Patent Application
20060135952
The present invention generally relates to corrective lenses and, in particular, to devices and methods for adjusting an intraocular implant to impart improved visual acuity.
A common problem that affects vision, especially in later life, is the development of cataracts, which cause the natural crystalline lens to become cloudy. A surgical procedure is known to correct cataracts wherein the natural lens is removed and an artificial intraocular lens (IOL) is inserted in its place that replaces the focusing power of the natural lens. Typically the IOL is a homogeneous element comprising a plastic, a hydrogel, or silicone, for example, that may be substantially rigid or foldable for insertion. Bicomposite IOLs are also known that comprise a first material in the optic portion and a second material in the haptic portion.
However, perfect vision is rarely restored after cataract removal, and the patient is typically required to wear glasses to provide one or both of distance and near vision. This can be addressed in some cases with the use of a multifocal lens, an implantable contact lens, or an intracorneal lens implant.
In commonly owned U.S. Pat. No. 6,663,240 is described a method of manufacturing an IOL that has been customized to provide optimum vision for an eye that has previously experienced corneal refractive surgery. One of the embodiments disclosed in the U.S. Pat. No. 6,663,240 patent includes a two-step procedure in which a primary lens is implanted in a first surgery and a second, supplementary lens is implanted in a second surgery following data collection on the results of the implantation of the primary lens.
It would be beneficial to provide an IOL and a method for implanting same that is customizable in situ to provide optimal vision following cataract surgery.
The present invention, a first aspect of which includes a system for providing improved vision to a patient having undergone an intraocular lens implantation, comprises a device for measuring an aberration in an eye of a patient having an intraocular lens implanted therein. Computer software is resident on a processor and is adapted to calculate an IOL modulation refraction profile prescription for correcting the measured aberration. Means are also provided for altering the refractive profile of a sector of the intraocular lens in situ according to the calculated prescription.
The method of the present invention comprises the steps of measuring an aberration in an eye of a patient having an intraocular lens implanted therein and calculating a refraction profile prescription for correcting the measured aberration. The method also includes the step of altering a refractive index of a localized sector of the intraocular lens in situ according to the calculated prescription.
The features that characterize the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawing. It is to be expressly understood that the drawing is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawing.
A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings in which like reference numbers indicate like features and wherein:
A description of the preferred embodiments of the present invention will now be presented with reference to
A method 100 (
Using the data collected from the wavefront measurement system, computer software 13 resident on a processor 14 is used to calculate a refraction profile prescription for correcting the measured aberration (block 103). Such a calculation may comprise, for example, applying the equation:
δn=W(x,y)/t
where W(x,y) is the measured wavefront aberration, (x,y) are the normalized coordinates, and t is the thickness of intraocular lens sector to be altered.
Next a refractive profile of a sector 15 of the intraocular lens 11 is altered in situ according to the calculated prescription. Such an alteration is preferably made by delivering a laser beam 16 to the intraocular lens sector 15 in such as way as to modify the intraocular lens sector's refractive profile in a desired pattern commensurate with the calculated refractive prescription (block 104). The refractive index of the material changes as a function of laser intensity and exposure time until a saturation value is reached.
The particular IOL 11 for use with the present system 10 and method 100 comprises a material that is susceptible to refractive index alteration by the laser beam 16. In an exemplary embodiment as illustrated in
The central layer 18 may comprise, for example, a substantially transparent material that can be “micromachined” with the use of the laser beam 16. For example, small regions of the central layer 18 can be superheated to cause multiphoton absorption and avalanche ionization, which will effect a refractive index modification in a very small volume. Alternatively, the central layer 18 may comprise a material doped with a molecule susceptible to photochemical modification by the laser beam 16. However the refractive index modification is achieved, the central layer 18 is isolated from the rest of the eye 12 by the enveloping layers 17,19, and thus the eye 12 is protected from any “hot spot” that is induced. An exemplary material for the enveloping layers 17,19 may comprise an acrylic. The central layer 18 may comprise a material such as poly-methyl methacrylate (PMMA), which changes state upon superheating, although this is not intended as a limitation.
In a particular embodiment, the laser beam 16 is delivered from a pulsed, variable-frequency laser 20 that is adapted to micromachine the central layer 18, which then acts as a phase plate. Preferably the laser beam 16 is scanned under the direction of a delivery system 21 that includes a spatial light modulator and other optical elements to achieve the desired refractive index pattern.
A focusing lens 22 is positioned in the beam path upstream of the eye 12. The focusing lens preferably has an F-number (F/#) that provides a depth of focus (dof) substantially matching a thickness t 23 of central layer 18.
dof=2.44λ(F/#)2
which approaches, as dof approaches t,
F/#=(t/2.44×)1/2
In order to monitor the progress of the procedure, a beamsplitter 24 is positioned upstream of the focusing lens 22, directing a portion of the beam 16 to a monitor such as a video camera 25.
Once the refractive-index-changing procedure is complete, preferably the eye 12 should be measured again for any remaining aberration (block 105), in case additional alteration should be performed to the IOL 11 (block 106).
In the foregoing description, certain terms have been used for brevity, clarity, and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for description purposes herein and are intended to be broadly construed. Moreover, the embodiments of the apparatus illustrated and described herein are by way of example, and the scope of the invention is not limited to the exact details of construction.
Having now described the invention, the construction, the operation and use of preferred embodiments thereof, and the advantageous new and useful results obtained thereby, the new and useful constructions, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.
