hyaloid canal
{{Short description|Canal running from the optic nerve to the lens}}
{{Use dmy dates|date=June 2023}}
{{Infobox anatomy
| Name = Hyaloid canal
| Latin = canalis hyaloideus
| Image = Gray869.png
| Caption = Horizontal section of the eyeball. (Hyaloid canal labeled running through the centre.)
| Image2 =
| Caption2 =
| Precursor =
| System =
| Artery =
| Vein =
| Nerve =
| Lymph =
}}
File:Schematic diagram of the human eye en.svg
The hyaloid canal (Cloquet's canal and Stilling's canal{{cite web
| title = hyaloid canal
| work = mondofacto.com
| url = http://www.mondofacto.com/facts/dictionary?hyaloid+canal
| accessdate = 20 December 2010
| archive-url = https://web.archive.org/web/20160303191729/http://www.mondofacto.com/facts/dictionary?hyaloid+canal
| archive-date = 3 March 2016
| url-status = dead
}}) is a small transparent canal running through the vitreous body from the optic nerve disc (at the punctum caecum) to the lens. It is formed by an invagination of the hyaloid membrane, which encloses the vitreous body.
In the fetus, the hyaloid canal contains a prolongation of the central artery of the retina, the hyaloid artery, which supplies blood to the developing lens. Once the lens is fully developed the hyaloid artery retracts and the hyaloid canal contains lymph. The hyaloid canal appears to have no function in the adult eye, though its remnant structure can be seen.{{cite journal
| title = Persistence of Cloquet's Canal in Normal Healthy Eyes
| date = Nov 2006
| journal = Am J Ophthalmol
| volume = 142
| issue = 5
| pages = 862–864
| doi = 10.1016/j.ajo.2006.05.059
| pmid = 17056372
| first1=Larry | last1=Kagemann
| first2=Gadi | last2=Wollstein
| first3=Hiroshi | last3=Ishikawa
| first4=Michelle | last4=Gabriele
| first5=Vivek | last5=Srinivasan
| first6=Maciej | last6=Wojtkowski |author6-link=Maciej Wojtkowski
| first7=Jay | last7=Duker
| first8=James | last8=Fujimoto
| first9=Joel | last9=Schuman
| pmc=1939820
}}
Contrary to initial belief,{{cite journal
| author = T. P. Anderson Stuart
| authorlink = Thomas Peter Anderson Stuart
| date = 29 March 1904
| title = The function of the hyaloid canal and some other new points in the mechanism of the accommodation of the eye for distance
| journal = The Journal of Physiology
| volume = 31
| issue = 1
| pages = 38–48
| issn = 0022-3751
| doi =10.1113/jphysiol.1904.sp001021
| pmid = 16992721
| pmc = 1465472
}} the hyaloid canal does not facilitate changes in the volume of the lens. The lens volume changes by less than 1% over its range of accommodation.{{cite journal |last1=Marussich |first1=Lauren |title=Measurement of Crystalline Lens Volume During Accommodation in a Lens Stretcher. |journal=Investigative Ophthalmology & Visual Science |date=2015 |volume=58 |issue=8 |pages=4239–4248 |doi=10.1167/iovs.15-17050 |pmid=26161985 |pmc=4502455 }} Furthermore, lymph, being liquid, is incompressible, so even if the volume of the lens did change, the hyaloid canal could not compensate for it.