MXPA00012408A - Patient fixation system and method for laser eye surgery - Google Patents

Abstract

The invention enhances the alignment between the eye (E), and a laser beam (14) of a laser eye surgery system (10) using a visual fixation system (38), the fixation system (38) often having an adjustable optical train (58). The optical train (58) of the fixation system (38) allows an eye (E) having a significant refractive error to be accurately focused at a fixation target (60). To accommodate the refractive error, the adjustable optical train (58) will often project an image of the target (60) so that the projected image is in focus in front of or behind the plane of the patient's eye (E). The present invention also encompasses the calculation of the proper projection distance to accommodate the refractive error of the eye (E), the calculation preferably based at least in part on the eye glass prescription for that eye (E).

Description

•. PATIENT FIXATION SYSTEM AND METHOD FOR EYE SURGERY WITH LASER BACKGROUND OF THE INVENTION 5 1. Field of research In general terms, this invention relates to systems, devices and methods of laser eye surgery and, in particular, offers a fixation system that adjusts to the focus of the patient. It can adjust the refractive errors of the patient's eye, presenting an objective before the eye to focus, and thus increase the patient's ability to stabilize the eye when seeing the objective. In some embodiments, this invention allows patients to maintain the fixed approach and have a better stabilization of the target during changes of the refractive characteristics of the eye, coordinating the focus settings of the target system with a photorefractive therapy. Therefore, this invention is especially useful to increase the accuracy and efficacy of laser eye surgical procedures such as keratectomy. photorefractive (PRK), phototherapeutic keratectomy (PTK), laser keratomileusis in situ (LASIK), among others. Selective photoablation of corneal tissues takes advantage of the exact alignment between the eye and a beam of therapeutic laser. Usually, eye procedures The laser with known uses an ultraviolet or infrared laser to remove a microscopic layer of stromal tissue from the ocular cornea to alter its refractive power. The laser removes the selected portion of the corneal tissue usually to correct ocular refractive error. Ultraviolet laser ablation results from the photodecomposition of the corneal tissue, which usually does not cause significant thermal damage to the adjacent and underlying tissues of the eye. The irradiated molecules are fragmented into tiny volatile pieces, breaking photochemically and directly intermolecular bonds. The laser ablation procedures can eliminate the determined stroma of the cornea for different purposes such as correcting myopia, hyperopia, astigmatism and the like. Control over the distribution of ablation energy in the cornea can be provided by a variety of systems and methods, including the use of ablatable masks, fixed and movable openings, controlled scanning systems, eye movement tracking mechanisms and Similar. These laser eye surgery systems are adapted to be used while the patient is awake. The position of the patient's head will often be stabilized using a headrest pillow, a chin support, a teether or the like. The patient can further increase the alignment between the eye and the therapeutic laser beam by focusing on a target during the procedure. Among the known objectives of visual fixation is the light-emitting diode (LED), which is optically placed at approximately 25 cm. front of the patient. Unfortunately, patients do not wear corrective lenses during photorefractive surgery. As a result, for many patients the goal may be blurry or out of focus. A more serious consequence is that the optical characteristics of the patient's eye can change significantly during laser eye surgery. Then, you can risk the patient's ability to keep his eye steady by seeing the target. In fact, the patients expressed that during the surgery they lost the location of the blurred targets. This can cause the patient to move away from the objective, degrading the alignment between the eye laser system and the eye, and thereby reducing the accuracy and efficacy of the refractive therapy. Considering the above, it is desirable to offer better ophthalmological systems, devices and methods. It is especially desirable to provide better techniques to stabilize the eye with a significant refractive error during the laser eye surgery procedure. It is even more desirable to have better methods and devices so that from the beginning an alignment with a patient fixation system is established and maintained in order to have a greater stabilization of the eye before and during laser surgery and other therapeutic and diagnostic procedures for the patient. eye. 2. Description of the background technique. U.S. Patent No. 4478449 describes a microscopic operation incorporating an eye fixation device. U.S. Patent No. 5549597 describes an in situ axis alignment module for determining the astigmatic axis of a patient and aligning the cylindrical axis of a laser ablation system for ophthalmic surgery. U.S. Patent No. 5258787 describes an ophthalmological device having an optical illumination system for directing light to a particular point of the eye and an optical observation system for observing an image of said point. U.S. Patent No. 5557352 discloses a method and device for measuring visual acuity and refraction of the human eye during and immediately after eye surgery.

COMPENDIUM OF THE INVENTION This invention generally provides better devices, systems and methods of laser eye surgery. In general, the invention improves the alignment between the eye and the laser beam of the laser eye surgery system using a visual fixation system with an optical train. The optical train of the fixation system allows an eye with a significant refractive error to accurately focus on the fixation objective.

To adjust the refractive error, the optical train will often project an image of the objective so that the image is focused at an option opposite the flat surface of the patient's eye or behind it. This invention also comprises calculating the projection distance itself to adjust the refractive error of the eye, preferably the calculation is based at least in part on the graduation of the telescope for that eye. A particular advantage of this invention is that it allows the patient to focus on the target system (and minimize misalignment with it) while the eye has significant refractive changes. For example, a patient undergoing photorefractive therapy for a 4.0 diopter hyperopia will have a significant change in the refractive configuration of the eye during therapy. In order to maintain the alignment between the changing eye and the laser beam, this invention dynamically varies the flat image of the projected image of the objective. At first, the image of the objective will be projected posterior to the plane of the hyperopic eye. While the refractive configuration of the eye is gradually corrected, the projected image of the objective can be moved away from the flat surface of the patient's eye. Ideally, a computer controller dynamically varies the position of the projected image of the objective in coordination with photorefractive therapy. When the photorefractive therapy develops progressively, the adjustable optical train of the fixation system can also be adjusted in the same way, for example by turning a tower to select an alternative lens of the optical train. While the adjustable optical train helps the patient focus on the fixation target, the invention greatly improves the patient's ability to stabilize the eye while undergoing these changes. As a result, the accuracy and effectiveness of the laser reconstruction process is increased. In a first aspect, this invention offers a method of laser eye surgery. The method comprises the projection of a target at a first eye distance. This projection allows the objective to be located in the focus of the eye. The eye is stabilized by seeing the objective through the cornea. The refraction of the stabilized eye is altered by selectively moving a portion of the cornea. The objective is projected towards the altered eye at a second distance from the eye so the objective is located in the focus of the altered eye. In many embodiments, an optical train of the lens will be adjusted to move a projected image of the lens from the first to the second distance. For example, when refractive therapy comprises a treatment for hyperopia, the image at the beginning can be placed posterior to the cornea. Conversely, when refraction is altered in order to decrease myopia, the image will first be placed anterior to the cornea. The image will usually move further away from the eye when the refractive error is corrected. For example, during laser keratomileusis in situ the distance between the projected image and the plane of the eye increases during therapy. In other embodiments, particularly where the refraction that alters the rhythm develops as a series of progressive improvements to a refractive error of the eye, the image of the objective will be adjusted in a series of corresponding progressive changes. Alternatively, a well-designed Fresnel zone plate can simultaneously produce multiple images of the target at the focus of the patient's eye and / or behind it. Another proposal would be to use a holographic optical element as if it were a well-designed diffractive optical hologram or a plate of the Fresnel zone in order to project a previously selected image of the target in the different directions desired, before and after the eye. Projected lens images may have different colors (or similar) in different positions. Alternatively, it is possible to project a continuum of images of the objective in order to define a line along the optical axis. Thus, the patient will see the image of the objective in the part of the line that corresponds to the distance between the eye and the location of the objective image. Preferably the first distance will be calculated taking into account at least partially the prescribed graduation of the glasses. Also, at least one intermediate distance can be calculated based on an intermediate refractive configuration of the eye. For example, this intermediate configuration can be measured or calculated by taking into account the known photoablative effects of the laser beam during photorefractive therapy. A processor can simultaneously adjust the optical train and control the photoablative reconstruction of the cornea so that the objective remains essentially in the focus of the eye throughout the procedure. In another aspect, this invention provides a method comprising projecting an objective toward the eye with a refractive error. The objective is projected so that a focused image of the objective is at a previously calculated distance from the eye, so the objective appears as if it were in the focus of the eye. The eye is stabilized by seeing the target projected through the cornea. In another aspect, this invention provides a system of laser eye surgery that reconstructs the cornea of the patient's eye. This system comprises a laser that produces a beam to photoablat a part of the cornea. The emission optics are optically coupled to the laser in order to effect a predetermined change in the refraction of the cornea with the laser beam. An optical train of the lens is coupled with the emission optics to help the patient stabilize the eye. The optical train is able to project the objective towards the eye in a wide range of separation distances in relation to the eye. This allows the system to adjust many refractive configurations of the cornea of an eye.

Preferably, a computerized controller couples the emitting optics of the laser system to the optical train of the lens so that it moves an image of the objective in coordination with changes in the cornea. This allows the image to be located in the focus of the eye despite the changes in refraction that occur. The movement of the image can be smooth and gradual, or perhaps progressive. Preferably, at least a portion of the emission optics and the lens attachment system are aligned coaxially. In some embodiments, the optical stream can simultaneously project a wide range of distances, typically using an optical holographic element, a plate in the Fresnel zone or the like. In general, it is preferred to project the objective towards the eye so that it appears within an angular sub-tension of less than 80 arc minutes of the pupil of the eye. In yet another aspect, this invention provides a system of laser eye surgery to correct refractive errors of an eye. This system consists of a laser that produces a beam to selectively remove a part of the eye cornea. The optics of emission in an optical path of the beam transmit it towards the cornea in order to alter the eye from a first to a second refractive configuration. The lens fixation system includes a lens and an objective lens. The optics of the lens are aligned with the optical path for the purpose of maintaining alignment between the eye and the laser beam. The optics of the objective project it to a first and second distance. The objective is located in the focus of the eye when the cornea is in the first configuration and the objective is projected in the first distance. The objective is also located at the focus of the eye when the cornea presents the second configuration and the objective is projected at the second distance.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a perspective of the laser surgery system according to the principles of this invention. Figure 2 shows a perspective view of some of the optical components of an eye surgery system similar to that of Figure 1, including an adjustable lens fixation system. Figure 3 is a schematic of the laser eye surgery system of Figure 1 and illustrates a method for its use. Figures 4A-4E illustrate by means of a scheme the adjustable optical trains for varying the projection distance of the objective image in order to adjust the refractive defects of an eye before and / or during the optical measurement or the therapeutic procedure. FIGS. 5A-5C illustrate, by means of a diagram, the optical trains that project a target at different distances from a plane of an eye at the same time. Figure 6 shows by means of a scheme a method for progressively altering the refractive configuration of the eye.

Figures 7A and 7B are schematics of the method for determining lens distances and lens positions based on the graduation of the patient's lenses. Figure 8 is a schematic of the control method and fits a lens image for fixation during a refraction procedure.

DESCRIPTION OF SPECIFIC MODALITIES This invention generally focuses on structures, systems and methods for measuring and / or treating a human eye. The techniques of this invention generally increase the alignment between the eye and the treatment or measurement device. The known ophthalmological apparatuses often have structures to support the patient's head, such as a pillow, a chin rest, a mordedera, among others. The invention presents a visualization objective to the eye that is located in the focus of the patient despite the fact that his eye presents a frequent and significant refractive error, improving in an important degree the ability of the patient to stabilize the vision with the focused objective. Therefore, the systems, devices and methods of this invention will be used in conjunction with devices such as corneal topographic machines, autorefractors and, in particular, laser eye surgery systems. The techniques of this invention are specifically adapted for use during procedures that significantly alter the refractive configuration of the eye. Maintaining proper alignment between the eye and such intervention devices can greatly improve the effectiveness of a therapeutic procedure. For example, the photoablable reconstruction of the cornea to correct a refractive error takes advantage of the exact alignment between the reconstructing laser beam and the eye. By increasing the patient's ability to focus on the objective of the visual fixation system, the accuracy and efficiency of the reconstruction process is improved. Therefore, while the visual fixation system of this invention can be applied in a wide range of eye measures and therapies, the most immediate application will be in the field of laser eye surgery, in order to improve the benefits of keratectomy. photorefractive (PRK), phototherapeutic keratectomy (PTK), laser keratomileusis in situ (LASIK), etc. Referring to Figure 1, a laser eye surgery system 10 includes one 12 that produces a laser beam 14. The laser 12 is optically coupled to the laser emission optics 16, which directs the laser beam 14 to the eye of the patient P. A support structure of the emission optics (not shown here for clarity) extends from the frame 18 holding the laser 12. A microscope 20 is installed in the support structure of the emission optics.

The laser 12 usually consists of excimer laser, and ideally of a fluorinated argon laser that produces pulses of laser light with a wavelength of about 193 nm. The laser will be primarily designed to facilitate a stabilized feedback fluence in the patient's eye, through emission optics 16. It is also possible to use this invention with alternative sources of ultraviolet or infrared radiation, in particular with those that are adapted to bring down the corneal tissue in a controlled manner without causing significant damage to adjacent tissues and / or underlying eye. In general, the laser 12 and the emitting optics 16 will direct the laser beam 14 to the eye of the patient P by monitoring a computer 22. Typically, the computer 22 will selectively adjust the laser beam 14 to expose portions of the cornea to the pulsations of the laser energy in order to carry out a predetermined reconstruction of the cornea and modify the refractive characteristics of the eye. The laser beam 14 can be adjusted to generate the desired reconstruction using different optional mechanisms. The laser beam 14 can be selectively limited by using one or more variable apertures. In the North American patent No 5713892 an exemplary system of variable aperture with a variable iris and a slit of variable width is described.; the full description is incorporated herein by reference. The laser beam can also be adapted by varying the size and deflection of the laser spot from an eye axis, as described in US Pat. No. 5683379 and in the co-pending US Patent Application No. 08/968380, filed on 12 November 1997, which are incorporated in their entirety to the present invention by reference. However, other alternatives are possible, such as scanning the laser beam on the surface of the eye and controlling the number of beats or the time at each location, as described, for example, in US Pat. No. 4665913 (is incorporated in its entirety to the present invention by reference); the use of masks in the optical path of the laser beam 14 which performs the ablation to vary the profile of the incident beam in the cornea, as described in US Patent Application No. 08/468898, filed on June 6, 1995 (is incorporated in its entirety to the present invention by reference); or similar. There is an extensive patent literature on computer programs and control methodology for this type of laser-made techniques. Generally the laser system 10 will have components and subsystems, as should be understood by experts in the field. For example, spatial and / or temporal integrators may be included to control the distribution of energy in a laser beam, as described in U.S. Patent No. 5646791, which is incorporated in its entirety by reference to the present invention. In order to understand this invention it is necessary to describe in detail a filter / evacuator of ablation residues and other auxiliary components of the laser eye surgery system that are not necessary for the interpretation of the invention. The patient's head P will be firmly supported, especially fixed, in a special chair 24. The position of the eye with respect to the laser emission optics is regularly affected by the movement of the chair 24. Therefore, the chair 24 it is adjusted by a drive mechanism 26 that can move the patient in three dimensions to laterally and axially place the cornea of the eye at a predetermined target treatment site. Alternately, at least a portion of the laser emission optics can be moved to align the laser beam 14 with the cornea. The laser system 10 will generally comprise a programmable controller 27. The controller 27 may have a conventional PC system that includes standard user interface devices such as keyboard, monitor, among others. The controller 27 will generally include an input device such as a magnetic or optical disk drive, an Internet connection or the like. These input devices will often be used to download an executable code from a tangible storage medium 29 incorporating the methods of this invention. The tangible storage means 29 can be a flexible disk, an optical disk, a data tape, etc., while the controller 27 will include the memory boards and other standard components of modern modern computing systems for storing or executing this code . With respect to Figure 2, several of the components of the emission optics 16 are illustrated with adjacent subsystems of the laser beam. After passing a laser energy detector 28, the beam 14 from the laser 12 is directed through an opening circle 32. Then, the laser beam goes to a beam splitter 34 which directs it 14 along the a treatment axis 36 up to the eye E. Particularly important in this invention is a fixation system which is adjusted to the focus of the patient 38. This system assists the patient in keeping the eye E in the proper orientation, as will be described in detail later. Often a patient positioning system will help the laser system operator to put the patient in an appropriate position to receive the treatment. A virtual reticle projection system 42 can project a reticle into the microscope, as shown. The illumination of the eye can be achieved with a circular lamp 44 and oblique lamps 46, while the suction nozzle 48 subtracts the photodeposition waste. In the exemplary embodiment, the objective 50 of the microscope 20 (see Figure 1) is structurally coupled to the elements of the first stage of the laser emission optics 16. A microscope axis 52, a projection axis 54 of a patient fixation system 38 and a treatment axis 36 of a laser beam 14 are aligned coaxially to the adjacent eye E. The alignment of the microscope 20, the patient fixation system 38 and the laser beam 14 are illustrated schematically in Figure 3. In general, the patient fixation system 38 includes a light source 56 and an optical train of the objective 58. The optical train 58 has the ability to project objectives 60a, b, ... at different distances. More specifically, the optical train 58 can project targets 60 at different separation distances 62a, b, ... from a plane P of the eye E. The optical train will often (but not always) be adjusted using an adjustment mechanism for vary the separation distance. For a given refraction of the eye E, a projected image will usually only be found at the focus within a limited extent of separation distances from the eye. If the eye E has a small refractive error, the objective 60 will be located in the focus of the eye when the optical train 58 projects the image of the objective very far from the plane P of the eye, therefore the separation distance is at least of a meter. Patients with myopia will usually perceive the objective 60 being in focus when the optical train 58 projects the image of the anterior objective to the plane P of the eye E, as to the separation distances 62a or 62b. Should be the more advanced myopia, the separation distance shorter: in order to adjust a myopia of advanced degree, the objective 60 is projected to a separation distance 62b significantly shorter in front of the eye E with respect to the separation distance 62a longer used to adjust a more moderate myopia of the eye E. Similarly, the different degrees of hyperopia can be adapted by projecting the objective 60c, 60d, posterior to the plane P by varying the separation distances 62c, 62d. The benefits and challenges of maintaining alignment with the eye E take on special importance during laser eye surgery. During this (and some other procedures), the bright lights are directed toward the axis together with the fixing objective (e.g., from the circular lamp 44 and / or the oblique lamps 46 as shown in Figure 2). These lights will reduce the contrast of the objective image that the patient sees and will degrade the quality of the objective image when viewed. Unfortunately, these bright lights have positive repercussions on other aspects of the laser procedure, such as the improvement of the eye image offered by an operating microscope. The corneal surface regularly dries out during laser eye surgery. In fact, an epithelial layer will be removed from the cornea before reconstruction using a laser, a brush or a scraping tool, which can leave the cornea rough. A rough and dry cornea will scatter light from the patient's fixation system and other sources of illumination, in addition to reducing the contrast of the image. When the contrast of the objective image is put at risk and the objective is out of focus (due to refractive error of the eye, temporary and / or permanent changes in the eye during the procedure, etc.), the patient can not Being able to see the target, it is also possible to lose the alignment between the eye and the laser. The loss of alignment between the eye E and the laser beam 14 can have many negative implications. Laser eye systems that track the eye and terminate therapy after loss of alignment may temporarily or permanently interrupt ablation so that therapy is delayed or not completed. If therapy continues despite misalignment, the laser reconstruction process may produce unfocused ablation and may cause astigmatism in the eye. In order to assist the patient in establishing and maintaining the desired orientation of the eye E, the visual fixation system 38 may include any type of adjustable optical alternative trains as illustrated in Figure 4A-E. In the embodiment of Figure 4A, a light emitting diode (LED) projects the light by means of a moving lens 66 in order to project an image of the objective 68 at different separation distances from the plane P. The location of the objective image 68 may vary when translating axially lenses 66. Similar variation in the separation distance can occur without substantially varying the size of the lens by axially translating a lens 72 relative to a laser diode 70 in which the lens is optically coupled with the laser diode, as illustrated in Figure 4B.

It is preferable that the adjustable optical train be computer controlled and synchronized with the laser reconstruction process. When the laser ablates the cornea and alters the refractive configuration of the eye, the adjustable optical train varies the separation distance according to the dynamic computer control so that the image of the objective, as seen by the patient, is maintained basically in focus. In general, the laser reconstruction process will last between approximately 10.0 seconds and 3.0 minutes, and the computer will control the emission optics of the laser surgery system. It is possible that the optical train is adjusted taking into account the real-time topographic measurements of the cornea during the photoablation process. Alternatively, the computer will vary, during reconstruction, the adjustable optical train according to the calculated intermediate eye configurations. As an alternative for the optical target trains that are gradually adjusted and shown in Figures 4A and B, the visual fixation system of Figure 4C facilitates progressive adjustments of the separation distance. A light source 76 emits the light that will pass through the first lens 78a installed in a rotating lens holder 80. When the lens holder is rotated, as indicated, the alternative lens 78b, 78c ... is selected, consequently the lens is gradually changed. separation distance of the optical train. The focal lengths of the alternative lenses are chosen in such a way that light is projected to a small space within the desired distance of separation from the corneal plane P of the eye. In relation to Figure 4D, by incorporating more lenses to the previous optical trains it is possible to obtain greater advantages. For example, it is repeatedly advisable to maintain the angular under-tension of the objective characteristics within 80 minutes of the patient's pupil arc. In the visual fixation system of Figure 4D, an aperture 82 allows the system to project an objective into the desired shape, i.e. a cross, a circle or a crosshair. The optical train has a translatable flat concave lens 84 with a focal length of -25 mm. and an adjacent flat convex lens 85 with a focal length of 50 mm. In addition, it has a biconvex lens 86 with a focal length of 150 mm. placed at 300 mm. of the corneal plane of the patient's eye Q. When transferring the lens 84, the image of the projected objective can be suitably placed in the case of patients with a refractive error of between +5 and +5 diopters. For an opening with a physical size of 1.0 mm, this optical system can limit the opening of the images to 15 minutes of arc over the total range of +5 to +5 diopters. The preferred embodiment of the optical train comprises the elements shown in Figure 4E. The lens 86 has a focal length of 150 mm. and it is placed at 300 mm. Of the eye. The lens 85 has a focal length of 50 mm. and it is 325 mm. of the lens 86 and 135 mm. of objective 82. Lens 84 has a focal length of -25 mm. and can slide almost 100 mm. from the lens 85 to the objective 82 in order to present the focused target for refractions of the corneal plane in a range of +5 to -15 D. In this configuration, a lens of 1 (one) mm. will subtend almost 15 min. of arc in the plane of the patient's pupil. In an exemplary embodiment, two mirrors are placed on the optical train to facilitate alignment. The first mirror 81 is positioned adjacent the lens 86. Changes to the angle of the mirror 81 will compensate the projection axis of the objective 36 near the plane of the eye as shown in the offset projection axis of the objective 39a. Therefore, the mirror 81 is rotated to create a laser treatment shaft 36 coaxial with the projection axis of the objective 39. The second mirror 89 is placed almost at 300 mm. of the lens 86 and adjacent the lens 85. The second mirror 89 projects close to the plane of the eye. Hence, the changes in the angle of the mirror 89 will not basically compensate the projection axis of the objective 39 in the plane of the eye, but they will modify the angle of the projection axis of the laser 39 as shown by the rotation of the projection axis 39b. Accordingly, the second mirror 89 is rotated to maintain the images the patient sees aligning them so that the eye will not move when viewing the images of the fixation target at different separation distances when the refraction of the eye changes during surgery . An even more alternative fixation system is shown in Figure 5a. In addition to projecting a single image of the target at an adjustable separation distance, the fixation system of Figure 5a simultaneously projects several images of the objective 88a, b, c ... The image of the objective that is closest to being located in the proper separation distance will be basically at the focus of the patient's axis, while the rest of the objective images are blurred. While projecting an objective at different projection distances, the light from its source 76 passes through an element of multiple projections 87. It is possible to use the various optical structures as a multiple projection element 87. For example, a plate The well-designed Fresnel zone will produce a maximum of multiple anterior or posterior diffractions to the patient's eye. Another proposal is to use an optical holographic element (HOE) as an optic or diffractive hologram suitably designed to project a previously chosen form of the target for desired positions before or after the eye. Thanks to these multiple projection elements, the need for dynamic control systems is eliminated or the complexity thereof is reduced for the optical target train of laser eye surgery systems. A multiple projection element would be a diffractive optic 89 that produces multiple aperture images 82, as shown in Figure 5B. A source of diffractive optics 89 is the Digital Optics Corporation of North Carolina. The diffractive optics 89 is preferably projected by the lens 86 in the plan P with a magnification of 1.0. It is possible to calculate without difficulty the suitable focal lengths of the diffractive optics 89 in order to project multiple anterior and posterior images to the plane P. In relation to FIG. 5C, it is also possible to visually project different objective images to the eye. An alternative diffractive optic 89 'represents a broadband light source 76' at distances that vary along with the wavelength. For example, the images of a red objective 88r, a green 88g and a blue 88bl are separated and subsequently transmitted or re-rendered towards the eye E at the appropriate focal lengths, dimensions, etc., by means of the 86 'optical recreation system. These visually distinct lens images (in this case, the color changes) can positively indicate to the patient the progress of a photorefractive procedure, when the color of the objective appears to change in a predictable manner. When the laser selectively removes portions of the cornea, it is possible that the aberrations are temporarily ablative in the eye. It is possible to divide a refractive treatment into a series of treatments that would improve little by little the refractive error of the eye in order to reduce any kind of harmful effects that aberrations in the patient's vision could cause (which could limit for a moment the ability of the patient to focus on the objective of visual fixation, probably producing correctable damage to the vision of the eye in the event that the ablation process has to be permanently terminated before the conclusion). Even when these secondary treatments are practiced immediately to the other, this method will decrease the aberrations created during the ablation process. Figure 6 shows the scheme of this aspect of the present invention. A patient with a spherical refractive error of -10 (minus ten) diopters can be corrected with a series of two corrective treatments of two diopters. At the beginning, the imaging system will project a target at a separation distance of 0.1 meter in front of the patient. A first series of laser pulses 14a will selectively eliminate the first portion 90a of stroma S, consequently a correction of two diopters of the patient's myopia will be made. At this point, the target can be projected at an appropriate separation distance for -8.0 diopters of myopia, which would mean 0.125 meters in front of the plane of the patient's eye. Fortunately, after the first portion of the treatment, the E eye receives the benefits of a partial treatment that decreases its refractive error. This allows you to focus accurately on the image of the adjusted objective (or an image of a different objective in which the multiple simultaneous projection fixation system can be applied), as well as the net benefit in case the therapy has to be left in this point. Subsequently, the second series of laser pulses 14b can be directed directly to the eye as long as the eye is seeing the adjusted target, eliminating a second 90b portion of stromas S. Once again a correction of two diopters is made. The process of gradual reconstruction is repeated in the form of secondary treatments until the refraction of the patient reaches the desired end point. Favorable factors exist even if the treatment is interrupted in a secondary treatment. For example, one part of the eye has a portion of stromal removed and another part does not, the resulting aberration or astigmatism of the eye will be in a limited state compared to the methods in which the laser beam removes the stroma in the final stage together with a portion of the eye and then continuing to perform ablation on an alternative portion of the eye, which could result in significant aberrations.

In addition, the present invention includes the calculation of the separation distance for the projection of the objective image for visual fixation taking into account at least partially the prescribed graduation of the spectacles. When the refraction of the patient is known before the laser eye surgery (or other ophthalmological measurements or therapies), it is possible to adjust the visual fixation system in order to project the objective that will be basically in the focus of the patient. This increases the efficiency and speed of the measurement or the surgery process. Figure 7A is a schematic showing a method for calculating the separation distance. First of all, the separation distance between the objective image and the corneal plane P is calculated from the prescribed graduation of the glasses. In the case of patients with spherical prescriptions, the position of the objective is calculated using the formula: D where S is the distance of separation in meters and D is the spherical component of the prescribed graduation of the patient's glasses in diopters. In the case of patients with astigmatism, the spherical equivalent of the prescribed graduation of the glasses can be used in place of the spherical component. In a preferred embodiment, the prescribed graduation of the patient in the corneal plane is used to calculate the separation distance, as shown in Figure 7A. The separation distances for the prescriptions of the corneal plane from +5 to 15 are specified in Table 1. Likewise, this table shows the separation between the flat concave lens 84 and the flat convex lens 85 in the embodiment shown in Figure 4D. After calculated, the positions can be stored in the computer's memory and used whenever necessary, as shown in Figure 7B. The fact that the values are stored facilitates the execution of the computer program because the computer does not need to perform any more calculations.

During surgery, the position of the lens and the intensity of the objective illumination can be actively controlled as indicated in the scheme of Figure 8. Initially, the image of the objective is placed according to the prescribed prescription of the patient. In the case of intensity, its adjustment is advisable in the modalities in which the intensity of the objective image varies with the distance of the separation. Treatment begins and is monitored until it is completed. During the treatment, the intermediate graduation of the patient's glasses is calculated by taking the initial graduation of the glasses minus the amount of the complete treatment. When the calculated graduation of the glasses reaches a predetermined value, the lens moves to project the image of the lens to a new separation distance corresponding to the estimated graduation of the glasses. Similarly, when the latter reaches a predetermined value, the intensity of the illumination of the objective is changed to a value relative to the prescribed graduation of the spectacles. Due to the variability of the surgery technique, the physician can determine from the beginning the intensity of the objective illumination and then change it by the estimated graduation of the patient's glasses. When the treatment is finished, the monitoring and associated calculations stop. While it is true that the exemplary modality was described with a certain degree of detail, by way of examples and in order to facilitate its understanding, a range of modifications, changes and adaptations may be obvious to those skilled in the art. That is, the optical train of the objective setting system may also include a series of alternately eligible lenses that correct an astigmatism present at the start or provisionally imposed on the eye during laser surgery. It is possible that the adjustment of the lens fixation system compensates for a significant temporal change in refraction when an anterior portion or a flap of the cornea moves during the LASIK procedure. Therefore, the scope of the present invention is limited exclusively to the appended claims.

Claims (31)

1. A method of laser eye surgery that: projects an objective toward the eye at a first distance from it so that the objective is located at the focus of the eye; stabilizes the eye by seeing the objective through the cornea; alters the refraction of the stabilized eye by shaping a portion of the cornea; and projects the target towards the altered eye at a second distance from the eye so that the target is located at the focus of the altered eye.

2. The method of claim 1 further adjusts an optical target train in order to move the projected image of the target from the first distance to the second distance.

3. In the method of claim 1, the step of altering the refraction reduces the degree of hyperopia and the image is located posterior to the cornea during the first projection stage.

4. In the method of claim 1, the step of altering the refraction reduces the degree of myopia and the image is anterior to the cornea during the first projection stage.

5. In the method of claim 1, the step of refractive alteration consists of a series of gradual improvements of the refractive error of the eye.

6. In the method of claim 2, the objective adjustment step moves the image farther from the eye.

7. In the method of claim 2, the step of altering the refraction is performed as a series of gradual improvements of the refractive error of the eye and the objective adjustment stage consists of a series of gradual changes in the optical train of the eye. objective in order to move the image from the first to the second distance.

8. In the method of claim 2, the step of adjusting the objective is progressively carried out during the refraction alteration step so that the objective mainly follows at the focus of the eye.

9. In the method of claim 8, the step of adjusting the lens includes putting into operation a focusing mechanism of the optical train of the lens.

10. In the method of claim 1, the steps of projection one and two are performed at the same time using an optical holographic element or a plate of the Fresnel zone.

In the method of claim 1, the first distance is also calculated by taking into account at least partially the prescribed graduation of the glasses.

12. In the method of claim 11, at least an intermediate distance between the first and second distance is calculated taking into account at least partially the intermediate refractive configuration of the eye during the refraction alteration stage and the objective is projected to an intermediate distance while the eye is in the intermediate refractive configuration.

13. In the method of claim 2, in addition, an optical target train is simultaneously fitted with a processor in order to move the projected image of the objective while controlling the refraction alteration stage with the processor so that the objective it is located mostly in the focus of the eye.

14. In the method of claim 1, the refractive alteration step includes the photoablation of the cornea portion with the laser beam in order to correct the refractive error of the eye, likewise the projected objective is coaxially aligned with the a treatment axis for the laser beam.

15. A method consisting of: the projection of an objective towards the eye with a refractive error so that an image of the objective moves away from the eye by a previously calculated separation distance and the objective is located at the focus of the eye; and the stabilization of the eye by seeing the projected objective through the cornea of the eye.

16. The method of claim 15 calculates the separation distance taking into account at least partially the prescribed graduation of the glasses.

17. The method of claim 15 alters the refraction of the stabilized eye by selectively removing a portion of the. cornea in order to reduce the refractive error.

18. A laser eye surgery system for reconstructing the cornea of a patient's eye, which consists of: a laser to produce a beam for ocular surgery on a portion of the cornea. the emission optics optically aligns with the laser so that it causes a predetermined change in the refraction of the cornea with the laser beam; an optical train of the lens aligned with the emission optics to help the patient to stabilize the eye, the optical train of the lens has the ability to project the objective towards the eye in different distances of separation from it in order to adjust its various refractive corneal configurations .

19. The laser system of claim 18 has an optical train of the target that is adjusted and a controller that couples the emission optics with the optical train of the objective so that the optical train moves an image of the objective from the first one. at the second distance of separation from the eye in coordination with the change in the cornea from a first to a second refractive configuration, wherein the image is located at the focus of the eye when it is in the first refractive configuration and the image, in the first separation distance; and where the image is also located in the focus of the eye when it is in the second refractive configuration and the image in the second separation distance.

20. In the laser system of claim 19, a signal from the controller to the optical train of the lens produces a gradual movement of the image while the laser beam changes the refraction of the eye little by little keeping the objective basically at the focus of the eye.

21. In the laser system of claim 20, a lens of the optical train of the lens is moved in response to the signal from the controller.

22. In the laser system of claim 19, the controller and optical train are adapted to move the image from the first to the second separation distance little by little.

23. In the laser system of claim 22, the controller transmits the laser beam to the cornea in order to perform several partial treatments, with each partial treatment the refractive error of the eye is reduced.

24. In the laser system of claim 22, the optical train of the lens is composed of many optical elements to be chosen alternately. The change between the elements to choose gradually modifies the projection plane of the image of the projected objective from the optical train.

25. In the laser system of claim 18, the emitting optics defines an optical axis and at least a portion of the projection axis of the objective of the fixation system is coaxial with the axis of the treatment.

26. In the laser system of claim 18, the optical train of the lens has a holographic optical element so that the optical train can project the image at the same time at different distances.

27. In the laser system of claim 18, the optical train of the objective projects the objective toward the eye so that it is located within an angular sub-tension of less than 18 arc minutes in the pupil of the eye.

28. The laser system of claim 18 further has a location light projection system for projecting the light rays of the situation; the situation rays that cut transversally a corneal location in order to provide the position of the patient with respect to the emission optics; and a microscope aligned with the emission optics to see an enlarged image of the cornea. In this system, an image of the reticulum can be superimposed with the enlarged image of the cornea when it is seen through a microscope.

29. A system of laser eye surgery that serves to correct refractive defects of an eye. The laser system consists of: a laser that produces a beam to selectively remove a portion of the eye's cornea; emitting optics in an optical path from the laser beam to the laser itself, the emitting optics transmits the ha2, towards the cornea in order to change the refractive configuration of the eye, from the first to the second; a lens fixation system with a lens and a projection axis of the lens, the projection axis of the lens aligned with the optical path in order to maintain alignment between the eye and the laser beam, the lens fixation system with the ability to project the objective to a first and second distance, in which the objective is located in the focus of the eye when the cornea has the first configuration and the projection of the objective is in the first distance and in which the objective is located in the focus of the eye when the cornea has the second configuration and the projection of the objective is in the second distance.

30. In the laser system of claim 29, an image of the objective in the first distance is in visual terms different from the image in the second distance in order to indicate the progress of correction of the refractive error to the patient.

31. In the laser system of claim 30, the images of the lens are of different colors. The objective fixation system has a diffractive lens with a negative dispersion.