Among the most devastating is microbial keratitis, or corneal ulceration, which has increased 435 percent in the last 40 years. Mild anterior chamber reaction Studies have shown that the incidence of microbial keratitis is about 4 per 10,000 lens wearers per year for those wearing daily wear soft contact lenses and almost 21 per 10,000 wearers per year for those wearing extended-wear soft contacts. Wearing contacts overnight is the single most important risk factor and can increase the risk of developing microbial keratitis as much as 30 percent, according to some studies. 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.