Therefore it is typically recommended that steroids be used briefly to aid in symptom resolution, and that anti-amoebic agents be used both during, and for several weeks after topical steroid use. Surgical treatment
Surgical debridement of an infected cornea can also be used to reduce organism load and excise devitalized tissue from the cornea. It may also improve the efficacy of medical therapy by promoting penetration of medication into deeper layers of the cornea. In cases of corneal ulceration or perforation, or if corneal scarring is severe, corneal transplant may be required. This typically involves full thickness transplantation of the cornea from a healthy donor eye. The size of the graft should be kept as small as possible, as larger grafts carry a great risk of host rejection, and due to the possibility of graft revision surgery. While surgery is capable of restoring vision by replacing a damaged cornea, it also carries risks of recurrent Acanthamoeba infection or graft failure. For this reason, anti-amoebic medications should be started prior to surgery, and continued for several weeks afterward. If there is suspicion or evidence of recurrent infection, cultures should be sent. If cultures are positive, anti-amoebic therapy should be continued for 6 months.Outcomes following surgery are typically much better for patients who receive surgery for vision improvement following infection resolution, and therefore all efforts should be made to maximize medical management before attempting surgery. Epidemiology
A study in Austria reported a total of 154 cases of Acanthamoeba keratitis over a 20-year period.
Soft contact lenses are more adherent to the corneal surface than hard lenses, which allows the Acanthamoeba organism to bind to mannosylated glycoproteins on the corneal surface. Expression of these proteins on the corneal surface is increased by contact lens use. This increase in glycoprotein content, along with microtrauma to the corneal epithelial surface due to contact lens use increases the risk for infection. Once the organism has gained access to the surface of the eye, it is able to invade through the epithelium and Bowmans layer. In some cases, the infection can then group around corneal nerves, producing radial deposits (radial keratoneuritis), and causing extreme pain. These are features also seen in viral and bacterial keratitis, and may be misleading. The organism is also capable of invading deeper into the cornea; using metalloproteases it is able to penetrate deep into the stroma of the cornea. As the disease progresses, it may penetrate through the cornea but very rarely causes infection inside the eye (endophthalmitis) due to a robust neutrophil response in the anterior chamber.While the vast majority of cases of Acanthamoeba keratitis occur in contact lens wearers, there have been many cases of Acanthamoeba described in those who do not wear contact lenses, especially outside the United States. In non-contact lens users, the greatest risks for developing Acanthamoeba infection are trauma and exposure to contaminated water. Further predisposing factors include contaminated home water supply, and low socioeconomic status.