Purpose: The aim of this study was to investigate the time-course of changes in choroidal thickness (ChT) following complete mydriasis induced by compound tropicamide.
Methods: ChT was measured by OCT with the enhanced-depth imaging technique (Spectralis HRA+OCT, Heidelberg Engineering, Germany) at nine locations of the fundus: subfoveal ChT (SFChT) and ChT at 1 mm and 3 mm from the fovea in four quadrants. Mydriasis was induced with compound tropicamide (0.5% tropicamide plus 0.5% phenylephrine hydrochloride, three doses at 5-minute intervals). Measurements were conducted prior to the instillation and at 0, 30, and 60 min following complete mydriasis. Results at different time-points were compared using repeated-measures ANOVA to investigate the time-course of the changes.
Results: Thirty-nine subjects (mean age 11.9±2 years; 16 males and 23 females) were enrolled in the study. Compound tropicamide resulted in a statistically significant decrease in SFChT at 0, 30, and 60 min after complete mydriasis, as compared to baseline (-5±4 μm, -12±4 μm, and -13±4 μm, respectively; all P<0.0001). No significant changes were detected in the parafoveal choroid except at 1 mm temporal (T1mm) and nasal (N1mm) to the fovea at 30 and 60 min (T1mm: -6±4 μm and -7±5 μm at 30 and 60 min; N1mm: -6±4 μm and -7±5 μm at 30 and 60 min, respectively; all P<0.0001). Repeated-measures ANOVA showed a significant interaction between the time after complete mydriasis and the effect of the mydriasis agent.
Conclusions: Complete mydriasis induced by compound tropicamide led to choroidal thinning, and the magnitude varied over time.