Computer image analysis of ultrasound biomicroscopy of primate accommodation

Abstract

Purpose To assess and correct images of the eye for movements that can confound the evaluation of the presence, direction, and magnitude of intraocular movement of the crystalline lens equator during centrally induced ciliary muscle contraction (accommodation). Methods Ultrasound biomicroscopic (UBM) video images of a cynomologus monkey crystalline lens were obtained from an independent source. The images, prior to, during, and following electrical stimulation of the Edinger-Westphal (EW) nucleus were compared for evidence of movement of the crystalline lens equator. Extraocular eye movements were assessed by use of objective computer imaging analysis techniques. Results Extraocular eye movements were identified and reduced by using objective computer imaging analysis techniques to register and realign the corneal images. Highly significant corrections are required to effect corneal realignment. Analysis of paired and registered images from this data source indicates that any movements of the primate lens equator are not detectable when maximum accommodation was induced by EW stimulation. Conclusions The displacement of the edge of the primate crystalline lens equator during electrically induced contraction of the ciliary muscle is a small displacement phenomenon, only analysable after confounding extraocular movements are removed from the compared images.

Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

“…It has been suggested that centripetal movements of the crystalline lens edge during accommodation are an artifact due to extraocular eye movements (Schachar and Kamangar, 2005), and that in fact the lens edge moves towards the sclera during accommodation. In this study, lens edge movements were measured from a fixed reference mark on the cornea and clearly showed a centripetal movement away from the sclera during both pharmacologically and EW stimulated accommodation, in accordance with previous studies (Croft, Glasser, Heatley, McDonald, Ebbert, Dahl, Nadkarni and Kaufman, 2006;Fincham, 1937b;Glasser, Wendt and Ostrin, 2006;Grossmann, 1903;Wilson, 1997).…”

Accommodation of the human lens capsule using a finite element model based on nonlinear regionally anisotropic biomembranes

“…When the ciliary muscles contract, the zonules are released from tension, causing the lens body to become more curved, allowing the eye to focus on nearby objects (Alpern 1969;Fisher 1969;Burd et al 2002). An alternative theory of accommodation states that during accommodation, relaxing of the ciliary muscles cause the equatorial zonules to pull on the lens capsule, resulting in steepening of the central anterior region and flattening at the equator (Schachar 1992(Schachar , 1999Schachar et al 1993;Schachar & Bax 2001;Chien et al 2003;Schachar & Kamangar 2006). …”

Assessing intraocular lens accommodation

“…Ultrasound biomicroscopy (UBM) was used to measure the radius of curvature of the convexity of the silicone that extended through the central opening of the anterior plate under conditions of cycloplegia and cyclospasm. 6,7 Ben-nun and Alió did not control for spurious eye movements relative to their imaging devices. Because it has been established that the cornea does not change shape or thickness during accommodation, 2-5 the Figure 7 from the paper by Ben-nun and Alió before (A) and after (B) the administration of pilocarpine.…”