Presbyopia: The First Stage of Nuclear Cataract?

McGinty, Susan J.; Truscott, Roger J.W.

doi:10.1159/000090645

Cited by 57 publications

(32 citation statements)

References 209 publications

(133 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This close association and aggregation of crystallins occurs normally and accounts for the hardening of the nucleus in most non-primate animal models that do not rely on accommodation. In humans the hardening of the nucleus is delayed for about four decades, but it should be emphasized that nuclear hardening during the onset of presbyopia usually precedes the formation of age-related nuclear cataracts (McGinty and Truscott, 2006). This raises the question of how a densely packed and dehydrated nuclear cytoplasm can produce excess light scattering.…”

Section: Discussionmentioning

confidence: 99%

Analysis of nuclear fiber cell cytoplasmic texture in advanced cataractous lenses from Indian subjects using Debye–Bueche theory

Metlapally

Costello

Gilliland

et al. 2008

Experimental Eye Research

View full text Add to dashboard Cite

Alterations in ultrastructural features of the lens fiber cells lead to scattering and opacity typical of cataracts. The organelle-free cytoplasm of the lens nuclear fiber cell is one such component that contains vital information about the packing and organization of crystallins critical to lens transparency. The current work has extended analysis of the cytoplasmic texture to transparent and advanced cataractous lenses from India and related the extent of texturing to the nuclear scattering observed using the Debye-Bueche theory for inhomogeneous materials. Advanced age-related nuclear cataracts (age-range 38-75 years) and transparent lenses (age-range 48-78 years) were obtained following extracapsular cataract removal or from the eye bank, at the L. V. Prasad Eye Institute. Lens nuclei were Vibratome-sectioned, fixed and prepared for transmission electron microscopy using established techniques. Electron micrographs of the unstained thin sections of the cytoplasm were acquired at 6500X and percent scattering for wavelengths 400-700 nm was calculated using the Debye-Bueche theory. Electron micrographs from comparable areas in an oxidative-damage sensitive (OXYS) rat model and normal rat lenses preserved from an earlier study were used, as they have extremely textured and smooth cytoplasms, respectively. The Debye-Bueche theoretical approach produces plots that vary smoothly with wavelength and are sensitive to spatial fluctuations in density. The central lens fiber cells from advanced cataractous lenses from India and the OXYS rat, representing opaque lens nuclei, produced the greatest texture and scattering. The transparent human lenses from India had a smoother texture and less predicted scattering, similar to early cataracts from previous studies. The normal rat lens had a homogeneous cytoplasm and little scattering. The data indicate that this method allowed easy comparison of small variations in cytoplasmic texture and robustly detected differences between transparent and advanced cataractous human lenses. This may relate directly to the proportion of opacification contributed by the packing of crystallins. The percent scattering calculated using this method may thus be used to generate a range of curves with which to compare and quantify the relative contribution of the packing of crystallins to the loss of transparency and scattering observed.

show abstract

Section: Discussionmentioning

confidence: 99%

Analysis of nuclear fiber cell cytoplasmic texture in advanced cataractous lenses from Indian subjects using Debye–Bueche theory

Metlapally

Costello

Gilliland

et al. 2008

Experimental Eye Research

View full text Add to dashboard Cite

show abstract

“…If antioxidant compounds in the nucleus become oxidized, they must diffuse to back to the metabolically active cells at the lens surface to be reduced or re-synthesized. With increasing age, the rate of diffusion in the lens cytoplasm is significantly reduced [75,[78][79][80] and oxidized glutathione levels in the lens nucleus increase [75,81,82]. Small increases in oxygen exposure, which might be tolerated by a younger lens, may lead to protein oxidation and nuclear cataract in older individuals.…”

Section: Oxygen Toxicity and The Formation Of Nuclear Cataractsmentioning

confidence: 99%

“…The increasing stiffness of the lens is thought to account for presbyopia, the loss of accommodative amplitude and the resulting loss of near vision that invariably becomes evident in the fifth decade of life [80,86]. Many age-related changes in lens biochemistry have been described that may contribute to lens hardening.…”

Section: Oxygen and Lens Aging: A 'Theory Of Everything'mentioning

confidence: 99%

Maintaining transparency: A review of the developmental physiology and pathophysiology of two avascular tissues

Beebe

2008

Seminars in Cell & Developmental Biology

111

View full text Add to dashboard Cite

The lens and cornea are transparent and usually avascular. Controlling nutrient supply while maintaining transparency is a physiological challenge for both tissues. During sleep and with contact lens wear the endothelial layer of the cornea may become hypoxic, compromising its ability to maintain corneal transparency. The mechanism responsible for establishing the avascular nature of the corneal stroma is unknown. In several pathological conditions, the stroma can be invaded by abnormal, leaky vessels, leading to opacification. Several molecules that are likely to help maintain the avascular nature of the corneal stroma have been identified, although their relative contributions remain to be demonstrated. The mammalian lens is surrounded by capillaries early in life. After the fetal vasculature regresses, the lens resides in a hypoxic environment. Hypoxia is likely to be required to maintain lens transparency. The vitreous body may help to maintain the low oxygen level around the lens. The hypothesis is presented that many aspects of the aging of the lens, including increased hardening, loss of accommodation (presbyopia), and opacification of the lens nucleus, are caused by exposure to oxygen. Testing this hypothesis may lead to prevention for nuclear cataract and insight into the mechanisms of lens aging. Although they are both transparent, corneal pathology is associated with an insufficient supply of oxygen, while lens pathology may involve excessive exposure to oxygen. Keywords hypoxia; neovascularization; cataract; avascular; oxygen Developmental PhysiologyThe lens and cornea have physiological similarities and structural differences. In spite of their different anatomical features, for both tissues to maintain transparency, their cells must obtain needed metabolites and be protected from harmful influences from the environment. The manner in which the lens and cornea manage these physiological challenges and the impact of these solutions on their function and pathology are the topic of this review.A dominant feature of the physiology of the lens and cornea of most mammals is their avascular nature in adult life. The cornea is avascular at all stages of its development. In mammals, the fetal lens is invested with a network of capillaries that regresses late in fetal or early postnatal life.

show abstract

“…Presbyopia results in complete loss of accommodation by around age 50, and age-related increases in lens stiffness are often proposed as the dominant factor (Fisher, 1971(Fisher, , 1973Glasser and Campbell, 1999;Heys et al, 2004;Weeber et al, 2005). A recent article suggested a possible link between presbyopia and subsequent cataract development from increasing nuclear stiffness (McGinty and Truscott, 2006).…”

Section: Introductionmentioning

confidence: 99%

Mapping age-related elasticity changes in porcine lenses using bubble-based acoustic radiation force

Erpelding

Hollman

O’Donnell

2007

Experimental Eye Research

View full text Add to dashboard Cite

Bubble-based acoustic radiation force aims to measure highly localized tissue viscoelastic properties. In the current investigation, acoustic radiation force was applied to laser-induced bubbles to measure age-related changes in the spatial distribution of elastic properties within in vitro porcine lenses. A potential in vivo technique to map lens elasticity is crucial to understanding the onset of presbyopia and develop new treatment options. Bubble-based acoustic radiation force was investigated as a technique to measure the spatial elasticity distribution of the lens in its natural state without disrupting the lens capsule.Laser-induced optical breakdown (LIOB) generated microbubbles in a straight line across the equatorial plane of explanted porcine lenses with 1 mm lateral spacing. Optical breakdown occurs when sufficiently high threshold fluence is attained at the focus of femtosecond pulsed lasers, inducing plasma formation and bubble generation. A two-element confocal ultrasonic transducer applied 6.5 ms acoustic radiation force-chirp bursts with the 1.5 MHz outer element while monitoring bubble position within the lens using pulse-echoes with the 7.44 MHz inner element. A crosscorrelation method was used to measure bubble displacements and determine exponential time constants of the temporal responses. Maximum bubble displacements are inversely proportional to the local Young's modulus, while time constants are indicative of viscoelastic properties.The apparent spatial elasticity distributions in 41 porcine lenses, ranging from 4 months to 5 years in age, were measured using bubble-based acoustic radiation force. Bubble displacements decrease closer to the porcine lens center, suggesting that the nucleus is stiffer than the cortex. Bubble displacements decrease with increasing lens age, suggesting that porcine lenses become stiffer with age. Bubble-based acoustic radiation force may be well-suited as a potential in vivo technique to spatially map elastic properties of the lens and guide therapeutic procedures aimed at restoring accommodation.

show abstract

Presbyopia: The First Stage of Nuclear Cataract?

Cited by 57 publications

References 209 publications

Analysis of nuclear fiber cell cytoplasmic texture in advanced cataractous lenses from Indian subjects using Debye–Bueche theory

Analysis of nuclear fiber cell cytoplasmic texture in advanced cataractous lenses from Indian subjects using Debye–Bueche theory

Maintaining transparency: A review of the developmental physiology and pathophysiology of two avascular tissues

Mapping age-related elasticity changes in porcine lenses using bubble-based acoustic radiation force

Contact Info

Product

Resources

About