SU1084009A1 - Apparatus for biometry of the eye - Google Patents

Abstract

EYE BIOMETRIC DEVICE containing a slit lamp with a camera, characterized in that, in order to improve biometrics accuracy by obtaining a topographic picture of the structures of the anterior part of the eye in true dimensions, it is equipped with an overlay prism installed on the slit lamp illuminator, while the prism is complete glass with a refractive index of 1.336-1.657, one angle at its base is straight and the other is 52-58 °.

Description

 j

about

00

four;

with

Vi / r. /

This invention relates to medicine and can be applied in ophthalmology for obtaining an optical section of an anterior eye section in photographs.

A device for biometrics of the eye is known, which contains a slit lamp with a camera.

However, when taking photographs, the further calculation of the parameters of the structures of the anterior chamber (depth, cross section of the optical section, the curvature of the anterior surface of the lens, the configuration of the anterior surface of the iris) does not correspond to the true dimensions of the cornea and requires an individual mathematical treatment for each measurement case. The refractive power of the cornea greatly changes the true dimensions of the structures of the anterior chamber. Having mathematical methods of error correction is extremely complex and requires a large number of indirect parameters, which increases the inspection time and the complexity of data processing.

The purpose of the invention is to increase the accuracy of biometrics by obtaining a topographic picture of the structures of the anterior eye in real times (measures.

The goal is achieved by the fact that the device for biometrics of the eye, which contains a slit lamp with a camera, is equipped with an overlaying prism on the eye, mounted on the illuminator of a slit lamp, while the prism is made of glass with a refractive index of 1.336-1.657. one corner at its base is straight and the other is 52-58.

FIG. 1 shows the device, a general view of FIG. 2 is a prism of device j in FIG. 3 - the course of rays in a prism.

The device for biometrics of the eye contains a photo-slit lamp-1 mounted on a coordinate table with a camera (not shown), on the illuminator and at the focus of which a prism 2 is rigidly fixed, contacting in a liquid layer of 3 4%

a solution of carboxymethylcellulose with apex of the cornea.1 4. A prism 2 is made of optical glass with a refractive index of 1.336-1.657, one angle at its base is straight and the other is 52-58 °.

The device works as follows.

The light beam from the slit light source of the photo-slit lamp 1, the passage through the prism 2 and the layer 3 of a 4% carboxymethylcellulose solution with a cornea vertex 4, apr - falls into the anterior eye section 5.

A ray of light passing through a prism enters the front camera. The distance AB, which lies in the slit beam of light, is transmitted by the prism as segment x on the same scale. The magnitudes on the optical images are calculated trigonometrically as follows:

ac ab-tg ci,

CF ac-cos, CF

Df

. cos tf

CF-cos tA X 0

cos H as- cos / ь cos with /

cos f

tg flC -cos / 3- coscA

 abcos V

d, jb, (, 4 are determined from the following system of equations, and (O to –IK angles at the base of the prism and observation, respectively.

sind n glass

p carboxymethylcellulose / 3

sin зы (KMTs)

at

sind

 N glass

ft U) -H: with W + JP - 90;

li

3 of this system, the magnitudes of the cosines of the angles are written as follows:

cos (r cos (tc;

y- 90).

sin (u + y- 90)

cos | l glass

cos l cos

w - arc sin

sin (Ui +, y- 90)

n glass sin jcuarc sin n glass tg about n glass D KIWu, Kllz il about 45, teach By choosing the viewing angle t (1) we get 1 + 0.02, when the angle at the bottom of the prism uP varies from 52 to 58. Within these image transfer accuracy of 2%. At a base angle of a prism of 55 (average range value) x: AB 1.007; This proves that the prism reproduces sagittal distances in the anterior chamber of the eye at the exit from the lateral oblique face in true absolute dimensions. Since the refraction of the rays in the system of the anterior chamber fluid — the cornea — carboxymethylcellulose can be neglected due to similar values of their refractive indices (the anterior chamber fluid is 1.336, the cornea is 1, .72 carboxymethylcellulose and the prism substance) is significant W + g - 90) (LJL) + Y - 90) - arc sin n glass only the refraction at the border of carboxymethyl cellulose and the substance of the prism plays a role in the construction of rays in a prism. Provided that the prism is made of crown glass with a refractive index of 1.500, and the refractive index of carboxymethylcellulose is 1.336, the angle at the base of the prism, ensuring the equality of the measured and observed objects, must be equal to 55. Thus, the application of the invention makes it possible to obtain true relationships in the photographs and the absolute dimensions and structures of the anterior part of the eye, which is extremely important for studying the anterior part of the eye, both in normal conditions and in various types of pathology, which greatly improves the accuracy of biometrics.

Claims (1)

EYE BIOMETRY DEVICE containing a slit lamp with a camera, characterized in that, in order to increase the biometric accuracy by obtaining a topographic picture of the structures of the anterior part of the eye in true dimensions, it is equipped with a prism superimposed on the eye mounted on a slit lamp illuminator, with a prism made of glass with a refractive index of 1,336-1,657, one angle at its base is straight, and the other is 52-58 °. 1 1084009