RU2798761C1 - Method of predicting visual acuity at a distance of 40 cm after phacoemulsification with implantation of an intraocular lens with an increased depth of focus - Google Patents

Abstract

FIELD: ophthalmology.

SUBSTANCE: method of predicting visual acuity at a distance of 40 cm in the long-term period after phacoemulsification with implantation of an intraocular lens with an increased depth of focus implemented due to its posterior surface characterized by the following: Lenstar LS900 optical biometry is performed at the preoperative stage, based on the results of which the sum of the distances of the depth of the anterior chamber and half the thickness of the native lens is calculated, then individually for the patient a prediction of visual acuity at a distance of 40 cm without additional means of correction is made.

EFFECT: prediction of visual acuity based on preoperative optical biometric data.

1 cl, 5 dwg, 3 ex

Description

The invention relates to medicine, in particular to ophthalmology, and can be used to predict the effectiveness of presbyopia correction using lenses with increasing depth of focus (EDOF) technology applied to the posterior surface of an artificial lens, which will improve the selection of patients who are suitable for this type of intraocular correction, reduce the percentage of dependence on glasses at distances desired for the patient, and also prevent lens explantation if the patient is dissatisfied with the results of surgical treatment.

For intraocular correction of presbyopia, different methods are used to generate multiple image foci. Among them are monovision, implantation of multifocal, pseudo-accommodating and lenses with an increased depth of focus. Multifocal and EDOF lenses use diffractive, refractive, and refractive-diffractive techniques to form a multifocal image.

The described version of the IOL with EDOF technology has several diffraction rings on the back surface of the optical part, located at different angles, due to which, in the presence of certain surface characteristics, it allows extending the focus range of the refracted light. For example, a monofocal IOL is characterized by the convergence of refracted light rays at one point (Fig. 1a - the focus is marked in white). For the formation of monovision, it is desirable to have bilateral monofocal pseudophakia, when the vision of one eye has a focus for good distance vision, and a weak degree of myopia is created on the fellow eye for vision at approximate distances of interest to the patient. When a bifocal lens is implanted, two foci of refraction of rays are formed in one eye (Fig. 1b - the foci are highlighted in white). And when rays pass through a lens with EDOF technology, one, two or three foci formed by the lens optics are not observed (Fig. 1c - prolonged focus is marked in white). Thus, there is no division of the light flux over several focal lengths, but conditions are created for the same quality of vision at a given range of distances. The innovative concept of EDOF for intraocular correction of aphakia is to expand the range of vision while increasing its quality, as well as reducing negative optical phenomena [Ang R., 2020. A comparative evaluation of visual, refractive, and patient-reported outcomes of three extended depth of focus ( EDOF) intraocular lenses. Clinical Ophthalmology, 14, 2339-2351]. In addition, trifocal lenses give a significant loss of image quality due to a decrease in contrast sensitivity at medium distances compared to far and near foci [Shah S., 2015. Visual outcomes after cataract surgery: multifocal versus monofocal intraocular lenses. J Refract Surg, 31(10), 658-666. Greenstein S., 2017. Quest for spectacle independence: a comparison of multifocal intraocular lens implants and pseudophakic monovision for patients with presbyopia. Semin Ophthalmol, 32(1), 111-115].

On the recommendation of the manufacturer, the IOL with EDOF technology is used to form a continuous focus and good vision in patients at a distance from far to 70-800 cm from the object under consideration, which is not suitable for visualizing objects located closer, for example, at a distance of 40 cm - standard for reading distance. Thus, the described lens provides high sharpness and quality of vision, not inferior to monofocal for distance vision (Fig. 2) and multifocal correction for medium distances [Attia M., 2017. Clinical evaluation of an extended depth of focus intraocular lens with the salzburg reading desk. J Refract Surg, 33(10), 664-669]. Also, according to some data, EDOF lenses give the best contrast sensitivity in mesopic conditions and perform no worse than trifocal lenses in light conditions [Medeiros A., 2017. Comparison of visual outcomes after bilateral implantation of a diffractive trifocal intraocular lens and blended implantation of an extended depth of focus intraocular lens with a diffractive bifocal intraocular lens. Clinical Ophthalmology, 11, 1911-1916].

In addition, the Extended Depth of Focus technology creates a 1.5 D “plateau”, whereby the defocus curve shows an increase in the visual range of 1.0 D. Due to this, according to the manufacturer's study at medium distances with binocular vision at medium distances (66 cm), in 96.6% of cases visual acuity was at least 20/25 (0.8). And in 84.4% of cases, at least 20/32 (0.6) near, which can determine a high level of spectacle independence [Ota Y., 2020. Binocular visual function after staged implantation of extended-depth-of-focus intraocular lens targeting emmetropia and -0.5 diopter: A prospective comparison. Plos One, 15 (8), 1-11]. While for the bifocal lens AcrySof ^® ReSTOR ^® +2.5 diopters, designed for far and medium distance foci, there were no significant differences in the level of complete or almost complete independence from the use of glasses from the AcrySof ^® monofocal IOL (Alcon - AcrySof ^® IQ ReSTOR ^® +2.5 D Multifocal Intraocular Lenses Model SV25T0 Instructions for Use CODE: 2015OTH0188).

Numerous studies have published different data on visual acuity at 40 cm for this type of IOL. On average, it fluctuates around 0.4 [Sudhir R., 2019. AcrySof IQ PanOptix intraocular lens versus extended depth of focus intraocular lens and trifocal intraocular lens: a clinical overview. Asia Ras J Ophthalmol (Phila), 8, 335-349]. However, many publications describe a large percentage of patients who, with bilateral implantation of EDOF lenses, do not use spectacle correction for distance, middle and near distances. It often exceeds 70% [Spadea L., 2021. Visual performances of a new extended depth-of-focus intraocular lens with a refractive design: a prospective study after bilateral implantation. Therapeutics and Clinical Risk Management, 17, 727-738].

Today in ophthalmology, several methods are used to correct presbyopia. In addition to Extended Depth of Focus (EDOF) lenses, two- and three-focal (multifocal IOLs) and pseudo-accommodating lenses are being considered, as well as monovision technology. Each option is not without drawbacks and is a certain compromise in the struggle for independence from spectacle correction. Multifocal IOLs have a significant decrease in spatial contrast sensitivity due to the division of the light flux into several focal planes, as well as a decrease in visual acuity outside the focal zones [Takhtaev Yu.V., 2008. Intraocular correction of ametropia and presbyopia. Abstract of the dissertation for the degree of Doctor of Medical Sciences, 38 pages. Vinnitsky D.A., 2020. Surgical rehabilitation of patients with cataracts and implantation of trifocal and bifocal intraocular lenses. Abstract for the degree of Candidate of Medical Sciences, 23 pages], in addition, due to a certain design of refractive surfaces, they can cause glare and halo, which impede the activity of patients in conditions of light with a decrease in illumination. Pseudo-accommodating IOLs do not fully repeat the physiology of the accommodation process and cannot meet the required accommodation volume of 2.5-3.0 diopters, including due to capsular bag fibrosis that occurs by the 6th month of the postoperative period, due to which there is a decrease in axial excursions optical part of the lens [Pepose J., 2007. Visual performance of patients with bilateral vs combination Crystalens, ReZoom, and ReSTOR intraocular lens implants. American Journal of Ophthalmology, 144, 347-357].

Monovision technology also does not provide prolonged focus, which gives good vision over the entire range of described distances. For each eye separately, a single focus is formed, they give a different magnification of objects on the retina and difficulty in merging images when transmitting a signal from the corresponding zones to the central nervous system. Thus, this method of correction requires no less neuroadaptation than the implantation of multifocal IOLs, and is also associated with impaired stereovision [Belikova E.I., 2011. Correction of presbyopia by pseudophakia with monovision and multifocal intraocular lenses. Ophthalmological statements, 3 (IV), 49-52].

The optical design of the lens with an extended depth of focus implemented on its back surface provides a contrast sensitivity over the entire range of focal lengths that is not worse, and for some frequencies and lighting conditions even better than multifocal intraocular lenses, providing a higher quality of vision, while negative effects less pronounced in the form of a halo [Teshigawara T., 2021. The effect of age, postoperative refraction, and pre- and postoperative pupil size on halo size and intensity in eyes implanted with a trifocal or extended depth-of-focus lens. Clinical Ophthalmology, 15, 4141-4152]. In addition to high distance visual acuity, there is a high level of no need to wear glasses for medium distances (93-95%) and for near (70%) [Kohnen T., 2019. Visual performance and the extended depth of focus intraocular lens for treatment selection. Eye, published online, 26 April 2019].

At the moment, there is no known method for the preliminary assessment of visual acuity at near distances when implanting lenses with an increased depth of focus. It could be extremely useful in choosing the method of intraocular correction, taking into account the needs of a particular patient and the individual anatomy of his eye.

A more likely independence from spectacle correction due to high visual acuity is observed in patients with trifocal lens implantation. The patient has good distance vision, at a distance of 60-80 cm (depending on the configuration of the IOL) and at a distance of 40 cm. However, there is a decrease in visual acuity at intermediate distances. In addition, there is a significant decrease in contrast sensitivity at high frequencies due to the division of the light flux into several focal planes. These defects are less typical for lenses with EDOF technology, which makes them more preferable from the point of view of the physiology of vision, especially for people with high requirements for the quality of vision, and also introduces limitations for some professions.

The solution of this problem is ensured by the fact that in the method for predicting visual acuity at a distance of 40 cm in the long-term period after phacoemulsification with implantation of an intraocular lens with an increased depth of focus, optical biometry "Lenstar LS900" is performed at the preoperative stage, based on the results of which the sum of distances of the anterior chamber depth is calculated and half the thickness of the native lens, then according to the scheme in Fig. 5 individually for the patient make a prediction of visual acuity at a distance of 40 cm without additional means of correction.

The technical result when using the method is the prediction of visual acuity at near distances (40 cm) according to the Golovin-Sivtsev table after phacoemulsification with implantation of a lens with an increased depth of focus based on preoperative optical biometry data, including measurement of the axial length of the eye (AL), the depth of the anterior chamber ( ACD) and native lens thickness (LT). On FIG. Figure 3 shows the form of optical biometrics Lenstar LS900 for the right (OD) and left eye (OS), which indicates the depth of the anterior chamber of the eye (ACD - anterior chamber depth - the distance from the anterior surface of the cornea to the anterior surface of the lens, as well as AD - aqueous depth - distance from the posterior surface of the cornea to the anterior surface of the lens). In accordance with this, further in the terminology, the depth of the anterior chamber is used as the distance from the anterior surface of the cornea to the anterior surface (capsule) of the native lens.

Given the high cost of this type of IOL and the high expectations placed on implantation by patients, the use of lenses with a complex optical design should be more predictable in terms of the result achieved and the patient's possible quality of life. Our postoperative follow-up revealed a difference in near visual acuity for different anatomical parameters of the eye against the background of equally high uncorrected distance visual acuity and regardless of the level of residual ametropia.

The invention is illustrated in FIG. 1, which shows the convergence of refracted light beams characteristic of IOLs with different numbers of foci (monofocal, bifocal, and EDOF), and FIG. 2 showing defocus elongation for an EDOF lens compared to a monofocal lens in binocular vision at 6 months. Due to the described increase in the depth of the imaged space, good vision is created at a certain range of distances. The eye biometric terminology used in the Lenstar LS900 is shown in FIG. 3, where the abbreviation ACD denotes the depth of the anterior chamber, equal to the distance from the anterior surface of the cornea to the anterior surface of the native lens along the visual axis, and the abbreviation LT is the thickness of the native lens. Accordingly, the distance to its center is equal to half the value of LT. The proposed method predicts visual acuity at a distance of 40 cm and is illustrated by the graph shown in FIG. 4, which shows the dependence of two parameters: the sum of the depth of the anterior chamber (ACD) and half the thickness of the native lens (LT) at the preoperative stage according to the Lenstar LS900 and visual acuity at a distance of 40 cm in the long-term period after phacoemulsification. On this graph, a significant inverse high correlation of the discussed parameters is determined (correlation coefficient -0.66, its significance level p=0.0008). Thus, with relatively transparent optical media, when the possibility of detailed biometrics of eye distances is feasible, a sufficiently accurate prediction of visual acuity at a distance of 40 cm is possible. Fig. 5 is a scheme by which it is possible to determine visual acuity at a distance of 40 cm without additional means of spectacle correction after implantation of an intraocular lens with an increased depth of focus technology by the anatomical distance from the anterior surface of the cornea to the center of the native lens (lens thickness divided in half) of a particular patient.

The proposed method has no analogues. Manufacturers and previous studies report an average percentage of patients who, after implanting lenses with EDOF technology, do not use or practically do not use glasses. The publications give average values for near visual acuity, but do not explain the reason for the wide variation in these values. We also obtained an average visual acuity at a distance of 40 cm 0.4±0.2, which corresponds to the data of the manufacturer and other researchers. However, the range of variation of this indicator was from 0.2 to 0.7, which explained the fact that there were patients who did not use glasses at any distance after implanting a lens with an extended depth of focus. Low deviations from the planned refraction in the cases participating in the drawing up of the scheme cannot explain the reasons for low or high visual acuity at near distances (the average visual acuity for the distance was 1.00 ± 0.15 with an average spherical equivalent of subjective refraction -0.08 ± 0.22 diopters). Our earlier works have shown that the position of the center of the native lens has the maximum proximity to the posterior surface of the IOL implanted during phacoemulsification [Dzilikhov A.A., 2021. Evaluation of the influence of the parameters of the native lens on the postoperative depth of the anterior chamber in patients with different lengths of the anterior-posterior axis eyes. Report at the XIV Russian National Ophthalmological Forum]. Since it is the posterior surface of the lens under consideration that ensures the presence of an elongated focus, this explains the high correlation dependence of the obtained visual acuity at close distances on the assumed position of the forming optical surface relative to the cornea.

Distinctive features that provide the advantage of the proposed method:

1. the method involves predicting visual acuity at a distance of 40 cm and beyond with high accuracy;

2. the method does not use data on the patient's preoperative refraction, the axial length of his eye as a guideline for determining the focal range of a lens with an increased depth of focus;

3. the method uses in the calculation the depth of the anterior chamber of the phakic eye and the thickness of the native lens, obtained by optical biometry "Lenstar LS900";

4. the method allows to explain to the patient his possibilities when implanting lenses with EDOF technology with a high probability for his reasonable choice in favor of one or another presbyopia correction technology, taking into account all the positive and negative qualities of each of them;

5. The method will increase the percentage of patients who do not use spectacle correction and reduce the proportion of possible explantations of lenses of the described technology due to patient dissatisfaction with the results of surgical treatment.

Thus, the method for predicting near visual acuity after phacoemulsification with the implantation of a lens with an increased depth of focus, implemented due to its posterior surface, with high accuracy allows us to assume the possibilities of visual work and the distance of the clear vision planes of the patient according to the measured preoperative parameters of his eye using optical biometry "Lenstar LS900", which makes the choice of the patient regarding the method of intraocular correction of presbyopia more reliable and conscious.

Clinical examples

In 2021, patient K., 55 years old, was admitted to the VmedA Ophthalmology Clinic for cataract surgery and the desire to implant an intraocular lens to correct presbyopia. The surgeon chose an IOL with EDOF technology with a power of 25.5 diopters. The range of vision was agreed with the patient from the most distant focal plane to the average distances that suited the patient in connection with professional employment. In the postoperative period for more than 6 months after the operation, observation revealed high visual acuity without correction, which corresponded to 1.0 when determined using a sign projector. However, the patient reported no need for glasses either for computer work (medium distances), as determined by the type of IOL implanted, or for reading. Visual acuity at a distance of 40 cm was 0.7 without correction. When analyzing the initial biometric data, the calculated distance to the center of the native lens was 5.34 mm.

Also in 2021, patient A., 81 years old, was admitted to the VmedA Ophthalmology Clinic for cataract surgery with a wish to implant a multifocal intraocular lens. The surgeon chose an IOL with EDOF technology with a power of 22.0 diopters with average anatomical parameters of the eye corresponding to the initial emmetropia. By the 3rd month of the postoperative period, a high distance visual acuity without correction was established, corresponding to 0.9, and when simple myopic astigmatism was corrected at 0.75 diopters, reaching 1.0. However, the patient complained about the inability to read even after bilateral IOL implantation with EDOF technology. Visual acuity at a distance of 40 cm was 0.1 without correction, with the addition of presbyopic correction with a spherical glass of 2.0 diopters, it increased to 0.7. When analyzing the initial biometric data, the calculated distance to the center of the native lens was 5.70 mm, which, in terms of distances inside the eye, significantly exceeds the indicator of patient K.

In addition, a good example is patient B., 54 years old, who was operated on for cataracts in 2021 at the VmedA Ophthalmology Clinic. The surgeon chose the same EDOF IOL with a power of 13.0 diopters with a toric component of 3.75 diopters with anatomical parameters of the eye corresponding to high myopia and complex myopic astigmatism. In the postoperative period for more than 6 months after surgery, the observation revealed a high visual acuity of 1.2 without correction. The patient used a personal computer without difficulty and read without any means of additional correction. Visual acuity for a distance of 40 cm was 0.7. When analyzing the initial biometric data, the calculated distance to the center of the native lens was 5.06 mm, which, according to the diagram we proposed, corresponds to the obtained high visual acuity for near vision even with an axial length of the eye exceeding 26 mm.

Thus, an indicator equal to the distance from the anterior surface of the cornea to the center of the native lens is a reliable predictor of the ability to read small text from a distance of 40 cm when implanting lenses with increased depth of focus technology.

Claims (1)

A method for predicting visual acuity at a distance of 40 cm in the long-term period after phacoemulsification with implantation of an intraocular lens with an increased depth of focus implemented due to its posterior surface, characterized in that optical biometry "Lenstar LS900" is performed at the preoperative stage, based on the results of which the sum is calculated distances of the depth of the anterior chamber and half the thickness of the native lens, then individually for the patient make a prediction of visual acuity at a distance of 40 cm without additional means of correction.

Images