Crystalline lens power and astigmatism calculation in myopia by swept-source optical coherence tomography: A pilot study.

Abstract

Purpose: To calculate the crystalline lens power and astigmatism, as well as their changes following cycloplegia, in individuals with myopia using swept-source optical coherence tomography (SS-OCT).

Methods: Participants were divided into two groups according to axial length (AL). Crystalline lens parameters, including power, lens thickness (LT), anterior chamber depth (ACD), and astigmatism, were measured with SS-OCT and analysed before and after cycloplegia. The lensmaker's equation was used to calculate lens power, and differences between three consecutive measurements < 22.5 degrees was set as the screening criterion for meridian direction measurement repeatability.

Results: Sixty-three eyes met the screening criterion on the anterior surface both before and after cycloplegia was included. The majority of eyes exhibited lens astigmatism ranging from + 0.76 D to + 1.50 D on both anterior and posterior surfaces. Before cycloplegia, 61 eyes (96.8%) had with-the-rule (WTR) astigmatism on the anterior surface. Meanwhile, 25 eyes met the criterion on posterior surface, of which 21 eyes (84.0%) had against-the-rule (ATR) astigmatism. After cycloplegia, 60 eyes (95.2%) had WTR astigmatism on the anterior surface. Meanwhile, 23 eyes met the criterion on posterior surface, of which 19 eyes (82.6%) had ATR astigmatism. After cycloplegia, there were significant changes in the lens power, astigmatism, thickness, and ACD.

Conclusions: Astigmatism of crystalline lens on the anterior and posterior surfaces was mainly WTR and ATR, respectively, with similar refractive power. After cycloplegia, changes in parameters and refractive power of the lens mainly occur on the anterior surface.