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Mary Ann Croft, T Michael Nork, Jared P McDonald, Gregg A Heatley, Elke Lütjen-Drecoll, Paul L Kaufman; CILIARY MUSCLE AND CILIARY PROCESS’ AREA: AGING CHANGES VERSUS LENS DIMENSIONS AT REST AND DURING ACCOMMODATION. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1948.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the aging changes in the resting ciliary muscle (CM) and ciliary processes (CP) area and shape in aging human and monkey eyes, and to correlate the aging changes with lens thickness in resting and accommodated eyes.
The eyes of 8 rhesus monkeys (aged 8-22 yrs) and 8 human subjects (aged 19-65 yrs) were studied. Maximum accommodative responses were induced in the human eyes by 2 drops of 4% pilocarpine and in the monkey eyes by electrical stimulation of the Edinger-Westphal nucleus. Ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz) images were collected in the region of the lens/capsule, and ciliary body in both species.
In the young human subjects (aged 19-23), the shape of the resting CM was similar to that of the middle-aged subjects (28-34) and older subjects (49-65) and very similar to the resting shape of the ciliary muscle in the monkey eyes at any age.The area of the CPs increased significantly with age (Slope=0.007 ± 0.002 mm2 /yr; p<0.02); while accommodative amplitude significantly decreased with the increased amount of CP area (Slope= -28.6 ± 7.8 D/mm2; p<0.02).The thickness of the resting lens (slope=3.4 ± 0.7 mm/mm2 ; p=0.01), the accommodated lens thickness (slope=2.6 ± 0.7 mm/mm2; p<0.01) and the accommodative lens thickening (slope=-0.8 ± 0.3 mm/mm2 ; p<0.03) were dependent upon the amount of resting CP area. The greater the lens thickness the greater the CP area in either the resting or accommodated state, and the accommodative lens thickening decreased with increased CP area.
The age-related increase in CP area may be related to the increase in anterior CM thickness reported previously and this could be due to the additional force required to pull against the CM’s posterior restriction. However, there are no direct zonular attachments to the CPs. Alternatively, CP thickening could be due to age related accumulation of proteins in the region of aqueous formation (Lütjen-Drecoll). Increased CP area may have implications for aqueous inflow, IOP, accommodation and lens thickness. In vivo by UBM, the CM shape in the aging human is similar to the aging rhesus monkey, consistent with predictive relevance of the monkey eye to the human eye in biomechanical modeling.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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