Change in shape of the aging human crystalline lens with accommodation (original) (raw)
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Aging of the human crystalline lens and anterior segment
Vision Research, 1994
Changes in the unaccommodated human crystalline lens were characterized as a function of subject age for 100 normal emmetropes over the age range H-70 yr by Scheimpflug slit-lamp photography. With increasing age, the lens becomes thicker sagittally, but since the distance from the cornea to the posterior lens surface remains unchanged, this indicates that the center of lens mass moves anteriorly and the anterior chamber becomes shallower. Sagittal nuclear thickness is independent of age, but both anterior and posterior cortical thicknesses increase with age, shifting the location of the nucleus and the central sulcus in the anterior direction. The amount of light scattered by the lens at high angles, as represented by normalized and integrated lens densities from the digitized images, increases with increasing age in an exponential fashion. Similar relationships to age are observed for the major anterior zone of discontinuity (maximum density) and the central sulcus (minimum density). The relationships of these results to accommodation and presbyopia are discussed. Accommodation Aging Anterior chamber Presbyopia Slit-lamp Scheimpflug photography Image processing
Investigative Ophthalmology & Visual Science, 2008
Magnetic resonance imaging (MRI) was used to map the refractive index distribution in human eye lenses in vivo and to investigate changes with age and accommodation. METHODS. Whole-eye MR images were obtained for sagittal and transverse axial planes in one eye each of 15 young (19 -29 years) and 15 older (60 -70 years) subjects when viewing a far (ϳ6 m) target and at individual near points in the young subjects. Refractive index maps of the crystalline lens were calculated by using a procedure previously validated in vitro.
MRI study of the changes in crystalline lens shape with accommodation and aging in humans
Journal of Vision, 2011
Magnetic Resonance Imaging was used to study changes in the crystalline lens and ciliary body with accommodation and aging. Monocular images were obtained in 15 young (19-29 years) and 15 older (60-70 years) emmetropes when viewing at far (6 m) and at individual near points (14.5 to 20.9 cm) in the younger group. With accommodation, lens thickness increased (mean T 95% CI: 0.33 T 0.06 mm) by a similar magnitude to the decrease in anterior chamber depth (0.31 T 0.07 mm) and equatorial diameter (0.32 T 0.04 mm) with a decrease in the radius of curvature of the posterior lens surface (0.58 T 0.30 mm). Anterior lens surface shape could not be determined due to the overlapping region with the iris. Ciliary ring diameter decreased (0.44 T 0.17 mm) with no decrease in circumlental space or forward ciliary body movement. With aging, lens thickness increased (mean T 95% CI: 0.97 T 0.24 mm) similar in magnitude to the sum of the decrease in anterior chamber depth (0.45 T 0.21 mm) and increase in anterior segment depth (0.52 T 0.23 mm). Equatorial lens diameter increased (0.28 T 0.23 mm) with no change in the posterior lens surface radius of curvature. Ciliary ring diameter decreased (0.57 T 0.41 mm) with reduced circumlental space (0.43 T 0.15 mm) and no forward ciliary body movement. Accommodative changes support the Helmholtz theory of accommodation including an increase in posterior lens surface curvature. Certain aspects of aging changes mimic accommodation.
Biometric changes of the crystalline lens during accommodation
Spektrum der Augenheilkunde, 2020
Background To measure intralenticular biometrical changes during accommodation. Material and methods This prospective study included two different age groups of volunteers (18-25 years and 30-39 years) and in each age group three different groups of ametropia (emmetropic, myopic, and hyperopic volunteers). All volunteers were measured using partial coherence interferometry (ACMaster, Carl Zeiss Meditec, Germany) in an unaccommodated and an accommodated state. Intralenticular biometric changes concerning anterior and posterior cortex and lens nucleus were analysed. Results In total, 104 eyes of 104 volunteers were included in this study. During accommodation in the group of subjects in their 20s, the following changes were observed: In the emmetropic group, the nucleus thickness increased by +0.414 mm, whereas the anterior cortex and posterior cortex thickness remained relatively constant at-0.006 mm (-0.186 mm to 0.046 mm) and +0.008 mm (-0.008 mm to 0.024 mm), respectively. Conclusions The increase of the human crystalline lens with age is characterised by a higher increase in cortex thickness than in nucleus thickness. During accommodation, the thickening of the lens is primarily explained by the thickening of the lens nucleus.
Changes in the internal structure of the human crystalline lens with age and accommodation
Vision Research, 2003
Scheimpflug images were made of the unaccommodated and accommodated right eye of 102 subjects ranging in age between 16 and 65 years. In contrast with earlier Scheimpflug studies, the images were corrected for distortion due to the geometry of the Scheimpflug camera and the refraction of the cornea and the lens itself. The different nuclear and cortical layers of the human crystalline lens were determined using densitometry and it was investigated how the thickness of these layers change with age and accommodation. The results show that, with age, the increase in thickness of the cortex is approximately 7 times greater than that of the nucleus. The increase in thickness of the anterior cortex was found to be 1.5 times greater than that of the posterior cortex. It was also found that specific parts of the cortex, known as C1 and C3, showed no significant change in thickness with age, and that the thickening of the cortex is entirely due to the increase in thickness of the C2 zone. With age, the distance between the sulcus (centre of the nucleus) and the cornea does not change. With accommodation, the nucleus becomes thicker, but the thickness of the cortex remains constant.
Vision Research, 1999
The biometric, optical and physical properties of 19 pairs of isolated human eye-bank lenses ranging in age from 5 to 96 years were compared. Lens focal length and spherical aberration were measured using a scanning laser apparatus, lens thickness and the lens surface curvatures were measured by digitizing the lens profiles and equivalent refractive indices were calculated for each lens using this data. The second lens from each donor was used to measure resistance to physical deformation by providing a compressive force to the lens. The lens capsule was then removed from each lens and each measurement was repeated to ascertain what role the capsule plays in determining these optical and physical characteristics. Age dependent changes in lens focal length, lens surface curvatures and lens resistance to physical deformation are described. Isolated lens focal length was found to be significantly linearly correlated with both the anterior and posterior surface curvatures. No age dependent change in equivalent refractive index of the isolated lens was found. Although decapsulating human lenses causes similar changes in focal length to that which we have shown to occur when human lenses are mechanically stretched into an unaccommodated state, the effects are due to nonsystematic changes in lens curvatures. These studies reinforce the conclusion that lens hardening must be considered as an important factor in the development of presbyopia, that age changes in the human lens are not limited to the loss of accommodation that characterizes presbyopia but that the lens optical and physical properties change substantially with age in a complex manner.
The shape of the aging human lens: curvature, equivalent refractive index and the lens paradox
Vision Research, 2001
Scheimpflug slit images of the crystalline lens are distorted due to the refracting properties of the cornea and because they are obliquely viewed. We measured the aspheric curvature of the lens of 102 subjects ranging in age between 16 and 65 years and applied correction for these distortions. The procedure was validated by measuring an artificial eye and pseudophakic patients with intraocular lenses of known dimensions. Compared to previous studies using Scheimpflug photography, the decrease of the radius of the anterior lens surface with age was smaller, and the absolute value for the radius of the anterior and posterior lens surface was significantly smaller. A slight decrease of the posterior lens radius with age could be demonstrated. Generally, front and back surfaces were hyperbolic. Axial length was measured of 42 subjects enabling calculation of the equivalent refractive index of the lens, which showed a small, but highly significant decrease with age. These new findings explain the lens paradox and may serve as a basis for modelling the refractive properties of the lens.
Presbyopia and the optical changes in the human crystalline lens with age
Vision Research, 1998
Lenses from 27 human eyes ranging in age from 10 to 87 years were used to determine how accommodation and age affect the optical properties of the lens. A scanning laser technique was used to measure focal length and spherical aberration of the lenses, while the lenses were subjected to stretching forces applied through the ciliary body/zonular complex. The focal length of all unstretched lenses increased linearly with increasing age. Younger lenses were able to undergo significant changes in focal length with stretching, whereas lenses older than 60 years of age showed no changes in focal length with stretching. These data provide additional evidence for predominantly lens-based theories of presbyopia. Further, these results show that there are substantial optical changes in the human lens with increasing age and during accommodation, since both the magnitude and the sign of the spherical aberration change with age and stretching. These results show that the optical properties of the older presbyopic lens are quite different from the younger, accommodated lens.
Changes in Lens Thickness and Amplitude of Accommodation with Age
International Journal of Anatomy Radiology and Surgery, 2020
Introduction: The human crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina and, by changing shape, it adjusts focal distance and this function of the lens is called accommodation. Accommodation is the way, the eye increases optical power as it is necessary to produce a clear image of an object when it draws near the eye. Ageing reduces the ability of the lens to change shape, to adjust for close or distance vision. Aim: To study the changes of lens thickness and Amplitude of Accommodation (AA) with age. Materials and Methods: In this cross-sectional study, 40 healthy females were recruited from September to December 2018. The right eyes of 40 healthy participants were divided into two groups, the group 1 of 20 younger subjects (age range 18 to 28 years, mean age 21.9±2.73 years), and group 2 of middleaged 20 subjects (age range 40 to 50 years, mean age 44.6±3.95 years). The lens thickness a...