Background: Millions of people in Germany wear contact lenses every day. Deficient contact lens hygiene can lead to corneal infection. Contact lens-associated keratitis usually has a highly acute presentation and can cause long-term visual loss.
Methods: This review is based on pertinent publications retrieved by a selective search in PubMed, as well as on relevant metaanalyses, Cochrane reviews, and reports by national and international health care authorities.
Results: 23-94% of contact lens wearers report associated discomfort and eye problems. The annual incidence of contact lens-associated keratitis is 2-4/10 000. It is due to bacteria in 90% of cases, and much less commonly to acanthamoebae and fungi. The pathogens generally arrive with the contact lens on the surface of the eye and can penetrate into the corneal tissue because the tear film under the lens is not swept away from the ocular surface by the eyelids, and corneal epithelial changes are often present as well. Corneal infiltration that is diagnosed early is often self-limited, but advanced bacterial infection usually requires intense topical antibiotic treatment. Some severe infections can only be eradicated by emergency corneal transplantation; this is the case in 20-30 % of fungal and acanthamoebic infections.
Conclusion: The wearing of contact lenses, particularly soft ones, is associated with a risk of microbial keratitis if proper contact lens hygiene is not exercised. Contact lens-associated keratitis very rarely causes permanent damage to eyesight (0.6 cases per 10 000 contact lens wearers per year). The use of contact lenses always calls for meticulous care.