Autosomal recessive cornea plana: In vivo corneal morphology and corneal sensitivity

PURPOSE. Autosomal recessive corneal plana (RCP) is a rare corneal anomaly with unknown pathogenesis and a high incidence in Finland. The aim was to e xamine corneal sensitivity and the morphology of different corneal layers a nd subbasal nerves in RCP patients. METHODS. Three patients with a diagnosed autosomal recessive cornea plana w ere examined. Corneal sensitivity to different modalities of stimulation wa s tested in four corneas using noncontact esthesiometry. Tissue morphology of three corneas was evaluated, and in two corneas thickness of corneal lay ers was measured using in vivo confocal microscopy. RESULTS. Corneas of RCP patients appear to have mechanosensory, polymodal, and cold-sensitive nerve terminals. RCP patients had normal sensation thres holds for chemical, heat, and cold stimulation but a high threshold for mec hanical stimulation. Their capacity to discriminate Increasing intensities of stimulus was reduced, except for cold stimuli. Thickness of the epitheli al layer was reduced, whereas total corneal and stromal thicknesses were sl ightly reduced or close to normal values. In all cases Bowman's layer was a bsent. Subbasal nerves had abnormal branching patterns. The arrangement of anterior keratocytes was altered, showing clustered and irregularly shaped nuclei. Increased backscattering of light in confocal microscopy through fo cusing (CMTF) profiles was observed throughout the stroma. Epithelial and e ndothelial cells appeared to be regular in shape. CONCLUSIONS. The present study revealed qualitative and quantitative altera tions in corneal sensitivity, cellular morphology, and the thickness of cor neal layers in RCP patients.