Distribution of the Crystalline Lens Power In Vivo as a Function of Age (original) (raw)
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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.
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
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.
Optical power of isolated human crystalline lens
To characterize the age dependence of isolated human crystalline lens power and quantify the contributions of the lens surfaces and refractive index gradient. METHODS. Experiments were performed on 100 eyes of 73 donors (average 2.8 Ϯ 1.6 days postmortem) with an age range of 6 to 94 years. Lens power was measured with a modified commercial lensmeter or with an optical system based on the Scheiner principle. The radius of curvature and asphericity of the isolated lens surfaces were measured by shadow photography. For each lens, the contributions of the surfaces and the refractive index gradient to the measured lens power were calculated by using optical ray-tracing software. The age dependency of these refractive powers was assessed. RESULTS. The total refractive power and surface refractive power both showed a biphasic age dependency. The total power decreased at a rate of Ϫ0.41 D/y between ages 6 and 58.1, and increased at a rate of 0.33D/y between ages 58.1 and 82. The surface contribution decreased at a rate of Ϫ0.13 D/y between ages 6 and 55.2 and increased at a rate of 0.04 D/y between ages 55.2 and 94. The relative contribution of the surfaces increased by 0.17% per year. The equivalent refractive index also showed a biphasic age dependency with a decrease at a rate of Ϫ3.9 ϫ 10 Ϫ4 per year from ages 6 to 60.4 followed by a plateau.
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.
Change in shape of the aging human crystalline lens with accommodation
Vision Research, 2005
The objective was to measure the change in shape of the aging human crystalline eye lens in vivo during accommodation. Scheimpflug images were made of 65 subjects between 16 and 51 years of age, who were able to accommodate at least 1 D. The Scheimpflug images were corrected for distortion due to the geometry of the camera and the refraction of the cornea and anterior lens surface, which is necessary to determine the real shape of the lens. To ensure accurate correction for the refraction of the anterior lens surface, the refractive index of the crystalline lens must be determined. Therefore, axial length was also measured, which made it possible to calculate the equivalent refractive index of the lens and possible changes in this index during accommodation.
Optical Power of the Isolated Human Crystalline Lens
Investigative Ophthalmology & Visual Science, 2008
PURPOSE. To characterize the age dependence of isolated human crystalline lens power and quantify the contributions of the lens surfaces and refractive index gradient. METHODS. Experiments were performed on 100 eyes of 73 donors (average 2.8 Ϯ 1.6 days postmortem) with an age range of 6 to 94 years. Lens power was measured with a modified commercial lensmeter or with an optical system based on the Scheiner principle. The radius of curvature and asphericity of the isolated lens surfaces were measured by shadow photography. For each lens, the contributions of the surfaces and the refractive index gradient to the measured lens power were calculated by using optical ray-tracing software. The age dependency of these refractive powers was assessed. RESULTS. The total refractive power and surface refractive power both showed a biphasic age dependency. The total power decreased at a rate of Ϫ0.41 D/y between ages 6 and 58.1, and increased at a rate of 0.33D/y between ages 58.1 and 82. The surface contribution decreased at a rate of Ϫ0.13 D/y between ages 6 and 55.2 and increased at a rate of 0.04 D/y between ages 55.2 and 94. The relative contribution of the surfaces increased by 0.17% per year. The equivalent refractive index also showed a biphasic age dependency with a decrease at a rate of Ϫ3.9 ϫ 10 Ϫ4 per year from ages 6 to 60.4 followed by a plateau. CONCLUSIONS. The lens power decreases with age, due mainly to a decrease in the contribution of the gradient. The use of a constant equivalent refractive index value to calculate lens power with the lens maker formula will underestimate the power of young lenses and overestimate the power of older lenses.
Hyperopia and Lens Power in an Adult Population: The Shahroud Eye Study
Journal of Ophthalmic and Vision Research, 2015
Purpose: To explore the relationship between lens power and refractive error in older adults following age-related hyperopic shifts. Methods: From the Shahroud Eye Cohort Study, subjects aged 55-64 years without clinically significant cataracts (with nuclear opacity of grade 0 to 1) were included to maximize the proportion of subjects with age-related hyperopic shifts that normally occur between 40 to 60 years of age, before interference from the myopic shift due to nuclear cataracts. Mean axial length (AL) values, corneal power, anterior chamber depth, lens thickness, and lens power were analyzed and compared among three refractive groups (myopes, emmetropes, and hyperopes). Results: A total of 1,006 subjects including 496 (49.63%) male subjects were studied. Corneal power was similar in all refractive groups. Hyperopes had + 1.69 diopters higher mean spherical equivalent refractive error and − 0.50 mm shorter AL than emmetropes. Myopes had 0.67 mm longer AL than emmetropes. Hyperopes had significantly increased lens thickness as compared to emmetropes (4.42 vs. 4.39 mm respectively). In this adult sample, the hyperopic group had lower lens power (+22.29 diopters vs. +22.54 diopters in emmetropes, P = 0.132). Myopes had similar lens power as emmetropes. Conclusion: Axial length is the principal determinant of refractive errors. Lens power may have importance in determining hyperopia in adults free of cataract.
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.
On the ocular refractive components: the Reykjavik Eye Study
Acta Ophthalmologica Scandinavica, 2007
Purpose: To study the correlation between ocular refraction and the refractive components (corneal power, lens power and axial length) in a population-based sample of normal subjects. Methods: We analysed the refractive and biometric findings for 723 right eyes (325 males and 398 females) comprising a population-based random sample of citizens 55 years and older participating in the Reykjavik Eye Study. Measurements of refraction, corneal curvature (by keratometry), anterior chamber depth, lens thickness and axial length (all by ultrasound biometry) were used to calculate crystalline lens power. The correlation and regression between refraction and ocular refractive components (corneal power, anterior chamber depth, lens power and axial length) were studied by distributional statistical methods. Results: Refraction (spherical equivalent) showed a significant negative correlation with axial length (r ¼ -0.59, P < 0.0001), lens power (r ¼ -0.26, P < 0.0001) and corneal power (r ¼ -0.16, P < 0.0001). There were significant negative correlations between axial length and corneal power (r ¼ -0.44, P < 0.0001) and between axial length and lens power (r ¼ -0.44, P < 0.0001). Based on multiple linear regression analysis, refraction could be correlated with corneal power, lens power and axial length in combination with a correlation coefficient of 0.98 (P < 0.0001). Conclusion: This study confirms that ocular refraction is statistically significantly correlated with not only axial length but also lens power and (to a lesser extent) corneal power. The variation and correlations of crystalline lens power were considerablepossibly indicating this component's modulatory effect on ocular refraction during growth. We conclude the refractive error of the eye to be a multifactorial condition involving a complex interplay between the cornea, the lens and the length of the eye.