AAPS PharmSciTech

, 10:796 | Cite as

Development of an Ex Vivo Method for Evaluation of Precorneal Residence of Topical Ophthalmic Formulations

  • Quan Liu
  • Youmin WangEmail author
Research Article


This paper describes the development of an ex vivo perfusion method for the evaluation of topical ophthalmic formulations. The perfusion system developed consisted of a perfusion chamber, two precision pumps to control the in/out flow rates to simulate the tear flow rate, and a fluorescence microscope imager. Freshly excised rat cornea was used as a biomembrane. Fluorescein (FITC) was used as a marker. Residence time was determined by measuring fluorescence intensity over time after application of the formulation to the cornea. In addition, viscoelastic properties of the formulations were measured and correlated to the retention times. The perfusion method easily differentiated formulations based on the retention time on the cornea: For example, a 0.3% hydroxypropyl methylcellulose formulation had a short retention time of <10 min. Addition of 0.25% carboxymethylcellulose increased the retention time from less than 10 min to over 16 min, and addition of 0.1% Carbopol further increased retention time to over 40 min. For alginate formulations, the retention time was significantly longer in the presence of 0.06% calcium chloride than that of 0.006% calcium chloride. The longer residence time at a higher Ca++ concentration can be attributed to the greater elastic modulus associated with the gel. Interestingly, however, a hyaluronate formulation displayed a very long retention time but has low viscoelastic moduli. This suggests that the mucoadhesive properties may not always be discernable by the rheological properties. The ex vivo perfusion method may in fact provide more meaningful information with regard to retention times of formulations.

Key words

ex vivo ophthalmic formulation perfusion residence retention 



The authors wish to thank Paul Grosenstein for providing rat cornea used in this study.


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Copyright information

© American Association of Pharmaceutical Scientists 2009

Authors and Affiliations

  1. 1.Department of Pharmaceutical Sciences, School of PharmacyTemple UniversityPhiladelphiaUSA
  2. 2.DEV-PDU-3Novartis Pharmaceuticals CorporationEast HanoverUSA

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