A Study Based on CASIA2: What the Subtle Changes Has Taken Place in the Shape of the Crystalline Lens After Cycloplegia?

Abstract

Background: To evaluate the shape of the crystalline lens biometry and the diopter before and after cycloplegia using the CASIA2 swept-source (SS) optical coherence tomography (OCT) system on the anterior segment.Methods: This is a retrospective study. Children and adolescents (26 males and 29 females, aged 4–21 years) with simple ametropia were selected for optometry and CASIA2 imaging at 2 separate visits before and after cycloplegia. Diopter is derived from the spherical power (S) obtained by optometry. The Biometric parameters of the crystalline lens, including anterior chamber depth (ACD), anterior and posterior curvature of the lens (ACL and PCL), lens thickness (LTH), lens decentration(LD), lens tilt(LT), and the equivalent diameter of the lens (LED), were measured by CASIA2. The differences of these parameters before and after cycloplegia were compared, and the relationship between them was analyzed.Results: Fifty-five participants (106 eyes) were initially enrolled. The differences were statistically significant(P<0.05) in S (t=-7.026, P=0.000), ACD (t=-8.796, P=0.000), ACL (t=-13.263, P=0.000) and LTH（t=7.363, P=0.000）before and after cycloplegia. The change of PCL (t=1.557,P=0.122), LD (t=0.876, P=0.383), LT (t=0.440, P=0.661) and LED（t=-0.351, P=0.726） was not statistically significant (P>0.05). There was a significant (P<0.05) correlation between the change in S and ACL(r=0.466, P=0.000),LTH (r=-0.592, P=0.000),and LED (r=0.223, P=0.021) but not between the PCL(r=0.19, P=0.051), LD (r=-0.048, P=0.0628) and LT (r=-0.022, P=0.822). Furthermore, the change of ACD is closely related to the change of crystal morphology. However, in children and adolescents, we found that the change of crystal morphology will not have anything to do with age.Conclusion: The morphological changes of the lens before and after cycloplegia are mainly the ACL and LTH, but there is no difference in the PCL, LD, LT, and LED. In the adolescent population, the change of S is related to the change of ACL, LED and LTH. However, age gets nothing to do with the shape of the crystalline lens. For different refractive states (myopia, hyperopia, emmetropia), whether groups of different ages can reach the same conclusion needs further research.