Schachar Ronald A, Schachar Ira H, Kumar Shubham, Feldman Eitan I, Pierscionek Barbara K, Cosman Pamela C
Department of Physics, University of Texas at Arlington, Arlington, TX, USA.
North Bay Vitreoretinal Consultants, Santa Rosa, CA, USA.
Sci Rep. 2024 Mar 11;14(1):5896. doi: 10.1038/s41598-024-56563-8.
How the human eye focuses for near; i.e. accommodates, is still being evaluated after more than 165 years. The mechanism of accommodation is essential for understanding the etiology and potential treatments for myopia, glaucoma and presbyopia. Presbyopia affects 100% of the population in the fifth decade of life. The lens is encased in a semi-elastic capsule with attached ligaments called zonules that mediate ciliary muscle forces to alter lens shape. The zonules are attached at the lens capsule equator. The fundamental issue is whether during accommodation all the zonules relax causing the central and peripheral lens surfaces to steepen, or the equatorial zonules are under increased tension while the anterior and posterior zonules relax causing the lens surface to peripherally flatten and centrally steepen while maintaining lens stability. Here we show with a balloon capsule zonular force model that increased equatorial zonular tension with relaxation of the anterior and posterior zonules replicates the topographical changes observed during in vivo rhesus and human accommodation of the lens capsule without lens stroma. The zonular forces required to simulate lens capsule configuration during in vivo accommodation are inconsistent with the general belief that all the zonules relax during accommodation.
人类眼睛如何聚焦于近处，即如何进行调节，在165多年后仍在评估之中。调节机制对于理解近视、青光眼和老花眼的病因及潜在治疗方法至关重要。老花眼在人生的第五个十年会影响100%的人群。晶状体被包裹在一个半弹性的囊膜中，囊膜上附着有称为小带的韧带，这些韧带介导睫状肌的力量来改变晶状体的形状。小带附着在晶状体囊膜的赤道处。根本问题在于，在调节过程中，是所有小带都松弛，导致晶状体的中央和周边表面变陡，还是赤道部小带张力增加，而前后小带松弛，导致晶状体表面周边变平、中央变陡，同时保持晶状体的稳定性。在此，我们通过一个气球囊膜小带力模型表明，赤道部小带张力增加，同时前后小带松弛，能够重现恒河猴和人类在无晶状体基质情况下，晶状体囊膜在活体调节过程中所观察到的地形变化。模拟活体调节过程中晶状体囊膜形态所需的小带力，与普遍认为的调节过程中所有小带都会松弛的观点不一致。
