18 February 2009 Optical coherence tomography in estimating molecular diffusion of drugs and analytes in ocular tissues
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Proceedings Volume 7163, Ophthalmic Technologies XIX; 71631H (2009); doi: 10.1117/12.810635
Event: SPIE BiOS, 2009, San Jose, California, United States
Abstract
Aside from other ocular drug delivery methods, topical application and follow up drug diffusion through the cornea and sclera of the eye remain the favored method, as they impose the least pain and discomfort to the patient. However, this delivery route suffers from the low permeability of epithelial tissues and drug washout, thus reducing the effectiveness of the drug and ability to reach its target in effective concentrations. In order to better understand the behavioral characteristics of diffusion in ocular tissue, a method for noninvasive imaging of drug diffusion is needed. Due to its high resolution and depth-resolved imaging capabilities, optical coherence tomography (OCT) has been utilized in quantifying the molecular transport of different drugs and analytes in vitro in the sclera and the cornea. Diffusion of Metronidazole (0.5%), Dexamethasone (0.2%), Ciprofloxacin (0.3%), Mannitol (20%), and glucose solution (20%) in rabbit sclera and cornea were examined. Their permeability coefficients were calculated by using OCT signal slope and depth-resolved amplitude methods as function of time and tissue depth. For instance, mannitol was found to have a permeability coefficient of (8.99 ± 1.43) × 10-6 cm/s in cornea (n=4) and (6.18 ± 1.08) × 10-6 cm/s in sclera (n=5). We also demonstrate the capability of OCT technique for depth-resolved monitoring and quantifying of glucose diffusion in different layers of the sclera. We found that the glucose diffusion rate is not uniform throughout the tissue and is increased from approximately (2.39 ± 0.73) × 10-6 cm/s at the epithelial side to (8.63 ± 0.27) × 10-6 cm/s close to the endothelial side of the sclera. In addition, discrepancy in the permeability rates of glucose solutions with different concentrations was observed. Such diffusion studies could enhance our knowledge and potentially pave the way for advancements of therapeutic and diagnostic techniques in the treatment of ocular diseases.
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Mohamad G. Ghosn, Valery V. Tuchin, Kirill V. Larin, "Optical coherence tomography in estimating molecular diffusion of drugs and analytes in ocular tissues", Proc. SPIE 7163, Ophthalmic Technologies XIX, 71631H (18 February 2009); doi: 10.1117/12.810635; http://dx.doi.org/10.1117/12.810635
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KEYWORDS
Diffusion

Tissues

Optical coherence tomography

Sclera

Glucose

Cornea

Eye

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