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Irene Siso-Fuertes, Danilo Andrade de Jesus, Hema Radhakrishnan; Relationship between ciliary muscle and accommodative response across age groups. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2061.
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Presbyopia is a condition affecting people over 45 years of age worldwide. Understanding accommodative ability in older subjects has been a major challenge. We conducted an experimental cross-sectional study to investigate the changes in the ciliary muscle (CM) dimensions with accommodation in different age groups.
Eighteen subjects aged between 18 to 75 years were included and divided into 3 age groups: Group 1 - (18 to 29 years), Group 2 - (30 to 40 years), Group 3 - (40 years and over). Healthy participants (mean spherical equivalent: -0.63 D with astigmatism less than 1.25D) with no history of ocular pathology or surgery were enrolled. Accommodative response (AR) measurements and CM images at three different accommodative demands (0, 2.5 and 4D) were taken with Visante Anterior-Segment Optical Coherence Tomographer (OCT; Carl Zeiss Meditec). A MATLAB code was developed to measure the CM thickness at 2 (CMT2), 2.5 (CMT25) and 3 (CMT3) mm from the scleral spur in a semi-automated way. In order to acquire the AR we used a Hartman-Shack aberrometer (IRX3, Imagine Eyes) programmed to present fixed stimuli from 0D to 4D of accommodation in 0.50D steps.
Linear regressions showed that the correlation between age and CMT at all 3 points measured was not statistically significant (p > 0.05). Friedman test revealed statistically significant (p < 0.05) CM thickness changes with accommodation in age group 2 for CMT2 and CMT25 and in age group 3 for CMT3 (Figure 1). The slope of the AR and the absolute value of the CMT slope negatively correlated in age group 1 while a positive correlation was found for age groups 2 and 3.
Our findings support the lenticular theory of presbyopia. CM is invariant with age but does change in thickness with accommodation. Older people with stiffer crystalline lenses, present a bigger change in CM in order to more accurately accommodate, while young people with easily deformable lenses exhibit less CM change when their accommodative response is more accurate.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Figure 1: CMT for the 3 age groups at three accommodative demands. Each CMT represents the blue line segmented in the CM in-vivo image example. (*) in dicate statistically significant differences (p < 0.05)
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