Purchase this article with an account.
Mary Ann Croft, T Michael Nork, Jared P. McDonald, Gregg A Heatley, Elke Luetjen-Drecoll, Paul L Kaufman; ACCOMMODATION & PRESBYOPIA: MOVEMENTS OF THE ACCOMMODATIVE APPARATUS IN THE PRESENCE OF THE IRIS AND LENS. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2477.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To elucidate the accommodative movements of the iris and its effect on accommodative aqueous fluid redistribution and other relevant components of the accommodative apparatus.
A stimulating electrode was inserted in the E-W nucleus of four iridic rhesus monkeys (ages 6-23 yrs) to induce accommodation. Maximum accommodative responses were elicited and the eye imaged using ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz) and endoscopy in the region of iris, lens, ciliary muscle, zonular attachments and vitreous during the accommodative response. Various contrast agents (i.e., triamcinolone) were used to enhance visualization of the intraocular structures and fluid movements.
During stimulation of the E-W nucleus the eyes converged, the pupil constricted by 0.90 ± 0.03 mm and there was 11.8 ± 1.6 (n=4) diopters of accommodation (the accommodative triad).During maximum accommodation the iris bowed backward in the region of the circumlental space by 0.05 ± 0.01 mm and 0.12 ± 0.02 mm in the young and older eye respectively (p<0.05), suggesting accommodative fluid displacement toward the vitreous compartment and anterior hyaloid. The iris in the region of the pupil moved forward with the anterior movement of the lens surface. The anterior chamber shallowed by 0.31 ± 0.01 mm and 0.09 ± 0.01 in the young and older eye, respectively. The lens thickened by 0.61 ± 0.01 mm and 0.25 ± 0.01mm in the young and older eye, respectively. 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. Similar accommodative movements were seen in the aniridic eye.
The absence of the iris does not change the normal accommodative fluid movements or the movements of the accommodative apparatus itself compared to the iridic eye. The fluid redistribution likely facilitates the accommodative lens reshaping and elimination of waste through the TM. Factors that drive the accommodative fluid redistribution will be discussed (i.e. accommodative vitreous structural/fluid movements, lens reshaping). The age-related increased backward bowing of the iris may result in chafing of the peripheral iris by the lens; a possible connection with pigmentary glaucoma will be discussed.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
This PDF is available to Subscribers Only