Method for selecting an intra-ocular lens to be implanted in cataract surgery

A METHOD FOR SELECTING THE INTRA OCULAR LENS TO BE IMPLANTED IN A CATARCT SURGERY υρπυρ πτη’3 rpry-γιη nurw ηνπΛ no’tp

Inventor: Yaacov Rozenman

A METHOD FOR SELECTING THE INTRA-OCULAR LENS TO BE IMPLANTED IN A CATARCT SURGERY

FIELD OF THE INVENTION

The present invention relates to a method for selecting the correct artificial intra-ocular lens (IOL) to be implanted in a cataract surgery. More specifically, the present invention relates to a method for selecting said lens by measuring part or all of the optical parameters of the eye during the cataract surgery, after the removal of the natural lens and calculating the power of the IOL using these parameters.

BACKGROUND OF THE INVENTION

About 70% of all eye surgeries are cataract surgeries. A cataract is formed when the natural lens of the eye, responsible for focussing the light and producing sharp images, becomes cloudy and hardens, resulting in a deterioration of visual function.

The lens of the eye is clear at birth, but is one of the first parts of the body to show the effects of aging. Cataracts are the leading cause of vision loss among adults age 55 and older. In fact, poor vision from cataracts affects about 60 percent of all adults over age 60. However, cataracts can also develop as a result of a direct or an indirect trauma to the eye, metabolic deficiencies, heredity or medications, thus they affect all ages. A cataract surgery involves the removal of the clouded lens and the implantation of a new artificial intra-ocular lens (IOL). The clouded lens is either removed mtactthrough a 6 -12 mm incision or is dissolved by a high frequency ultrasound (phaco emulsification). This second method, which requires a much smaller incision, approximately 3 mm, becomes the more 1 favorable method for cataract removing. These surgeries are done under local anesthesia while the patient is in full consciousness and can cooperate with the surgeon.

It is the common procedure in all cataract surgeries to exploit the opportunity of lens replacement and to improve the patient vision, not only by overcoming the opacity problems due to the cataract, but by correcting the refractive errors of the operated eye as well. In other words, the implanted intra-ocular lens (IOL) is chosen so that the eye after the operation has a preselected refractive error, irrespective of the refractive error prior to the cataract extraction. The selection of the IOL is based on careful measurements of the optical parameters of the eye, i.e., the cornea radius of curvature, the total length of the eye (axial length), the distance between the cornea and the lens (anterior chamber depth), and the thickness of the lens.

With all the progress in the measuring techniques of these optical parameters, still at about 20% of the cases, unsatisfactory results are obtained and the implanted lens that replaces the natural lens does not function optimally. This is typically due to the fact that the wrong artifical lens was selected for implantation, because, when the measurements were taken of the patients eye (before the surgery), opacification of the lens produced inaccurate results.

Many efforts have been made in order to improve the measurements of the optical parameters of the eye in order to select a correct artificial lens. However, to correctly measure optical parameters of the eye, the cooperation of the patient is often needed. For example, in order to accurately measure the axial and the anterior chamber lengths, it is very important that all the optical elements of the eye be aligned along the visual axis of the eye. Such alignment is possible if the patient can focus his eye on a specific point. But if the patient suffers from a full cataract, he cannot focus his eye on a point he cannot see. Another serious drawback, also directly resulting from the cataract condition, is 2 that due to the lens opacity, no optical instruments can be employed in order to measure parameters which depend also on the back chamber of the eye, i.e., on parts that are behind the opaque lens. Therefore the axial and anterior chamber lengths are measures by ultrasound although they are less accurate than optical measurements.

The attitude to the optical parameters measurements according to the present invention in order to overcome these problems is completely different. According to the present invention the measurements are performed during the surgery, after the removal of the natural lens and before implanting the new artificial lens.

Since the measurements are performed after the removal of the lens, there is no blockage of light passage, thus it is possible to perform optical measurements by employing optical instruments, and since most of cataract surgeries are done under local anesthesia, it is possible to perform the measurements with the patient’s cooperation.

Another advantage of the present invention is that there is no need to examine the patient on a separate visit prior to operation, thus the present inventions saves valuable time for both physician and patient.

It is the aim of the present invention to provide a better and more accurate method for measuring the optical parameters of the eye that are necessary for choosing the correct refraction power of the IOL and in particular for measuring the axial and the anterior chamber lengths.

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SUMMARY OF THE INVENTION

The present invention relates to a method for selecting the correct intra-ocular lens (IOL) to be implanted in a cataract surgery. The novelty of the present invention is that measuring the optical parameters of the eye, that are needed in order to choose the correct intra-ocular lens, are performed during the cataract surgery, after the removal of the old (natural) lens.

The method of the present invention comprising the following steps: a) removing the natural lens of the eye; b) measuring at least one of the optical parameters of said eye, needed in order to calculate the power of the IOL; c) calculating the power of the IOL by using the parameters measured in step b and if necessary parameters that were measured prior to surgery.

The specific optical parameters, needed in order to calculate the power of the IOL, are the cornea power, the axial length, the anterior chamber length, and the length from the cornea to the posterior capsule.

The parameters measured in step (b) can be measured by any method known in the art, preferably by optical methods.

According to the present invention part or all of the measurements that are done in step (b) could be done with the patient's cooperation.

The axial length is measured by any known in the art technique and corresponding instruments for measuring said length and wherein the anterior chamber length is measured by any known in the art technique and corresponding instruments for measuring said length. 4