Demonstration of an anterior diffusional pathway for solutes in the normal human eye with high spatial resolution contrast-enhanced dynamic MR imaging.
OBJECTIVE
The present studies were conducted to determine whether a diffusional pathway for solutes exists from the ciliary body stroma to the anterior chamber of the human eye. The existence of such a pathway has been demonstrated in rabbits and monkeys, but such a pathway in humans would necessitate a shift in the physiological paradigm of the blood-aqueous barrier.


METHODS
Seven normal human volunteers (five men, two women; age range, 27 to 59 years) underwent nine dynamic T1-weighted, spin-echo MR imaging studies, using intravenous, gadolinium-based contrast agents.


RESULTS
In all cases, signal intensity rose rapidly in the ciliary body. In all subjects, there was a measurable latent rise in signal strength (enhancement) in the anterior chamber. Signal enhancement typically occurred in the angle of the anterior chamber earlier, and to a greater degree, than within the center of the chamber. Increased signal within the posterior chamber was significantly less than in the anterior chamber, with measured increases probably attributable to volume averaging.


CONCLUSIONS
These findings are consistent with the existence of an anterior diffusional pathway in the human eye. The model warrants further testing.
Bert
Robert J
RJ
Department of Radiology, Health Sciences Center, University of Colorado, Denver, Colorado 80262, USA. robert.bert@uchsc.edu
Caruthers
Shelton D
SD
Jara
Hernan
H
Krejza
Jaroslaw
J
Melhem
Elias R
ER
Kolodny
Nancy H
NH
Patz
Samuel
S
Freddo
Thomas F
TF
D000328:Adult; D000867:Anterior Chamber / Q000378:metabolism*; D001082:Aqueous Humor / Q000378:metabolism*; D001692:Biological Transport; D018916:Blood-Aqueous Barrier; D002924:Ciliary Body / Q000378:metabolism*; D003287:Contrast Media; D004058:Diffusion; D017352:Echo-Planar Imaging; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008297:Male; D008875:Middle Aged
D003287:Contrast Media; D019786:Gadolinium DTPA