IV.D. Physiology of Accommodation and Role of the Vitreous Body

Coleman, D. Jackson; Silverman, Ronald H.; Lloyd, Harriet O.

doi:10.1007/978-1-4939-1086-1_28

Cited by 2 publications

(1 citation statement)

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“…This strand which extends from the posterior vitreous zonule insertion zone to the lens equator is termed the PVZ INS‐LE structure ( Figure ) and is referred to as such hereafter in this paper. The PVZ INS‐LE is distinct from and not to be confused with the vitreous zonule that extends from the posterior insertion zone and attaches to the plexus at the walls of the ciliary processes and then changes direction to become the anterior zonule that attach to the lens near the equator, as described by Rohen and as described by Coleman et al . as ‘accessory zonules.’ The PVZ INS‐LE courses in a straight line from the posterior insertion zone to the posterior lens equator and attaches to it – without attaching to the plexus at the ciliary processes.…”

Section: Introductionmentioning

confidence: 97%

Accommodative movements of the lens/capsule and the strand that extends between the posterior vitreous zonule insertion zone & the lens equator, in relation to the vitreous face and aging

Croft

Heatley

McDonald

et al. 2015

Ophthalmic Physiologic Optic

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Purpose To elucidate the dynamic accommodative movements of the lens capsule, posterior lens and the strand that attaches to the posterior vitreous zonule insertion zone and posterior lens equator (PVZ INS-LE), and their age-related changes. Methods Twelve human subjects (ages 19–65 years) and twelve rhesus monkeys (ages 6–27 years) were studied. Accommodation was induced pharmacologically (humans) or by central electrical stimulation (monkeys). Ultrasound biomicroscopy was used to image intraocular structures in both species. Surgical procedures and contrast agents were utilized in the monkey eyes to elucidate function and allow visualization of the intraocular accommodative structures. Results Human: The posterior pole of the lens moves posteriorly during accommodation in proportion to accommodative amplitude and ciliary muscle movement. Monkey: Similar accommodative movements of the posterior lens pole were seen in the monkey eyes. Following extracapsular lens extraction (ECLE), the central capsule bows backward during accommodation in proportion to accommodative amplitude and ciliary muscle movement, while the peripheral capsule moves forward. During accommodation the ciliary muscle moved forward by ~1.0 mm, pulling forward the vitreous zonule and the PVZ INS-LE structure. During the accommodative response the PVZ INS-LE structure moved forward when the lens was intact and when the lens substance and capsule were removed. In both the monkey and the human eyes these movements declined with age. Conclusions The accommodative shape change of the central capsule may be due to the elastic properties of the capsule itself. For these capsule/lens accommodative posterior movements to occur, the vitreous face must either allow for it or facilitate it. The PVZ INS-LE structure may act as a “strut” to the posterior lens equator (pushing the lens equator forward) and thereby facilitate accommodative forward lens equator movement and lens thickening. The age-related posterior restriction of the ciliary muscle, vitreous zonule and the PVZ-INS LE structure dampens the accommodative lens shape change. Future descriptions of the accommodative mechanism, and approaches to presbyopia therapy, may need to incorporate these findings.

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Section: Introductionmentioning

confidence: 97%