Role of Confocal Microscopy in the Diagnosis of Fungal and Acanthamoeba Keratitis

Purpose

To investigate the role of confocal microscopy as a diagnostic modality in microbial keratitis and to determine inter- and intraobserver variation in the analysis and interpretation of confocal microscopy findings.

Design

Prospective, double masked, nonrandomized, observational clinical trial.

Participants

We included 146 consecutive patients with clinically suspected microbial keratitis.

Methods

Confocal microscopy and microbiology evaluation of study participants.

Main Outcome Measures

Sensitivity, specificity, and positive and negative predictive values of confocal microscopy in diagnosing fungal and Acanthamoeba keratitis compared with microbiologic evaluation, as well as the intra- and interobserver variation in interpretation of confocal scans.

Results

We included 148 cases of infiltrative keratitis. Of the 103 microbiologically proven cases of Acanthamoeba or fungal keratitis, the confocal microscope was able to identify fungal filaments or Acanthamoeba cysts in 91 cases with either fungal or Acanthamoeba keratitis with a sensitivity of 88.3% (95% confidence interval [CI], 82.2–94.5) and a specificity of 91.1% (95% CI, 82.8–99.4). The interobserver agreement in interpreting the scans was good (kappa = 0.6; phi = 0.617). The intraobserver agreement was kappa = 0.795 and phi = 0.807.

Conclusions

The confocal microscope seems to be an accurate and reliable diagnostic modality in the etiologic diagnosis of fungal and Acanthamoeba keratitis.

Financial Disclosure(s)

Proprietary or commercial disclosure may be found after the references.