Abstract
Purpose:
Changes occurring in the choroid are associated with in ocular growth in many studies with animals. Since the cholinergic system may be involved in regulating choroidal thickness, we assessed whether the anticholinergic agent- homatropine alters choroidal thickness in humans.
Methods:
Fourteen young healthy adults (27.92 ± 4.05 years of age) participated in this randomized, placebo-controlled crossover study. Choroidal thickness was measured with a spectral domain OCT (SOCT- Copernicus HR) prior to, as well as 30 and 60 minutes following the instillation of one drop of 2% homatropine hydrobromide or placebo (0.3% hydroxypropyl methylcellulose). All measurements were carried out on the right eye only. The pre- and post-drop OCT images (6 mm width horizontal and vertical line scans centred on the fovea) were manually segmented to calculate subfoveal and parafoveal (1.5 mm from the center of the fovea) choroidal thickness.
Results:
The subfoveal choroidal thickness in the OCT scans underwent a small but significant thickening after instillation of topical homatropine when compared to the placebo (ANOVA, p<0.001). The mean change in choroidal thickness following homatropine instillation was 8 ± 4 μm and 12 ± 6 μm after 30 and 60 minutes respectively. The parafoveal choroid also exhibited increase with time after homatropine instillation in all quadrants (p<0.01). However, only the temporal and nasal parafoveal choroid showed significant change in thickness after 60 min when compared to the placebo (both p<0.05).
Conclusions:
Instillation of homatropine results in an increase in choroidal thickness. These data provide insights into the mechanism regulating choroidal thickness in human eyes and suggests that the cholinergic signalling may be involved in this process.
Keywords: 605 myopia •
452 choroid •
674 receptors