This prospective study showed that in vivo confocal microscopy can be used to noninvasively diagnose limbal stem cell deficiency with a high degree of concordance with impression cytology.
The main advantages of in vivo confocal microscopy were that it was capable of differentiating conjunctival-type from corneal-type epithelium covering the corneal surface with a high level of agreement with the gold standard (impression cytology) in clinically suspected limbal stem cell deficiency.
Moreover, the authors add, a morphologic analysis of the limbal superficial and deep epithelial structures was possible, showing alterations of the normal anatomy in eyes with total or partial limbal stem cell deficiency. These latter features included loss of the palisades of Vogt, which presented fibrotic changes and irregular stromal and epithelial architecture, and changes affecting the regular limbal epithelial transition with cellular cystic and pleomorphic alterations.
They note that normal limbal palisade structures could be detected only partially in five of the seven patients in whom the diagnosis of limbal stem cell deficiency was excluded. Conversely, in all cases in which abnormal epithelium was found on the corneal surface, normal in vivo confocal microscopy features of limbal structures were significantly altered. These cases demonstrated abnormal palisades of Vogt and alterations of the normal limbal transition features of the superficial epithelium. This was seen in both total and partial limbal stem cell deficiency.
They write that in all patients affected by total limbal stem cell deficiency, palisades of Vogt were completely absent. Also, in four of the eight eyes that showed partial limbal stem cell deficiency, palisades of Vogt were not detectable despite the partial maintenance of a regular superficial limbal epithelial transition. In these cases, the presence of corneal-type epithelium in the central and paracentral areas of the cornea would suggest that some limbal stem cells, in the absence of their normal limbal "niche," are surviving and functioning to generate epithelial cells with the corneal phenotype. This supports results from a recent study that postulated that central basal cells could sustain the central corneal cell mass until stressed or damaged.
The authors conclude that the principal diagnostic value of in vivo confocal microscopy examination was discovering that the presence of abnormal corneal epithelium associated with limbal alterations in one or more quadrants was highly suggestive of limbal stem cell deficiency. This suggests a possible application in the field of limbal stem cell transplantation surgery: during the preoperative phase to confirm the diagnosis and to assess the degree of limbal damage, and after surgery to evaluate the clinical success and the constitution of the corneal epithelium and limbal anatomy.