# Therapeutic Hydrogel Lenses and the Antibacterial and Antibiotic Drugs Release
## 4 Discussion
This finding indicates that the amount of chloramphenicol released from all lenses was anyway enough to cause bacterial growth inhibition anyway. This situation occurs for a pure _S. thipymurium_ strain devoid of any resistance. It is likely that in the clinical situation having a higher amount of antibiotic released for the lens could decrease the risk of antibiotic-resistance occurrence. Our study has several limitations. Nevertheless, this appears to be the first report to highlight the importance of selecting contact lens parameters to optimize drug therapy to the ocular surface; their hydration can be helpful in minimizing infections, and the properties of the materials (oxygen transmissibility) are important for the development of corneal neovascularization [21]. Corneal and conjunctival alterations can also be found in contact lens wearers. In these cases, the reduced supply of oxygen to the ocular surface interferes with corneal metabolism by inducing corneal hypoesthesia and increasing conjunctival sensitivity. Chronic use of contact lenses can also induce mechanical stimulation of nociceptors and the activation of sub-acute inflammation with the release of inflammatory mediators [22]. The future appears promising for drug-eluting contact lenses, but several challenges remain to be overcome regarding processing and storage issues, lack of use in the elderly population, regulatory issues, and high costs of clinical studies and cost-benefit analyses. The use of therapeutic contact lenses in the USA involves a very large market (45 million contact lens wearers) that is counteracted by refractive surgery, but this type of lens has been and will be more precisely used because patient compliance is often high, with patients often facing exacerbation of their disease if they do not accept what is prescribed by the doctor. A contact lens with a burst release is superior to eye drops in terms of improved bioavailability, but this benefit is possibly not adequate to justify the increased cost from the use of contact lenses, particularly if more than one lens may be needed each day. However, advances in contact lens design now allow users to wear lenses continuously for a few weeks [23], which provides an ideal platform for extended release of ophthalmic drugs. Furthermore, numerous other in vitro and in vivo studies have been conducted, including large in vivo studies with significant numbers of humans or animals, using commercial contact lenses soaked in various molecules to release into the eyes, including dexamethasone phosphate, chloromycin, gentamicin or carbenicillin, kanamycin, tobramycin, ciprofloxacin,floxacin [24] and lomefloxacin [24]. These studies clearly demonstrated an increase in bioavailability with the use of drug-eluting contact lenses compared to eye drops. The increased bioavailability leads to increased drug concentrations in the cornea and aqueous humor, which, in turn, can extend the therapeutic effect compared to that of eye drops [25]. Indeed, these recent advances have led to the development of several approaches for extended delivery of a variety of ophthalmic drugs including the glaucoma drug timolol, the dry eye drug cyclosporine, the anti-inflammatory dexamethasone, the anesthetic lidocaine, antibiotics, antivirals, and antifungals. It is now feasible to design continuous-wear silicone hydrogel contact lenses that release drugs for long durations, thus affording the possibility of continuous drug delivery without lens replacement for 2-4 weeks [26]. However, this evidence-based review has clearly demonstrated that comfort cannot be considered in isolation but is contact lens-specific and depends on the surface and bulk properties of the material, the lens design characteristics, and the modality of use of the contact lens; comfort may also be significantly influenced by the replacement frequency and interaction with any lens care system that may be used.