Acute eye redness, or red eye syndrome, is a symptom of inflammatory eye irritation, which is usually caused by toxins, pathogens, viruses or bacteria in the ocular environment. This is an acute reaction that is usually associated with continuous use of contact lenses. It may also be an accompanying phenomenon of certain eye diseases including glaucoma, conjunctivitis, keratitis or uveitis. During continuous wear, lenses accumulate metabolites and other harmful substances produced by bacteria. These substances, together with bacteria, irritate the eye and may eventually cause inflammation. During sleep, due to the closed eyes, the cornea receives only a small amount of oxygen, an amount that is even further reduced by the presence of contact lenses. This leads to acidification of the ocular environment, which then becomes a breeding ground for many undesirable bacteria. Redness caused by continuous wearing of contact lenses is manifested immediately after waking up and is accompanied by tearing, burning, itching, pain and photophobia.