Surgery – Instruments – Light application
Reexamination Certificate
1999-12-23
2002-07-16
Gibson, Roy D. (Department: 3737)
Surgery
Instruments
Light application
C606S006000, C606S011000, C606S004000
Reexamination Certificate
active
06419671
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to vision correction systems. In one embodiment, the present invention relates to a simplified optical feedback system which can be integrated into existing laser eye surgery systems to provide feedback regarding the progress of the changes in refractive characteristics of the eye, optionally allowing real-time measurements of the rate of change in quality of the ocular optical system of the eye during vision correction surgery.
Known laser eye procedures generally employ an ultraviolet or infrared laser to remove a microscopic layer of stromal tissue from the cornea of the eye to alter the refractive characteristics of the eye. The laser removes a selected portion of the corneal tissue, often to correct refractive errors of the eye. Ultraviolet laser ablation results in photodecomposition of the corneal tissue, but generally does not cause significant thermal damage to adjacent and underlying tissues of the eye. The irradiated molecules are broken into smaller volatile fragments photochemically, directly breaking the intermolecular bonds.
Laser ablation procedures can remove the targeted stroma of the cornea to change the cornea's contour for varying purposes, such as for correcting myopia, hyperopia, astigmatism, and the like. Control over the distribution of ablation energy across the cornea may be provided by a variety of systems and methods, including the use of ablatable masks, fixed and moveable apertures, controlled scanning systems, eye movement tracking mechanisms, and the like. In known systems, the laser beam often comprises a series of discrete pulses of laser light energy, with the total shape and amount of tissue removed being determined by the shape, size, location, and/or number of a pattern of laser energy pulses impinging on the cornea. A variety of algorithms may be used to calculate the pattern of laser pulses used to reshape the cornea so as to correct a refractive error of the eye.
Although known algorithms have generally been successful in calculating the pattern of laser energy to apply to correct standard vision errors, current vision correction systems would be further improved if they could monitor the changes actually taking place during a photorefractive procedure. Known ablation algorithms often assume a uniform ablation rate, so that each pulse of laser energy is expected to remove a uniform depth of corneal tissue. Although this is often a valid approximation, ablation depths may vary significantly with changes in environmental conditions, such as at different humidities or the like. Ablation depths may also vary locally, such as with the phenomenon called “central islands,” a slightly reduced central ablation depth sometimes experienced within a large area ablation. As a result of ablation depth inconsistencies, touch-up procedures are sometimes performed following laser surgery after the eye has healed in order to further reshape the cornea and provide the desired vision performance. Furthermore, as healing can take several months, these touch-up surgeries can create a substantial inconvenience for a patient. To avoid this delay, laser surgery systems would benefit greatly from having some type of concurrent feedback.
Treatment of still further refractive errors of the eye have also been proposed, including treatment of irregular corneas and the like. Hartmann-Shack wavefront sensor topography devices are now being developed to accurately measure the optical characteristics of the eye. Theoretically, custom ablation patterns derived from such measurement systems may allow correction of small irregular errors with sufficient accuracy to reliably provide visual acuities of better than 20/20. Unfortunately, the wavefront sensors proposed to date have been quite bulky, so that it may be difficult and/or impossible to incorporate these measurement devices into the existing laser surgery systems now in use. While it may be possible to include an alternative off-axis cornea measurement system in known treatment devices, the accuracy of such off-axis systems may not be as good as desired, particularly for treatment of minor irregular errors of the eye so as to maximize visual acuity. Hence, alternative techniques are needed to provide feedback on the actual progress of an ablation. Such feedback techniques might provide substantial benefits over conventional procedures, where a patient generally waits for the epithelium or flap covering the ablated stromal surface to heal before the eye is further evaluated and before “touch up” surgery can be performed to further reshape the cornea.
In light of the above, it would be desirable to provide improved ophthalmological systems, devices, and methods. It would be particularly desirable to provide enhanced techniques for verifying the success of a laser eye surgery procedure. It would further be desirable if these devices could be easily integrated into existing laser eye surgery systems, as well as in newly developed surgery systems. At least some of these objectives will be met by the system and method of the present invention described hereinafter and in the claims.
SUMMARY OF THE INVENTION
The present invention provides improved laser eye surgery devices, systems, and methods. More particularly, the present invention provides devices, systems and methods which can provide measurements of the refractive error in the eye before, during, and/or after vision correction surgery, often while the patient is positioned for laser treatment and aligned with the laser delivery system. The present invention allows adjustments to be made during the vision correction operation, without having to wait for post-surgery analysis regarding the success of the surgery. This is particularly useful when the patient's eye has unusual characteristics which may not have been accounted for and/or if there are unanticipated difficulties in the operation, such as an error in measuring the original patient prescription, human operator error, variations in humidity, or the like. By taking advantage of a relatively simple system for determining the optical properties of a patients eye, with many of the system components already being included on known laser treatment workstations, the present invention may be used to provide vision better than 20/20.
In a first aspect, the invention provides an eye treatment system for performing vision correction on an eye. The eye has retina and ocular optics including a cornea. The system comprises projection optics arranged to project a reference image through the ocular optics and onto the retina when the eye is positioned for treatment. Imaging optics are oriented to acquire an evaluation image from the retina through the ocular optics. The evaluation image is defined by the reference image as projected through the ocular optics and imaged through the ocular optics. An energy transmitting element is positioned relative to the imaging optics to transmit treatment energy toward the cornea for altering the ocular optics.
In many embodiments, at least a portion of the portion of the projection optics and/or the imaging optics will be coaxially aligned with the treatment energy. Typically, the energy transmitting element comprises a laser, with the energy comprising a corneal ablation laser beam directed along a beam path. Beam splitters can be provided to separate the beam path from an imaging path of the imaging optics, a projection path of the projection optics, and the like, with the projection and imaging paths each having at least a portion coaxially aligned with the beam path of the laser beam.
Advantageously, the imaging optics may comprise a microscope such as the microscopes often included in laser eye surgery systems to image the cornea for optically directing a resculpting procedure. Such corneal imaging microscopes may be modified to allow imaging of the evaluation image from the retina by including additional and/or selectable lenses along the imaging path, by providing sufficient travel of movement of the mi
Gibson Roy D.
Townsend and Townsend & Crew LLP
VISX Incorporated
Vrettakos Peter J
LandOfFree
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