Simultaneous real-time imaging of the ocular anterior segment including the ciliary muscle during accommodation

Abstract

We demonstrated a novel approach of imaging the anterior segment including the ciliary muscle using combined and synchronized two spectral domain optical coherence tomography devices (SD-OCT). In one SD-OCT, a Complementary Metal-Oxide-Semiconductor Transistor (CMOS) camera and an alternating reference arm was used to image the anterior segment from the cornea to the lens. Another SD-OCT for imaging the ciliary muscle was equipped with a light source with a center wavelength of 1,310 nm and a bandwidth of 75 nm. Repeated measurements were performed under relaxed and 4.00 D accommodative stimulus states in six eyes from 6 subjects. We also imaged dynamic changes in the anterior segment in one eye during accommodation. The biometry of the anterior segment and the ciliary muscle was obtained. The combined system appeared to be capable to simultaneously real-time image the biometry of the anterior segment, including the ciliary muscle, in vivo during accommodation.

An analytical method for predicting the geometrical and optical properties of the human lens under accommodation

“…The surface area decrease was calculated as 3.28% over 6 D, which is comparable to the experimental MRI estimate of 4.78% ± 2.29% over the same accommodative range (0-6 D) in the study by Hermans et al [18]. This study gives values of 175.9 ± 2.8 mm 2 and 167.5±2.9 mm 2 for the unaccommdated and 6 D accommodated lens, respectively. The regression formula for 27 isolated lenses provided in Urs et al [34] gives a value of 170.5 ± 9.2 mm 2 ; usually, the isolated lenses assume the fully accommodated state.…”

“…This is the unaccommodated state, in which the lens is kept under constant tension. Experimental support for this most commonly accepted Helmholtzian theory includes, amongst many others, an interesting paper by Shao et al (2013) showing real-time imaging of accommodative changes in the anterior segment of the eye [2]. While experimental efforts show that lenticular spherical aberration (SA) becomes more negative with accomodation, it is clear that increasing surface curvatures cause more positive SA; thus the accommodative decrease in lenticular radii should produce more positive SA.…”

Quantification of the ciliary muscle and crystalline lens interaction during accommodation with synchronous OCT imaging

“…The trade-off of averaging is that the temporal resolution is reduced by a factor of two. We also tested if image contrast could be further improved by positioning the inner apex near the zero delay position [27]. However, we did not notice an improvement in image contrast compared to positioning the conjunctival surface near the zero delay position.…”

“…The only previous report on the biometry of the crystalline lens and ciliary muscle during dynamic accommodation used a combination of two SD-OCT systems which acquired images asynchronously with different frame rates for the lens and ciliary muscle (8.33 and 7.0 fps, respectively) [26,27]. The asynchronous image acquisition, lower frame rate, and uncertainty in time delay between image acquisition and onset of the accommodation stimulus resulted in large variability and uncertainty in the measured dynamic parameters significantly impacting the ability to gain insight into the dynamics of accommodation [26].…”

“…MRI provides distortionfree images of the entire eye, but its slow acquisition speed limits its application to the study of static accommodation. Recently, Shao et al [26,27] demonstrated joint but asynchronous acquisition of anterior segment and ciliary muscle images during accommodation using two separate SD-OCT units operating at central wavelengths of 840 nm and 1310 nm. The lack of precise synchronization combined with the moderate acquisition speed (~7-8 frames per second) of their systems limits the ability to accurately and precisely characterize the mutual temporal relationship between the dynamic changes occurring in the ciliary muscle and the resulting changes in the crystalline lens.…”