Dynamic performance of accommodating intraocular lenses in a negative feedback control system: A simulation-based study

Schor, Clifton M.; Burns, Christopher D.

doi:10.1016/j.compbiomed.2006.03.008

Cited by 10 publications

(4 citation statements)

References 43 publications

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“…Increased neural effort to mold an aging crystalline lens is suggested by an increase in the response AC/A ratio and a decrease in the response CA/C ratio within the linear range of the accommodative stimulus–response function (Fincham, 1951). However, in contradiction to the expected increase in near-pupillary constriction, Kasthurirangan and Glasser (2006) observed no change or even a slight reduction in the magnitude of monocular near-pupillary constriction between 14 and 45-yr-old subjects—an age range over which there is a dramatic reduction in the compliance of the crystalline lens (Schor, Bharadwaj, & Burns, 2007; Weeber et al, 2005). This suggests that differences in neural effort to achieve the accommodative response may contribute only little to the increased Δpd of adults.…”

Section: Discussionmentioning

confidence: 79%

Pupil responses to near visual demand during human visual development

Wang

Candy

2011

Journal of Vision

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Pupil responses of adults to near visual demands are well characterized but those of typically developing infants and children are not. This study determined the following pupil characteristics of infants, children and adults using a PowerRefractor (25 Hz): i) binocular and monocular responses to a cartoon movie that ramped between 80 and 33 cm (20 infants, 20 2–4-yr-olds and 20 adults participated) ii) binocular and monocular response threshold for 0.1 Hz sinusoidal stimuli of 0.25 D, 0.5 D or 0.75 D amplitude (33 infants and 8 adults participated) iii) steady-state stability of pupil responses at 80 cms (8 infants and 8 adults participated). The change in pupil diameter with viewing distance (Δpd) was significantly smaller in infants and 2–4-yr-olds than in adults (p < 0.001) and significantly smaller under monocular than binocular conditions (p < 0.001). The 0.75 D sinusoidal stimulus elicited a significant binocular pupillary response in infants and a significant binocular and monocular pupillary response in adults. Steady-state pupillary fluctuations were similar in infants and adults (p = 0.25). The results suggest that the contribution of pupil size to changes in retinal image quality when tracking slow moving objects may be smaller during development than in adulthood. Smaller monocular Δpd reflects the importance of binocular cues in driving near-pupillary responses.

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Section: Discussionmentioning

confidence: 79%

Pupil responses to near visual demand during human visual development

Wang

Candy

2011

Journal of Vision

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“…Studies relying on static measurements require a separate recording for each individual accommodative demand, which typically limits these studies to measurements at few accommodative states in 1 D or 2 D step increments. Being able to evaluate the dynamics of accommodation can be useful in understanding the closed-loop system that drives ciliary muscle contraction based on retinal image cues [ 43 ]. The system can be programmed to present accommodation stimuli other than ramp and step types, including rectangular or sinusoidal stimuli.…”

Section: Discussionmentioning

confidence: 99%

“…The combined system presented in this manuscript can dynamically measure the refraction and biometry changes that occur in accommodation. An effective accommodation restoration technique will need to be evaluated dynamically in natural accommodation [ 43 ]. For instance, dynamic imaging studies of accommodating IOLs (aIOL) demonstrated the lack of interaction of the ciliary muscle with the aIOL to induce accommodation.…”

Section: Discussionmentioning

confidence: 99%

Dynamic refraction and anterior segment OCT biometry during accommodation

Durkee,

Ruggeri,

Rohman

et al. 2024

Biomed. Opt. Express

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Accommodation is the process by which the eye changes focus. These changes are the result of changes to the shape of the crystalline lens. Few prior studies have quantified the relation between lens shape and ocular accommodation, primarily at discrete static accommodation states. We present an instrument that enables measurements of the relation between changes in lens shape and changes in optical power continuously during accommodation. The system combines an autorefractor to measure ocular power, a visual fixation target to stimulate accommodation, and an optical coherence tomography (OCT) system to image the anterior segment and measure ocular distances. Measurements of ocular dimensions and refraction acquired dynamically on three human subjects are presented. The individual accommodative responses are analyzed to correlate the ocular power changes with changes in ocular dimensions.

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“…20 Although many investigators have observed a contraction and matrix remodeling of the post-surgical capsule that reflects altered mechanics, few computational studies have focused on the effects of cataract surgery on the capsule and all such studies have assumed normal tissue mechanics. 13,22,29 We submit that there is a pressing need to model the evolving geometry, structure, and properties of the lens capsule following cataract surgery, which is a prerequisite for understanding capsule-implant interactions. Such modeling can be initiated by borrowing ideas from other areas of soft tissue growth and remodeling (G&R) mechanics.…”

Section: Introductionmentioning

confidence: 99%

Computational Model of Evolving Lens Capsule Biomechanics Following Cataract-Like Surgery

Pedrigi

Humphrey

2010

Ann Biomed Eng

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Cataract surgery is an invasive procedure whereby lens fibers are removed through a permanent central hole, or capsulorhexis, in the surrounding lens capsule and replaced with an artificial intraocular lens (IOL). Remnant lens epithelial cells subsequently transdifferentiate to a more contractile and synthetic wound-healing phenotype, which causes significant structural and mechanical adaptations of the residual lens capsule. The goal of this study is to present a computational model capable of capturing salient features of the biomechanical evolution of the lens capsule following cataract-like surgery. The model is shown to predict marked long-term increases in thickness and stiffness of the lens capsule nearest the edge of the capsulorhexis comparable to reported measurements. Such models represent a first step toward understanding better the long-term interactions between the residual lens capsule and implanted IOL, thus initiating a new paradigm for the design of improved IOLs, including those having an accommodative feature.

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Dynamic performance of accommodating intraocular lenses in a negative feedback control system: A simulation-based study

Cited by 10 publications

References 43 publications

Pupil responses to near visual demand during human visual development

Pupil responses to near visual demand during human visual development

Dynamic refraction and anterior segment OCT biometry during accommodation

Computational Model of Evolving Lens Capsule Biomechanics Following Cataract-Like Surgery

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