Accommodation, presbyopia: quantification of lens, iris and vitreous accommodative movements and aging

Session Details

Session Title: LASIK and Imaging

Session Date/Time: Tuesday 10/10/2017 | 14:00-15:20

Paper Time: 14:31

Venue: Room 4.1

First Author: : M.Croft USA

Co Author(s): :    T. Nork   J. McDonald   G. Heatley   E. Lütjen-Drecoll   P. Kaufman        

Abstract Details

Purpose:

Our earlier work reported on the accommodative response in the aniridic eye of the rhesus monkey. Herein we describe the accommodative response in the presence of the iris. Our goal is to elucidate the accommodative movements of the lens, ciliary muscle, iris and the role of the vitreous in the young and aged monkey eye as these findings are likely applicable to human accommodative mechanisms and presbyopia therapies.

Setting:

Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, USA,Department of Anatomie University Erlangen Nürnberg, Germany

Methods:

A stimulating electrode was inserted in the E-W nucleus of six iridic and five iridectomized rhesus monkeys (ages 4-24 yrs) to induce accommodation. The eyes were imaged using ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz, 20mHz), and endoscopy in the region of iris, lens, ciliary muscle, zonular attachments and vitreous during maximum accommodative responses. The visualization of the intraocular structures and fluid movements were enhanced by intravitreal injection of various contrast agents (i.e., triamcinolone, fluorescein). In addition, new and improved UBM instrumentation was used to image the entire globe and obtain quantification and more detail of the accommodative movements of the vitreous in relation to accommodative lens movements.

Results:

In the iridic eye during stimulation of the E-W nucleus the eye accommodated by 15.3 ± 1.15 (n=3) diopter and the pupil constricted by 0.90 ± 0.03 mm. During maximum accommodation the ciliary muscle moved forward and inward while the anterior chamber shallowed (by 0.31 ± 0.01mm young; 0.09 ± 0.01 older), central lens thickened (by 0.61 ± 0.01 mm young; 0.25 ± 0.01mm older) and the iris in the region of the pupil moved forward with the anterior movement of the lens surface. However, in the region of the circumlental space, the peripheral iris bowed backward (by 0.05 ± 0.01 mm young; 0.12 ± 0.02 mm older: p<0.05), suggesting accommodative fluid displacement toward the vitreous compartment and anterior hyaloid in the presence of the iris. The central vitreous moved posteriorly during accommodation (by 0.37 ± 0.02 mm young; 0.23 ± 0.05mm older: p<0.05). During accommodation the posterior pole of the lens moved posteriorly by 0.30 ± 0.02 mm and 0.10 ± 0.3 mm in the young and older eye, respectively in accord with the posterior central vitreous movements. Cloquet’s canal could be visualized by UBM and the entire canal moved posteriorly with the posterior lens pole movement during accommodation, while the peripheral vitreous membrane moved anteriorly. Similar accommodative movements were seen in the aniridic eye.

Conclusions:

The normal accommodative fluid movements and the movements of the accommodative apparatus itself are not dependent on the presence or absence of the iris. The posterior accommodative movement of Cloquets canal may facilitate lens reshaping. The accommodative fluid redistribution may facilitate elimination of waste through the TM and accommodative lens reshaping. Factors that drive the accommodative fluid redistribution will be discussed.

Financial Disclosure:

receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented, research is funded, fully or partially, by a company producing, developing or supplying the product or procedure presented