Presbyopia is an age-related ocular disorder where accommodative ability declines so that an individual's focusing range is insufficient to provide visual clarity for near and distance vision tasks without corrective measures. With age, the eye exhibits changes in biomechanical properties of many components involved in accommodation, including the lens, sclera, and ciliary muscle. Changes occur at different rates, affecting accommodative biomechanics differently, but individual contributions to presbyopia are unknown. We used a finite element model (FEM) of the accommodative mechanism to simulate age-related changes in lens stiffness, scleral stiffness, and ciliary contraction to predict differences in accommodative function. The FEM predicts how ciliary muscle action leads to lens displacement by initializing a tensioned unaccommodated lens (Phase 0) then simulating ciliary muscle contraction in accommodation (Phase 1). Model inputs were calibrated to replicate experimentally measured lens and ciliary muscle in 30-year-old eyes. Predictions of accommodative lens deformation were verified with additional imaging studies. Model variations were created with altered lens component stiffnesses, scleral stiffness, or ciliary muscle section activations, representing fifteen-year incremental age-related changes. Model variations predict significant changes in accommodative function with age-related biomechanical property changes. Lens changes only significantly altered lens thickening with advanced age (46% decrease at 75 years old) while sclera changes produced progressive dysfunction with increasing age (23%, 36%, 49% decrease at 45, 60, and 75 years old). Ciliary muscle changes effected lens position modulation. Model predictions identified potential mechanisms of presbyopia that likely work in combination to reduce accommodative function and could indicate effectiveness of treatment strategies and their dependency on patient age or relative ocular mechanical properties.
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http://dx.doi.org/10.1007/s10237-023-01767-6 | DOI Listing |
Introduction: Cataract surgery has been reported to have a reducing effect on intraocular pressure (IOP) in glaucomatous and non-glaucomatous eyes. This effect seems to be more noticeable in eyes with narrow angles (NAs) than in eyes with open angles (OAs). Decrease in IOP may be a result of the increase in anterior chamber angle (ACA) and Schlemm canal (SC) after cataract surgery.
View Article and Find Full Text PDFBMC Ophthalmol
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Department of Ophthalmology, The First Affiliated Hospital of Bengbu Medical University, Bengbu, Anhui, 233004, China.
Objectives: To evaluate the effects of short-acting cycloplegic agents, tropicamide and compound tropicamide, on ocular biological parameters and choroid thickness.
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Sci Rep
January 2025
Privatpraxis Prof Jonas und Dr Panda-Jonas, Heidelberg, Germany.
Bruch´s membrane (BM) is firmly connected posteriorly to the optic nerve head through the peripapillary choroidal border tissue, and anteriorly through the longitudinal ciliary muscle to the scleral spur. We assessed, whether a difference in the contractile state of the ciliary muscle influences the position of the posterior BM by lifting the posterior BM pole, i.e.
View Article and Find Full Text PDFTransl Vis Sci Technol
January 2025
Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA.
Purpose: Although the lens undoubtedly plays a major role in presbyopia, altered lens function could be in part secondary to age-related changes of the ciliary muscle. Ciliary muscle changes with accommodation have been quantified using optical coherence tomography, but so far these studies have been limited to quantifying changes in ciliary muscle thickness, mostly at static accommodative states. Quantifying ciliary muscle thickness changes does not effectively capture the dynamic anterior-centripetal movement of the ciliary muscle during accommodation.
View Article and Find Full Text PDFPediatr Pulmonol
January 2025
Department of Pediatric Chest Diseases, Faculty of Medicine, Gazi University, Ankara, Turkey.
Background And Objectives: Patients with primary ciliary dyskinesia (PCD) have a reduction in exercise capacity from the early stages. Although there are studies investigating these patients' lower extremity exercise capacity using various methodologies, there needs to be more research on the functional exercise capacity of the upper extremities. This study aimed to compare pulmonary function, upper extremity functional exercise capacity, muscle oxygenation, muscle strength, and physical activity level in children with PCD and controls.
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