Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Eye prosthesis – Intraocular lens
Patent
1997-09-24
2000-04-04
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Eye prosthesis
Intraocular lens
128898, A61F 216
Patent
active
060455780
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an optical treatment method.
This invention has particular but not exclusive application to the treatment of focusing disorders of the human eye, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications such as to prevent the progression of focusing disorders of the eye such as myopia and hyperopia.
Common conditions which lead to reduced visual acuity are myopia and hyperopia, for which correctional lenses in the form of spectacles, or rigid or soft contact lenses, are prescribed. The conditions are generally described as the imbalance between the length of the eye and the focus of the optical elements of the eye, myopic eyes focusing in front of the retinal plane and hyperopic eyes focusing behind the retinal plane. Myopia typically develops because the axial length of the eye grows to be longer than the focal length of the optical components of the eye, that is, the eye grows too long. Hyperopia typically develops because the axial length of the eye is too short compared with the focal length of the optical components of the eye, that is, the eye does not grow enough.
The corrective lenses are used to alter the gross focus of the eye to render a clearer image at the retinal plane, by shifting the focus from in front of the plane to correct myopia, or from behind the plane to correct hyperopia, respectively. However, the corrective approach to the conditions does not address the cause of the condition but is merely prosthetic.
Most eyes do not have simple myopia or hyperopia, but have myopic astigmatism or hyperopic astigmatism. Astigmatic errors of focus cause the image of a point source of light to form as two mutually perpendicular lines at different focal distances. In the foregoing discussion, the terms myopia and hyperopia are used to include simple myopia or myopic astigmatism and hyperopia and hyperopic astigmatism respectively.
In normal or emmetropic adult eyes, light from both distant and close objects and passing through the central or paraxial region of the aperture or pupil is focused by the crystalline lens inside the eye close to the retinal plane where the inverted image is sensed. It is observed however that most normal eyes exhibit a positive longitudinal spherical aberration, generally in the region of about +0.50 Diopters (D) for a 5 mm aperture, meaning that rays passing through the aperture or pupil at its periphery are focused +0.50 D in front of the retinal plans when the eye is focused to infinity. As used herein the measure D is the dioptric power, defined as the reciprocal of the focal distance of a lens or optical system, in meters.
The spherical aberration of the normal eye is not constant. For example, accommodation, that is, the change in optical power of the eye derived primarily through change to the internal crystalline lens causes the spherical aberration to change from positive to negative.
Emmetropisation is the process whereby eye growth is self-regulated to achieve an optimum match between the optics and axial length of the eye. Emmetropisation is responsible for the leptokurtosis apparent in refractive error distribution in humans and has been demonstrated to act in various animals to compensate for visual deprivation induced refractive errors. Juvenile-onset myopia is a common form of refractive error beginning in childhood and progressing up until the mid to late teens.
Whilst the length of the eye increases throughout life, growth is most pronounced during childhood. It has been observed that spherical aberration of the eye changes with age in children (Stine, 1930; Jenkins, 1963), from negative spherical aberration in children younger than about 6 years of age when focused on distant objects, to positive spherical aberration at about 6-7 years of age. Most adults display positive spherical aberration of the eye focussed at infinity for the remainder of their lives.
It is proposed that the emmetropisation process can be regulated by
REFERENCES:
patent: 4883350 (1989-11-01), Muckenhirn
patent: 4909621 (1990-03-01), Evans
patent: 4957506 (1990-09-01), Mercier
Collins Michael John
Wildsoet Christine Frances
O'Hara Kelly
Queensland University of Technology
Rost Kyle W.
Willse David H.
LandOfFree
Optical treatment method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical treatment method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical treatment method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-360919