# Therapeutic Hydrogel Lenses and the Antibacterial and Antibiotic Drugs Release
## 1 Introduction  
Therapeutic lenses provide analgesic and protective effects by shielding epithelial defects and acting as a physical bandage for the corneal surface. The coverage of the corneal surface reduces the symptoms caused by the exposure of the corneal nerve endings. In the last decade, membrane hydrogel used has further expanded due to both the improvement of lens materials and the expansion of therapeutic indications. Furthermore, hydrophilicity could increase the bioavailability of pharmacological preparations in solution. These lenses, which can incorporate and absorb water-soluble molecules, are soaked with eye drops to increase the contact time between the pharmacological preparation and the ocular surface [1]. Multiple investigations of various commercially available lenses and different drugs have allowed for conclusions to be made into the factors that influence drug uptake and release in vitro such as nature of the material backbone, the overall lens water content and surface charge, [2]. Daily-wear lenses are manufactured with silicone hydrogel. Other hydrogel materials offer lens manufacturers a very positive and consistent patient response compared to silicone hydrogel lens materials [3]. A series of poly (2-hydroxyethyl methacrylate) (pHEMA) hydrogels containing crosslinked \(\beta\)-cyclodextrintrin-hyaluronan (\(\beta\)-CD-crHA) with tear-protein adsorption resistance and sustained drug delivery have been developed as contact lens materials for eye diseases. Copolymers of HEMA and methacrylate acid are the most used materials for disposable soft lenses and typically have a water content in the 55-60% range (in the vial or blister). During wear, these lenses lose approximately 10% of their water content and accumulate a substantial amount of protein because positivelycharged tear proteins and lysozyme precipitate onto the negatively charged lens [4]. Poly-HEMA is a hydrophilic hydrogel with high water content and has been widely used in biomedical applications, including contact lenses and ophthalmic drug delivery systems, due to its safety and excellent biocompatibility [5]. Ionic lenses can absorb a thicker layer of protein than nonionic lenses, with the former adsorbing primarily lysozyme [6]. Hydrogel lenses with higher water content adsorb larger amounts of protein [7]. Hydrogel materials were the most common lens materials for decades, until the recent successful development of truly complex soft lenses (i.e., the silicone hydrogel polymer complex), which account for up to 65% of today's modern contact lenses. These hydrogels show adequate light transparency, oxygen permeability, and swelling for use as contact lenses [8]. Oxygen transmission through the silicone hydrogel complex is six times higher than through lenses made with \"simple hydrogel materials.\" However, instillation of the silicone molecular component carries with it an inherent hydrophobicity, meaning that a silicone hydrogel polymer contact lens does not intimately interact with the precorneal tear film. Indeed, this complex polymer repels the tear film, much as the surface of a newly waxed car repels water. This hydrophobic characteristic is directly responsible for the high (up to 50%) frequency of dry eye symptoms in silicone hydrogel polymer lens wearers [9]. Silicone hydrogel contact lenses were found to be effective and well-tolerated bandage lenses [10]. However, the penetration of a drug can be greatly improved by prolonging its contact time with the eye. Hydrophilic contact lenses can be used as an adjuvant to drug delivery. Drugs penetrate hydrophilic contact lenses at a rate that depends on the pore size between the cross-linkages of the three-dimensional structure of the lens, the concentration of the drug in the solution, and the molecular size of the drug. [11]. In rabbits' eyes, an increased intraocular gentamicin level was found in eyes fitted with hydrophilic contact lenses [12]. Frequently, alterations in corneal sensitivity result from refractive surgery, corneal surgery and cataract surgery.