Fig. 5.3 In vivo imaging of corneal lymphatic vessels in a pathologically vascularized murine cornea using in vivo confocal microscopy. The HRT II with the Rostock cornea module shows black, empty appearing, and nearly cell-free lymphatic vessels (arrow) next to smaller, erythrocyte-filled blood vessels (arrowhead)

Imaging of Corneal Lymphatic Vessels

Lymphatic vessels in the cornea are not visible using slit-lamp magnification. That is due to their lumen being nearly free of cells and their absent basement membrane thus given too low contrast to surrounding extracellular matrix. Nonetheless, in recent years, new technologies have been developed to visualize corneal lymphatics:

(a)In vivo confocal microscopy using the HRT II and the Rostock cornea module: Using that approach, we and others were able to visualize lymphatic vessels in rodent corneas. The empty appearing, dark, and cell-free lymphatics could be identified by injection of dyes and subsequent immunohistochemistry. That approach should in the future also be applicable to patients in the clinic (Fig. 5.3).

(b)In vivo multiphoton imaging: This even more precise approach allows for unequivocal identification of immunohistochemically labeled lymphatics in the living cornea [35].

Based on the great advances in imaging lymphatics in vivo in animal models, it is likely that in the near future, visualization of lymphatics also in human corneas in the clinic will be possible. That would allow for precise risk assessment prior to keratoplasty by analyzing whether a vascularized high-risk cornea does contain lymphatic vessels in addition or not.