Soft Contact Lenses for Controlled Ocular Delivery: 50 Years in the Making

Abstract

The use of contact lenses as ocular bandages for drug delivery was envisioned nearly 50 years ago by Wichterle and co-workers. Despite the therapeutic advantages that can be obtained, this application has to face up to the poor affinity shown by commercially available contact lenses for most ophthalmic drugs, resulting in small amounts of drug being loaded and short time of therapeutic levels in the eye structures. Novel strategies that appeared in the beginning of 21st century, for example coating lenses with vitamin E, incorporation of drug nanocarriers or application of molecular imprinting technology, are becoming relevant tools for development of true drug/contact lens combination products that may be available for ocular therapy in the foreseeable future.

Sustained drug release by contact lenses for glaucoma treatment—A review

“…The affinity of the drug to the contact lens depends on the nature of both, in an ambivalent situation. If the affinity is too high, the formulation exhibits a high stability but the drug is not released, while if the affinity is too low, the drug will be poorly retained by the CLs and will be released very quickly, exhibiting a peak concentration in the eye followed by a steep decline, meaning that therapeutic levels are not attained 30 . The drug-CLs affinity depends also on the drug's molecular weight, which for values between 300-500 Da is released from the CLs in the order of minutes to hours [51][52][53][54][55] .…”

“…It involves the use of a template drug and functional monomers during the CLs polymerization process which results in the formation of macromolecular memory sites with a suitable size and chemical groups to stably accommodate the drug 30 . The molecularly imprinted pockets mimic the drug's receptors and its structurally similar analogs, therefore increasing the drug loading capacity, while providing an adequate release rate 69,70 (Fig.…”

“…Due to their superior ability to retain water, the hydrophilic CLs can be used for long periods of time (up to 6 nights and 7 days) 30 .…”

Contact lenses as drug controlled release systems: a narrative review

“…SHCLs represented a significant leap for further research on CLs as ophthalmic drug controlled release systems (DCRS). [1][2][3][4] Several factors emphasize their singular importance in the field of ocular therapeutics: the approximately 125 million worldwide CL wearers; well-studied CL biocompatibility and transparency; the familiarity of their use with minimal effect on ocular functions and a large residence time in the eye. Eye physiological and anatomical constraints compromise the correct drug concentration and optimal absorption of pharmacological agents at the specific action site requiring multiple dosage of eye drops eventually associated with noncompliance, overdosing and unwanted systemic side effects.…”

Chitosan/alginate based multilayers to control drug release from ophthalmic lens

“…The efforts made by many researchers in the last decades to optimize drug delivery through soft contact lenses (SCLs) have been described in several recent reviews [1][2][3]. In the case of cataracts which are, nowadays, one of the most frequent eye diseases, other devices have been investigated to prevent postoperative infectious complications after surgery, namely, therapeutic intraocular lenses (IOLs) [4][5][6].…”