Macular Corneal Dystrophy: In Vivo Confocal and Structural Data

Objective: To demonstrate the corneal morphologic aspects obtained with in vivo confocal microscopy (CM) and light and electron microscopy of specimens obtained from the same patients with macular corneal dystrophy (MCD). Design: Case series. Participants: Five consecutive patients affected by MCD undergoing penetrating keratoplasty (PK) in 1 eye. Methods: The patients were examined with the slit-lamp, optical pachymetry, and CM before undergoing PK. The corneal buttons were processed for light, transmission, and scanning electron microscopy. Main Outcome Measures: Corneal in vivo CM, corneal light, and electron microscopy. Results: Confocal microscopy showed areas of altered reflectivity in basal epithelial cells, which appeared hyperreflective or completely white. In the anterior stroma, rectilinear hyperreflective areas were shown. The stroma was characterized by a granular appearance of both keratocytes and extracellular matrix. Dark striae of different length and orientation were present in the middle and posterior stroma. The corneal endothelium showed polymegethism and cells containing bright granules in their cytoplasm. The histopathologic study demonstrated areas of thickened Bowman’s layer covered by an epithelium reduced in height. The Bowman’s layer thickenings were due to the accumulation of free or vesiculated material of different electron density. The keratocytes showed intracytoplasmatic vesicles, whereas the extracellular matrix presented a large quantity of intercellular electronlucent material and parallel lamellae with an undulated course. Occasional macrophages, filled with vesicles of granular-filamentous material and evident podosomes, were observed. Descemet’s membrane was formed by a normal anterior banded zone and a posterior nonbanded zone of honeycombed aspect. The endothelial cells showed a large number of intracytoplasmic vesicles. Conclusions: The structural changes observed with the histopathologic methods give an account and provide an explanation for the pathologic changes demonstrated by CM in the course of MCD. This may contribute to the understanding of in vivo imaging, allowing a better, noninvasive study of the disease evolution.