WO2014086672A1

WO2014086672A1 - Eye implant and method for producing same

Info

Publication number: WO2014086672A1
Application number: PCT/EP2013/075073
Authority: WO
Inventors: Thomas Neuhann; Wolfgang G.K. Müller-Lierheim
Original assignee: Miro Gmbh
Priority date: 2012-12-03
Filing date: 2013-11-29
Publication date: 2014-06-12
Also published as: DE102012023635A1

Abstract

The invention relates to a method for producing an eye implant, in which method a target topography for at least one of the two surfaces of the optical lens area is determined, after which at least one of the two surfaces of a standard lens blank is machined in a manner controlled by the defined target topography, and the topgraphy thereby produced on the at least one lens surface is measured and compared with the target topography.

Description

Eye implant and method for its manufacture

The invention relates to an eye implant with an aberration of the eye correcting optical lens area, and a method for its preparation.

The optical system of the eye primarily involves the cornea (cornea) as the entrance lens, the iris (iris) as the variable diameter ring (pupil) and the lens of the eye. The line of sight of the eye is determined by six muscles. The eye can adapt its imaging system to the brightness of the environment by changing the diameter of the pupil. The lens is attached to a circular muscle via fibers (zonular fibers). The contraction of this circular muscle causes a relaxation of the zonular fibers and thereby a greater curvature of the lens surfaces, with the result that the focal length of the lens is reduced. As a result, images are remotely imaged sharply on the retina at a distance, instead of distant images. This process is called accommodation. The ability of the iris to change the diameter of the pupil and the elasticity and thereby accommodative ability of the lens decrease with age. The current methods of ophthalmology, optometry and ophthalmic optics for the improvement of vision are primarily concerned with the correction of errors in the optical system of the eye. Particular mention should be made here of spectacles, contact lenses, refractive surgical interventions for changing the curvature of the cornea, intraocular contact lenses (ICL) implanted in the anterior chamber of the eye, intraocular lenses implanted after removal of the natural lens, and iris and natural lens or intraocular lens implanted additional lenses.

Spherical, rotationally symmetric lenses and refractive corneal interventions serve to correct the average focal length of the eye. In spherical lenses as well as in the eye, the focal lengths of light rays passing through the center of the lens or optical system differ from those passing through the periphery of the optics. This deviation is called spherical aberration. It can be corrected by aspherical (rotationally ellipsoidal) optical surfaces. In practice, several correction approaches are used in this respect: correction only of the spherical aberration of the lens or the surgically altered cornea, correction of the spherical aberration of the lens used in combination with the known from the literature average spherical aberration of the human eye, as well as individual correction of the System from a specific patient's eye and the used lens or corneal correction.

The human eye is not exactly rotationally symmetric. Significant deviations are termed astigmatism. Toric lenses (cylindrical lenses) or a toric form of corneal change are used to correct astigmatism.

But even aspheric-toric lenses do not consider all the errors of the optical system of the eye. The surfaces of the cornea and lens have asymmetrical irregularities. In addition, the corneal vertex (apex), pupil center, lens vertex, and the point of sharpest vision of the retina (fovea) are usually not on one axis. Rather, the eye orients itself in such a way that the object, which is to be examined exactly, on the Point of the sharpest vision (fovea) is imaged without regard for additional optical errors of the eye. Patent EP 0 954 255 B1 or US Pat. No. 6,215,096 B1 describes a method for calculating optics, by means of which a sharp imaging of images on the retina of the human eye can be achieved.

The actual resolution of the retina is limited to ideal imaging by the diffraction of the light. Two spatially separated points are still distinguishable when the light intensity maximum of the second point in the 1. Diffraction minimum of the first point lies. At 4 mm pupil opening and 600 nm wavelength of light, this corresponds to a distance of about 4 μηη on the retina. The diameter of the receptors at the point of sharpest vision in the retina (fovea) is about 1 to 3 μηη. This means, among other things, that even with ideal imaging of the human eye, a mapped stripe pattern can never lead to moire effects.

The accommodation ability of the eye, ie the ability to vary the focal point by changing the lens curvature, decreases continuously from the birth of the human. In the normal-sighted eye of a 45-year-old, therefore, objects that are less than 40 cm apart are generally no longer sharply imaged on the retina. Remedy either a reading glasses or a multi-strength or progressive lenses or a bifocal contact lens. In the case of multi-intensity, progressive spectacles and bifocal contact lenses, the direction of view determines the focal length of the visual aid. The removal of the clouded eye lens (cataract) with subsequent implantation of an intraocular lens leads to the loss of accommodation ability of the eye. Here come isolated, but with so far little success, so-called accommodating intraocular lenses used. In addition, bi- or multifocal intraocular lenses are implanted in 1 to 2 percent of the cases, the optics of which have diffractive or refractive two or three focal lengths. In these intraocular lenses, the patient always sees sharp and blurred images simultaneously on the retina. Neither near nor far is the total amount of light available. As further measures for improving the optical system of the eye, the use of prismatic lenses in spectacles and contact lenses for correcting errors in the relative direction of both eyes (squint) are known, as well as magnifying vision aids in pathologically reduced image resolution of the retina.

The object of the invention is to provide an eye implant implantable in the eye, which, taking into account the signal processing in the eye following the optical imaging, leads to sharp vision in the distance and nearness.

This object is achieved by the features of claim 1. In claim 7, a method for producing the eye implant according to the invention is given. The subclaims contain developments of the invention.

The eye implant according to the invention can be used as an intraocular lens which replaces the natural eye lens. Further, in addition to the natural eye lens remaining in the eye, the eye implant may be used to correct aberrations. Further, the eye implant may be implanted in addition to an intraocular lens replacing the natural eye lens.

By means of the eye implant according to the invention, aberrations of the eye are corrected to such an extent that the eye has a far point of the image of 0.7 m and a defocusing tolerance of at least approximately ± 1.5 diopters. Compared with expected manufacturing tolerances and deviations from precise positioning in the eye and inoperative and postoperative expected changes in the eye, the eye implant proves to be robust.

When the eye implant according to the invention is created, the signal processing in the neural vision system following the optical imaging on the retina of the eye is taken into account.

The process of seeing is composed a) projecting images of the environment using the optical system of the eye on the retina of the eye; b) converting optical stimuli striking the receptors of the retina into neuronal signals of the ganglion cells (nerve cells) in the retina , c) the transmission of the visual signal from the ganglion cells through the optic nerve (axons of the ganglion cells) and the processing of the neuronal signals in the side bumps of the thalamus, as well as the forwarding of signals to and their further processing in the primary visual cortex of the brain, d ) the transmission of signals to the secondary visual cortex and the cerebrum, and their analysis in the secondary visual cortex and cerebrum.

The retina contains two types of light receptors, namely about 120 million rods and about 6 million cones. The rods are responsible for the detection of faint signals. The cones are responsible for the high spatial resolution of objects and the color recognition. There are three different types of cones, which differ in the wavelength of the light absorption maximum. The highest density of the cones is at the point of sharpest vision of the retina (fovea centralis, visual cavity, depression of about 1, 5 mm diameter in the center of the macula lutea, yellow spot). The highest density of the rods is at the periphery of the fovea centralis.

The total of about 126 million light receptors send their signals to only about 1 million ganglion cells (nerve cells), whose nerve fibers (neuronal fibers, axons) form the optic nerve (optic nerve). Of the 1 million axons, about 10 percent go to the superior colliculus to control eye movement, pupil size and accommodation, and the remaining 90 percent to the lateral cusps of the thalamus (lateral geniculate body, CGL) for visual perception. Nerve cells (neurons) consist of the cell body (Sorna), neuron fibers (axons) with branches and branches (dendrites). Each neuron can receive signals (nerve impulses, neuronal impulses) from many upstream neurons and forward them to many downstream neurons. Neuronal signals are electrical pulses in the range of 100 millivolts based on chemical processes. The neuron discharges ('fires') in an all-or-nothing process. The stimulus amplitude is converted into the frequency and regularity of the nerve impulses. After each pulse, the neuron needs at least 1 to 2 milliseconds recovery break, ie the maximum 'fire rate' is 500 to 800 pulses per second. Even without stimulus, the neurons fire at a low rate (spontaneous rate). The stimulus amplitude is therefore limited by the maximum rate of fire and the spontaneous rate.

The impulse is sent from the cell body of the neuron (Sorna) to the axon. The axon end is located near the dendrites or the cell body of a subsequent neuron, but spatially separated by a gap (synapse). The impulse is transmitted through the release of a chemical substance (neurotransmitter) by the presynaptic neuron. Neurotransmitters attach to the cell membrane of the postsynaptic neuron. Depending on the type of neurotransmitter and postsynaptic cell membrane, the presynaptic impulse may be stimulating (increasing the rate of firing) or inhibiting (reducing the rate of firing) on the postsynaptic neuron. Each neuron usually receives stimulating and inhibitory impulses from several other neurons, which together increase, decrease or leave the own impulse rate in comparison with the spontaneous rate.

In the interaction of neurons is simplified to distinguish between linear circuit, convergence circuit and convergence circuit with lateral (lateral) inhibition. In the linear circuit, there is exactly one synapse between a receptor neu ron and the forwarding neuron, and the signal generated in the receptor neuron is passed only to this one forwarding neuron. All synapses are exciting, which means a linear transmission of the signal without processing. In the convergence circuit, several receptor neurons converge with their axons to the next and secondarily te level, where all synapses are exciting. This leads to an increase in the detection of weak signals, at the same time the spatial resolution of the retina decreases. In the lateral inhibition convergence circuit, the receptor neurons converge at the next higher level of neurons; at the same time, the synapses of lateral neurons on the next higher level are inhibitory. This leads to maximum arousal when the stimulus has a certain spatial extent ('ΟΝ-area') and inhibition at further spatial extent ('OFF-area'). Among other things, the convergence circuit with lateral inhibition is the basis for the "image sharpening" that already begins at the retinal level in relation to the retina. In the retina, the interconnection of the receptors (cones and rods) with the relaying ganglion cells is linear, convergent and convergent with lateral inhibition by the bipolar, horizontal and amacrine cells. The convergence of the rods is responsible for the high photosensitivity, the ganglion cells 'fire' only with simultaneous excitation by several rods. The cones in the fovea centralis are connected linearly with the ganglion cells, which contributes to the higher spatial resolution. The area of the retina to which a single higher-level neuron responds is referred to as the receptive field of that neuron.

The optical imaging quality of the average human eye is relatively poor. The surfaces of the cornea and lens have asymmetrical irregularities. In addition, the corneal vertex (apex), pupil center, lens vertex and the point of sharpest vision of the retina (fovea centralis) are usually not on one axis. Nevertheless, the eye orients itself so that the subject to be closely observed is imaged at the point of sharpest vision (fovea) without regard for any additional optical aberrations of the eye. That the eye nevertheless perceives sharp images, owes it to its ability to 'image sharpening', which already begins in the retina.

A sharp point of the environment is imaged by the imaging function of the eye on the retina as a light intensity distribution across a plurality of receptors. Only the neural image sharpening leads to the perception of a sharp point. Even in old age, the human eye still has an accommodation of about 0.75 dioptres. Since the natural eye lens is not accommodated at this age, this 'rest accommodation' is presumably due to a defocusing tolerance due to the above-described neuronal image sharpening ability of the eye. Taking advantage of this new finding, the defocusing tolerance of the eye implant according to the invention is increased to about ± 1.5 diopters by improving the optical imaging quality, and the optical lens area of the eye implant is adjusted so that the eye is at an image distance (far point) of about 0.7 m without Accommodation of the optical lens area is corrected. When the eye is set to a far point at a distance of 0.7 m, images are most sharply imaged on the retina when the eye is located at a distance. By increasing the optical imaging quality of the optical lens area to about ± 1.5 diopters, full visual acuity is achieved in the distance and near without accommodating the lens.

A complete correction of the aberrations of the eye is neither necessary nor desirable because for the vision in the dark, the simultaneous excitation of several rods is required for color vision, the signals of three complementary cones must be present on a ganglion simultaneously, operation-related corneal changes are to be expected and Eye as a living organism is subject to constant minor changes. Furthermore, in the implantation of lenses, manufacturing tolerances as well as slight rotation, decentration, tilting and displacement of the lens along the optical axis of the eye must be assumed.

Before implantation, the eye is measured biometrically (topography of anterior and posterior surface of the cornea, axial length of the eyeball and phakic intraocular lenses and intraocular contact lens position, and topography of the anterior and posterior surfaces of the lens) and from these measurements in combination with the planned position of the lens in the eye and the refractive index of the lens material, the surface topography is calculated as a target topography of the lens to be implanted in the eye. In order to determine the properties of the refractive components of the eye, it is preferable to examine the anterior segment of the eye. For this purpose, for example, a pseudo-poppy camera with which contactless sectional images of the anterior chamber of the eye can be taken. These images allow analysis of the entire cornea, anterior chamber and the natural lens. Geometric data such as central radii, corneal aspiration, various curvatures of the cornea, the angle of the chamber, the chamber volume as well as the chamber height of the anterior chamber and also lens opacities can be analyzed. For example, EP 1074214 B1 discloses such a search of the anterior eye section.

From the analysis data, advantageously, the future location of the intraocular lens to be implanted can also be accurately predicted.

From these data obtained in the analysis, as well as the known refractive indices, in particular of the cornea and the ocular aqueous humor, a target topography on one of the two lens surfaces or for both lens surfaces is calculated for the intraocular lens. It also takes into account the lens material to be used for the intraocular lens. These may be commercially available polymers, such as MMA / HEMA copolymers. A suitable lens material is also known, for example, from WO 2007/062864.

However, the lens can be made of any implantable optical grade material.

The manufacture of the optic of the eye implant; In particular, the individual, implantable lens is carried out using standard methods, one of the optical surfaces having a standard geometry (spherical, aspherical or toric) and can be produced by turning, casting or injection-compression molding. The second optical surface is preferably produced with a suitable for the production of freeform surfaces, programmable lathe, wherein lathes is given preference, in which a subsequent polishing of the surface can be omitted. From the target topography machine data are calculated, which are suitable for controlling a mechanically machining the surface of a standard lens blank. Depending on these machine data, the machining takes place on the surface of the standard lens blank, for example in a suitable turning or milling machine. Preferably, a turning and / or milling machine is used, with which the processing of the lens surface is carried out with such precision that a subsequent polishing is not required. Preferably, a diamond tool is used in the lathe. The standard lens blank from which the individual intraocular lens is made by mechanical machining is preferably a lens blank made by injection-compression molding. In this way, one obtains a lens blank with exactly predetermined dimensions on the lens surfaces, from which, starting the desired topography is generated by the mechanical machining.

When injection-compression molding, it is also possible to mold the feel, which serves to fix the intraocular lens in the eye, to the lens body.

The quality control of the topography of the optics designed as open spaces preferably takes place by analysis of the measured, in particular the reflected wavefront, wherein the desired surface is selected as a mathematical reference and deviations of the topography are calculated from the expected wavefront by analyzing the measured wavefront. The wavefront measurement is preferably performed at a wavelength at which the unreflected light is absorbed by the lens material to minimize the interference of the reflected wavefront of the front surface of the optic with reflections from the back surface of the optic.

The measurement of the topography of the lens surface can take place, for example, with the aid of a wavefront sensor which is designed as a Shack-Hartmann sensor. The Shack-Hartmann sensor contains an arrangement of microlenses in the focal plane of which a spatially resolving light sensor, which can be designed, for example, as a CCD sensor, is arranged. The measured topography causes wavefronts, which cause a deflection of the foci of the microlens Senanordnung on the spatially resolving light sensor. From this, measurement results for the topography produced on the lens surface can be obtained.

The measurement using the Shack-Hartmann sensor can be measured in the transmitted light method in which the light used in the measurement is irradiated through the optical lens area. However, it is also preferable to use a reflective measuring method in which light reflected on the lens surface is detected by the Shack-Hartmann sensor. These measuring methods are known, for example, from DE 20 2008 004 608 A1 for detecting lens flaws.

A topography sensor which scans the surface of the optical lens area and which is designed as a distance sensor or angle sensor can also be used for the topography measurement on the lens surface. Such a topography sensor is known, for example, from WO 2009/124767.

The measured topography of the optical lens area is compared with the target topography. For this, the measurement results are converted to the format of the target topography. However, it is also possible to adapt the target topography to the format of the measured topography for the comparison.

On the implant surface, the desired topography can be produced on one of the two surfaces. However, it is also possible to produce on both lens surfaces (front and back of the eye implant) respective topographies which are individually designed to correct the ametropia resulting from the ocular components.

In the attached FIG. 1, the various steps for producing the ocular implant, in particular an intraocular lens, in a flow diagram are shown for one exemplary embodiment.

Claims

claims

1 . Eye implant with an aberration of the eye correcting optical lens area, characterized in that the optical lens area for the adjustment of the eye is formed to a far point at a distance of about 0.7 m with a defocusing tolerance of at least ± 1.5 diopters.

2. Eye implant according to claim 1, characterized in that the remote point adjustment is determined from the biometrically measured data of lying before the eye retina optically effective eye components.

The ophthalmic implant of claim 1 or 2, characterized in that the optical lens portion has a front surface facing the corneal anterior surface and an anterior surface facing the crystalline lens, the topography of the anterior surface and / or the posterior surface being adapted for aberration correction.

4. Eye implant according to one of claims 1 to 3, characterized in that at least one surface of the optical lens area is machined mechanically.

5. Eye implant according to one of claims 1 to 4, characterized in that the implant surface is unpolished.

6. Eye implant according to one of claims 1 to 5, characterized by its design as an intraocular lens or as an implantable auxiliary lens in addition to an intraocular lens or in addition to the natural eye lens.

7. A method for producing an eye implant according to one of claims 1 to 6, characterized in that after determining a target topography for at least one of the two surfaces of the optical lens area controlled by the specific target topography at least one of both surfaces of a standard lens blank is machined and that the topography thus produced is measured on the at least one lens surface and compared with the target topography.

8. The method according to claim 7, characterized in that the standard lens blank is produced by injection compression molding.

9. The method according to claim 7 or 8, characterized in that the optical data of at least one of the following eye components: cornea, anterior chamber, natural lens, position of the natural lens relative to the cornea, axis length of the eyeball for the determination of the target topography are measured biometrically.

10. The method according to any one of claims 7 to 9, characterized in that geometric data and / or refractive indices of the eye components are used for the determination of the target topography.

1 1. Method according to one of claims 7 to 10, characterized in that from the determined data of the eye, the seat of the intraocular lens to be implanted in the eye is determined.

12. The method according to any one of claims 7 to 1 1, characterized in that the measured data of the topography produced by mechanical machining on the lens surface and the data of the target topography for the comparison are converted into a uniform format.