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Ophthalmic analysis system for measuring the intraocular pressure in the eyeRelated Patent Categories: Surgery, Diagnostic Testing, Testing Aqueous Humor Pressure Or Related Condition, Measuring Force Required To Produce Standard Or Measured Eye Flattening (applanation)Ophthalmic analysis system for measuring the intraocular pressure in the eye description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060241367, Ophthalmic analysis system for measuring the intraocular pressure in the eye. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD [0001] The invention relates to an ophthalmic analysis system for measuring the intraocular pressure in the eye (eye internal pressure) according to the preamble of claim 1. BACKGROUND [0002] Serious health impairments can be triggered by an elevated intraocular pressure. In particular, the optic nerve can be damaged by the elevated intraocular pressure which causes so-called glaucoma with restrictions of the visual field. [0003] Three basic principles are known for checking the intraocular pressure, namely impression tonometry, applanation tonometry and noncontact tonometry. The impression tonometer measures the depth of the indentability of the cornea caused by a metal stamp loaded with a known weight. For the same weight the indentability is inversely proportional to the intraocular pressure, that is the indentability is greater, the lower is the intraocular pressure and conversely. A disadvantage with impression tonometry is that the placement of the tonometer and the impression of the metal stamp additionally increase the intraocular pressure so that the measured pressure does not correspond exactly to the actual intraocular pressure. Furthermore, the placement of the stamp on the cornea of the patient's eye is relatively stressful for the patients. [0004] Furthermore, so-called applanation tonometers are also known for measuring the intraocular pressure, its measurement being based on application of the applanation principle. The applanation principle starts from Ingbert's law which states that the pressure in a spherical container filled with liquid corresponds to the counterpressure which flattens a certain surface of this sphere. The intraocular pressure can be measured on the basis of this law in two different ways. According to a first alternative, a tonometer with constant weight can be used and the flattened surface can be measured. According to an alternative method of measurement, the force required to flatten a known surface of constant size is used. A Perkins applanation tonometer is known, which consists of a plastic cylinder whose lower planar end is provided with a gradation. A magnifying glass is located at the upper end. After instilling a fluorescent liquid into the conjunctival sac, the diameter of the applanated corneal surface can be determined by optical reading off on the gradation scale. In this case, the intraocular pressure is determined by means of a constant force. [0005] In addition, an applanation tonometer operating on the principle of an applanated surface of constant size is known. In this case, the cornea is flattened using the quadrilateral base of a glass prism. The intraocular pressure is measured by intensifying the pressure of the prism on the eye until the flattened circular region of the cornea is at the same level as the four sides of the prism base. A disadvantage with applanation tonometers again is that as a result of the deformation of the cornea by means of an actuating element, considerable stress is produced for the patients. [0006] So-called noncontact tonometers were developed to avoid this stressing produced by contact with a deforming tool. In these noncontact tonometers actuating devices are provided for deforming the cornea with which the cornea is deformed free from contact. For this purpose, a puff of compressed air is produced for example and directed onto the cornea. In known noncontact tonometers air puffs are directed onto the eye in the direction of the optic axis whereby the cornea is increasingly flattened and finally indented. To measure the deformation of the cornea, an obliquely incident bundle of parallel light rays is directed onto the cornea and the light reflected by the cornea is measured as a measurement signal. For this purpose, the reflected light can be intercepted by a light sensor, for example, where the light intensity measured by the light sensor varies as a function of the applanation of the cornea caused by the air flow. [0007] A disadvantage in all known methods of measurement is that when measuring the intraocular pressure, the counterpressure caused by the elastic deformation of the cornea is not taken into account. This is because the cornea itself is stretched over the vitreous body in the fashion of an elastic membrane so that during the measurement of the intraocular pressure a certain amount of force is required for its deformation which is included in the measurement results in a falsifying manner. This falsification is of a different magnitude in different patients since the properties of the cornea, especially its thickness and elasticity, vary within certain limits. SUMMARY [0008] Starting from this prior art, it is thus the object of the present invention to propose a new ophthalmic analysis system for measuring the intraocular pressure which avoids the disadvantages of the previously known prior art. [0009] This object is solved by an analysis system according to the teaching of claim 1. [0010] Advantageous embodiments of the invention are the subject matter of the dependent claims. [0011] The analysis system according to the invention is based on the basic idea of recording split images of the cornea before and/or during and/or after the deformation of the cornea, which show the state of the cornea in a plane of intersection. These split images are analyzed in the analysis device by means of suitable image processing methods and provide additional information on the state of the cornea which can be taken into account when deducing the intraocular pressure. [0012] The thickness of the cornea has a major influence on the measured values and thus on the result of measurement of the intraocular pressure since the cornea as an elastically deformable membrane opposes the deformation force applied by the actuating device with a counterforce which does not depend on the intraocular pressure itself and can therefore falsify the measurement of the intraocular pressure. It is thus particularly advantageous if the thickness of the cornea is deduced from split images of the cornea. Taking into account the known elasticity characteristics of the cornea, the counterforce applied by the cornea during the elastic deformation can be estimated from the thickness of the cornea and taken into account as an influential factor when deducing the intraocular pressure. [0013] Alternatively or additionally to determining the thickness of the cornea as an influential factor, the curvature of the cornea can also be derived from the split images of the cornea. The curvature of the cornea also influences the measurement results and should thus be taken into account when deducing the intraocular pressure. [0014] In addition, it is also possible to determine the light scattering of the cornea from the split images of the cornea. The light scattering of the cornea has a specific relationship to the elasticity characteristic of the cornea so that the elasticity of the cornea can be deduced from the light scattering. [0015] It is fundamentally arbitrary which method of measurement is used to measure the intraocular pressure itself and for the derivation in the analysis system. For example, the known reflected light methods can be used for this purpose, where the split images recorded according to the invention are then used, for example, merely to correct for the influence produced by the elastic deformation of the cornea. However, it is especially advantageous if the intraocular pressure is also deduced from the split image recordings of the deformed cornea. These split image recordings represent the deformation of the cornea caused by the actuating device extraordinarily exactly and thus contain the image information required to deduce the intraocular pressure. For example, during the deformation of the cornea a plurality of split images can be recorded successively as a series of images so that the split image with the greatest deformation of the cornea can then be extracted in the following image analysis. The intraocular pressure can then simply be derived from this image of the cornea with the greatest deformation taking into account the thickness of the cornea. [0016] The equipment used to obtain the split image recordings of the cornea is fundamentally arbitrary. It is especially disadvantageous if the observation system comprises a slit projector which can project a light slit onto the cornea. Slit projectors of this type are known from ophthalmology. The necessary illumination principle of the slit projector is based on the fact that the refractive media of the ocular anterior chamber are not transparent but significant scattering takes place at said media, especially in the short-wavelength fraction of the visible light. This has the result that a focused light beam, that is in the present case the projected light slit which is passed through the optical media of the eye, makes the ocular structures and in particular the cornea visible as a split image when viewed laterally since the light is scattered at different intensities on passage through the different materials, especially on passage through the cornea. The slit-shaped light beam thereby produces an image plane which runs through the ocular body in cross section so that the split images to be recorded using the observation system lie specifically in this image plane defined by the light slit. [0017] In order to be able to record the split images illuminated by the light slit, the observation system should comprise a recording device which is arranged so that the image plane illuminated by the slit projector can be recorded at least partly. [0018] In order to enhance the image quality, at least one objective, that is a lens arrangement can be arranged between cornea and recording device. Using this lens arrangement the image plane of the cornea illuminated by the slit projector is imaged on a recording plane in the recording device. [0019] In order to achieve a large depth of focus in the split images, the arrangement of the image plane in the cornea illuminated by the slit projector, the principal plane of the lens system between the cornea and the recording device (objective plane) and the recording plane of the recording device should satisfy the Scheimpflug condition. This rule developed from the photographs of Scheimpflug prescribes that the image plane, the objective plane and the recording plane are arranged at angles such that they intersect in a common axis. By tilting the recording plane relative to the object plane, the image plane can be brought into an arbitrary spatial position wherein image points are detected in the depth of focus which cannot otherwise be sharply imaged at the same time when the image plane is perpendicular. [0020] For contact-free deformation of the cornea it is particularly advantageous if a flow pulse of a gaseous medium, especially air, can be applied to the surface of the cornea using the actuating device. The stressing of the patients through such an air jet is relatively very small and is not perceived as very stressful because of its shortness. [0021] The actuating device can be constructed by providing a pressure chamber with a nozzle orifice directed onto the eye to be examined. As a result of a short-term increase in the pressure in the pressure chamber, the gas located in the pressure chamber flows out through the nozzle orifice and in this way forms the desired flow pulse on the surface of the eye. The increase in the pressure in the pressure chamber can be achieved for example, by moving a mechanically driven stamp in a cylindrical opening of the pressure chamber. Continue reading about Ophthalmic analysis system for measuring the intraocular pressure in the eye... Full patent description for Ophthalmic analysis system for measuring the intraocular pressure in the eye Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Ophthalmic analysis system for measuring the intraocular pressure in the eye patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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