While the danger to individuals seems small, the fact that more than 26 million people wear contact lenses makes corneal infections a major public health concern. Differentiating microbial from aseptic keratitis is important because the management is different and the potential risk from microbial keratitis is so much greater. Aseptic keratitis is an inflammatory condition related to toxic, allergic or hypoxic conditins. Unfortunately, laboratory tests cannot always distinguish between the two. The clinical comparison in the box accompanying this article may be helpful.
All contact lenses reduce oxygen transmission to the cornea.
They cause corneal swelling and damage epithelial cells to a varying degree. They trap bacteria and other debris and develop a biofilm coating that is difficult to remove with popular one-step cleaning processes. Contact-lens wear has been trivialized, leading to poor consumer education and lax compliance with cleaning regimens. While poor lens hygiene and inadequate cleaning systems increase the risk of infection, good hygiene does not offer complete protection. Wearing contact lenses overnight is the No. 1 risk factor and should be discouraged.