people go too long before replacing their contacts, wearing lenses designed for 1, 14, or 30 days of wear for multiple months or years. while this does save on the cost of lenses, it risks permanent damage to the eye and even loss of sight. for non silicone-hydrogel lenses, one of the major factors that causes complications is that the contact lens is an oxygen barrier. the cornea needs a constant supply of oxygen to remain completely transparent and function as it should; it normally gets that oxygen from the surrounding air while awake, and from the blood vessels in the back of the eyelid while asleep. the most prominent risks associated with long-term, chronic low oxygen to the cornea include corneal neovascularization, increased epithelial permeability, bacterial adherence, microcysts, corneal edema, endothelial polymegethism, dry eye and potential increase in myopia. much of the research into soft and rigid contact lens materials has centered on improving oxygen transmission through the lens. silicone-hydrogel lenses available today have effectively eliminated hypoxia for most patients. mishandling of contact lenses can also cause problems. corneal abrasions can increase the chances of infection. when combined with improper cleaning and disinfection of the lens, a risk of infection further increases. decreased corneal sensitivity after extended contact lens wear may cause a patient to miss some of the earliest symptoms of such complications. the way contact lenses interact with the natural tear layer is a major factor in determining lens comfort and visual clarity. people with dry eyes are particularly vulnerable to discomfort and episodes of brief blurry vision. proper lens selection can minimize these effects. long-term wear (over five years) of contact lenses may "decrease the entire corneal thickness and increase the corneal curvature and surface irregularity." long-term wear of rigid contacts is associated with decreased corneal keratocyte density and increased number of epithelial langerhans cells. all contact lenses sold in the united states are studied and approved as safe by the fda when specific handling and care procedures, wear schedules, and replacement schedules are followed. current research contact lens sensors to monitor the ocular temperature have been demonstrated. a large segment of current contact lens research is directed towards the treatment and prevention of conditions resulting from contact lens contamination and colonization by foreign organisms. clinicians tend to agree that the most significant complication of contact lens wear is microbial keratitis and that the most predominant microbial pathogen is pseudomonas aeruginosa. other organisms are also major causative factors in bacterial keratitis associated with contact lens wear, although their prevalence varies across different locations. these include both the staphylococcus species (aureus and epidermidis) and the streptococcus species, among others. microbial keratitis is a serious focal point of current research due to its potentially devastating effect on the eye, including severe vision loss. one specific research topic of interest is how microbes such as pseudomonas aeruginosa invade the eye and cause infection. although the pathogenesis of microbial keratitis is not well understood, many different factors have been investigated. one group of researchers showed that corneal hypoxia exacerbated pseudomonas binding to the corneal epithelium, internalization of the microbes, and induction of the inflammatory response. one way to alleviate hypoxia is to increase the amount of oxygen transmitted to the cornea. although silicone-hydrogel lenses almost eliminate hypoxia in patients due to their very high levels of oxygen transmissibility, they also seem to provide a more efficient platform for bacterial contamination and corneal infiltration than other conventional hydrogel soft contact lenses. one study showed that pseudomonas aeruginosa and staphylococcus epidermis adhere much more strongly to unworn silicone hydrogel contact lenses than conventional hydrogel lenses and that adhesion of pseudomonas aeruginosa was 20 times stronger than that of staphylococcus epidermidis. this might partly explain why pseudomonas infections are the most predominant. however, another study conducted with worn and unworn silicone and conventional hydrogel contact lenses showed that worn silicone contact lenses were less prone to staphylococcus epidermidis colonization than conventional hydrogel lenses. besides bacterial adhesion and cleaning, micro and nano pollutants (biological and manmade) is an area of contact lens research that is growing. small physical pollutants ranging from nanoplastics to fungi spores to plant pollen adhere to contact lens surfaces in high concentrations. it has been found that multipurpose solution and rubbing with fingers does not significantly clean the lenses. a group of researchers have suggested an alternative cleaning solution, poppr (polymer on polymer pollution removal). this cleaning technique takes advantage of a soft and porous polymer to physically peal pollutants off of contact lenses. another important area of contact lens research deals with patient compliance. compliance is a major issue pertaining to the use of contact lenses because patient noncompliance often leads to contamination of the lens, storage case, or both. however, careful users can extend the wear of lenses through proper handling: there is, unfortunately, no disinterested research on the issue of "compliance" or the length of time a user can safely wear a lens beyond its stated use. the introduction of multipurpose solutions and daily disposable lenses have helped to alleviate some of the problems observed from inadequate cleaning but new methods of combating microbial contamination are currently being developed. a silver-impregnated lens case has been developed which helps to eradicate any potentially contaminating microbes that come in contact with the lens case. additionally, a number of antimicrobial agents are being developed that have been embedded into contact lenses themselves. lenses with covalently attached selenium molecules have been shown to reduce bacterial colonization without adversely affecting the cornea of a rabbit eye and octyl glucoside used as a lens surfactant significantly decreases bacterial adhesion. these compounds are of particular interest to contact lens manufacturers and prescribing optometrists because they do not require any patient compliance to effectively attenuate the effects of bacterial colonization. one area of research is in the field of bionic lenses. these are visual displays that include built-in electric circuits and light-emitting diodes and can harvest radio waves for their electric power. bionic lenses can display information beamed from a mobile device overcoming the small display size problem. the technology involves embedding nano and microscale electronic devices in lenses. these lenses will also need to have an array of microlenses to focus the image so that it appears suspended in front of the wearer's eyes. the lens could also serve as a head-up display for pilots or gamers. drug administration through contact lenses is also becoming an area of research. one application is a lens that releases anesthesia to the eye for post-surgery pain relief, especially after prk (photorefractive keratectomy) in which the healing process takes several days. one experiment shows that silicone contact lenses that contain vitamin e deliver pain medication for up to seven days compared with less than two hours in usual lenses. another study of the usage of contact lens is aimed to address the issue of macular degeneration (amd or age-related macular degeneration). an international collaboration of researchers was able to develop a contact lens that can shift between magnified and normal vision. previous solutions to amd included bulky glasses or surgical implants. but the development of this new contact lens, which is made of polymethyl methacrylate, could offer an unobtrusive solution. in popular culture christopher lee as the title character in dracula (1958) in one of the first uses of contact lens with makeup in films films one of the earliest known motion pictures to introduce the use of contact lenses as a make-up artist's device for enhancing the eyes was by the innovative actor lon chaney in the 1926 film the road to mandalay to create the effect of a character who had a blind eye. dr. rueben greenspoon applied them to orson welles for the film citizen kane in 1940. in the 1950s, contact lenses were starting to be used in british color horror films. an early example of this is the british actor christopher lee as the dracula character in the 1958 color horror film dracula, which helped to emphasize his horrific looking black pupils and red bloodshot eyes. tony curtis wore them in the 1968 film the boston strangler. contact lenses were also used to better emphasize the sinister gaze of the demonic characters in 1968's rosemary's baby and 1973's the exorcist. colored custom-made contact lenses are now standard makeup for a number of special effects-based movies. usage demas gn (1989). "ph consistency and stability of contact lens solutions". j am optom assoc. 60 (10): 732–4. pmid 2584587. the ph of contact lens solutions has been implicated in the comfort of contact lenses on insertion. "eye care". clh. retrieved 20 november 2014. "how to put contacts in your eyes". coopervision. retrieved 20 november 2014. use plain soap without any heavy moisturizers or perfumes. rinse well and dry your hands. again, this is to prevent transmitting anything unwanted to your eyes.