Cogan syndrome: confocal microscopy assessment of corneal damage

To perform in vivo assessment of corneal alterations in patients with Cogan syndrome (CS) and to correlate these findings with prior histopathologic descriptions.

Four consecutive patients (8 eyes) presenting with typical CS underwent confocal microscopy examination. At the moment of evaluation, ocular inflammation was quiescent in all the patients. The images were studied singularly, and then compared to those obtained from 5 healthy controls. Statistical analysis was performed with Student t test.

All the cases showed multiple brightly reflective deposits in the stroma with moderate reflectivity of the surrounding stromal tissue. The outer corneal layers and the endothelium were spared. In 3/4 of the patients, the nerve fibers of the subepithelial plexus were thin and poorly reflective, with interruptions and lack of the typical branching pattern. No cells different from keratocytes could be detected in either case or control eyes. Corneal vascularization was present in one case. In CS-affected eyes, corneal thickness was 552+/-62 microm on average, and endothelial cell count was 2466+/-288 cells/mm(2). Statistical significance was not reached compared to the control group.

Confocal microscopy was able to provide detailed images of corneal alterations in CS. This confirmed the interstitial nature of the keratitis and showed an excellent accordance with prior histopathologic findings. The absence of inflammatory cell infiltration may be explained by the prolonged control of ocular inflammation in our patients, which may also have limited stimuli for corneal neovascularization.