Case 234. Acanthamebic keratitis (44 y-o F)
Smear preparation of painful ring-shaped keratitis in a contact lens wearer
Key words : Acanthamoeba castellani, keratitis, herpetic keratitis
A ring-shaped turbidity is seen on the cornea (gross findings). In an advanced stage, a disk-shaped white lesion is formed.   A cyst of Acanthamoeba castellani stained by Parker innk-KOH solution. A wrinkled double-layered cyst wall is characteristic. The nucleus is not visible.
Another view of the cyst of Acanthamoeba castellani with the thick, wrinkled cyst wall (Papanicolaou).   Reference case 234A
Another case of acanthamebic keratitis. Brushing cytology from the cornea, showing numbers of acanthoamoebic cysts (Papanicolaou). Wrinkled, double-layerd cyst wall is pathognomonic.
Reference case 234A
High powered view of the acanthamebic cysts in brushing cytology specimen (Papanicolaou). High powered view demonstrates a varying degree of cytoplasmic maturation within the cysts.
  Reference case 234A
Cultured Acanthamoeba castellani (Papanicolaou). Nuclei are not evident in the cyst form.
Reference case 234B
The turbid cornea surgically removed from a 43 y-o female with advanced stage of illness, who received corneal transplantation (HE). Trophozoites of Acanthamoeba with a centrally located karyosome are seen among the collagen fibers of the removed cornea.
  Scanning electron micrograph of trophozoites of Acanthoamoeba castellani
The surface of the acanthoamebic trophozoites reveals acanthopodia formation (irregular process-like structure). Acanthamoeba is a ubiquitous free-living protozoa widely distributed in the water and soil. Keratitis is closely related to wearing a contaminated soft contact lens.
Reference case 234C
Scarred herpetic keratitis, surgically removed for corneal transplantation (38 y-o M) (HE). The epithelial layer is ulcerated and mild inflammatory infiltration is seen in scarred collagenous bundles. HSV antigen was undetectable.