The thickness of the choroidal membrane plays a pivotal role in ocular health, yet recent findings suggest common treatments may not have the anticipated impact.
A study performed at the Ufa Eye Research Institute examined the short-term effects of the two commonly used eye drop medications—pilocarpine and cyclopentolate—on the choroidal thickness (CT) and subfoveal choroidal thickness (SFCT) of healthy young adults. The research team, led by M.M. Bikbov and colleagues, assessed whether the counteracting effects of these medications, one which stimulates and the other which relaxes the ciliary muscle, would influence the thickness of the choroidal membrane.
Twenty-one healthy participants, with ages ranging from 15.7 to 25.8 years, were enrolled for the study. Each participant received one drop of 1% cyclopentolate administered to their right eye and one drop of 1% pilocarpine to their left eye. Using optical coherence tomography (OCT), measurements of SFCT and midperipheral choroidal thickness were recorded both at baseline and thirty minutes post-instillation.
Notably, the study results indicated no statistically significant changes in thickness following the treatments with either medication. Specifically, after cyclopentolate application, SFCT changed minimally, showing variations of -2.9 μm to 10.5 μm, and pilocarpine similarly yielded fluctuations of 3.9 μm to 5.8 μm. Neither treatment resulted in meaningful alterations, regardless of examiner or analytical method.
"Application of cyclopentolate 1% and of pilocarpine 1% did not result in statistically significant change in choroidal thickness..." the authors reported, reinforcing the findings' consistency across various evaluation metrics involving the data collected.
The authors outlined the study results, indicating no discernible influence of the medications on the position of the Bruch's membrane or the anterior-posterior axis of the eye. Consequently, indications remain unclear on the degree to which medical mydriasis influences axial length measurement outcomes, which is particularly relevant for procedures like cataract surgery.
Drugs such as pilocarpine act as non-selective muscarinic receptor agonists prompting ciliary muscle contraction, theoretically drawing the Bruch's membrane slightly anteriorly and affecting choroidal thickness. Conversely, cyclopentolate acts as a muscarinic antagonist, positing the opposite interaction. Previous studies have yielded mixed results with topical drug applications—some reporting changes to the choroidal thickness under different conditions, depending on drug type and application methods.
The discrepancies surrounding the effects on choroidal thickness may reflect differences in study design, drug concentrations, or variations intrinsic to the test population. The authors suggest future research might explore higher doses or alternative methods to establish clearer relationships between ciliary muscle activity and choroidal dimensions.
Going forward, the study emphasizes how time-sensitive choroidal assessments may not always be influenced by pharmacological manipulation of ciliary muscle tone, leading to uncertainty about the necessity of certain procedures or preventative measures, particularly for patients with conditions sensitive to choroidal thickness.
To sum up, this research contributes to the growing body of knowledge surrounding ocular pharmacology, demonstrating the complexity of drug interactions within the eye and shedding light on important areas for future examination.