Abstract
Optical coherence tomography (OCT) offers new options for imaging the ciliary muscle allowing direct in vivo visualization. However, variation in image quality along the length of the muscle prevents accurate delineation and quantification of the muscle. Quantitative analyses of the muscle are accompanied by variability in segmentation between examiners and between sessions for the same examiner. In processes such as accommodation where changes in muscle thickness may be tens of microns- the equivalent of a small number of image pixels, differences in segmentation can influence the magnitude and potentially the direction of thickness change. A detailed analysis of variability in ciliary muscle thickness measurements was performed to serve as a benchmark for the extent of this variability in studies on the ciliary muscle. Variation between sessions and examiners were found to be insignificant but the magnitude of variation should be considered when interpreting ciliary muscle results.
Highlights
The ciliary muscle has a key role in vision as one of the tissues involved in the biomechanical changes leading to accommodation
We report intra- and inter-examiner variability of measurements of ciliary muscle thickness and thickness change during accommodation from two experienced examiners
Intra- and inter-examiner variability of ciliary muscle thickness and thickness change measurements during accommodation derived from optical coherence tomography (OCT) images was reported
Summary
The ciliary muscle has a key role in vision as one of the tissues involved in the biomechanical changes leading to accommodation. In the classical Helmholtz theory of accommodation, the muscle contracts and shifts anteriorly and inwardly, relaxing the zonular fibers connected to the crystalline lens, subsequently producing the change in lens shape essential to accommodation. Despite this important role, little is known about how the muscle and its contractability changes with age. Ultrasound biomicroscopy (UBM) provides images of the muscle throughout its entire depth [2,3,4,5,6,7], but its resolution (0.1 mm) is insufficient to precisely quantify changes with accommodation, its contrast is limited, and it requires contact with the eye. In vivo images of the muscle have been acquired with OCT at high resolution [9,10,11,12] and dynamically during accommodation [9, 11]
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