Evaluating relaxed ciliary muscle tone in presbyopic eyes

Abstract

Purpose Studies of age-related changes in ciliary muscle (CM) morphology and contractility have variously reported that CM weakens or strengthens with age. In response, the aim of this study was to evaluate relaxed CM tone in vivo in pre-presbyopic and presbyopic patients using a predictor value (P-CM). Methods Two groups of eyes-40 eyes of 40 healthy volunteers with a mean age of 28.1 +/- 5.8 years and 40 eyes of 40 healthy volunteers with a mean age of 56.6 +/- 7.3 years-formed the sample for this prospective, observational cross-sectional study. Used to evaluate relaxed CM tone, P-CM was calculated as the difference between the change in mean anterior chamber depth (ACD) and lens thickness (LT) before and after cycloplegia, as measured with swept-source optical biometry. Results The P-CM for relaxed CM tone was 0.04 +/- 0.04 mm in pre-presbyopic participants, 0.06 +/- 0.03 mm in presbyopic ones, and significantly greater in presbyopic patients (p = .018). Conclusion The statistical significance of P-CM between pre-presbyopic and presbyopic eyes might not signify clinical significance, since the difference was close to the repeatability limits for swept-source optical biometry. When relaxed, CM tone does not diminish with presbyopia according to changes in anterior chamber parameters due to cycloplegia.