Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Eye prosthesis – Intraocular lens
Patent
1997-04-28
2000-01-11
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Eye prosthesis
Intraocular lens
A61F 216
Patent
active
060131012
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an intraocular lens assembly, for implantation into the human eye, which permits accommodation in response to the contraction and relaxation of the ciliary muscles.
BACKGROUND OF THE INVENTION
Normally when a person focuses on an object disposed at a distance from the eye, focusing is achieved by virtue of the contraction of the ciliary muscles which affects the curvature of the lens and thereby its focal length. The process whereby the eye is able to focus on objects over a wide range of distances from the eye is called "accommodation". It is known, during cataract operations, for example, to remove material from the lens capsule and replace it by an intraocular lens implant. The simplest of such implants are fixed lenses having a single focal length. Such lenses do not provide for any accommodation by the eye for the distance of objects and therefore are of relatively limited utility.
An improved type of lens for implantation provides a number of focal lengths. Some of the light impinging the lens is subjected to focusing at each of the different focal lengths of the lens. This type of lens does provide for a broader range of focus for the eye. Only a portion of the light, however, is focused on the retina of the eye for any of the focal lengths. Thus, if an object is focused by one of the focal lengths, only 25-50% of the light will be focused, the remainder will be only partly focused or unfocused. This results in a reduction of contrast of the focused object and a reduction in visual acuity.
A number of proposals have been made for changing the focal length of the lens in response to the natural accommodation mechanism of the eye. While these adaptive lens proposals exist on paper, none of them are commercially available and, as far as is known to the applicant, none have been reported as having been implemented in humans.
One type of adaptive lens comprises an artificial lens whose shape is changed in response to the contraction and expansion of the ciliary muscle. This type of lens is proposed in U.S. Pat. Nos. 4,842,601 to Smith, 4,888,012 to Horn et al. and 4,253,199 to Banko.
Two other types of adaptive lenses are described in U.S. Pat. No. 4,994,082 to Richards et al. Some embodiments described in this patent comprises one or two lenses whose position in the plane perpendicular to optic axis of the eye is adjusted by a mechanical structure effected by the ciliary muscle of the eye. A second type of embodiment utilizes two lenses (comprising a compound lens) whose spacing along the optical axis is adjusted to change the focal power of the compound lens. U.S. Pat. No. 5,275,623 to Sarfarazi show a similar type of compound adaptive lens. U.S. Pat. No. 4,892,543 to Turley describes a compound system comprising a fixed lens having curved posterior and anterior surfaces and a second component which is positioned axially posterior of the lens. During accommodation, the movable component is forced against the posterior surface of the lens. The movement and subsequent distortion of the movable portion results in a change in the focal power of the compound lens.
U.S. Pat. Nos. 4,790,847 to Woods, 5,152,789 to Willis, 4,409,691 to Levy and 4,254,509 to Tennant describe adaptive lens systems utilizing a simple intraocular lens. These systems have focusing capabilities which are achieved by axially shifting the lens in response to normal contraction and expansion of the ciliary muscle resulting from changes in range between the eye and an object under observation. These patents (and the Turley and Richards et al. patents) describe similar systems for providing motion of the lens. In each case the ciliary muscle controls zonules, which in turn provide tension to a lens capsule in which the lens system is mounted. The extremities of the capsule press against a radially compelled, spring-like structure which also forms a relatively large angle of somewhat less than 90.degree. with the optical axis of the eye. The lens is positioned on the optical axis. Relaxa
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International Search Report and Annex.
International Preliminary Examinaton Report.
Acuity (Israel) Limited
Willse David H.
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