RU2484793C1 - Method of correcting bilateral aphakia - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medicine, namely to ophthalmology. Intraocular lens (IOL) with optic power, intended for distance vision is implanted into leading eye, lens for near vision being implanted into fellow eye. Optic power of leading eye IOL is calculated for mild degree myopia, 1/2 depth of IOL focus. After IOL implantation into leading eye, its maximal distance vision acuity is checked and presbiopic spectacle correction, required for patient's professional activity at near distance, is selected. Into fellow eye implanted is IOL for near vision with optic power, calculated by formula: D=D_1/2F+Dspectacles*R where DD_1/2F is optic power of leading eye IOL, calculated for mild degree myopia, equal 1/2 of IOL focus depth with high vision acuity in dioptre, F is depth of focus of leading pseudophakic eye with vision acuity, required for patient's professional activity, Dspectacles is minimal spectacle presbiopic correction, required for patient's professional activity at near distance, in dioptre, R is coefficient of recalculation of spectacle correction into additional optic power of intraocular lens.

EFFECT: method ensures simultaneously high distance and near vision functions without additional spectacle correction.

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Description

The invention relates to medicine, and more particularly to ophthalmology.

A known method for the correction of aphakia using monofocal intraocular lenses (IOLs), in which IOLs are implanted in the leading eye for distant vision, and in the paired eye for near vision, RF patent No. 2139698. Despite the fact that in this method, when choosing the optical power of the IOL for near vision, the anatomical parameters of the patient’s eye, the depth of focus of the artifact eye and the minimum visual acuity and the optimal distance for working near the patient are taken into account, however, this method does not take into account the functional state of the retina. (In some patients, a resolution of more than 1.0 and empirically revealed that these patients are able to read without additional spectacle correction with myopia in 1.0-1.5 diopters). It is known that the degree of anisometropia affects such important functions of the visual analyzer as the summation and suppression of visual images with binocular vision, therefore, with a minimum degree of anisometropia, one can expect the effect of summation and higher values of vision and contrast sensitivity, which provides higher visual functions in the distance and near without additional spectacle correction.

The technical result of the invention is the provision of high visual functions simultaneously into the distance and near without additional spectacle correction.

The technical result is achieved by the fact that in the method of correction of bilateral aphakia, including implantation of an intraocular lens (IOL) with the optical power intended for distant vision into the leading eye, and in the paired eye for close vision, according to the invention, the optical power of the leading eye IOL is calculated for myopia weak degree, 1/2 of the depth of focus of the IOL, after IOL implantation in the leading eye, check its maximum visual acuity in the distance and select the presbyopic spectacle correction necessary for the patient’s professional activity nta near, and IOLs are implanted in the paired eye for near vision with optical power calculated by the formula

where D _{1 / 2F} is the optical power of the IOL of the leading eye, calculated for a weak degree of myopia, equal to 1/2 the depth of focus of the IOL with high visual acuity in diopter,

F is the depth of focus of the leading artifact eye with visual acuity required by the patient for professional activities,

Daughters - the minimum spectacle presbyopic correction necessary for the professional activity of the patient close to, in diopter,

R is the coefficient of conversion of spectacle correction to the additional optical power of the intraocular lens.

To calculate R, you can use a formula that takes into account the anatomical parameters of the eye

n is the refractive index of the intraocular fluid and the vitreous, equal to 1.336;

k is the depth of the anterior chamber (meters);

L is the length of the eye (meters);

Dp is the optical power of the cornea (diopter).

In case of artifact, IOL does not accommodate, therefore, the intraocular correction of aphakia of one eye into the distance and the other for near vision can provide simultaneous vision without additional spectacle correction. Depending on the location of the object in question (far or near), an image of different definition is formed on the retinas of both eyes. These images are transmitted to the higher cortical centers, where, depending on the physiology of the patient (the presence of the leading eye, the absence of sensory prevalence), they merge into a single binocular visual image. The quality of binocular vision under these conditions depends on the difference in optical powers of the two implanted IOLs. This value should be minimal, but sufficient to provide good near vision. Therefore, our method suggests taking into account not only the increase in the depth of focus that occurs on the artifact eye, the anatomical and physiological characteristics of the eye and the distance required for professional activity of the patient near, but also the initial state of the retina, allowing its ability to exceed 1.0.

The method is illustrated by the figure, which shows the curves of the dependence of visual acuity in the distance from defocusing with spherical lenses (spectacle glasses). Visual axis is plotted along the Y axis, and the optical power of a spherical lens is shown along the X axis. Curve 1 represents the averaged defocus curve of an artifact eye with an IOL after implantation, designed for a weak degree of myopia equal to 1 / 2F - the depth of focus of the artifact leading eye at a selected visual acuity, necessary for calculation. Curve 2 represents the defocusing of the paired eye after IOL implantation, curve 3 represents the defocusing with two eyesight (binocular visual acuity).

Defocusing of vision with negative lenses, equivalent to displacement of the optotype by a distance inversely proportional to the optical power of the lens while maintaining the angular size of the image. So an additional optical power of 0 diopters corresponds to the location of the object at infinity; - 0.5 diopters - the distance to the object is 2 m; - 2 diopters - the distance to the object is 0.5 m; - 3 diopters - 0.33 meters; and so on. The maximum visual acuity of the leading eye, calculated on emmetropia, curve 1 depth of focus Fvis at a given visual acuity, the optical power of the IOL for implantation in the paired eye is calculated by formula 1. After implantation, the defocusing curve of the paired eye will take a position in the figure, curve 2. In this case, the paired eye provides nearby visual functions. The maximum of curve 2 corresponds to some optical power of the spectacle correction, which is associated with the additional (to emmetropia) optical power of the intraocular lens, calculated by the formula 1. Binocular vision (two-eye vision), curve 3, tracks the defocus curve of the lead eye with distance vision and the defocus curve a pair of eyes with near vision. At intermediate distances, as a rule, an increase in binocular visual acuity is observed compared to monocular.

The method is as follows: the patient undergoes a preoperative examination for the absence of pathology of the visual analyzer, sensory prevalence and determination of the leading eye, then, based on the biometry and keratometry of the leading eye, the optical power of the IOL for mild myopia is calculated and implanted into the leading eye. After implantation, distance visual acuity is measured and presbyopic spectacle correction necessary for the patient’s professional activity is selected. Then calculate the optical power of the artificial lens according to the formula 1.

Example. Patient A., 60 years old, came in November 2011 about the initial cataract of both eyes. Visual acuity before the operation of both eyes = 0.3-04 is not corrected. Preoperative examinations showed that electrophysiological studies were normal and the patient does not have a pronounced sensory prevalence and the right eye is the leading one. From a conversation with the patient it was established that he is an artist. Vision near him is necessary for professional activity and for reading. It was decided to carry out cataract phacoemulsification with the implantation of monofocal IOLs of the Alcon AcrySof Natural model.

After biometrics and keratometry of the leading eye, the optical strength of the IOL for mild myopia was calculated, the value of which was determined according to the graph using a stencil of the average defocus curve for a specific IOL taking into account the required visual acuity for distance, which was +18.5 diopters. and phacoemulsification of the leading eye cataract with IOL implantation was performed. The visual acuity of the leading eye was 1.0 sph -0.25 diopters 1.2. From the anamnesis it is known that visual functions were the same in both eyes, and a preoperative examination did not reveal a pathology. Therefore, the required vision for working near was selected using presbyopic spectacle correction. The minimum “+” value of the glass required for near vision was used in the calculation according to the proposed formula 1. In this case, the magnitude of the glass was 1.25 diopters. Further, biometrics of the paired eye were performed and the anteroposterior axis of the eye were determined L = 24.0 mm and the anterior chamber depth k = 3.0 mm. Keratometry determined the optical power of the cornea of the double eye Dp = 44.5 diopters.

The optical power of the intraocular lens intended for implantation in the paired eye is calculated according to formulas 1 and 2

A lens with an optical power of +18.5 diopters, which is closest to the calculated one, was selected for implantation.

Cataract phacoemulsification with implantation of an IOL of calculated optical power was also performed on the paired eye. The visual acuity of the double eye was: 0.7 sph -1.25 with cyl -0.5 ax.6O = 1.0, spheroequivalent -1.5 diopters.

Binocular visual acuity without correction was equal to: distance = 1.0, near = 0.9. This allows the patient to do without glasses both with distance vision and reading near.

Claims (1)

A method for the correction of bilateral aphakia, including implantation of an intraocular lens (IOL) with the optical power intended for distant vision into the leading eye, and close vision for the paired eye, characterized in that the optical power of the leading eye IOL is calculated for mild myopia, ½ depth focus of the IOL, after IOL implantation in the leading eye, its maximum visual acuity in the distance is checked and presbyopic spectacle correction necessary for the professional activity of the patient is selected near, and IOLs are implanted in the paired eye for near vision optical power calculated according to the formula:
D = D _{1 / 2F} + D points · R,
where D _{1 / 2F} is the optical power of the IOL of the leading eye, calculated for a weak degree of myopia equal to ½ of the depth of focus of the IOL with high visual acuity in diopter,
F is the depth of focus of the leading artifact eye with visual acuity required by the patient for professional activities,
D glasses - the minimum presbyopic correction for glasses necessary for the professional activity of the patient near, in diopter,
R is the coefficient of conversion of spectacle correction to the additional optical power of the intraocular lens.

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