Effect of Tropicamide on crystalline Lens rise in low-to-moderate myopic eyes

BACKGROUND: Cycloplegics have been reported to induce changes in the lens thickness. However, the studies of correlation between cycloplegia and the lens position are limited. This study aims to investigate changes in crystalline lens rise (CLR) and other anterior segment parameters after inducing cycloplegia with tropicamide. METHODS: In this consecutive case study, 39 children (20 boys and 19 girls; mean age, 9.51 ± 1.75 years, mean spherical equivalence [SE], − 1.9 ± 1.5 D) with low-to moderate myopia were examined using CASIA 2 both before and after 30 min of administering 5-cycles (each 5 min apart) of 0.5% tropicamide. Measurements included CLR, crystalline lens thickness (CLT), mean radius of curvature of the anterior/posterior surface of the lens (Rf_ave/Rb_ave), anterior chamber depth (ACD), anterior chamber width (ACW), and central corneal thickness (CCT). Correlations of CLT and CLR with ACD, SE, and age were assessed respectively. RESULTS: CLT and CLR decreased significantly after cycloplegia (p < 0.001 and p < 0.001, respectively); whereas CCT, ACD, and Rf_ave increased (p = 0.008, p < 0.001, p < 0.001, respectively). A positive correlation was found between CLR and SE (r = 0.565, p < 0.001). However, a negative correlation between ACD and CLR was found before and after cycloplegia (r = − 0.430, p = 0.006; r = − 0.342, p = 0.035, respectively). CONCLUSIONS: The crystalline lens appeared thinner and moved backward after cycloplegia. ACD increased mainly due to the backward movement of the crystalline lens. These results aid in elucidating the impact of crystalline lens changes during the process of accommodation.