Intraocular cannula for continuous, chronic drug delivery. Histopathologic observations and function
K. Miki, R. Patterson and S. J. Ryan
An indwelling cannula for drug delivery was implanted in rabbit eyes.
Rabbits were followed up for as long as 1 1/2 years after surgery. They
showed almost no adverse effects as a result of the implantation, and
cannula patency was demonstrated by the injection of fluorescein sodium
through the cannula at various times following surgery. Histopathologic
studies using light and electron microscopy were performed at various times
to determine the effect of cannula implantation on the eye. Cellular
proliferation along the cannula after 1 1/2 years was limited to the region
immediately adjacent to the wound and rarely extended to the surrounding
retina or ciliary body. The proliferative tissue at the wound site
originated mainly from the episclera; the retina and the choroid at the
posterior fundus remained intact. Photoreceptor cell metabolism was studied
by light microscopic autoradiography following intraocular injection of
tritiated leucine to assess photoreceptor outer-segment renewal.
Autoradiography showed normal receptor uptake of leucine. A broad band of
radioactive labeling of the outer segments resulted from continuous,
chronic drug delivery, while a narrow band of labeling resulted from a
single intravitreous injection. These data indicate that the cannula system
continuously delivered tritiated leucine into the vitreous cavity. We
believe that the implanted intraocular cannula, which allows continuous
drug delivery on a relatively long-term basis, will be a valuable technique
for research and possibly clinical studies.
