DD265553A1 - ARRANGEMENT FOR DETECTING THE HORN SKIN TOPOLOGY OF THE EYE - Google Patents

Abstract

Rapid and accurate detection of the corneal topology is accomplished by providing a plurality of point source light sources in a defined geometric arrangement, the beam paths of which are directed to the cornea and intersect at a point within the eye, the reflection image of the light sources on the corneal surface an imaging system is transferred to a raster-shaped arrangement of photoreceptors which is connected to a transmitter. Applicable to the eye examination.

Description

Field of application of the invention

The invention relates to a detection system for describing the cornea of required parameters in order to create corneal models by means of which the geometry of the cornea can be assessed.

Characteristic of the known technical solutions

It is already known to project one or more test patterns on the cornea and to assess the change in the reflex image.

In keratometric methods, the test objects are illuminated ring structures. The virtual image resulting from reflection on the cornea is photographically registered or received by photodetector arrangements. The information to be gained by the methods relating to the structure of the cornea is also limited to the detection of a subdomain defined by the ring. Complete detection of the corneal surface and the generation of an adequate Mo ^ pIIs are not possible, as is of particular importance in individual contact lens fitting and postoperative assessment of the corneal surface.

Object of the invention The aim of the invention is to realize a fast and accurate detection of the entire corneal topology. Explanation of the WtMm of the invention

The object of the invention is an optical arrangement which provides sufficient data in a very short time to produce a model sufficient for characterizing the corneal surface. The object is achieved in that a plurality of point-shaped light sources ir. A defined geometric arrangement are provided, the beam paths are directed to the cornea and intersect at a point in the interior of the eye, wherein the reflection image of the light sources on the Ho'nhautOiXjrfläche over an imaging system is transmitted to a raster-shaped arrangement of photoreceptors, which is connected to a Aueverteelektronik, it being particularly advantageous that the grid-shaped arrangement is a CCD matrix that the geometric arrangement of the light sources corresponds to a spherical surface on which the light sources evenly are distributed and the transmitter is connected to a monitor for displaying a model of the detected corneal topology.

The invention enables the acquisition of measurement data in the IR range, wherein the patient is not burdened by reflected on dio pupil light marks. An on-lino evaluation of the measured data can be carried out With the aid of a mathematical model, the corneal surface can be approximately described and a type classification into spherical surfaces, aspherically rotationally symmetrical surfaces, cylindrical or other surfaces where ^r o 'r .. For the freely named types the necessary quantitative parameters are determined at the same time.Thus, a computer-aided design and adjustment of contact lenses as well as a diagnostic evaluation of normal and abnormal corneal geometries are made possible.Time-consuming adjustments of contact lenses on the basis of previous techniques are significantly shortened by the possibility of typing and The possibilities for custom-made products are also improved.

Ausführungsbelsplel The invention is explained below with reference to schematic drawings.

FIG. 1 shows the structure of an arrangement according to the invention, FIG. 2, in a schematized beam path

On a spherical hemisphere is a finite number of IR transmitters 2, S ₁ ... S ₁ , which operates modulated in the pulse mode

be and have a fixed angle 12 to each other, arranged rotationally symmetrical.

The virtual image of the transmitter structures reflected by the cornea 1 of the patient's eye is transmitted through objectives 3, 4, aperture S

and splitter cubes β imaged onto a CCD receiver matrix. The image is done with a fixed magnification.

The IR transmitter reflexes, which are modulated radiated, thereby generate adequate, modulated and on the receiver matrix

evaluated reception reflexes. Each position-oriented IR transmitter 2 on the spherical hemisphere can be a position-oriented

Receiver pulse to be assigned to the matrix 7. The electronic evaluation of the received coded transmission pulses takes place via an electronic signal word 8

with another evaluation unit 9.

The basis for the evaluation and linking of the measured data is a mathematical model described below. By means of fixed alignment marks 11 is achieved that the Augenachso the patient only by fixed angular amounts

can deviate both vertically and horizontally from the lens axis.

The adjustment of the measuring arrangement via a Kreuztischverstellung 13 in three coordinates, up on the situation dor Measuring marks a centering of the system is reached. The observation of the patient's pupil takes place by the operator 10. Based on the presentation in Fiji. 2, the mathematical relationships which are used to determine the Underlying corneal model. Between the sizes s and h (coordinates of a point B of the corneal anterior surface with respect to the corneal axis A in FIG

the optical axis of the system) and the quantities η (distance ÖÄ - 5P) and y (distance of the transmitter from the optical axis) has the following relationship:

where h is obtained from y "(distance of the image product s" from the optical axis, starting from the image axes of the telezontric recording system.) By means of the relation (1), the coordinates for a profile curve can be approximated by iteration as follows:

For Si = s (hi) (i number of the transmitter or reflex point s' or pixel s "on a fixed meridian) one obtains starting

from the known sizes

y ₀ »0, h - 0, S ₀ « 0, y _{i (} h |, ni (i - 1 ... n)

2. .11 / 2

/ U.S.

If the discrete values s / "S ¹ Ih ₁ ) O-1... Η) of the point on dom meridian j -1 ... 8 are calculated from the measured data si" and the device parameters according to the iteration (2), as shown below, determines an approximation formula for the anterior surface of the cornea, from which the desired parameters of the cornea, the typing, the graph in sectional images, the comparison with base curves of contact lenses from a present assortment or earlier profiles of the same cornea (for therapeutic purposes) can be derived.

Procedure:

Construction of Prolil Curves s' = S ¹ Ih) al & cubic balancing splines Test for rotatlonity trio

no Yes

Construction of handled construction of approximate formula

Cut lines for the anterior surface of the cornea

Approximate area (sections as two-dimensional, parabolic

perpendicular to the optical axis) Intel polarization spline function

Determination of the desired

geometric parameters of

Cornna

typing

Specification of cleats

Comparison with other base curves

The representation of the surface model determined from the measured values takes place on a monitor

Claims (5)

1. An arrangement for detecting the corneal topology of the eye, characterized in that a plurality of point-shaped light sources are provided in a defined geometric arrangement, the beam paths are directed to the cornea and intersect at a point inside the eye, wherein the reflection image of the light sources the corneal surface is transmitted via an imaging system on a grid-like arrangement of photoreceptors, which is connected to a transmitter. 2. Arrangement according to claim 1, characterized in that the grid-shaped arrangement is a CCD matrix. 3. Arrangement according to claim 1 or 2, characterized in that the geometric arrangement dor light sources corresponds to a spherical surface on which the light sources are evenly distributed. 4. Arrangement according to one of claims 1-3, characterized in that the transmitter is connected to a monitor for displaying a model of the determined corneal topology. 5. Arrangement according to one of claims 1-4, characterized in that the light sources emit infrared light. For this 1 page drawings