Measurement and prediction of lateral diffusion within human sclera.
OBJECTIVE
Drug delivery via the sclera is a promising approach to retinal disorder treatments that require access to the posterior segment of the eye. To complement existing studies of transverse diffusion across the sclera, this study examined lateral diffusion within the sclera parallel to the scleral surface.


METHODS
Using sulforhodamine as a model hydrophilic drug, rates of diffusion were measured in strips of human cadaveric sclera for up to 1 week. Data were analyzed with a mathematical model based on theoretical expressions for one-dimensional diffusion.


RESULTS
Measurable amounts of sulforhodamine were detected at distances of 5 and 10 mm from the sulforhodamine donor reservoir at 4 hours and 3 days, respectively. The effective lateral diffusivity of sulforhodamine was determined to be 3.82 x 10(-6) cm2/s, which is similar in magnitude to the transverse diffusivity. The theoretical model agreed with experimental values with an average error of 39%.


CONCLUSIONS
This study shows that the lateral diffusion of sulforhodamine in human sclera is slow and localizes to the site of administration.
Jiang
Jason
J
Emory Eye Center, Emory University, Atlanta, GA 30332-0100, USA.
Geroski
Dayle H
DH
Edelhauser
Henry F
HF
Prausnitz
Mark R
MR
D001692:Biological Transport; D005456:Fluorescent Dyes / Q000493:pharmacokinetics*; D006801:Humans; D008433:Mathematics; D008962:Models, Theoretical; D012590:Sclera / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D014966:Xanthenes / Q000493:pharmacokinetics*
D005456:Fluorescent Dyes; D014966:Xanthenes; C034657:Texas red