1. Field of the Invention
The present invention relates generally to the fields of ophthalmology and ophthalmic surgery. More specifically, the present invention relates to a measurement tool and methods for measuring and planning placement of toric ocular implants to at least minimize post-operative astigmatism.
2. Description of the Related Art
Modern cataract surgery has embraced the benefits of placing not only spherical or aspheric intraocular lenses (IOLs) into the eye, but also toric IOLs which help to control astigmatism in the eye. The goal of toric, or astigmatic, IOLs is to correct, approximately, either the complete cylinder optics in the eye usually coming from the cornea and to maximize contrast sensitivity or to provide a desired amount of cylinder that can provide for reasonable depth of field in the eye which gives the patient a reasonable amount of far to near vision. With this higher level of sophistication of IOL designs the precise location of the axis of the IOL and overall positioning within the eye and its relation to the cornea and/or pupil and/or other structures of the eye must be obtained to achieve the ideal outcome.
Correcting even small or moderate amounts of astigmatism, such as less than 2D, does require high precision in proper placement. With the advent of multi-focal IOLs, this is even more critical as many multi-focal designs, for example, diffractive IOLs, do not perform well with any residual astigmatism in the eye. Small errors on the level of 3-5 degrees in placing the axis of the IOL in the eye can lead to large 10-20% loss of effective correction of the toric IOL. The higher level optical performance of modern “Premium” IOLs″ require the ophthalmic surgeon to improve his/her surgical planning and techniques to obtain optimal vision performance for his patient with implantation of a toric IOL. This improved methodology also applies to other toric implants in the eye, such as Toric ICL's or anterior chamber lenses and even corneal inlays. Correcting astigmatism in the eye with an implant generally requires placing a toric optical surface at the correct degree of rotation to cancel other sources of astigmatism in the eye such that when the optical image focuses on the retinal there is no optical cylinder, or a desired amount, if such is planned. With a toric IOL placement to replace the natural lens of the eye and as with most cataract surgeries today, the rotational placement of the IOL within the eye at the precise meridian to cancel the astigmatism from the cornea is planned prior to placement for an ideal outcome.
However, correctly planning the placement of toric IOLs today must overcome a series of poorly controlled measurements and marks that are all error prone and subject to changes. This results in a poorly controlled outcome in positioning the toric IOL for optimal vision correction. Given the challenges in accurately marking, measuring and placing toric IOLs, most surgeons, therefore, do not attempt the extra work required to maintain the controlled measurements necessary to adequately provide for the ideal toric IOL positioning and for this the patient's ultimate vision is sacrificed.
It is a recognized goal in the art of toric IOL surgery generally to place the IOLs toric power at the correct location in the eye to minimize or reduce to zero the astigmatism generated by the cornea. Thus, having a more direct correlation of the positioning of the IOL to the corneal topography and its optical powers would be a preferred system. The prior art is deficient in the lack of methods for measuring accurately and planning the placement of toric intraocular implants such that astigmatism in a patient's post-operative vision is corrected or minimized. The present invention fulfills this longstanding need and desire in the art.
The present invention is directed to a measurement tool for implantable non-spherical asymmetric optics. The measurement tool comprises a viewable rotatable angular caliper superimposable over an image of an eye. The caliper comprises a pair of axes through the circle forming the angular caliper and intersecting at a point corresponding to a corneal vertex when superimposed over the eye and a plurality of markings around the circumference each corresponding to angular degrees from the axes.
The present invention also is directed to a method for optimally placing non-spherical asymmetric optics in an eye of a patient. The method comprises making reference marks at one or more points of interest on an eye and measuring the corneal topography of the marked eye to map its metrics of a steep axis, a flat axis and an angle of corneal astigmatism. The measurement tool described herein is superimposed over the corneal topographic image of the eye and an optimal angle of an optical zone on the cornea is determined for placement of the non-spherical asymmetric optics. The non-spherical asymmetric optic is positioned to coincide with the optimal angle of the optical zone. The present invention is directed to a related method further comprising step of measuring residual total astigmatism of the eye after placing the asymmetric optic into the eye to determine whether to further minimize or eliminate the residual astigmatism or to leave it to provide depth of focus.
The present invention is directed further to a method for correcting astigmatism in vision of a patient having cataract surgery. The method comprises measuring a corneal topography to pre-determine astigmatism in a cornea of the patient's eye and determining an angle within an optical zone of interest on the cornea of the eye for an optimal astigmatic correction based on metrics determined from the corneal topography. Using the measurement tool described herein, the surgical placement into the eye of an implantable non-spherical asymmetric optic is planned and the implantable non-spherical asymmetric optic is positioned to coincide with the optimal angle for the optical zone of interest. The present invention is directed to another related method to further minimize or eliminate post-operative residual astigmatism. The residual astigmatism is measured after the implantation. A new rotation and axis for the implanted non-spherical asymmetric optic required to minimize or to eliminate the residual astigmatism is calculated. The implanted non-spherical asymmetric optic is repositioned thereby further minimizing the post-operative residual astigmatism.
The present invention is directed further still to a computer program product for use in execution in a computer of a method for planning a surgical implantation of non-spherical asymmetric optics into one or both eyes of a patient where the computer has at least a memory and a processor. The computer program product comprises a data module, a lens selection module and a surgical plan module. The data module is configured to input into user-entered fields first values for at least IOL spherical power, surgically induced astigmatism and incision location and to output into calculated fields second values, calculated from the first inputted values, for at least lens data, an axis of placement of the non-spherical asymmetric optics in the one or both eyes and an expected residual astigmatism. The lens selection module is configured to select the non-spherical asymmetric optics based on the calculated values. The surgical plan module is configured to plan and to display a surgical implantation of the non-spherical non-spherical asymmetric optics based on the calculated values and the lens selection. The present invention is directed to a related computer program product where the data entry module is configured further to edit the inputted first values and recalculate outputted second values based on a post-operative residual astigmatism value.
The present invention is directed further still to a computer readable medium that tangibly stores the instructions for execution in a computer of a method for planning a surgical implantation of non-spherical asymmetric optics into one or both eyes of a patient where the computer has at least a memory and a processor. The method comprises steps for inputting into user-entered fields first values for at least IOL spherical power, surgically induced astigmatism and incision location, outputting into calculated fields second values, calculated from the first inputted values, for at least lens data, an axis of placement of the non-spherical asymmetric optics in the one or both eyes and an expected residual astigmatism. The method comprises a step for selecting the non-spherical asymmetric optics based on the calculated values and a step planning and displaying a surgical implantation of the non-spherical asymmetric optics based on the calculated values and the lens selection. The present invention is directed to a related computer readable medium comprising one or more of the method steps inputting first values for one or more of axial length, anterior chamber depth, central corneal thickness, lens thickness, or retinal thickness, outputting calculated values for one or more of pre-operative corneal astigmatism, a cross cylinder result for a corneal plane, cylinder power at the IOL plane, or cylinder power at the corneal plane or editing the inputted first values and recalculating outputted second values based on a post-operative residual astigmatism value.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention. These embodiments are given for the purpose of disclosure.
So that the matter in which the above-recited features, advantages and objects of the invention, as well as others which will become clear, are attained and can be understood in detail, more particular descriptions and certain embodiments of the invention briefly summarized above are illustrated in the appended drawings. These drawings form a part of the specification. It is to be noted, however, that the appended drawings illustrate preferred embodiments of the invention and therefore are not to be considered limiting in their scope.
As used herein, the term, “a” or “an” may mean one or more. As used herein in the claim(s), when used in conjunction with the word “comprising”, the words “a” or “an” may mean one or more than one. As used herein “another” or “other” may mean at least a second or more of the same or different claim element or components thereof.
As used herein, the term “or” in the claims refers to “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or”.
As used herein “another” or “other” may mean at least a second or more of the same or different claim element or components thereof. “Comprise” means “include.”
As used herein, the term “about” refers to a numeric value, including, for example, whole numbers, fractions, and percentages, whether or not explicitly indicated. The term “about” generally refers to a range of numerical values (e.g., +/−5-10% of the recited value) that one of ordinary skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In some instances, the term “about” may include numerical values that are rounded to the nearest significant figure.
As used herein, the term “toric” refers to the shape of an intraocular lens having two different curves instead of one which is utilized to correct both astigmatism and near- or farsightedness. A “toric intraocular contact lens” (ICL) refers to a very thin toric lens that are placed behind the iris and on top of the natural lens of the eye.
As used herein, the term “patient” refers to an individual or subject who has surgically received an intraocular implant and/or has surgically had placement of an intraocular implant corrected post-operatively and/or has been evaluated as a candidate for intraocular implantation. Preferably surgical procedures are or have been performed utilizing the toric calculator and toric caliper presented herein.
In one embodiment of the present invention there is provided a measurement tool for implantable non-spherical asymmetric optics, comprising a viewable rotatable circular caliper superimposable over an image of an eye, where the caliper comprises a pair of axes through the circle forming the caliper and intersecting at a point corresponding to a corneal vertex when superimposed over the eye; and a plurality of markings around the circumference each corresponding to angular degrees from the axes. In this embodiment, the circumference of the caliper superimposes approximately around the limbus of the eye.
In another embodiment of the present invention, there is provided a method for optimally placing non-spherical asymmetric optics in an eye of a patient, comprising the steps of making reference marks at one or more points of interest on an eye; measuring the corneal topography of the marked eye to map its metrics of a steep axis, a flat axis and an angle of corneal astigmatism; superimposing the measurement tool described supra over the corneal topographic image of the eye; determining, via the measurement tool, an optimal angle of an optical zone on the cornea for placement of the non-spherical asymmetric optic; and positioning the non-spherical asymmetric optic to coincide with the optimal angle of the optical zone.
Further to this embodiment, the method comprises the step of measuring residual total astigmatism of the eye after placing the non-spherical asymmetric optic into the eye to determine whether to further minimize or eliminate the residual astigmatism or to leave it to provide depth of focus. In an aspect of this environment, the residual astigmatism is further minimized or eliminated and method comprises the steps of subtracting corneal astigmatism from the residual total astigmatism to determine the current angle of the implanted non-spherical asymmetric optic; calculating a rotation of the implanted non-spherical asymmetric optic required to minimize or eliminate the residual astigmatism; calculating the angle between the marks on the eye and a new axis of the implanted non-spherical asymmetric optic; and rotating the implanted non-spherical asymmetric optic the calculated amount to coincide with the new calculated angle.
In both embodiments and aspects the optical zone metrics may comprise determining the sphero-cylindrical shape that is best fit to the optical zone of the corneal topography or of a corneal wavefront. Further, the step of determining the optimal angle for placement of the non-spherical asymmetric optic may comprise measuring one or more angles formed by one or more first axes each having a vertex coincident with one of the reference marks and a second axis comprising one of the metrics, where the first and second axes each have a vertex coincident with a central vertex in the eye whereby the non-spherical asymmetric optic position coincides with the axes. For example, the other vertex(ices) of the first axis(es) may comprise one of the reference mark(s). Also, the second axis may be coincident with a steep axis of the corneal topography curvature. In addition, the central vertex may be located in the center of the cornea, the pupil or the entrance pupil or the center of corneal topographic map or is located at a corneal anomaly.
In both embodiments and aspects thereof, the corneal topography may include one or both of wavefront or aberrometry measurements or measurements of other optical aberrations. Also, the optical aberration may be astigmatism. In addition, the non-spherical asymmetric optics may be implantable toric intraocular lenses or implantable toric intraocular contact lenses.
In yet another embodiment of the present invention, there is provided a method for correcting astigmatism in vision of a patient having cataract surgery, comprising the steps of measuring a corneal topography to pre-determine astigmatism in a cornea of the patient's eye; determining an angle within an optical zone of interest on the cornea of the eye for an optimal astigmatic correction based on metrics determined from the corneal topography; planning, via the measurement tool of claim 1, surgical placement into the eye of an implantable non-spherical asymmetric optic; and positioning the implantable non-spherical asymmetric optic to coincide with the optimal angle for the optical zone of interest.
In a further embodiment, the method comprises the steps of measuring residual astigmatism after the post-operative implantation, calculating a new rotation and axis for the implanted non-spherical asymmetric optic required to minimize or to eliminate the residual astigmatism; and repositioning the implanted non-spherical asymmetric optic thereby further minimizing the post-operative residual astigmatism. In both embodiments the steps of determining the metrics of the optical zone of interest and the optimal angle for placement of the non-spherical asymmetric optic comprises are as described supra. Particularly, the central vertex, the first ax(es), the second axis the non-spherical asymmetric optics, reference marks and their positions on the cornea or the sclera are as described supra.
In yet another embodiment of the present invention there is provided a computer program product for use in execution in a computer of a method for planning a surgical implantation of non-spherical asymmetric optics into one or both eyes of a patient, where the computer has at least a memory and a processor, the computer program product comprising a data module configured to input into user-entered fields first values for at least IOL spherical power, surgically induced astigmatism and incision location and to output into calculated fields second values, calculated from the first inputted values, for at least lens data, an axis of placement of the non-spherical asymmetric optics in the one or both eyes and an expected residual astigmatism; a lens selection module configured to select the non-spherical asymmetric optics based on the calculated values; and a surgical plan module configured to plan and to display a surgical implantation of the non-spherical asymmetric optics based on the calculated values and the lens selection.
Further to this embodiment, the data entry module is configured to edit the inputted first values and recalculate outputted second values based on a post-operative residual astigmatism value. In both embodiments the inputted first values further may comprise one or more of axial length, anterior chamber depth, central corneal thickness, lens thickness, or retinal thickness. Also, in both embodiments the outputted calculated values further may comprise one or more of pre-operative corneal astigmatism, a cross cylinder result for a corneal plane, cylinder power at the IOL plane, or cylinder power at the corneal plane.
In yet another embodiment of the present invention, there is provided a computer readable medium tangibly storing the instructions for execution in a computer of a method for planning a surgical implantation of non-spherical asymmetric optics into one or both eyes of a patient, where the computer has at least a memory and a processor, the method comprising the steps of inputting into user-entered fields first values for at least IOL spherical power, surgically induced astigmatism and incision location; outputting into calculated fields second values, calculated from the first inputted values, for at least lens data, an axis of placement of the non-spherical asymmetric optics in the one or both eyes and an expected residual astigmatism; selecting the non-spherical asymmetric optics based on the calculated values; and planning and displaying a surgical implantation of the non-spherical asymmetric optics based on the calculated values and the lens selection.
Further to this embodiment the method stored on the computer readable medium comprises the step of inputting first values for one or more of axial length, anterior chamber depth, central corneal thickness, lens thickness, or retinal thickness. In another further embodiment the method stored on the computer readable medium comprises the step of outputting calculated values for one or more of pre-operative corneal astigmatism, a cross cylinder result for a corneal plane, cylinder power at the IOL plane, or cylinder power at the corneal plane. In yet another further embodiment the method stored on the computer readable medium comprises the step of editing the inputted first values and recalculating outputted second values based on a post-operative residual astigmatism value.
Provided herein are methods, systems and tools for measuring and planning placement of non-spherical asymmetric optics, for example, but not limited to, toric ocular implants (most commonly Intra-Ocular Lenses—IOLs or Intra-Ocular Contact Lenses—ICLs) in the correct axis of the patient's eye for the patient to obtain the desired correction of astigmatism for the patient's post-operative vision. The measurement tool provided herein provides a means to correlate reference marks on the eye to corneal topography or refraction/wavefront measurements, such as internal optical aberrations or other measured visual properties of the eye that may interest an ophthalmic surgeon, in planning a surgical procedure, either pre-operative or post-operative, and in providing a complete metric system to accurately place toric or other asymmetric optics into the eye. Particularly, the measurement of corneal topography, more specifically, the steep axis of the cornea's curvature can be directly correlated to the marks on the cornea/sclera so a surgeon can reliably measure the angular difference and use this direct correlation to more accurately position the toric IOL to the appropriate axis to obtain precisely the visual outcome desired.
Thus, also provided herein are software applications, modules, computer readable media, and computer program products, etc. that enable a surgeon to use the toric calculator and toric calipers to plan a pre-operative surgical implantation of a non-spherical asymmetric toric lens or a post-operative implant correction thereof, as described in Example 2. As is known in the art, such software, modules, etc. can be tangibly stored in a computer or other electronic media, such as in a computer memory or other media storage device, retrieved therefrom and implemented therein. As also is known in the art, a computer or other electronic media comprises a memory, a processor, and, optionally, at least one network connection.
In order to place the axis of the toric IOL in the proper meridian, the ophthalmic surgeon must generate the proper metrics and system to use on the eye or through an imaging device such as a surgical microscope to achieve such measurements to guide him during surgery in placing the IOL at the right meridian and with ideal centration and positioning to the pupil and cornea and the eye's other components. The traditional procedure used to create such a metric system begins with the surgeon or a technician making a mark on the eye to determine the horizontal or 180 degree meridian as the patient is prepared for surgery. This typically involves the patient seated in front of a standard slit lamp observational microscope at which the patient is fixating on a coaxial light source. The observer determines that the patient has proper fixation and then uses a marking tool, usually blotted with an ink dye, and effectively pushes the marking tool down onto the cornea and/or the sclera of the eye to provide a “horizontal mark” for instance. This mark can be a short line or dot at the periphery of the cornea, usually at or across the limbus onto the sclera or “white of the eye”, so it can easily be observed at both the 3 o'clock and 9 o'clock positions, i.e., the 0 and 180 degree semi-meridians.
In marking the positions on the cornea or sclera a significant error is introduced as the patient's eye can move easily or rotate during the marking procedure. The technician or surgeon performing the markings can introduce many sources of error or bias in their alignment technique, etc. Once these marks are on the eye, they will represent theoretically the 180 degree or correct horizontal axis reference for the surgery. Errors in assuming that these marks are correct will be perpetuated in the process to determine the correct axis of IOL position.
Generally a surgeon uses these marks as a reference by which to measure the axis for the IOL placement using some standard caliper tools that demarcate the number of degrees from horizontal desired. There are a number of well-known and standard surgical measurement tools and methodologies useful to measure each of the 360 degrees around the eye from a reference point so that a subsequent mark can be made on the eye, for example, at 85 degrees, which represents the desired axis of final rotational placement of the IOL in the eye. Any errors in determining this 85 degree axis adds to the problem of controlling astigmatism. A toric IOL may have a corresponding mark or line such that, upon placement in the capsular bag of the eye as a replacement for the human lens, the IOL is rotated to align the mark on the IOL with the mark on the corneal limbus and sclera which denotes the final positioning of the IOL.
In general, the target axis for rotational placement of the IOL is determined so that once the IOL is placed correctly along this axis it will correct the cylinder of the cornea. Most toric IOLs are designed so that there is a mark on the lens that indicates one of its principle axes, either its axis of lower power or higher optical power. Usually the axis of lower power is marked and the IOL is positioned so that axis of lower power mark and the mark on the cornea or sclera which is intended to represent the axis of cylinder power that is greatest from the cornea are coincident. The corneal axis is generally referred to as the “steep axis” of the cornea. The axis of steepest curvature of the cornea then will provide the greatest optical power in a toric cornea. Therefore, it is presumed that when the IOL is rotationally positioned so that the marks on the cornea or sclera are aligned with the correlating marks on the IOL then the toric IOL should ideally neutralize the corneal astigmatism as planned.
There are a number of critical steps in measuring this process and there are errors associated with each of these steps. Currently, there is poor correlation of the placement of the IOL to the corneal topography or toric shape and power of the cornea. The standard metric systems used today by surgeon's reference marks on the eye are assumed to be horizontal or vertical and there is no true confirmation of this assumption. With cyclotorsion of the human eye from positioning the patient in the vertical to horizontal position, as needed for surgery, there are even greater sources of error introduced and what is considered horizontal in the eye when the patient is seated is clearly not the horizontal position when the patient is supine in most patients.
In addition the purely subjective nature of the observer in applying their technique to mark the “horizontal” axis of the eye given the patients head position, the quality of the ink marks and their potential to spread or blot and even to be non-visible over the few minutes until surgery occurs can affect the process. This can occur easily as fluids, such as artificial tears and anesthetic drops, are used on the eye. Furthermore, the use of surgical measuring tools such as angular calipers that are marked in 5 or 10 degree increments also leave a great deal of error and subjectivity in their use as a surgeon tries to find a target axis within one degree of accuracy given the accuracy required to truly provide the best vision.
As an improvement over the current standard implant planning technologies, the imaging tool and measuring system provided herein incorporate corneal topography measurements, with or without wavefront and/or aberrometry measurements, using known analog and/or digital imaging techniques and ocular measurements to directly correlate and measure the corneal topography and, therefore, its optical powers, including astigmatism, to the reference marks or positions on a patient's eye. Previously, marks on the cornea/sclera were at the horizontal axis, however, the measurement tool and methods of use provided herein eliminate this requirement. The reference marks may be placed anywhere that is convenient for the surgeon and that can be seen in the corneal topography image. This direct correlative measurement provides for increased precision in planning the surgical procedure and provides a simple guide for the surgeon to appropriately and correctly place the toric IOL.
Through imaging techniques of measuring the corneal topography, for example, Placido Disk imaging that simultaneously images the marks on the cornea/sclera, image processing can be used either manually or automatically to detect these two axes and/or marks and to determine the angular distance necessary to place the toric IOL to ideally control the astigmatism in the eye. In a representative embodiment, an angular caliper is used to draw a first line through the corneal vertex or center of the corneal topography map and the desired reference mark on the cornea/scleral part of the eye, through either manual or automatic detection means. This first line is followed by a second line that includes the corneal vertex and is coincident with the steep axis of the corneal topography curvature. This second line may be considered a principle meridian of the cornea's average toricity; for example, actually defining the steep meridian of the cornea. In this simple case the angular difference between these two lines that share a common point at the corneal vertex correlates to an ideal placement of the IOL to control astigmatism, as planned. Any variation in this plan can be measured if, in fact, an alternative amount of cylinder is desired as the outcome.
Utilizing modern software graphic techniques and analysis the corneal topography measurement that incorporates the image size to detect the marks on the cornea/sclera is sufficient to begin the toric caliper analysis and leads to a direct plan for surgery. A color printout can be easily generated or the output can be sent as a digital image or video to a monitor system, either through the operating microscope or generated on a video screen by superimposing the toric caliper measurements onto a live video image using image processing techniques, to locate anatomical landmarks, such as, but not limited to, the pupil and limbus. Alternatively, more sophisticated iris registration techniques may be used. The computer hardware, monitor and video equipment necessary to produce an image are well-known and standard in the art.
The goal of achieving a single data capture incorporating corneal topography analysis, optionally, with wavefront/aberrometry analysis, and the direct imaging of the reference marks made on the cornea/sclera enables direct correlative measurements to direct surgical planning. In practically all cases the handmade markings on the cornea/sclera are not perfectly symmetrical over the cornea's center or that of the corneal vertex or pupil or other central ocular landmark. This, however, is not of consequence as surgical planning can proceed from a minimum of one marking or multiple markings and each can provide a direct correlative measurement to the corneal topography, whether the steep axis of cylinder is desired or the flat axis or any semi-meridional analysis. The surgeon can select any feature of the corneal topography to use as his guide for placement of the toric or any customized optic as he desires the visual outcome to be.
1) A patient that has been predetermined (due most likely to a significant degree of corneal astigmatism) to receive a Toric IOL is first marked on the eye by a technician or doctor, such as, but not limited to, the 3 and 9 o,clock positions, to serve as a reference mark for the doctor in surgery.
2) The corneal topography measurement is taken with video imaging to see the marks on cornea, limbus or sclera. Optionally, this can be combined with aberrometry measurements or with other diagnostic measurements, such as axial length corneal pachymetry. This can also be performed with patient seated, or supine or in any position. In a supine position the device can be held manually or by a vertical stand.
3) With the CT and video image, for example, but not limited to, a digital image, the surgeon or technician can be shown a display with the CT map overlaying the video image. This could be a transparent map or semi-transpaterent or also a solid map, usually in color.
The color may denote the curvature of the cornea therefore its optical power, but can also denote elevation, etc.
4) The user can then select the Toric Caliper graphics and software to activate at anytime to now have an angular graphic display with angular calipers that can be set either manually or automated through software image processing and mathematical algorithms to most likely correlate the “surgeon's mark” (3 o'clock and 9 o'clock in this instance) to the steep axis (meridian of most refractive power) of the cornea as is typically done. The user can now use the angular information of the caliper to determine how many degrees from their surgeon's marks they need to use to place the Toric IOL in the proper alignment with the cornea.
For example, manually the user can place a semi-meridian marker axis over the steep axis of corneal topography (
This Toric Caliper can be centered on the Vertex Normal of the cornea which is the center of most corneal topography maps, but the Caliper could also be centered on other desired points on the eye as the user desired. Some examples are the “Visual Axis” or first light reflex off the cornea when a patient is properly fixating. It could also be the center of the pupil or entrance pupil as determined or it could be other points of interest such as the apex of the cornea or some corneal anomaly like a scar.
Again, the user can override an automatic system or manipulate a manual one to make any adjustments he sees necessary; for example, with irregular astigmatism. Or if there is little or no corneal astigmatism and the surgeon is planning to induce some desired astigmatism in the eye, which could be highly beneficial in giving the patient more depth of field optically, so that they can overcome Presbyopia and see near and far in a normal like manner.
5) Finally, once the user has positioned the cursors, or it has been done automatically by the software, then the user can confirm it is correct and is desirable, the user can actually select a display algorithm to present this information in a format for surgery, a surgical plan (
The toric caliper also is utilized for post-operative correction, if necessary. For example, if after a toric IOL or ICL implantation procedure, the axis is incorrect post-operatively, i.e., residual astigmatism is still present, the surgeon can utilize the toric calculator and toric caliper to determine the number of degrees and in what direction the toric implant must be rotated to further minimize the astigmatism. Preferably, this procedure is performed within 48 hours after surgery. Alternatively, it may be decided to leave the residual astigmatism to provide for depth of focus.
The software enables the toric caliper tool and creates the displays within a toric planner and IOL selection or evaluator modules. This enables a user to enter pertinent data from other sources to calculate the proper axis of alignment and cylinder power for the toric IOL or ICL implantation. The user enters a location that is 0 to 360 degrees from where the surgeon wants the cataract incision for surgery. However, whenever a cataract incision or any other type of incision to control astigmatism, such as a limbal relaxing incision (LRI) or incisions during astigmatic keratotomy (AK), is placed in the eye or cornea, a surgically induced astigmatism will occur. The toric planner module enables a user to incorporate such surgically induced astigmatism into the surgical plan for implantation.
In a representative example, a doctor makes the incision along the temporal side of the left eye at 5 degrees, slightly off the horizontal. Along that 5 degree meridian the cornea will flatten where the extent of flattening depends on size and length of the incision. With a standard cataract incision of 3 mm, flattening along the meridian across the incision averages 0.5 D. There also is a slight steepening in the perpendicular meridian at 95 degrees in this instance. This is referred as a coupling effect and may result in a total contribution of about 0.75 D of surgically induced astigmatism to the cornea. The software modules as described in Example 2 enable a user to account for such effects.
It is important to account for surgically induced astigmatism when planning the axis of a toric IOL implant. Surgically induced astigmatism creates a vector force which can now be predicted and summed with the pre-existing corneal astigmatism, if any, together with the optical cylinder in the toric IOL itself. What is now possible is to even select the toric IOL that is best suited for the eye and then use the toric caliper to mimic the cylinder of the cornea, IOL and surgically induced cylinder or astigmatism. This enables the surgeon to plan the surgery and to predict the outcome and, therefore, to better control the results. This can work not only for cataract surgery, but other forms like astigmatic keratotomy, even corneal transplant or corneal refractive surgery, especially with incisions.
Moreover, instead of relying on K readings, that is, the flat and steep axis of the cornea, to eventually align the IOL or ICL axis with respect thereto, there is improvement by looking at the “best fit” sphero-cylindrical shape or “optical” fit to the area over the cornea over a particularly desired optical zone. The optical zone can be chosen based on the patients pupil size, usually, the largest scotopic pupil size during darkness or may be selected by the optic zone of the IOL or ICL, if that is smaller, so that optical effects are optimized. This best fit can come from the cylinder terms of the Zernike Polynomial (Zernike Cylinder) fit which are incorporated into the toric planning software modules. This is an improvement over K readings obtained in keratometry. The best fit is generally more reproducible and takes into account the entire area of the cornea, such as, for example, over about a 5 mm zone, if the pupil size is that large, or over about a 3 mm zone for a smaller pupil. Alternatively, a least squares best fit method for a toric surface can be used. Mathematically, as is known in the art, there are several ways of doing this. This improves results optically in matching the toric IOL to the cornea over simple K readings. The steps to determine a best fit utilizing, for example, Zernike Cylinder terms, is enabled by the software modules in the Toric Planner
The following examples are given for the purpose of illustrating various embodiments of the invention and are not meant to limit the present invention in any fashion.
In this software, if the doctor does not agree or if the astigmatism is not as perfect and symmetric as it is in the case of Patient 2 then the doctor can alter these red and blue determinant lines of the steep and flat axes of the cornea. In that case a dotted version of the red and blue lines is left underneath so that the doctor can always see what the automated keratometry analysis shows. Also, he can use the mouse cursor and “pick up” the lines and rotate them to where he wants as this represents the corneal astigmatism which he then wants to correct or alter with the toric IOL that will go inside the eye.
As the Red and Blue Lines mostly are not touched and are determined, as per the automatic keratometer software, on the corneal topography, the user (in Manual Model uses the mouse cursor to “pick up” the black line off to the right of center and moves a semi-meridian black cursor line to usually cover half the red (steep axis) thereby demonstrating his “target” axis. Manually placing a black cursor line over the red axis tells the software this is where the user eventually wants the lower power axis (flat) of the toric IOL to reside.
The horizontal black axis or “reference axis” will remain completely across the screen and the user will then use the mouse cursor to go to the periphery (over the white of the eye) and “pick up” this full meridian reference axis and place it over the closest surgeon's mark that was made by an ink marker on the cornea or limbus or white of the eye (sclera). As in the case of Patient 1, the black “Hash mark”, which the surgeon made as his “Surgeon's Mark”, is below the horizontal by 9 degrees, so when he positions the reference line of the caliper down 9 degrees over the surgeon's mark, he is left with a completed plan for surgery.
The plan indicates that the angle from the Surgeon's mark (full black reference line) to the red axis of astigmatism that now has its upper half covered by the black semi-meridian “Target” cursor, denoting this is where he wants the final Toric IOL to be positioned to correct the steep meridian of the cornea. In the upper right are angle numbers that are colored to describe the angles now shown. Thus, for 99 degrees, the top number represents the angle from the now correctly placed reference line that is over the surgeon's mark to the Target Cursor, which is over the steep axis of the astigmatism, telling him that during surgery he needs to make a mark that is 99 degrees superior from the temporal (since it is the left eye that you see when the 3 o'clock Surgeon's mark is the temporal side of the eye) surgeon's mark.
Also, the surgeon will essentially do the same as above with the nasal surgeon's mark, putting the reference line over it and then taking the target semi- meridian line and overlaying it on the other half of the red steep axis of corneal astigmatism to get the angle that he should then measure and mark in surgery to make an inferior mark on the eye so he can line up the other side of the IOL. In this case that angle would be 112 degrees. Then, the doctor presses a button that says print surgical plan whereupon he receives a very simple summary of these two angles (99 degrees superiorly from the temporal markyand 112 degrees inferiorly from the nasal mark so that he takes this simple diagram that is usually in an upside down view (surgeon's view) to the OR.
The Data Entry module displays the entry fields and labels for the user-entered pre-op data and the calculated fields as shown in Table 1 (
The software also houses a database of lenses with varying cylinder power. A representative example is shown in Table 2.
A Data Entry module enables a dialog box (
Within the dialog for the user to choose the desired lens, the Lens Selection module displays 3 lens choices, or will display only two choices if the recommended lens is either a non-toric or the highest toric power. The software determines which lens choices to display based on the criteria in Table 4, as a representative example.
For Lens Option 2, this entire field will be left blank if the patient has low pre-existing astigmatism and non toric lens (0 cyl power) is the optimal, i.e., Lens Option 1, selection. Also, for Lens Option 3, this entire field will be left blank, if the patient has high pre-existing astigmatism and the highest cyl lens is the optimal, i.e., Lens Option 1, selection.
The Lens Selection module enables the user to select one of the 3 lens options as shown in Table 5. On the display, this button is greyed out until the pre-op data entry requirement is fulfilled by the user.
Once selected, the lens power at the corneal and IOL plane and the resulting expected residual astigmatism are displayed by the Surgical Plan module on the Surgical Plan page. The same dialog includes a drop down list with available lens models to choose from. An example of a lens selection screen where Lens Option 2 is recommended based on data input and selected by the user is shown in
The Toric Planner shows a screen with a map displaying a pre-adjusted caliper (
The software modules described herein enables a user to design a post-operative plan, if the patient's astigmatism still requires correction after implantation of a toric IOL, as shown in Table 6.
If necessary or desired the New Lens Placement can be changed and the lens placement symbol will appear with angle measurements between the current lens axis and the new planned lens axis until an optimum placement is obtained.
The software modules described herein enable a user to design a post-operative plan, if the patient's astigmatism still requires correction after implantation of a toric ICL, as shown in Table 7.
After step 740, the surgical plan can be edited as described herein.
One skilled in the art will appreciate readily that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those objects, ends and advantages inherent herein. The present examples, along with the methods, systems procedures and treatments described herein are presently representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention as defined by the scope of the claims.
This international application claims benefit of priority under 35 U.S.C. §119(e) of provisional application U.S. Ser. No. 61/465,891, filed Mar. 25, 2011, now abandoned, and provisional application U.S. Ser. No. 61/455,218, filed Oct. 15, 2010, now abandoned, the entirety of both of which are hereby incorporated by reference.
Number | Date | Country | |
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61465891 | Mar 2011 | US | |
61455218 | Oct 2010 | US |