The last 20 years has seen a tremendous increase in the use of contact lenses. Despite the recent trend towards fashionable eyewear and the advances in refractive surgeries, there are still approximately 1 million Australians who are currently wearing contact lenses. This is partly because of the variety of lens materials, replacement schedules, specialty designs, and convenient contact lens care systems available today.While there are many benefits of contact lenses, both cosmetic and therapeutic, contact lens wear is not without risk of complications. Ocular complications of contact lenses include iatrogenic (inappropriate fit, prescription or wearing schedule), patient non-compliance or misuse, as well as inherent problems with the patients tear film, lids, lashes, or meibomian glands. Contact lenses are implicated in the pathophysiology of many anterior segment disorders. Most commonly, these complications are due to hypoxia (oxygen deprivation to the cornea), mechanical stress, infection, or immunological factors. Soft contact lenses, also known as hydrogels, worn as extended wear (that is, up to a 7 consecutive day wearing schedule including overnight wear) have a significantly higher incidence (10-15 times the rate for daily wear hydrogels) of ocular complications. This is because corneal hypoxia is greatly exacerbated by overnight contact lens wear.A recent study found that in any given year, over 7% of all contact lens wearers experience an ocular complaint that is serious or bothersome enough to warrant a visit to their optometrist. The list of potential problems is long, and while many of the complaints are relatively minor, a few are potentially sight-threatening (see Table).Table: Possible complications of Contact Lens WearPotentially Sight Threatening Usually Not Sight Threatening Ulcerative bacterial keratitisCorneal edemaFungal and protozoal keratitisGiant papillary conjunctivitisSuperior limbic keratoconjunctivitis3-9...
