Abstract
Purpose:
The human sclera is a dense connective tissue that covers the eye. Physiologically it shows only diminished vascularity. The existence of lymph vessels has been discussed contradictorily. In this study we investigate the allocation of blood and lymph vessels in human sclera in the anterior, equatorial, and posterior region of all four quadrants.
Methods:
Human sclera of ten tissue donors (age: 64-79 years; in compliance with the Declaration of Helsinki) was analyzed for blood (CD31) and lymph vessel (LYVE1 and podoplanin) formation, using fluorescence, confocal and transmission electron microscopy. Different locations were analyzed for their vessel spreading at anterior, equatorial, and posterior part of the sclera in all four quadrants, taking into consideration the differences between the three scleral layers: episclera, stroma proper and lamina fusca.
Results:
Human sclera displayed specific locations of blood vessels within the eye. Whereas the stroma proper and the lamina fusca were devoid of blood and lymph vessels, the superficial layers of the sclera revealed a network of small-sized blood vessels (less then 20 μm in size) and LYVE1+ macrophages, but no LYVE1+/ podoplanin+ lymphatic vessels. Compared to anterior and equatorial regions LYVE1+macrophages were less frequent in the posterior part, whereas no difference in the amount of blood vessels was detectable.
Conclusions:
Blood vessels, but no lymphatic vessels are detectable in the healthy human sclera. Additionally, LYVE1+ macrophages are present in the superficial layers only. These cells may contribute to inflammatory neovascularization in pathological circumstances e.g. scleritis.
Keywords: 708 sclera •
419 anatomy •
609 neovascularization