Optical properties of the lens: An explanation for the zones of discontinuity

Bahrami, Mehdi; Hoshino, Masato; Pierscionek, Barbara K.; Yagi, Naoto; Regini, Justyn Wiktor; Uesugi, Kentaro

doi:10.1016/j.exer.2014.05.009

Cited by 25 publications

(40 citation statements)

References 38 publications

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“…In agreement with our findings, some authors have observed discontinuity zones using a Scheimpflug camera [20]. Castro and associates [21] have recently developed a swept-source optical coherent tomography SS-OCT able to characterize different features in the crystalline lens of older adults with and without a cataract.…”

Section: Discussionsupporting

confidence: 92%

System based on the contrast of Purkinje images to measure corneal and lens scattering

Santos¹,

Martínez-Roda²,

Ondategui³

et al. 2018

Biomed. Opt. Express

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Current methods to measure intraocular scattering provide information on the total scattered light, which consists of the combined contributions originating from different ocular structures. In this work, we propose a technique for the objective and independent assessment of scattering caused by the cornea and the lens based on the analysis of the contrast of the third and fourth Purkinje images. The technique is preliminarily validated first by using artificial eyes with different levels of corneal and lens scattering; second, it is validated in eyes wearing customized contact lenses to simulate corneal scattering and eyes with nuclear cataracts. Finally, it is tested on a larger population of eyes with cataracts and corneal disorders to prove its clinical usefulness.

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Section: Discussionsupporting

confidence: 92%

System based on the contrast of Purkinje images to measure corneal and lens scattering

Santos¹,

Martínez-Roda²,

Ondategui³

et al. 2018

Biomed. Opt. Express

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“…If we look at this behaviour in detail, we find that it corresponds with the so called zones of discontinuity. 44,45 These zones are also clearly seen in the first row of the Lens Opacity Classification System (LOCS) chart reproduced in Figure 6. It was found that the additional backscatter at this angle (in addition to the Rayleigh scatter), is spectrally neutral, and rises sharply for more close backward angles.…”

Section: Zones Of Discontinuity or Wasserspaltenmentioning

confidence: 79%

Intraocular light scatter, reflections, fluorescence and absorption: what we see in the slit lamp

Berg

2017

Ophthalmic Physiologic Optic

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Purpose: Much knowledge has been collected over the past 20 years about light scattering in the eye-in particular in the eye lens-and its visual effect, called straylight. It is the purpose of this review to discuss how these insights can be applied to understanding the slit lamp image. Results: The slit lamp image mainly results from back scattering, whereas the effects on vision result mainly from forward scatter. Forward scatter originates from particles of about wavelength size distributed throughout the lens. Most of the slit lamp image originates from small particle scatter (Rayleigh scatter). For a population of middle aged lenses it will be shown that both these scatter components remove around 10% of the light from the direct beam. For slit lamp observation close to the reflection angles, zones of discontinuity (Wasserspalten) at anterior and posterior parts of the lens show up as rough surface reflections. All these light scatter effects increase with age, but the correlations with age, and also between the different components, are weak. For retro-illumination imaging it will be argued that the density or opacity seen in areas of cortical or posterior subcapsular cataract show up because of light scattering, not because of light loss. Notes: (1) Light scatter must not be confused with aberrations. Light penetrating the eye is divided into two parts: a relatively small part is scattered, and removed from the direct beam. Most of the light is not scattered, but continues as the direct beam. This non-scattered part is the basis for functional imaging, but its quality is under the control of aberrations. Aberrations deflect light mainly over small angles (<1°), whereas light scatter is important because of the straylight effects over large angles (>1°), causing problems like glare and hazy vision. (2) The slit lamp image in older lenses and nuclear cataract is strongly influenced by absorption. However, this effect is greatly exaggerated by the light path lengths concerned. This obviates proper judgement of the functional importance of absorption, and hinders the appreciation of the Rayleigh nature of what is seen in the slit lamp image.

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“…This is a mechanical simulation software that can be controlled by parametric design language and is mainly used for Finite Element Analysis. Geometries of models were based on optical measurements of human lenses using X-ray interferometric analysis at the SPring-8 synchrotron [21]. Similar to previous studies [21,22], detailed geometrical parameters used to construct each model were determined by fitting two splines to optical images [21] in SolidWorks (ver.…”

Section: Methodsmentioning

confidence: 99%

Contributions of shape and stiffness to accommodative loss in the ageing human lens: a finite element model assessment

et al. 2019

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Ageing changes to the various components of the accommodative system of the eye lens contribute to the loss of focusing power. The relative contributions of each ageing component, however, are not well defined. This study investigates the contribution of geometric parameters and material properties on accommodation simulated using models based on human lenses aged 16, 35 and 48 years. Each model was tested using two different sets of material properties and a range of zonular fibre angles and compared to results from in vivo measurements. The geometries and material parameters of older and younger lens models were interchanged to investigate the role of shape and material on accommodative capacity. Results indicate that geometry has the greater role in accommodation.

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Optical properties of the lens: An explanation for the zones of discontinuity

Cited by 25 publications

References 38 publications

System based on the contrast of Purkinje images to measure corneal and lens scattering

System based on the contrast of Purkinje images to measure corneal and lens scattering

Intraocular light scatter, reflections, fluorescence and absorption: what we see in the slit lamp

Contributions of shape and stiffness to accommodative loss in the ageing human lens: a finite element model assessment

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