RU2201724C2 - Method for determining optical force of intraocular lens with intracapsular fastening for correcting ametropia - Google Patents

Abstract

FIELD: medicine. SUBSTANCE: method involves measuring eye length, anterior cornea surface curvature radius, cornea refraction, distance from anterior intraocular lens surface and cornea top, anterior chamber depth, natural lens thickness, intraocular lens optic and haptic part diameter and inclination angle of the haptic part with respect to optic part plane. EFFECT: high accuracy in determining focal power of the intraocular lens.

Description

 The invention relates to medicine, and more particularly to ophthalmology, and can be used to determine the optical power of an intraocular lens with intracapsular fixation for each particular patient before surgery.

где d - диаметр роговицы, мм,
R - радиус кривизны передней поверхности роговицы, мм.A known method for determining the optical power of the pupillary intraocular lens (Fedorov S.N., Kolinko A.I. Method for calculating the optical power of the intraocular lens // Bulletin of Ophthalmology. - 1967. - 4. - P. 27-31), which consists in determining the length of the eye , refraction of the cornea, the radius of curvature of its front surface, its diameter and the distance between the front surface of the intraocular lens and the apex of the cornea, and the optical power of the intraocular lens is determined by the formula:
Diol = 1336 / (L-p) • (1336-L • D) / (1336-p • D),
where Diol is the optical power of the intraocular lens, diopter.,
L is the length of the eye, mm
D - refraction of the cornea, diopters,
p is the distance between the front surface of the intraocular lens and the apex of the cornea, mm, determined by the formula:

where d is the diameter of the cornea, mm,
R is the radius of curvature of the anterior surface of the cornea, mm

 When using this method, the depth of the anterior chamber, the thickness of the natural lens, as well as the design features of the intraocular lens are not taken into account, which significantly reduces the accuracy of determining the optical power of the intraocular lens for a particular patient’s eye in transparent media.

 An object of the invention is to increase the accuracy of determining the optical power of an intraocular lens with intracapsular fixation for the correction of ametropia in transparent environments.

The technical result according to the invention is achieved by the fact that in the method for determining the optical power of an intraocular lens with intracapsular fixation for correction of ametropia, including measuring the length of the eye, the radius of curvature of the anterior surface of the cornea, the refraction of the cornea and the distance between the front surface of the intraocular lens and the apex of the cornea, an additional measure of the depth the anterior chamber and the thickness of the natural lens, the diameter of the optical part of the intraocular lens, the diameter of the haptic part, angle Pull the haptic portion to the optical part of the plane, and the optical power of the intraocular lens is determined by the formula:
Diol = 1336 / (L-p) • (1336-L • 333 / R) / (1336-p • 333 / R),
where Diol is the optical power of the intraocular lens, diopter;
L is the length of the eye, mm;
333 / R - standardized refraction of the cornea, diopters;
R is the radius of curvature of the anterior surface of the cornea, mm;
p is the distance between the front surface of the intraocular lens and the apex of the cornea, mm, determined by the formula:
p = a + 0.125b + (Dopt + Dgapt) / 2tgα,
where a is the depth of the anterior chamber, mm;
b is the thickness of the lens, mm;
α is the angle of inclination of the haptic to the plane of the optical part of the intraocular lens, deg .;
Dopt is the diameter of the optical part of the intraocular lens, mm;
Dgapt - the diameter of the haptic intraocular lens, mm

 These proportions are selected empirically. When determining the distance between the anterior surface of the intraocular lens and the apex of the cornea according to the invention, the preoperative depth of the anterior chamber and the thickness of the natural crystalline lens, the design features of the lens: the diameters of its optical and haptic parts, as well as the angle of inclination of the haptic part to the plane of the optical part are taken into account, which significantly increases the accuracy correction of ametropia in transparent environments.

 The method for determining the optical power of an intraocular lens with intracapsular fixation for the correction of ametropia was tested during 52 operations.

 Clinical example 1: a.k. 622421. Patient B., 40 years old. Diagnosis: Right eye - high degree hyperopia. Visual acuity of the right eye without correction of 0.1 with correction sph + 7.5 diopters. 1,0. Intraocular environments are transparent. According to the invention, the radius of curvature of the anterior surface of the cornea was measured: 7.8 mm, the length of the eye: 20.63 mm, the thickness of the transparent natural lens: 4.21 mm, the depth of the anterior chamber: 2.62 mm. For implantation, a model of an artificial lens with an optical diameter of 5.0 mm, a haptic of 11.0 mm and an angle of inclination of the haptic to the optics plane of the intraocular lens of 7 degrees was chosen.

 To measure eye length, anterior chamber depth, and lens thickness, the Ophthalmoscan Model 200 from Sonometrics Systems Inc. was used. (USA), radius of curvature of the anterior surface of the cornea - TOPCON autokeratometer (Japan), technological parameters of the IOL are indicated by the lens manufacturer in the product passport.

 Substituting the measured values in the formula, according to the invention received: Diol = 29.8 diopters.

 An artificial lens with an optical power of 30 diopters was implanted.

 1 month after surgery: visual acuity without correction of 1.0.

 Thus, thanks to the proposed method for determining the optical power of an intraocular lens with intracapsular fixation for the correction of ametropia with a transparent natural lens, the calculation accuracy is increased and the refractive error is minimized.

Claims (1)

A method for determining the optical power of an intraocular lens with intracapsular fixation for the correction of ametropia, including measuring the length of the eye, the radius of curvature of the anterior surface of the cornea, the refraction of the cornea and the distance between the front surface of the intraocular lens and the apex of the cornea, characterized in that it further measures the depth of the anterior chamber, the thickness of the natural the lens, the diameter of the optical part of the intraocular lens, the diameter of the haptic part, the angle of inclination of the haptic part to the plane of the optical the second part, and the optical power of the intraocular lens is determined by the formula
Diol = 1336 / (L - p) • (1336 - L • 333 / R) / (1336 - p • 333 / R),
where Diol is the optical power of the intraocular lens, diopter;
L is the length of the eye, mm;
333 / R - standardized refraction of the cornea, diopters;
R is the radius of curvature of the anterior surface of the cornea, mm;
p is the distance between the front surface of the intraocular lens and the apex of the cornea, mm, determined by the formula
p = a + 0.125b + (Dpt + Dgapt) / 2tgα,
where a is the depth of the anterior chamber, mm;
b is the thickness of the lens, mm;
α is the angle of inclination of the haptic to the plane of the optical part of the intraocular lens, deg .;
Dopt is the diameter of the optical part of the intraocular lens, mm;
Dgapt - the diameter of the haptic intraocular lens, mm