Contralateral Clinically Unaffected Eyes of Patients With Unilateral Infectious Keratitis Demonstrate a Sympathetic Immune Response

PURPOSE. To analyze the contralateral unaffected eyes of patients with microbial keratitis (MK) for any immune cell or nerve changes by laser in vivo confocal microscopy (IVCM). METHODS. A prospective study was performed on 28 patients with MK, including acute bacterial, fungal, and Acanthamoeba keratitis, as well as on their contralateral clinically unaffected eyes and on control groups, which consisted of 28 age-matched normal controls and 15 control contact lens (CL) wearers. Laser IVCM with the Heidelberg Retinal Tomograph 3/Rostock Cornea Module and Cochet-Bonnet esthesiometry of the central cornea were performed. Two masked observers assessed central corneal dendritiform cell density and subbasal corneal nerve parameters. RESULTS. The contralateral clinically unaffected eyes of patients with MK demonstrated significant diminishment in nerve density (15,603.8 +/- 1265.2 vs. 24,102.1 +/- 735.6 mu m/mm(2)), total number of nerves (11.9 +/- 1.0 vs. 24.9 +/- 1.2/frame), number of branches (1.7 6 0.2 vs. 19.9 +/- 1.3/frame), and branch nerve length (5775.2 +/- 757.1 vs. 12,715.4 +/- 648.4 mu m/mm(2)) (P < 0.001 for all parameters) compared to normal controls and CL wearers. Further, dendritiform cell density in the contralateral unaffected eyes was significantly increased as compared to that in controls (117.5 +/- 19.9 vs. 24.2 +/- 3.5 cells/mm(2), P < 0.001). CONCLUSIONS. We demonstrate a subclinical involvement in the contralateral clinically unaffected eyes in patients with unilateral acute MK. In vivo confocal microscopy reveals not only a diminishment of the subbasal corneal nerves and sensation, but also an increase in dendritiform cell density in the contralateral unaffected eyes of MK patients. These findings show bilateral immune alterations in a clinically unilateral disease.