Interaction with therapeutic soft contact lenses affects the intraocular efficacy of tropicamide and latanoprost in dogs M. HATZAV T. BDOLAH-ABRAM & R. OFRI Koret School of Veterinary Medicine, Hebrew University of Jerusalem, Rehovot, Israel Hatzav, M., Bdolah-Abram, T., Ofri, R. Interaction with therapeutic soft contact lenses affects the intraocular efficacy of tropicamide and latanoprost in dogs. J. vet. Pharmacol. Therap. doi: 10.1111/jvp.12263. Therapeutic soft contact lenses (TSCLs) are frequently used to support or pro- tect the cornea during healing. Our aim was to quantitatively evaluate the efficacy of topical medications in TSCL-fitted dogs and determine whether it is affected by the presence of TSCLs. In Phase I, pupil diameter was measured in eyes treated with tropicamide and in eyes covered with TSCLs and then treated with tropicamide, with 1-week intervals between sessions. In Phase II, intraocular pressure (IOP) was measured in uncovered and TSCL-covered eyes treated with latanoprost, with 1-week intervals between sessions. Tropi- camide caused significant mydriasis in both uncovered and TSCL-covered eyes (P = 0.005). On the other hand, latanoprost caused a significant decrease in IOP when applied to uncovered eyes (P = 0.002), but had no significant effect on IOP when applied to TSCL-covered eyes (P = 0.7). As we used the same dogs and identical TSCLs throughout the study, we conclude that the different outcomes of the two drugs are due to properties of the drugs themselves, or their formulations, affecting their interaction with the TSCLs. The clinical efficacy of topical drugs applied to TSCL-covered eyes may have to be determined for each drug and/or formulation. (Paper received 11 March 2015; accepted for publication 26 July 2015) Ron Ofri, Koret School of Veterinary Medicine, Hebrew University of Jerusalem, PO Box 12, Rehovot 7610001, Israel. E-mail: ron.ofri@mail.huji.ac.il Preliminary results were presented as an Abstract at the annual meeting of the European College of Veterinary Ophthalmologists, 2014, London, United Kingdom. INTRODUCTION Therapeutic soft contact lenses (TSCLs) are used in veterinary patients as bandages to support and protect the cornea during healing from various diseases (Maggs, 2013; Regnier, 2013), including corneal ulcers and spontaneous chronic corneal epithelial defects in dogs (Ledbetter & Gilger, 2013), and indo- lent ulcers in horses (Gilger, 2013). Use of TSCLs has also been recommended to reduce recurrence following symblepharon surgery (Hendrix, 2013) or keratectomy to remove superficial feline sequester (Stiles, 2013). TSCLs are commercially avail- able for all of these species, as well as in humans, and are becoming an increasingly popular treatment modality in veteri- nary practice. Regardless of the indication for their use, TSCLs are usually used as adjunct therapy and are not meant to replace medical treatment, as the diseased eyes still need to be medicated topi- cally. To allow such treatment, numerous methods are being developed to allow penetration and increase bioavailability of topical drugs applied to TSCL-covered eyes. The most basic technique is soaking the TSCL in a drug solution for a period of time before placing it on the eye. However, this method results in a one-time ‘pulse dose’ delivery system, as the drug cannot be replenished without removing the TSCL, and the amount and rate of drug delivery cannot be adequately con- trolled (Regnier, 2013). Indeed, in some cases, most of the loaded drug dose is released within a few hours (Souza et al., 2014). Furthermore, the high concentration of the drug and preservatives delivered in the initial pulse may expose the eye and the patient to an increased risk of toxic effects (Bar-Ilan & Neumann, 1997; Regnier, 2013). Therefore, more sophisti- cated methods are being developed to improve the use of TSCLs as a drug delivery system, including the incorporation of nanoparticles in the TSCL matrix before polymerization, coat- ing the TSCL with vitamin E to retard diffusion, application of molecular imprinting technology, and increasing drug-binding to the polymer (Bengani et al., 2013; Gonz alez-Chom on et al., 2013; Souza et al., 2014). However, these advanced delivery technologies are still in experimental stages and are not yet commercially available in © 2015 John Wiley & Sons Ltd 1 J. vet. Pharmacol. Therap. doi: 10.1111/jvp.12263