Once<unk>  is diagnosed, initiation of timely and appropriate treatment will have a significant impact on visual outcomes. Medical therapy aims to eradicate both trophozoite and cystic forms of<unk>  and also control the inflammatory response. Medical therapy Multiple classes of drugs have been found to be effective in killing the trophozoite form of<unk> , including anti-bacterial, anti-fungal, anti-protozoal, and anti-neoplastic agents. However, no single therapy has been found to eliminate both trophozoite and cystic forms, and to eradicate corneal infection. One class of medications used in treatment is the biguanides, which include polyhexamethylene biguanide (PHMB) 0.02% to 0.06% drops, and chlorhexidine 0.02 to 0.2% drops. These medications disrupt the cell wall of the trophozoite organism, leading to its death. However, these agents have shown limited efficacy against the cystic forms. Due to the efficacy of these drugs against the<unk> , as well as their low toxicity to the cornea, they are commonly used as the first line medications in the treatment of<unk> . Biguanides have also been found to act synergistically when used in combination with diamidines, with propamidine isethionate and hexamidine being the most commonly used. A limitation of diamidine use is relative corneal toxicity with long term use. A combined regimen of propamidine, miconazole nitrate, and neomycin has also been suggested. Due to the potential for negative longterm visual outcomes with<unk> , therapy is usually started with a combination of a biguanide and a diamidine. Early use of high dose dual therapy helps to eliminate both trophozoite and cyst forms of the organism, while also preventing deep penetration of cysts into the corneal stroma. Cysts that are not eradicated from the cornea will cause recurrence. The treatment is often initiated by instilling drops onto the surface of the eye every hour, 24 hours a day, for at least the first 48–72 hours. If an appropriate response to therapy, this may be reduced to hourly administrations during the day only, which is continued for several weeks to months. Beyond anti-amoebic therapies, there is also a role for topical steroids of anti-inflammatory medications in the treatment of<unk> . During infection, severe inflammation in the cornea and anterior chamber can cause more severe symptoms including pain and visual disturbance. Topical steroids may be used to reduce this inflammation and thereby alleviate symptoms. However, the role of steroids is typically very limited, because their dampening of the immune response may lead to worsening of the infection. Additionally, steroids can increase the number of trophozoites in the cornea by inducing excystation. 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<unk>  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.
Acanthamoeba keratitis
Herpes simplex keratitis
Fungal keratitis
Nummular keratitis
Neurotrophic keratitis
Diffuse lamellar keratitis
Peripheral ulcerative keratitis
Interstitial keratitis