Abstract
More than a century has passed since Allvar Gullstrand proposed his so called “mechanism of intracapsular accommodation” based on the concept that the change in lens power during accommodation can be larger if the lens is modeled by two different refractive indexes (cortex and nucleus) than if it is homogenous. Intracapsular accommodation of the original eye model proposed by Gullstrand is compared with that of a six-surfaces model eye built based on actual experimental data obtained with precise imaging techniques of the lens change during accommodation. The results show that nearly half (42%) of the accommodation of the Gullstrand model eye is produced by said mechanism, while a model eye based on actual data produces a small intracapsular dis-accommodation. The main reason for the discrepancy is the larger change in the radii of curvature of the lens nucleus during accommodation proposed by Gullstrand, which is necessary because his model likely did not take into account the reduction in the change in lens power produced by depth-of-focus.
Highlights
IntroductionSwedish ophthalmologist Allvar Gullstrand’s innovative development of the slit lamp and his careful development of a detailed optical model of the human eye earned him the Nobel Prize in 1911 for his studies on the optics of the eye
Swedish ophthalmologist Allvar Gullstrand’s innovative development of the slit lamp and his careful development of a detailed optical model of the human eye earned him the Nobel Prize in 1911 for his studies on the optics of the eye. In his acceptance speech, titled “How I found the mechanism of intracapsular accommodation” [1], he describes an innovative model of human eye accommodation, in which increasing optical power is achieved by a combination of curvature changes to the lens surface, already proposed by Young [2] and Helmholtz [3], and an original new change in power originating inside the lens which he named the “intracapsular mechanism of accommodation” (IMA)
The IMA of both eye models can be computed by subtracting the AA of the foursurface model from that of the six-surface model, resulting in 4.6 D and −0.28 D under paraxial approximation for Gullstrand and DB eye models, respectively
Summary
Swedish ophthalmologist Allvar Gullstrand’s innovative development of the slit lamp and his careful development of a detailed optical model of the human eye earned him the Nobel Prize in 1911 for his studies on the optics of the eye In his acceptance speech, titled “How I found the mechanism of intracapsular accommodation” [1], he describes an innovative model of human eye accommodation, in which increasing optical power is achieved by a combination of curvature changes to the lens surface, already proposed by Young [2] and Helmholtz [3], and an original new change in power originating inside the lens which he named the “intracapsular mechanism of accommodation” (IMA). We find that one of the most remarkable changes during accommodation is undergone by the surfaces of the nucleus, whose radii of curvature become much smaller
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