I came to the conclusion, based on my research, that the central canal (so called canalis Сloquet) connects the retrolental space directly to the bursa premacularis, and not to the optic nerve disc, as is commonly believed (Duke-Elder, 1961).
The dye from the central canal gets into the bursa premacularis and then reaches the prepapillary space through the canaliculus communicans Makhacheva. The latter connects the two canal systems of the vitreous body. Along with the central canal, which more accurately should be called the canalis lentico-macularis Makhacheva, there is another canal connecting the prepapillary space with the retrociliary cisterns, presumably in the upper-nasal segment. I named this canal: canalis optico-ciliaris Makhacheva.
Canalis lentico-macularis is connected to the branched system of cisterns that surround it, and reminds me of a tree with abundant foliage. Anastomoses of the canalis optico-ciliaris are not as extensive and are limited to a small area of the retrociliary cisterns near the orifice of the canal.
I hypothesize that the intravitreal canals play a role in the transport and exchange of nutrients and by-products by directing the flow of the liquids, as well as in maintaining the metabolic and hydrodynamic balance between the anterior and posterior segments of the eye.
The existence of a canal connecting the retrociliary cisterns with the prepapillary space can elucidate the pathogenesis of glaucoma.
The direct connection between the retrolental area and the bursa premacularis explains the occurrence of complicated cataracts in involutional and inflammatory macular conditions, as well as the complications in the posterior pole of the eye after lens removal and glaucoma surgery.
The central and optico-ciliary canals are characterized not only by anatomical autonomy, but also by biochemical specificity.
I observed something peculiar while performing a dissection on an autopsy eye of a female who died from a massive subarachnoid hemorrhage (Terson syndrome).
It came to my attention that both VB canals were filled with blood; however, the blood in the central canal was in a liquid state and could be traced to the retrolental space, while in the optico-ciliary canal and the prepapillary space, the blood was clotted.
I am assuming that the central canal and bursa premacularis might contain some common anticoagulant properties, which indicate both their integrity and the presence of a mechanism for the rapid drainage from the structures that are critical for the projection of the image onto the retina. In the optico-ciliary canal, which does not follow the visual axis, the presence of such an anticoagulant mechanism would not only be useless, but also harmful, since the optic nerve vessels can often be a source of an intraocular hemorrhage.
The canals are connected by means of the canaliculus communicans Makhacheva, which I was able to trace during a retrograde cannulation of the prepapillary space and the bursa premacularis.
I noted that when a dye is injected into the prepapillary space, the contrast agent fills the canalis optico-ciliaris, and then reaches the bursa premacularis and the canalis lentico-macularis through the canaliculus communicans. With retrograde cannulation of the bursa premacularis, the dye first fills the canalis lentico-macularis, then penetrates the prepapillary space through the canaliculus communicans and much later, with additional ink injection, penetrates into the canalis optico-ciliaris. This made me suggest the presence of a valve or mechanism that makes the retrograde filling of the canalis optico- ciliaris from the bursa premacularis somehow difficult. It is possible that this mechanism provides a unidirectional movement of fluid, and damage to this mechanism can contribute to the onset of glaucoma.
Undoubtedly, the vitreous body is a highly organized apparatus that performs important physiological functions including hydrodynamic balance and intraocular homeostasis, which are crucial for the ultimate visual functions.
