Structural design of contact lens-based drug delivery systems; in vitro and in vivo studies of ocular triggering mechanisms

Abstract

This study identifies and investigates the potential use of in-eye trigger mechanisms to supplement the widely available information on release of ophthalmic drugs from contact lenses under passive release conditions. Ophthalmic dyes and surrogates have been successfully employed to investigate how these factors can be drawn together to make a successful system. The storage of a drug-containing lens in a pH lower than that of the ocular environment can be used to establish an equilibrium that favours retention of the drug in the lens prior to ocular insertion. Although release under passive conditions does not result in complete dye elution, the use of mechanical agitation techniques which mimic the eyelid blink action in conjunction with ocular tear chemistry promotes further release. In this way differentiation between passive and triggered in vitro release characteristics can be established. Investigation of the role of individual tear proteins revealed significant differences in their ability to alter the equilibrium between matrix-held and eluate-held dye or drug. These individual experiments were then investigated in vivo using ophthalmic dyes. Complete elution was found to be achievable in-eye; this demonstrated the importance of that fraction of the drug retained under passive conditions and the triggering effect of in-eye conditions on the release process. Understanding both the structure-property relationship between drug and material and in-eye trigger mechanisms, using ophthalmic dyes as a surrogate, provides the basis of knowledge necessary to design ocular drug delivery vehicles for in-eye release in a controllable manner.

In vitro dissolution/release methods for mucosal delivery systems

“…This setup is widely employed for in vitro drug release testing from ocular inserts [50] and contact lenses [51]. Sometimes is also used in case of semisolid dosage forms [6], microparticles for nasal application [52] and thermosensitive gels for buccal application [53].…”

2022 Glenn A. Fry Award lecture: Enhancing clinical assessment for improved ophthalmic management

“…Our advancements in the understanding of contact lenses, particularly to reduce the drop out 166 linked with prior ocular surface disease, [167][168][169][170] have included better evaluation of lens fit, [171][172][173][174][175][176][177] the emergence of silicone hydrogel materials [178][179][180][181][182][183] along with their impact on ocular surface temperature 184,185 and corneal oxygen consumption, 186 lubricating solution delivery, [187][188][189] and nano-thickness surface coatings (to change surface lubricity while maintaining lens material bulk properties). 190,191 Our translational research on soft contact lens fit evaluation has led to a simplified recording method where centration/coverage, movement on blink on up-gaze, lag on horizontal gaze, and push-up recovery speed are graded on a 3-point scale 174 to inform clinical decision-making, 172 which has been adopted by the International Association of Contact Lens Educators.…”

We are being myopic about myopia control

“…Anisa Mahomed et al show how lenses could be manipulated to release pharmaceuticals into the eye, such as low dose atropine [11]. Scleral lenses as reviewed by Walker and colleagues and Sarah La Porta Weber could provide even better stability of lens optics than soft design and so may have a potential role in myopia control [12,13].…”