Corneal Densitometry as a Novel Technique for Monitoring Amiodarone Therapy.

ABSTRACT

PURPOSE: The clinical efficacy and toxicity of amiodarone may be determined more effectively by tissue deposition than by levels of the agent in serum. Therefore, corneal densitometry might be useful for therapeutic monitoring. The aim of the study is to evaluate Scheimpflug corneal densitometry in patients with amiodarone keratopathy (AK). DESIGN: Comparative case series. PARTICIPANTS: Sixty-six patients receiving amiodarone therapy and 66 healthy controls were consecutively enrolled in this study. METHODS: Patients were examined using the Oculus Pentacam (Wetzlar, Germany). MAIN OUTCOME MEASURES: Densitometry data from different corneal layers and different annuli were extracted, analyzed, and compared with densitometry values of healthy controls. Duration of treatment, cumulative dose, Orlando stage (slit-lamp biomicroscopy), and serum concentrations of amiodarone and N-desethylamiodarone also were determined, and the correlation to different densitometry data was evaluated. RESULTS: The total corneal light backscatter at total corneal thickness and at total diameter was significantly higher in the amiodarone group compared with the control group (AK group 28.3±5.2; control group 24.4±4.2; P < 0.001). Upon dividing the corneal surface into different layers at total thickness, the differences were significant in all layers (P < 0.001). The serum concentrations of the metabolite N-desethylamiodarone correlate with densitometry values, especially in the 0- to 2-mm annulus in the anterior layer (r = 0.419; P = 0.001), whereas the cumulative dose and duration of treatment correlate significantly with the densitometry values in the 0- to 2-mm annulus at total thickness (P = 0.014 and P = 0.022, respectively). CONCLUSIONS: Corneal densitometry is a useful, objective method for quantifying AK and can help in monitoring amiodarone therapy. The serum concentration of the active metabolite N-desethylamiodarone correlates with the extent of keratopathy in the anterior layer, whereas chronic changes in the stroma correlate with the cumulative dose and duration of treatment.