Refractive index of decapsulated bovine lens surfaces measured with a reflectometric sensor

Pierscionek, Barbara K.

doi:10.1016/0042-6989(94)90023-x

Cited by 8 publications

(4 citation statements)

References 15 publications

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“…6 (22,28), and r ¼ 1.18g/cm 3 and n ¼ 1.43 for bovine lenses used in Figs. 5 and 6 (29,30). We estimate that the conversion error due to sample-to-sample variations in r/n 2 is relatively small and does not affect the correlation between the Brillouin modulus and Young's modulus (see Supporting Material).…”

Section: Data Acquisition and Analysismentioning

confidence: 95%

In Vivo Measurement of Age-Related Stiffening in the Crystalline Lens by Brillouin Optical Microscopy

Scarcelli

Kim

Yun

2011

Biophysical Journal

187

155

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The biophysical and biomechanical properties of the crystalline lens (e.g., viscoelasticity) have long been implicated in accommodation and vision problems, such as presbyopia and cataracts. However, it has been difficult to measure such parameters noninvasively. Here, we used in vivo Brillouin optical microscopy to characterize material acoustic properties at GHz frequency and measure the longitudinal elastic moduli of lenses. We obtained three-dimensional elasticity maps of the lenses in live mice, which showed biomechanical heterogeneity in the cortex and nucleus of the lens with high spatial resolution. An in vivo longitudinal study of mice over a period of 2 months revealed a marked age-related stiffening of the lens nucleus. We found remarkably good correlation (log-log linear) between the Brillouin elastic modulus and the Young's modulus measured by conventional mechanical techniques at low frequencies (~1 Hz). Our results suggest that Brillouin microscopy is potentially useful for basic and animal research and clinical ophthalmology.

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Section: Data Acquisition and Analysismentioning

confidence: 95%

In Vivo Measurement of Age-Related Stiffening in the Crystalline Lens by Brillouin Optical Microscopy

Scarcelli

Kim

Yun

2011

Biophysical Journal

187

155

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“…To approximate the modification in dioptric power that the changes in volume in our experiments represent, the bovine lens photographs were further analyzed. The radii of curvatures at the two accommodative states were measured, and together with the A-P thickness (previously measured) plus the refrac- tive indexes for the lens, aqueous, and vitreous humor (21,22), the equivalent dioptric power of the bovine lens was computed using the Gullstrand's equation for thick lenses. From 11 bovine lenses, a mean value of 14.8 Ϯ 0.25 D was calculated for the unaccommodated (stretched) lens, whereas the value for the accommodated (relaxed) lens was 16.3 Ϯ 0.23 D. These values probably represent only a fraction of the total equivalent power for the whole simplified eye.…”

Section: Discussionmentioning

confidence: 99%

Volume change of the ocular lens during accommodation

Gerometta¹,

Zamudio²,

Escobar³

et al. 2007

American Journal of Physiology-Cell Physiology

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tion, mammalian lenses change shape from a rounder configuration (near focusing) to a flatter one (distance focusing). Thus the lens must have the capacity to change its volume, capsular surface area, or both. Because lens topology is similar to a torus, we developed an approach that allows volume determination from the lens cross-sectional area (CSA). The CSA was obtained from photographs taken perpendicularly to the lenticular anterior-posterior (A-P) axis and computed with software. We calculated the volume of isolated bovine lenses in conditions simulating accommodation by forcing shape changes with a custom-built stretching device in which the ciliary body-zonulae-lens complex (CB-Z-L) was placed. Two measurements were taken (CSA and center of mass) to calculate volume. Mechanically stretching the CB-Z-L increased the equatorial length and decreased the A-P length, CSA, and lens volume. The control parameters were restored when the lenses were stretched and relaxed in an aqueous physiological solution, but not when submerged in oil, a condition with which fluid leaves the lens and does not reenter. This suggests that changes in lens CSA previously observed in humans could have resulted from fluid movement out of the lens. Thus accommodation may involve changes not only in capsular surface but also in volume. Furthermore, we calculated theoretical volume changes during accommodation in models of human lenses using published structural parameters. In conclusion, we suggest that impediments to fluid flow between the aquaporin-rich lens fibers and the lens surface could contribute to the aging-related loss of accommodative power.lens volume calculation; intralenticular fluid movement; presbyopia; mammalian lens THE EYE IS ABLE TO FORM a clear image on the retina from objects situated within a wide range of distances due to a process called accommodation. In higher vertebrates, including humans, accommodation results from changes in crystalline lens shape and surface radii of curvature (13).When the ciliary muscle is relaxed and flattened against the sclera, the zonulae adjoining the ciliary body and the lens capsule are under tension and thus pulling eccentrically on the lens equator. This action causes the lens to adopt a relatively flattened shape with a larger equatorial diameter and a shorter A-P length, which allows focusing on virtual infinity (zero accommodation). When an individual focuses on a near object, the ciliary muscle contracts (shortening its distance to the lens equator), the zonulae relax, and the lens as a whole adopts a relatively rounded shape, which is its normal tendency. Physically, these changes in lens shape inevitably must involve changes in either capsular surface area or lens volume, or both.Classic theories of lenticular accommodation suggest that the volume of the intraocular crystalline lens remains constant during the accommodation process (16,17,30). No empirical studies have demonstrated that the volume actually stays constant. Because of the physical principle mentioned abov...

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“…For present purposes, a large number of shells may not be necessary, provided the accuracy is not significantly impaired by the use of a reduced number of iso‐indicial shells. The gradient index requirement may not be as critically important for extremely oblique rays, as suggested by the refractive index measurements in the equatorial plane by Pierscionek (1994). However, this would need to be experimentally confirmed.…”

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confidence: 94%

Peripheral light focusing as a potential mechanism for phakic dysphotopsia and lens phototoxicity

Kwok¹,

Daszynski²,

Кузнецов³

et al. 2004

Ophthalmic Physiologic Optic

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Our aim was to examine secondary image formation in the anterior segment caused by peripheral light focusing (PLF) in the human cornea, and in particular the crystalline lens. Non-sequential ray-tracing (OptiCAD) was applied to an anatomically based human eye model, which incorporates a gradient index crystalline lens. For analysis of the limbal effect, we varied the incident angle from 100 to 122 degrees, while for the crystalline lens effect, the incident angle was varied from 60 to 90 degrees. The corneal shapes studied included central radii from 7.4 to 8.2 mm with a range of shape factors. In each case, we computed the peak and average intensities, and the area of exposure at the limbus or lens periphery. The computation was repeated with a previous model eye for comparison. For the limbal effect, a peak intensity gain of x22.5 was found at an incident angle of 104 degrees which compares well with previous results. The average intensity gain at this angle was x7.5 over an area of 0.23 mm2. Steeper corneal curvature produced a greater PLF effect. For the crystalline lens effect, maximum UVA (365 nm) intensity gain peaked at x8.6 at 84 degrees with average intensity gain of x2.3. The area of UVA exposure peaked at 4.7 mm2 at 70 degrees. A relatively wide range (30 degrees ) of incident angles produced peak PLF gains of x3 or more in the lens. Significant focusing of light is directed to the nasal limbus, and to a lesser extent to the crystalline lens over a broad range of incident angles. PLF in the nasal cornea is reduced by an order of magnitude when a UV-blocking soft contact lens is used. The concentration levels and intraocular sites of PLF action on UV and visible light suggest a new mechanism of phakic dysphotopsia and lens phototoxicity.

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Refractive index of decapsulated bovine lens surfaces measured with a reflectometric sensor

Cited by 8 publications

References 15 publications

In Vivo Measurement of Age-Related Stiffening in the Crystalline Lens by Brillouin Optical Microscopy

In Vivo Measurement of Age-Related Stiffening in the Crystalline Lens by Brillouin Optical Microscopy

Volume change of the ocular lens during accommodation

Peripheral light focusing as a potential mechanism for phakic dysphotopsia and lens phototoxicity

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