Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
2001-10-01
2004-08-24
Casler, Brian L. (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
C351S205000, C351S221000, C351S246000
Reexamination Certificate
active
06779891
ABSTRACT:
BACKGROUND OF THE INVENTION
A longitudinal section through the human eye is shown schematically in FIG.
1
. The axial length AL of the human eye is usually measured by a contact ultrasound method. Other measuring methods are described in DE 3201801, U.S. Pat. No. 5673096 and DE 4446183 Al. The curvature of the cornea-cornca radius HHR is determined by means of known keratometers/ophthalmometers (DD 251497, U.S. Pat. Nos. 4,572,628, 4,660,946, 5,212,507, 5,325,134). The measurement of the anterior chamber depth VKT can be carried out by ultrasound or by means of a unit added to a slit lamp (anterior chamber depth gauge, adjustment via the slit lamp image).
These measurements, which are also important for selecting the intraocular lens IOL to be implanted, must be determined particularly before a cataract operation, but also to monitor the progress of schoolchildren's myopia and to detect aniseikonia. In clinical practice, it is common to measure these quantities by means of at least two devices (e.g., ultrasonic a-scan and automatic keratometer). The measured quantities are used in formulas for calculating the optical power of the IOL. Various errors influencing the choice of IOL can occur depending on the type of device used.
OBJECT AND SUMMARY OF THE INVENTION
It is the primary object of the invention to reduce these device-dependent measurement errors to a minimum.
In accordance with the invention, a combination device for non-contacting measurement of axial length and corneal curvature of an eye comprises an interferometer arrangement with adjustable path length difference, a first splitter cube which images the radiation of the interferometer arrangement on the eye, a photo-diode on which partial beams reflected during axial length measurement at the cornea and retina are coupled out via a second splitter cube and a focusing element, a plurality of light sources which are arranged concentric and symmetric to the optical axis of the eye and which illuminate the eye diagonal to the optical axis with a punctiform image for measurement of corneal curvature, and a camera on which the reflections of punctiform images of the light sources occurring at the cornea during measurement of corneal curvature are imaged via the first and the second splitter cubes, wherein a part of the radiation from the interferometer arrangement that is reflected on the cornea and retina is imaged on the camera for purposes of observation.
The invention also encompasses a method for determining the corneal curvature radius and/or the anterior chamber of a human eye.
According to the invention, all necessary parameters of the eye are advantageously determined by means of a device arrangement and corresponding measurement methods.
Necessary adjustments which make it possible to adjust the device to the patient are likewise realized in this arrangement.
The calculation of the IOL is also carried out by means of this device arrangement. Accordingly, there is also no lost or corrupted data in the transmission of measurements from various devices to the computer carrying out the IOL calculation. The invention and its advantages are described in more detail in the following with reference to schematic drawings.
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J Cataract Refract Surg—vol. 25. Nov. 1997 (pp. 1351-1355) “Measuring anterior chamber depth with the Orbscan Topography System” Auffarth, et al.
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Barth Roland
Behrendt Frank
Bergner Roland
Dietzel Burkhard
Doering Axel
Carl Zeiss Jena GmbH
Casler Brian L.
Reed Smith LLP
Sanders John R
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