Surgery – Instruments – Light application
Reexamination Certificate
1999-08-10
2001-08-28
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Light application
C606S004000, C606S010000, C606S011000, C606S012000, C606S013000, C607S089000, C128S898000
Reexamination Certificate
active
06280436
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates broadly to eye surgery. More particularly, this invention relates to refractive laser systems for eye surgery.
2. State of the Art
The excimer laser refractive surgery field has exploded over the past few years with many new lasers systems to correct human vision. These systems use an ultraviolet excimer laser to change the shape of the cornea in a calculated pattern which makes it possible for the eye to focus properly. For example, in the treatment of myopia, the laser is used to remove tissue from the cornea in order to flatten its shape. The correction of hyperopia is produced by steepening the cornea. The correction of astigmatism requires the laser to remove tissue in a more complex pattern. All of these procedures require precise shaping of the cornea which depends on accurate placement of the laser beam. Therefore, any eye movement can affect the placement of the laser beam.
Most currently approved broadbeam refractive laser systems and scanning spot systems do not incorporate eye tracking. Therefore, the patient is required to minimize eye movement during surgery by voluntarily fixating their eyes on a small light located just above the patient. When the average person fixates on something, he or she has about five saccadic eye movements per second. Saccadic eye movements are rapid, involuntary movements that are random in amplitude and direction. These movements can cause eccentricity of the laser beam, resulting in degraded laser vision correction predictability and visual quality.
Newer generation refractive laser systems that use small scanning spots, usually less than 1 mm in diameter, have implemented eye-tracking techniques that move the laser beam to adjust for eye movement. Early indications suggest that this approach provides a higher accuracy ablation by virtually eliminating shaping error caused by eye movement.
Nevertheless, there already exists a large number of broadbeam and scanning spot systems which are not provided with eye tracking capability. There is currently no available means by which to provide existing systems with eye tracking capability.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an eye tracking and positioning system for a refractive laser system which compensates for eye movement in a manner different than prior art eye tracking devices.
It is another object of the invention to provide an eye tracking and positioning system which is capable of being retrofit to existing broadband and scanning spot refractive laser systems without modifying any hardware in the laser system.
It is another object of the invention to provide a refractive laser system which is adapted to move the patient, and thus the eye of the patient, relative to the laser beam.
In accord with these objects, which will be discussed in detail below, an eye tracking and positioning system is provided for use with a refractive laser system which produces a laser for surgically reshaping the eye. The eye tracking and positioning system includes a means for capturing images of the eye, a computer, and a means for moving the patient relative to the laser beam. The computer preferably includes a video frame grabber which captures images from a camera of the laser system, and is programmed to perform an eye tracking algorithm with respect to the images. The eye tracking algorithm calculates the exact center of the eye pupil in the image, and compares the center with the desired location of the laser beam, as determined by a surgeon, with an image processing algorithm. If the relative location of the eye center and the laser beam fall outside a predetermined value, the means for moving the patient relative to the laser beam are activated. The means for moving the patient is preferably a surgical bed, surgical chair, or headrest which is motorized to move the patient relative to the laser beam (as opposed to moving the laser beam relative to the patient) to make the necessary adjustment to the current position of the eye and thereby counter the movement of the eye.
The eye tracking and positioning system of the invention may be retrofit to the existing broadbeam and scanning spot systems which do not already include eye tracking capability. Additionally, the eye tracking and positioning system may be provided as an integral part of new refractive laser surgery systems.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.
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Freeman James F.
Freeman Jerre M.
Williams Roy E.
Dvorak Linda C. M.
Farah Ahmed
Gallagher Thomas A
Gordon David P
Jacobson Davis S
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