JPH0472548B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an artificial crystalline lens and a method for manufacturing the same. More specifically, the present invention relates to an artificial crystalline lens for intraocular implantation used in aphakic eyes and a method for manufacturing the same. [Prior art] No matter what surgical method is used for cataract surgery,
There is no difference in that it is impossible to avoid becoming aphakic after surgery. A strong convex lens is required to correct the vision of aphakic eyes, that is, severe hyperopia due to the lack of a crystalline lens. However, even if good visual acuity is obtained when wearing glasses with strong convex lenses, image enlargement, field of view limitations, distortion due to aberrations and prism effects, and misperception of localization caused by these factors occur, which can occur in everyday life. It becomes a major hindrance to running a smooth life. Furthermore, in cases of monocular cataract, it is impossible to use glasses as a means of visual acuity recovery after surgery due to severe anisometropia. Contact lenses largely eliminate these optical deficiencies of eyeglasses and do not limit the field of vision. Additionally, contact lenses may allow binocular vision when used in a monocular aphakic eye, although they do not completely eliminate the aphakia. Therefore, contact lenses can be said to be a useful means for correcting aphakic eyes. However, contact lenses are cumbersome to put on and take off,
It cannot be used in all cases due to the difficulty of handling or the complexity of maintenance and management. Further, although high water content soft contact lenses are comfortable to wear, there are currently none that have sufficient resistance to withstand long-term use, and there is also a risk of corneal infection. Many people, including Links, have pointed out the difficulties in rehabilitation associated with wearing glasses or contact lenses. In particular, in the case of monocular cataracts, no matter how well the surgery is performed, if visual function cannot be restored, or in other words, binocular vision cannot be achieved, the practical value of the surgery is nil. Artificial lens implant or intraocular lens implant
implant) is a method of inserting an artificial crystalline lens into an aphakic eye after cataract surgery to artificially create a pseudophakic eye (pseudophakia) with functions similar to a phakic eye. The purpose is to solve the above problems. On November 29, 1949, at St. Thomas Hospital in London, Harold Ridley inserted a small lens made of polymethyl methacrylate (PMMA) into the pupillary area after extracapsular cataract removal surgery. The device was inserted between the back of the iris and the posterior capsule of the crystalline lens, successfully restoring vision. This report triggered the introduction of artificial lens insertion, which attracted attention as a new surgical treatment for aphakic eyes, and became the beginning of bringing light to cataract treatment, especially its rehabilitation. However, the so-called Ridley lens used by Harold Ridley had a diameter of 8.35 mm.
At 2.4 mm thick and weighing 110 to 165 mg (in air), it is significantly larger and 5 to 8 times heavier than current lenses, and there are no successful cases of Ridley lens implantation because it does not have a supporting part. On the other hand, it is said that there were also quite a few complications. By the way, the material for forming the artificial crystalline lens must have both biocompatibility and medical functionality as defined in medical polymer science, and must have at least the following properties. 1. Physical or chemical properties do not change even if kept in the eye for a long period of time. 2. Does not cause harmful reactions to ocular tissue, does not cause allergic or hypersensitivity reactions, and is not carcinogenic. 3. Optical properties are maintained. 4. Can be processed reproducibly. 5. Can be sterilized and does not cause any change. 6. Will not be destroyed by the slightest external force. 7. Is a transparent body with a refractive index of 1.336 or higher. Conventionally, glass, polymethyl methacrylate, and polyhydroxyethyl methacrylate have been used as materials for holding the lens, and artificial crystalline lenses made of polymethyl methacrylate are currently the most popular. [Problems to be Solved by the Invention] However, all of the artificial crystalline lenses currently in use do not have a refractive index distribution, regardless of the material. When such an artificial lens is worn, phenomena such as large aberrations and a narrow field of vision occur. Therefore, currently used artificial crystalline lenses do not allow their wearers to see to the same degree as normal humans. Therefore, it is an object of the present invention to provide an artificial crystalline lens. Another object of the present invention is to provide an artificial crystalline lens having a refractive index distribution. Still another object of the present invention is to provide an artificial crystalline lens that has small aberrations and provides a wide field of view. Still another object of the present invention is to provide an artificial crystalline lens whose refractive index changes continuously from the center to the periphery, similar to the actual human crystalline lens. Further objects and advantages of the present invention will become apparent from the description below. [Means and effects for solving the problems] According to the present invention, these objects and advantages of the present invention are achieved from the center to the periphery in both the optical axis direction and the direction perpendicular to the optical axis. This is achieved by an artificial crystalline lens characterized by a continuous or stepwise change in refractive index. Further, according to the present invention, the artificial crystalline lens of the present invention is provided by encapsulating in a mold a mixture of at least two types of monomers that provide polymers with different refractive indexes and different reactivities, and is exposed to actinic light while being rotated along both one axis and the other axis perpendicular to said axis, thus polymerizing the monomer mixture within the mold and aligning the monomer mixture in the direction of the optical axis and along the optical axis. In any direction perpendicular to
It can be produced by a first method characterized by producing a polymer mass whose refractive index continuously changes from the center toward the periphery. At least two types of monomers used in the first method need to have different reactivities. For example, when two types of monomers M ₁ and M ₂ are copolymerized, 2
Although there are two reactivity ratios r ₁ and r ₂ , it is necessary to use M ₁ and M ₂ where r ₁ and r ₂ are not equal. r ₁ is the reaction rate constant (k ₁₁ ) of the reaction in which M ₁ reacts with the active end derived from M ₁ versus the reaction rate constant (k ₁₂ ) of the reaction in which M ₂ reacts with the same active end. It is a ratio.
r ₂ is the ratio of the reaction rate constant (k ₂₂ ) of the reaction in which M ₂ reacts with the active end derived from M ₂ to the reaction rate constant (k ₂₁ ) of the reaction in which M ₁ reacts with the same active end. be. Therefore, for example, M ₁ with r ₁ >1, r ₂ <1,
In the case of M ₂ , since M ₁ is easier to polymerize than M ₂ ,
Assuming that the refractive index of the polymer is larger for the M ₂ polymer than for the M ₁ polymer, polymerization will progress from the periphery to the center and the refractive index will increase from the periphery to the center. A polymer mass is obtained in which the Preferred monomers that can be used in the first method include, for example,

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[Formula] CH ₂ = CH-CH ₂ -X;

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[Formula] (However, in the above formula, R is -CnH ₂ n+1 (n-1 to 10) or -C ₆ H ₁₁ or a fluorine-containing aliphatic group; X is

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〔Example〕

Hereinafter, the present invention will be explained in further detail with reference to Examples. Example 1 40 parts by weight of methyl methacrylate (MMA), 10 parts by weight of vinyl benzoate (VB) and 0.25 parts by weight of benzoyl peroxide (BPO) were thoroughly mixed.
Enclosed in a glass mold as shown in the figure, 56
℃ for 6 hours and then heat treated at 40℃ for about 1 day. The obtained polymer mass (lens) has a diameter of approximately 10 mm.
It was approximately 5 mm thick. The refractive index distribution of this material is shown in FIG. Figure 3a shows the refractive index distribution from the center to the periphery in the horizontal direction of the lens, and Figure 3b shows the refractive index distribution from the center to the periphery in the vertical direction of the lens. There is. The horizontal axis in FIG. 3 is the square of the generalized radius, r is the distance from the center (mm), and Rp is the distance from the center to the periphery (mm). FIG. 4 shows the refractive index distribution of the human crystalline lens. Figure 4 a shows the refractive index distribution in the thickness direction of the crystalline lens (direction from the front to the back of the body).
b in Figure 4 is the radial direction of the crystalline lens (left and right direction of the body)
shows the refractive index distribution. It can be seen that the lens having the refractive index distribution shown in FIG. 3 obtained in Example 1 has a refractive index distribution very similar to the refractive index distribution of the human crystalline lens shown in FIG. 4. Example 2 The same monomer mixture 4 used in Example 1 was sealed in a mold 1, and the mold 1 was rotated around the rotating shaft 2 with respect to the ring frame 5 as shown in FIG. The ring frame 5 was rotated around the rotating shaft 3, and the monomer mixture 4 was irradiated with ultraviolet rays for 8 hours at room temperature. These conditions were such that about 70% by weight of the monomer mixture was polymerized. The resulting mass obtained by the above ultraviolet irradiation was then treated at 70° C. for 20 hours to obtain a polymer mass having a refractive index distribution almost similar to that shown in FIGS. 3a and 3b. Example 3 10 parts by weight of diethylene glycol bisallyl carbonate (CR-39) and 0.1 parts by weight of benzoyl peroxide
Thoroughly mix the parts by weight, enclose it in the formwork, and
A polymer gel was produced by heating at ℃ for 160 minutes. This polymer gel was taken out by breaking the mold and kept at room temperature for 2 hours.
It was immersed in 2,2,2-trifluoromethyl methacrylate (3FMA) for an hour and then heat treated at 90°C for 20 hours. The obtained polymer mass (lens) exhibited a refractive index distribution as shown in FIG. Example 4 The same monomer mixture used in Example 3 was sealed in a mold and irradiated with ultraviolet rays for 5 hours at room temperature in the same manner as in Example 2. These conditions were such that about 25% by weight of the monomer mixture was polymerized. The polymer gel was then taken out in the same manner as in Example 3, immersed in 3FMA for 2 hours at room temperature, and then heat treated at 90°C for 20 hours. A polymer mass having a refractive index distribution almost the same as that of the polymer mass obtained in Example 3 was obtained. Example 5 10 parts by weight of β-methacrylate (BMMA) and 0.02 parts by weight of benzoyl peroxide were thoroughly mixed, sealed in a mold, and heated at 50°C for 100 minutes to produce a polymer gel. . This polymer gel was removed and soaked in 3FMA for 2 hours at room temperature, then 90
Heat treated at ℃ for 20 hours. A good polymer mass (lens) was obtained. [Effects of the Invention] The artificial crystalline lens of the present invention has a refractive index distribution, has small aberrations, and provides a wide field of view.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a mold for manufacturing the artificial crystalline lens of the present invention. In FIG. 1, a is a side sectional view, and b is a plan view. FIG. 2 is a schematic diagram of a device for simultaneously rotating the formwork of FIG. 1 in two orthogonal directions. FIG. 3 and FIG. 5 both show refractive index distributions of one embodiment of the artificial crystalline lens of the present invention. 3 a and 5 a are the refractive index distributions from the center to the periphery in the horizontal direction of the lens, and 3 b and 5 b are the refractive index distributions from the center to the periphery in the vertical direction of the lens. This is the refractive index distribution toward . FIG. 4 shows the refractive index distribution of the human crystalline lens. A in FIG. 4 is the refractive index distribution in the thickness direction of the crystalline lens, and b in FIG. 4 is the refractive index distribution in the radial direction of the crystalline lens. FIG. 6 is a schematic diagram of an embodiment of the artificial crystalline lens of the present invention having a support portion.

Claims (1)

[Claims] 1. An artificial body characterized by a refractive index that changes continuously or stepwise from the center toward the periphery in both the optical axis direction and the direction perpendicular to the optical axis. crystalline lens. 2. The artificial crystalline lens according to claim 1, wherein the refractive index continuously changes from the center toward the periphery in any of the above directions. 3. The artificial crystalline lens according to claim 1 or 2, wherein the refractive index of the central portion is larger than the refractive index of the peripheral portion. 4 A mixture of at least two types of monomers giving polymers with different refractive indexes and different reactivities is enclosed in a mold, and the mold is rotated both on one axis and on the other axis perpendicular to the axis. The monomer mixture is exposed to actinic light while being rotated along the axis of the frame, thus polymerizing the monomer mixture within the mold and causing the monomer mixture to polymerize in the direction of the optical axis and in the direction perpendicular to the optical axis, from the center to the periphery. A method for producing an artificial crystalline lens, characterized by producing a polymer mass having a continuously changing refractive index. 5 A polyfunctional monomer that provides a relatively high refractive index polymer is encapsulated in a mold, and the mold is rotated along both one axis and another axis perpendicular to the axis. The polyfunctional monomer is partially polymerized within the mold to form a gel-like prepolymer, and the gel-like prepolymer is removed from the mold. By diffusing a monomer that gives a polymer with a relatively low refractive index,
Next, the obtained diffuser is polymerized to produce a polymer mass whose refractive index continuously changes from the center toward the periphery in both the optical axis direction and the direction perpendicular to the optical axis. Characteristic manufacturing method for artificial crystalline lenses. 6. A polyfunctional monomer that provides a polymer with a relatively high refractive index and has two or more types of functional groups is encapsulated in a mold, and the mold is rotated in one axis and in another direction perpendicular to the axis. The polyfunctional monomer is partially polymerized within the mold, thereby forming a gel in which at least one functional group remains. A prepolymer in the form of a gel is produced, a compound reactive with the functional groups remaining in the gel-like prepolymer taken out from the mold is diffused, and the resulting diffuser is then reacted in the direction of the optical axis and the optical axis. A method for producing an artificial crystalline lens, characterized by producing a polymer mass whose refractive index continuously changes from the center toward the periphery in any direction perpendicular to the center.