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Mary Ann Croft, T Michael Nork, Jared P McDonald, Paul L Kaufman; ACCOMMODATIVE CILIARY MUSCLE CONTRACTION: CHOROID AND LENS THICKNESS MEASUREMENTS. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5572.
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© ARVO (1962-2015); The Authors (2016-present)
To detect choroid thickness changes during the accommodative response and how they may relate to the accommodative changes in the lens and ciliary muscle dimensions.
The eyes of 5 human subjects (aged 19-65 yrs) were studied. Homatropine (1 drop 5%) was used to relax the ciliary muscle and pilocarpine was used to induce maximum accommodative responses (2 drops 4%). Spectralis OCT (EDI mode) images were collected in the region of the optic nerve (ON) to image the choroid thickness. Ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz) images were collected in the region of the lens/capsule, and ciliary body. OCT and UBM images were collected in the resting and accommodated state.
In the young human subjects (ages 19-23), the thickness of the choroid in the region of the optic nerve was 343.6 ± 8.1 μm (mean± s.e.m.; n=2) and in the older subjects (ages 49-53) it was 136.4 ± 15.2 μm (n=3). During accommodation in the older subjects the choroid thinned by 12.7 ± 1.7 μm (p=0.01) to 123.8 ± 16.7 μm and the choroid/retina stretched by 1.15 ± 0.27 mm in the region of the ON. The resting lens thickness increased with age from 3.3 ± 0.15 mm (young eyes) to 3.9 ± 0.15 mm (older eyes). In the three older subjects the lens thickness increased by 0.12 ± 0.03 mm during accommodation.
Measurement of the choroid thickness is possible with the Spectralis OCT instrument using EDI mode and can be used to determine the accommodative changes in choroid thickness. The choroid thickness decreased with age and decreased during accommodation. It may be that the age-related choroid thinning is due to changes in the geometry of the accommodative apparatus to which it is attached (i.e. muscle/lens complex). Accommodative decrease in choroid thickness and stretch of the retina/choroid may indicate stress/strain forces in the region of the optic nerve during accommodation and may have implications for glaucoma. Measurements will be taken in additional human subjects and the results discussed.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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