Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
2001-06-05
2003-06-03
Lateef, Marvin M. (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
Reexamination Certificate
active
06572230
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ophthalmic instruments that aid in detection and diagnosis of eye disease, pre-surgery preparation and computer-assisted eye surgery (such as laser refractive surgery), including ophthalmic imaging and/or topography instruments (such as fundus cameras, corneal imaging devices, retinal imaging devices, corneal topographers, and retinal topographers) in addition to ophthalmic examination instruments (such as autorefractors, slit lamps and other indirect ophthalmoscopes).
2. Summary of the Related Art
The optical system of the human eye has provided man with the basic design specification for the camera. Light comes in through the cornea, pupil and lens at the front of the eye (as the lens of the camera lets light in). This light is then focused on the inside wall of the eye called the retina (as on the film in a camera). This image is detected by detectors that are distributed over the surface of the retina and sent to the brain by the optic nerve which connects the eye to the brain (as film captures the image focused thereon).
FIG. 1
shows a horizontal cross section of the human eye. The eye is nearly a sphere with an average diameter of approximately 20 mm. Three membranes—the cornea and sclera outer cover, the choroid and the retina—enclose the eye. The cornea
3
is a tough transparent tissue that covers the anterior surface of the eye. Continuous with the cornea
3
, the sclera
5
is an opaque membrane that encloses the remainder of the eye. The choroid
7
lies directly below the sclera
5
and contains a network of blood vessels that serves as the major source of nutrition to the eye. At its anterior extreme, the choroid
7
includes a ciliary body
9
and an iris diaphragm
11
. The pupil of the iris diaphragm
11
contracts and expands to control the amount of light that enters the eye. Crystalline lens
13
is made up of concentric layers of fibrous cells and is suspended by fibers
15
that attach to the ciliary body
9
. The crystalline lens
13
changes shape to allow the eye to focus. More specifically, when the ciliary muscle in the ciliary body
9
relaxes, the ciliary processes pull on the suspensory fibers
15
, which in turn pull on the lens capsule around its equator. This causes the entire lens
13
to flatten or to become less convex, enabling the lens
13
to focus light from objects at a far away distance. Likewise, when the ciliary muscle works or contracts, tension is released on the suspensory fibers
15
, and subsequently on the lens capsule, causing both lens surfaces to become more convex again and the eye to be able to refocus at a near distance. This adjustment in lens shape, to focus at various distances, is referred to as “accommodation” or the “accommodative process” and is associated with a concurrent constriction of the pupil.
The innermost membrane of the eye is the retina
17
, which lies on the inside of the entire posterior portion of the eye. When the eye is properly focused, light from an object outside the eye that is incident on the cornea
3
is imaged onto the retina
17
. Vision is afforded by the distribution of receptors (e.g., rods and cones) over the surface of the retina
17
. The receptors (e.g., cones) located in the central portion of the retina
17
, called the fovea
19
(or macula), are highly sensitive to color and enable the human brain to resolve fine details in this area. Other receptors (e.g., rods) are distributed over a much larger area and provides the human brain with a general, overall picture of the field of view. The optic disc
21
(or the optic nerve head or papilla) is the entrance of blood vessels and optic nerves from the bran to the retina
17
. The inner part of the posterior portion of the eye, including the optic disc
21
, fovea
19
and retina
17
and the distributing blood vessels in called the ocular fundus
23
.
A fundus camera is an optical instrument that enables a practitioner to view (and typically capture) an image of the ocular fundus
23
(or portions thereof) to aid the practitioner in the detection and diagnosis of disease in human eye. The fundus camera typically includes two different illumination sources—an observation source and a photographing source. The observation source, which is typically a halogen lamp or infra-red light source, is used during an observation mode of operation to view (observe) the ocular fundus
23
(or portions thereof) typically through a view finder. The photographing source, which is typically a xenon flash lamp, is used during a photographing mode of operation to photograph on film and/or capture on a CCD camera body an image of the ocular fundus
23
(or portion thereof).
The fundus camera includes an optical subsystem that illuminates the ocular fundus
23
and collects the light reflected therefrom to produce an image of the ocular fundus
23
. In the observation mode of operation, the observation source is activated (and the photographing source is de-activated). The optical subsystem illuminates the ocular fundus
23
with light produced from the observation source and collects the light reflected therefrom to produce an image of the ocular fundus
23
(or portions thereof) for view typically through a view finder. In the photographing mode of operation, the photographing source is activated (and the observation source is de-activated). The optical subsystem illuminates the ocular fundus
23
with light produced from the photographing source and collects the light reflected therefrom to produce an image of the ocular fundus
23
(or portions thereof) for capture on film or on the CCD camera body.
In addition, as is well known in the art, the optical subsystem of the fundus camera may include narrow band spectral filters for use in the photographing mode of operation to enable fluorescein angiography and/or indocyanine green angiography.
Examples of prior art fundus cameras are described in U.S. Pat. Nos. 4,810,084; 5,557,321; 5,557,349; 5,617,156; and 5,742,374; each herein incorporated by reference in its entirety.
Current fundus cameras suffer from the problem that the aberrations of the eye limit the resolution of the camera. More specifically, defocus such as myopia (near-sightedness) or hyperopia (far-sightedness) and astigmatism as well has many other higher order aberrations not only blur images formed on the retina (thus impairing vision), but also blur images taken of the retina of the human eye. A more detailed discussion of such aberrations is described by Williams et al. in “Visual Benefit of Correcting Higher Order Aberrations of the Eye,” Journal of Refractive Surgery, Vol. 16, September/October 2000, pg. S554-S559.
In U.S. Pat. Nos. 5,777,719; 5,949,521; and 6,095,651, Williams and Liang disclose a retinal imaging method and apparatus that produces a point source on a retina by a laser. The laser light reflected from the retina forms a distorted wavefront at the pupil, which is recreated in the plane of a deformable mirror and a Schack-Hartmann wavefront sensor. The Schack-Hartmann wavefront sensor includes an array of lenslets that produce a corresponding spot pattern on a CCD camera body in response to the distorted wavefronts. Phase Aberrations in the distorted wavefront are determined by measuring spot motion on the CCD camera body. A computer, operably coupled to the Schack-Hartmann wavefront sensor, generates a correction signal which is fed to the deformable mirror to compensate for the measured phase aberrations. As discussed in column 7, lines 14-37, after correction has been achieved via the wavefront sensing of the reflected retinal laser-based point source, a high-resolution image of the retina can be acquired by imaging a krypton flash lamp onto the eye's pupil and directing the reflected image of the retina to the deformable mirror, which directs the reflected image onto a second CCD camera body for capture. Examples of prior art Schack-Hartmann wavefront sensors are described in U.S. Pat. Nos. 4,399,356; 4,725,138; 4,737,621,
Lateef Marvin M.
Metrologic Instruments Inc.
Sanders John R.
Thomas J. Perkowski Esq., P.C.
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