RU2801024C1 - Method of orthokeratological impact on the cornea of the eye to control mild and moderate myopia. - Google Patents

Abstract

FIELD: medicine; ophthalmology.

SUBSTANCE: volume of absolute accommodation (VAA) of the eyes is determined, and with VAA 2.5–3.0 and a mild degree of myopia, an orthokeratological lens is installed with a clearance of the return zone of not more than 37 microns; with VAA 3.1–7.0 and a weak degree of myopia an orthokeratological lens is installed with a clearance of the return zone of 50 μm. With VAA of 8.0 or more and mild myopia an orthokeratological lens is installed with a clearance of 75 microns. With VAA 2.5–3.0 and moderate myopia an orthokeratological lens is installed with a clearance of the return zone of 37 microns. With VAA more than 3.0 and moderate myopia an orthokeratological lens is installed with a clearance of 75 microns.

EFFECT: method allows to carry out OK-impact on the cornea of the eye to control myopia after determining the volume of absolute accommodation.

1 cl, 2 ex, 3 dwg

Description

Orthokeratological treatment of the cornea is a topical method of vision correction and myopia control. It is known that the inhibition of myopia requires the creation of a sufficient refractive gradient (GR) from the center of the optical zone of OK exposure to the paracentral zone of accumulation (more than 8 diopters), which creates an add zone in the paracenter of the cornea. In addition, a complete neutralization of myopia is formed during OK exposure. These factors require a sufficient amount of absolute accommodation (OAA). However, the currently existing methods of OK-influence do not take into account the volume of absolute accommodation, which, with a weakened accommodation of the myopic eye, will cause even greater disturbances in accommodation and the risk of some ophthalmic complications.

The technical task is to develop a simple method of OK-impact on the cornea of the eye to control myopia by determining TAA.

The existing method for measuring TAA in patients without presbyopia is as follows [Rinskaya N.V., 2018, Myagkov A.V., 2016]:

- the patient is in full correction for the distance;

- the study is carried out monocularly using a phoropter;

- test target (this optotype is 1-2 lines larger than the optotype of the patient's best near visual acuity) is set at a distance of 40 cm from the patient's eyes;

- add negative lenses every 5-10 seconds in increments of 0.25D, until vision becomes impossible due to fuzziness;

- +2.5D must be added to the obtained value of the negative lens (accommodation amplitude, which should be spent to fix the target located at a distance of 40 cm) to obtain the patient's OAA;

- measure TAA of the opposite eye.

The formula for calculating OAA \u003d + 2.5D - (the added value of the optical power).

The refraction gradient during orthokeratological exposure is measured from the center of the cornea to the paracentral zone using tangential keratotopographic maps. Registered keratotopographs are used, such as TMS-4 Tomey. In this case, the central curvature is measured at the center of exposure and is expressed in diopters, the paracentral curvature is measured at the maximum point of the accumulation zone and is measured in diopters. The difference between them will be the refraction gradient (GR).

The formula for calculating GR = corneal curvature in the paracenter in diopters - corneal curvature in the center in diopters.

The specified clearance of the return zone of orthokeratological lenses is created by using the Orthotool software [Edward Cho, 2010].

The specified technical problem in ophthalmology is solved by creating a given tear clearance in the return zone of OK lenses no more than 37 microns, 50 microns and 75 microns, depending on the volume of absolute accommodation of the eye. It is known that a patient spends 2.5 diopters for vision at a distance of 40 cm. It is also known that GR on the cornea of the eye in relation to the center of the optical zone of OK exposure to the paracentral accumulation ring is formed even with a clearance in the return zone of 37 μm (at least 8-10 diopters), therefore, in order to avoid the difficulty of adapting to lenses or intolerance to their use, it is necessary to determine the OAA of the eye and create tear clearance in the return zone, depending on this value and the degree of myopia.

With TAA 2.5-3.0 and a mild degree of myopia, the use of OK exposure with more than 37 microns of clearance of the return zone is not recommended.

With TAA 3.0-7.0 and a mild degree of myopia, it is not recommended to use OK exposure with more than 50 µm clearance of the return zone.

With TAA of 8.0 or more and a weak degree of myopia, it is possible to use OK exposure with a clearance of 75 μm.

With moderate myopia and TAA 2.5-3.0, the use of a clearance of 37 is recommended, with a larger volume of accommodation it is possible to use a clearance of 75.

In contrast to the existing methods of OK-influence on the cornea of the eye, when the tear clearance in the return zone is an unknown value and a trade secret, or the clearance is given by a single value for one or another degree of myopia, this invention takes into account the role of the volume of absolute accommodation of the eye.

The method is characterized by the following clinical examples:

Example 1:

Patient M., 7 years old. Diagnosis: mild myopia in both eyes. Refraction sph - 1.25 diopters in both eyes. OAA 7 diopters OD, 7 diopters OS. OK exposure was used with a clearance of 50 μm in the return zone and the formation of a refractive gradient in the center of the cornea and in the accumulation zone of about 8.96 diopters for the right eye and 6.12 diopters for the left eye. The patient experienced comfort at near, intermediate, and far distances with a distance visual acuity of 1.0 in each eye.

Brief description of drawings:

Clearance at the peak of the return zone 50 µm

Refractive gradient from center to paracenter : OD about 8.96, OS about 6.12 diopters

Example 2:

Patient A., 8 years old. Diagnosis: moderate myopia in both eyes. Refraction sph - 3.5 diopters in both eyes. OAA 6.5 diopters OD, 6.5 diopters OS. OK exposure was used with a clearance of 75 μm in the return zone and the formation of a refraction gradient in the center of the cornea and in the accumulation zone of about 16 and 21 diopters for the right and left eyes, respectively. The patient experienced discomfort when working at close range (less than 40 cm), headaches in the evening. It is advisable to change the OK-impact with a clearance of 50 microns. With a clearance change of 50 µm, the patient received comfortable near and intermediate vision and a distance visual acuity of 1.0 for both eyes.

Brief description of drawings:

Clearance at the peak of the return zone 75 µm

Refractive gradient from center to paracenter : OD about 16 diopters, OS about 21.38 diopters.

Claims (1)

The method of orthokeratological impact on the cornea of the eye to control mild and moderate myopia, characterized in that the volume of absolute accommodation (OAA) of the eyes is determined, and with OAA 2.5-3.0 and a weak degree of myopia, an orthokeratological lens is installed with a clearance of the return zone of not more than 37 microns; with OAA 3.1-7.0 and a weak degree of myopia - with a clearance of the return zone of 50 μm; with TAA of 8.0 or more and mild myopia - with a clearance of 75 microns; with OAA 2.5-3.0 and moderate myopia - with a clearance of the return zone of 37 microns; with TAA more than 3.0 and moderate myopia - with a clearance of 75 microns.