CZ280372B6 - Multifocal intraocular lens - Google Patents

Abstract

A multifocal intraocular lens is made up of two or more pairs (1, 2) of segments of a circular sector shape. All segment pairs (1, 2) have an outer surface that is equally curved - spherical or aspherical - with each segment pair (1, 2) having a different refraction and the same frangible segments being opposed to each other. ŕ

Description

Multifocal intraocular lens

Technical field

The invention relates to a multifocal intraocular lens intended to replace an ophthalmic lens in the event of its surgical removal.

BACKGROUND OF THE INVENTION

The simplest intraocular lenses are simple couplings made in different refractions. Their disadvantage is the impossibility of accommodating and hence the necessity to use it for different close distances of the object of several different glasses.

There are known bifocal intraocular lenses in the original dual-zone design, i.e. a lens of typically 20 diopters with a central zone of higher refractive power. Later, aspherical intraocular lenses with continuously variable refraction, 20 diopters on the edge and 25 diopters in the middle were developed.

The lens may not be seated properly in the eye during surgery. Decentration can be up to 1.5 mm and tilt 10 deg, as reported by Atchinson D. A.: Optical design of poly (methyl methacrylate) intraocular lenses. J. Cataract Refract. Surgery, vol. 16, (1990), 178.

With a small iris diameter (strong illumination) of about 2 mm and an imperfect lens fit during surgery, the ratio of image intensities for near and far vision varies greatly due to the rotational symmetry of the lens.

A certain advantage of these lenses is their easy production by pressing.

Disadvantages of dual-zone and aspherical intraocular lenses are eliminated to some extent by refractive-diffractive lens, which is a classic intraocular lens with a circular diffraction grating on the back. A typical such lens is 6 mm in diameter and the diffraction grating has 20 to 40 zones as indicated in the Proceedings of the European Society of Cataract and Refractive Surgery. Paris 1992, and as described by Futhey J. A .: Diffractive bifocal intraocular lens. SPIE Vol. 1052 (1980) 142.

However, the production of these lenses is very expensive.

SUMMARY OF THE INVENTION

To a large extent, the multifocal intraocular lens of the present invention, consisting of at least two pairs of segments of circular sector shape with an equally curved front surface, each has a different refractive power and segments of the same refractive power are opposed.

Depending on the number of segment pairs, the lens may be bifocal, trifocal, possibly multi-focal.

The intraocular lens of the invention is largely independent of the eye and iris diameter.

-1GB 280372 B6

Overview of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic of a bifocal intraocular lens; FIG. 2 is a diagram showing the utilization of its area for various refractions depending on the rotation and decentration of the intraocular lens; and Fig. 4 is a diagram of the utilization of its area for various refractions depending on its rotation and decentration. The diagrams were designed for extreme conditions for intra-ocular lens decentration of 1 mm and iris diameter of 2.5 mm.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

The bifocal intraocular lens in Fig. 1 with a diameter of 6 mm was made of polymethacrylate and consists of two pairs of 1.2 segments. All segments have a front surface curvature equal to r = 7.52 mm. A pair of 1 segments has a planar back surface, a fracture D = 20.75. A pair of 2 segments has a rear surface curved r = - 73.96 mm, brittleness D = 22.86. The peak thickness is 2.5 mm. The difference in the height of adjacent segments on the diameter of 6 mm is 60 μιη.

Example 2

Fig. 3 shows a tripocal intraocular lens consisting of three pairs of 1, 2, and 3 segments. The lens material and diameter are the same as in Example 1. All segments have the same front surface curvature, r = 7.52 mm. A pair of 1 segments has a planar back surface, a refraction D = 20.75, a pair of 2 segments has a back surface curved, r = - 73.96 mm, a refraction D = 22.86, and a pair of 3 segments has a back surface curvature r = - 42, 86, refraction D = 24.4. The peak thickness is 2.5 mm. The difference between neighboring segments to 6 mm diameter is 60 μιη and 100 μπι.

Claims (1)

The intraocular lens of the present invention is intended to replace an ophthalmic lens. PATENTOVÉ Claims Multifocal intraocular lentil, marked u is that it is at least two couples (1, 2) segments a segment of a circular sector, with an identical curved front surface, each pair of segments having a different fracture and segments of the same fracture being opposed.