The Value of Cytology Smears for Acanthamoeba Keratitis

Table 1

Comparison of diagnostic approaches for Acanthamoeba keratitis.

Diagnostic modality	Advantages	Disadvantages
Microbiological culture	(i) Direct identification	(i) Low sensitivity [1]; (ii) Can take up to 1 week
Polymerase chain reaction (PCR)	(i) Specific; (ii) Fast	(i) Requires intact DNA [2]; (ii) Not readily available
In vivo confocal microscopy	(i) Immediate identification of double-walled cysts; (ii) Noninvasive	(i) Not readily available; (ii) Requires trained observer to recognize cysts in images [1]
Histopathology	(i) Specific; (ii) Requires several days for diagnosis; (iii) Multiple stains and/or immunoperoxidase studies can be done	(i) Requires significant tissue (corneal biopsy or keratoplasty specimen)
Cytological smear	(i) Minimally invasive; (ii) Identifies both empty and double-walled cyst; (iii) Fast; (iv) Biopsy easy to perform	(i) Organisms in deep stroma not easily represented
Electron microscopy	(i) Specific	(i) Requires weeks to process; (ii) Expensive and labor intensive; (iii) Practical only for small tissue samples