripetal rate of migration decreased with proximity to the center of the whorl (5.6 +/- 3.4 mu m/wk at 13 mu m from the whorl, 13.9 +/- 5.5 mu m/wk at 333 mu m from the whorl, and 25.9 +/- 8.6 mu m/wk at 698 mu m from the whorl). CONCLUSIONS. This study provides strong evidence that the living human sub-basal corneal nerve plexus is a highly dynamic structure, with continuous centripetal movement of identifiable branch points of up to 26 mu m/wk, creating dramatic pattern changes in the plexus over a 6-week period.