Multifocal Correction Research Articles

Cortical dynamics in visual areas induced by the first use of multifocal contact lenses in presbyopes

A common non-spectacle strategy to correct presbyopia is to provide simultaneous images with multifocal optical designs. Understanding the neuroadaptation mechanisms behind multifocal devices usage would have important clinical implications, such as predicting whether patients will be able to tolerate multifocal optics. The aim of this study was to evaluate the brain correlates during the initial wear of multifocal contact lenses (CLs) using high-density visual evoked potential (VEP) measures. Fifteen presbyopes (mean age 51.8 ± 2.6 years) who had previously not used multifocal CLs were enrolled. VEP measures were achieved while participants looked at arrays of 0.5 logMAR Sloan letters in three different optical conditions arranged with CLs: monofocal condition with the optical power appropriate for the distance viewing; multifocal correction with medium addition; and multifocal correction with low addition. An ANOVA for repeated measures showed that the amplitude of the C1 and N1 components significantly dropped with both multifocal low and medium addition CL conditions compared to monofocal CLs. The P1 and P2 components showed opposite behavior with an increase in amplitudes for multifocal compared to monofocal conditions. VEP data indicated that multifocal presbyopia corrections produce a loss of feedforward activity in the primary visual cortex that is compensated by extra feedback activity in extrastriate areas only, in both early and late visual processing.

Multifocal versus modified monovision corrections: A non-dispensing comparison of visual assessment in presbyopic neophytes.

To compare the visual performance of two simultaneous-vision soft multifocal contact lenses and to compare multifocal contact lens and its modified monovision counterpart in presbyopic neophytes. A double-masked, prospective, comparative study was conducted on 19 participants fitted with soft PureVision2 multifocal (PVMF) and clariti multifocal (CMF) lenses in random order. High- and low-contrast distance visual acuity, near visual acuity, stereopsis, contrast sensitivity, and glare acuity were measured. The measurements were conducted using multifocal and modified monovision design with one brand and then repeated with another brand of lens. High-contrast distance visual acuity showed a significant difference between CMF (0.00 [-0.10-0.04]) and PureVision2 modified monovision (PVMMV; -0.10 [-0.14-0.00]) correction (P = 0.003) and also between CMF and clariti modified monovision (CMMV; -0.10 [-0.20-0.00]) correction (P = 0.002). Both modified monovision lenses outperformed CMF. The current study did not show any statistically significant difference between contact lens corrections for low-contrast visual acuity, near visual acuity, and contrast sensitivity (P > 0.01). Stereopsis at near distance was significantly lower with both modified monovision (PVMMV: 70 [50-85]; P = 0.007, CMMV: 70 [70-100]; P = 0.006) and with CMF (50 [40-70]; P = 0.005) when compared to spectacles (50 [30-70]). Glare acuity was significantly lower with multifocal (PVMF: 0.46 [0.40-0.50]; P = 0.001, CMF: 0.40 [0.40-0.46]; P = 0.007) compared with spectacles (0.40 [0.30-0.40]), but no significant difference was noted between the multifocal contact lenses (P = 0.033). Modified monovision provided superior high-contrast vision compared to multifocal correction. Multifocal corrections performed better for stereopsis when compared to modified monovision. In parameters like low-contrast visual acuity, near acuity, and contrast sensitivity, both the corrections performed similarly. Both multifocal designs showed comparable visual performances.

Visual acuity and blur: An extended depth-of-focus model.

This article proposes a simple model that describes the quantitative relationship between visual acuity and defocus (as in defocus curves) in the presence of higher-order aberrations (HOA). The basis model for describing the relationship between visual acuity and blur was taken from Blendowske as a starting point to develop an extended model applicable to defocus curves. The basis of Blendowskes's data is extended by incorporating effects induced by HOA. Aberrometric refractive errors are transformed into a single blur quantity b, also termed dioptric distance, which serves as an input in both models. The possible influence of the axes of asymmetric aberrations and the pupil size is not included. The extended model has been used to generate reference data for a bi-aspheric multifocal correction profile for presbyopia. It provides reference data similar to what has been reported in the literature for that particular profile. The model proposed in this article can be used to determine depth-of-focus effects associated with the presence of HOA. The extended model seems to provide a valid description for defocus curves. Actual uncertainties in experimental data on unaided visual acuity, especially the frequent lack of information on pupil diameter, prevent meaningful numerical comparison and the refinement of both models. However, theoretical arguments are provided in support of the extended model.

Neuroadaptation to multifocal intraocular lenses: A new approach to solving the problem

The current trend towards the implantation of multifocal intraocular lenses is associated with the desire of patients to be independent of glasses and improve the quality of life. However, the brain in conditions of multifocal correction of aphakia works with several foci, which is unphysiological, energy-consuming and requires long-term neuroadaptation. With the depletion of brain resources in adulthood due to problematic neuroadaptation to multifocal intraocular lenses, the neuropsychic or somatic health of patients may deteriorate. The eye-brain system is evolutionarily adapted to aberrations within 1.5 diopters. It is proposed to form direct simple myopic astigmatism up to 1.5 diopters during monofocal correction of aphakia (by laser correction of corneal refraction or implantation of a spherical cylindrical intraocular lens). The specified refraction, expanding the focal area of the pseudophakic eye, provides the greatest (in comparison with other types of refraction) amount of pseudo-accommodation and, accordingly, independence from glasses. The proposed approach is physiological for the brain and does not cause problems with neuroadaptation.

In-market assessment of a toric multifocal monthly replacement silicone hydrogel contact lens

Purpose: A third of toric contact lens (CL) wearers are presbyopic, necessitating toric multifocal (TMF) correction to meet eye care professional (ECP) and wearer demands. A multi-practice, observational assessment was conducted to understand ECP fitting behaviour with TMFCLs and wearer satisfaction.

Development of new Methods of Selection of Multifocal Intraocular Correction in cataract Surgery

Development of new Methods of Selection of Multifocal Intraocular Correction in cataract Surgery

Simultaneous multisegmental and multifocal corrections of complex lower limb deformities with a hexapod external fixator

IntroductionExternal fixators are a part of the therapeutic arsenal used in the correction of complex pediatric lower limb deformities. These long iterative procedures, which are commonly performed over several months, strongly impact the lives of these children and their families. To reduce these drawbacks, we perform, whenever possible, a simultaneous multisegmental and/or multifocal correction of these deformities. HypothesisSimultaneous multilevel correction of complex pediatric deformities using external fixators does not result in more complications than sequential corrections. Materials and methodsSixteen patients were treated with this hexapod external fixator correction procedure. The mean age was 13.9 years. The corrections involved 12 femurs and 20 tibias, representing 53 osteotomies on 23 limbs. The quality of the correction was assessed by measuring the mechanical axis deviation (MAD), residual limb length discrepancy (RLLD) and a new, specifically defined, criterion called the “angular healing index” (AHI). Complications were assessed according to Lascombes’ classification. ResultsThe mean MAD went from 30 to 13.5 mm (P<.05) and the mean RLLD from 33.2 to 6.9 mm (P<.05). The mean AHI was 74.1 days/cm (16.7 to 319). The overall complication rate was 13/23 operated limbs or 56.5% (4.3% grade 1, 43.3% grade 2, 9.3% grade 3, and no grade 4). DiscussionOne-stage multilevel corrections of complex pediatric lower limb deformities represent a difficult technical challenge, and any reduction in treatment time must not adversely impact the quality of the results. The rate and severity of complications compared to monofocal/segmental procedures were no higher than that reported in the literature. This study demonstrated the feasibility of multisegmental and multifocal corrections, which reduced the total treatment duration compared to successive corrections, without adversely affecting the result or increasing the complication rate. Level of evidenceIV; retrospective study.

Quality of life of patients after phacoemulsification with implantation of trifocal intraocular lens

To study the QoL of patients with trifocal and monofocal intraocular lenses 1 year after cataract surgery. The study included 44 patients divided into two groups: in group 1 - after bilateral implantation of trifocal intraocular lenses, in group 2 - after bilateral implantation of monofocal intraocular lenses. The quality of life of patients in these groups was studied using the VF-14 questionnaire. Additionally, the NAVQ-10 questionnaire was used to study the QoL depending on near vision, satisfaction with the surgery outcome, and the presence and frequency of dysphotopsias. The quality of life of the patients with trifocal intraocular lenses is significantly higher than with monofocal intraocular lenses according to the VF-14 questionnaire (92.61±7.57 in group 1 and 60.96±3.99 in group 2, p<0.001). Using the NAVQ-10 questionnaire, 68.1% of patients with trifocal lenses were found to have no problems with near vision, 82% of them had high satisfaction with the operation result. 4.5% of patients had intensive dysphotopsias in the dark, 41.0% of patients reported light haloes around light sources during the dark hours and night-time, and 54.5% have not reported any dysphotopsias. Trifocal intraocular lenses ensure higher quality of life for patients after phacoemulsification when compared with monofocal lenses. Dysphotopsias have some effect on the QoL of patients with multifocal correction, but 82% of them are highly satisfied with the surgery outcome.

Modern optical methods of peripheral defocus correction

Experimental animal studies proved that by manipulating with the defocus one can slow down or speed up the eye growth. The leading mechanism among modern optical strategies of myopia progression treatment is to induce myopic defocus to retinal periphery or decrease the hyperopic defocus. This review sums up the data on peripheral refraction in orthokeratological, multifocal contact, and multifocal spectacle correction. The effectiveness of these methods in myopia control in children and teenagers is shown.

Pre-operative simulation of post-operative multifocal vision.

While multifocal intraocular lenses (MIOLs) are increasingly implanted to correct for presbyopia, how one sees with a multifocal correction is hard to explain and imagine. The current study evaluates the quality of various visual simulating technologies by comparing vision with simulated MIOLs pre-operatively and the implanted MIOLs post-operatively in the same patients. Two simulation platforms were used: (1) a custom-developed adaptiveoptics (AO) system, with two visual simulator devices: a spatial light modulator (SLM) and an optotunable lens operating under temporal multiplexing (SimVis); and (2) a wearable, binocular, large field of view SimVis2Eyes clinical simulator (SimVis Gekko, 2Eyes Vision, Madrid, Spain). All devices were programmed to simulate a trifocal diffractive MIOL (POD F, FineVision, PhysIOL). Eight patients were measured pre-operatively simulating the trifocal lens and post-operatively with implantation of the same MIOL. Through-focus decimal visual acuity (TF VA) was measured (1) monocularly in monochromatic light using a four-alternative-forced-choice procedure in the AO system; and (2) binocularly using a clinical optotype in white light. Visual simulations pre-operatively predict well the TF VA performance found post-operatively in patients implanted with the real IOL. The average RMS difference between TF curves with the different visual simulators was 0.05 ± 0.01. The average RMS difference between the TF VA curves with the SimVis pre-operatively and the real MIOL post-operatively was 0.06 ± 0.01 in both platforms, and it was higher in cataract eyes (0.08 ± 0.01, on average across simulators) than in eyes with clear lens. In either group the shape of the TF curves is similar across simulators and pre- and post-operatively. TF curves cross-correlated significantly between simulators (lag k = 0, rho = 0.889), as well as with results with the real MIOL implanted (lag k = 0, rho = 0.853). Visual simulations are useful programmable tools to predict visual performance with MIOLs, both in an AO environment and in a clinical simulator. Pre-operative visual simulations and post-operative data are in good agreement.

Multifocal Intraocular Lenses Implantation in Presbyopia Correction. Literature Review

Reduced dependence on glasses is an increasingly common expectation among those who want to take advantage of new surgical opportunities, especially for patients who lead an active lifestyle. Currently, due to the increase in the duration of active life in people over 40, there is a need for effective correction of presbyopia. Multifocal intraocular lenses are increasingly used in the treatment of presbyopia. After implantation of multifocal intraocular lenses most patients have no need for spectacle or contact vision. However, complications can affect the patient’s quality of life and level of satisfaction. The most common complications of multifocal correction are blurred vision and the presence of optical phenomena (“halo” and “glare”), associated with residual ametropia, clouding of the posterior capsule, large pupil size, anomalies of the wave front, dry eye and lens decentration. The main reasons for this are the failure to attempt to neuroadapt a patient, the dislocation of the lens, the residual refractive error and the clouding of the lens. The review presents the main features of various models of multifocal intraocular lenses, their implantation techniques, associated complications and methods for their correction. The development of multifocal correction of presbyopia and ametropia seems to be a promising direction in ophthalmic surgery.

Assessment of Clinical Trials for Devices Intended to Control Myopia Progression in Children

The increased prevalence of myopia in the United States and other regions of the world, and the sight-threatening problems associated with higher levels of myopia have led to great interest in research designed to reduce these rates. As most of the progression of myopia occurs in childhood, these investigations have been directed toward slowing the progression of myopia in children. Treatments described to potentially slow the progression of myopia have included pharmacological interventions, multifocal spectacles, and multifocal correction created by contact lenses. Although some contact lens clinical trials have demonstrated promising results in slowing the progression of myopia, many of these studies have significant limitations, including only short follow-up times, limited randomization, and incomplete masking. Such limitations have underscored the need to develop a more robust clinical study design, so that future studies can demonstrate whether contact lenses, as well as other medical devices, can be used in a safe and effective manner to control myopia progression. We review previous key studies and discuss study design and regulatory issues relevant to future clinical trials.

Multifocal Intraocular Lenses Clinical Assessment. Patient Selection for Multifocal Intraocular Correction

There are some multufocal intraocular corrections particular qualities compared to monofocal correction. Therefore, the patient’s careful selection, detail preoperative diagnosis, accurate intraocular lens power calculation are necessary to get the optimal clinical results. There are some disadvantages in the postoperative period, such as the contrast sensitivities reduction, dysphotopsia, neuroadaptation. In addition multifocal IOLs are expensive. The clinical studies include evaluating of visual acuity for different distances, defocus curve, spectacle independence, contrast sensitivity, aberrometry data. Additionally, complications after multifocal IOLs implantation and the reasons of explantation are analyzed. This review includes 36 articles (34 clinical studies and 2 meta-analysis) of the following aspects of multifocal intraocular correction: contrast sensitivity, aberrometry analysis, pupil influence on the visual outcomes, postoperative complications, analysis of explantation reasons, preoperative patient’s selection for multifocal correction.

Optimal orientation for angularly segmented multifocal corrections.

Evaluate the importance of orientation of multifocal lens designs with angular increments of addition. Optical properties of one monofocal and three multifocal designs were analysed with the visual Strehl ratio (VSOTF) metric through-focus (-1 to 5 D). Designs were tested in combination with the higher-order aberrations (HOAs) of 782 subjects (1564 eyes). Simulations included one monofocal, one bifocal (eight orientations), one trifocal (four orientations), and a 4-foci design (four orientations). Monocular and binocular performances of all designs were assessed by computing the area under the through-focus VSOTF plots, the through-focus range of acceptable optical performance, and, for binocular combinations, optical disparity between left and right eyes. Under monocular conditions, bifocal designs generated larger areas under the through focus VSOTF than trifocal designs and 4-foci designs. Specifically, bifocal designs divided vertically were optimal for 48% of eyes. Trifocal designs and 4-foci designs offered longer intervals of acceptable through-focus vision. Coma and spherical aberration values were correlated with the optimal orientation of multifocal corrections. The best binocular combination was achieved with a monofocal and a trifocal lens. The orientation of a multifocal design with angular areas affected the final optical properties of the combination (lens plus eye). The optical aberration distributions for our population of physiologically normal eyes demonstrated improved performance for some lens design orientations (i.e., left-right segments for 2-zone bifocals). Taking into account the HOAs of healthy patients, with special attention to coma and spherical aberration, will increase the optical quality of angularly divided multifocal solutions.

MODERN ASPECTS OF MULTIFOCAL INTRAOCULAR CORRECTION: A REVIEW

During the last decade multifocal intraocular lenses (IOL) became widely used in cataract surgery and proved to be effective in recovery of visual functions. Lots of clinical studies with different multifocal IOL models showed high effectiveness of multifocal correction to achieve good visual quality for far, intermediate, and near distances. Uncorrected visual acuity at a distance is equal to multifocal and monofocal correction, while uncorrected near vision is significantly better with multifocal IOLs. Additional segment position in asymmetric multifocal IOL models did not significantly influence on visual acuity. Multiple multifocal IOL designs (bifocal, trifocal) and ADD power level provide different functional results for near and intermediate distances which allows to select the specific IOL model depending on the patient`s needs. The review covers the following aspects of multifocal intraocular correction: update for classification of multifocal IOLs, visual acuity (functional results) at different distances after multifocal IOL implantation, comparison of clinical results with different multifocal IOL designs and add power levels, influence of add segment position in asymmetric multifocal IOLs on visual quality, comparison between multifocal and monofocal correction.

Temporal multiplexing to simulate multifocal intraocular lenses: theoretical considerations.

Fast tunable lenses allow an effective design of a portable simultaneous vision simulator (SimVis) of multifocal corrections. A novel method of evaluating the temporal profile of a tunable lens in simulating different multifocal intraocular lenses (M-IOLs) is presented. The proposed method involves the characteristic fitting of the through-focus (TF) optical quality of the multifocal component of a given M-IOL to a linear combination of TF optical quality of monofocal lenses viable with a tunable lens. Three different types of M-IOL designs are tested, namely: segmented refractive, diffractive and refractive extended depth of focus. The metric used for the optical evaluation of the temporal profile is the visual Strehl (VS) ratio. It is shown that the time profiles generated with the VS ratio as a metric in SimVis resulted in TF VS ratio and TF simulated images that closely matched the TF VS ratio and TF simulated images predicted with the M-IOL. The effects of temporal sampling, varying pupil size, monochromatic aberrations, longitudinal chromatic aberrations and temporal dynamics on SimVis are discussed.

Study on optical freeform surface manufacturing of progressive addition lens based on fast tool servo

Progressive addition lens (PAL) is currently the state-of-the-art in multifocal correction visual for freeform lens. The PAL is used to correct presbyopia by the distributing optical powers of the three zones, which are far zone, near zone and intermediate zone. As the dioptre of progressive zone varies continuously, the lenses realize simultaneously far view and near view by a pair of glasses. Because the PAL is a freeform surface with a variable radius of curvature, complex shape, processing difficulties, low efficiency, big fluctuation of interpolation error and so on. In this paper, the design surface is discretized by the constant angle method and compensates the path of the diamond tool nose radius with AKIMA interpolation method, which can identify the machine tool of the tool locus, and exploitable fast tool servo technology controls the diamond tools movement and path. MATLAB simulation results show that this method is generally more approximate to the ideal trajectory, which is not only to ensure that surface profile accuracy, but also meet the requirements of the processing efficiency and better control the surface profile.

Recherche d’indices électrophysiologiques de confort visuel après correction de la presbytie par lentilles de contact

Starting at 40years of age, prespyopia affects a quarter of the world population. Many techniques of presbyopia surgery have emerged in recent years. The purpose of this study was to compare monovision and multifocality and to identify clinical and electrophysiological predictive markers of visual comfort for each correction available in clinical practice. Ten presbyopic patients participated in this study. Patients received monovision and multifocal correction using contact lenses for three weeks each in a random order. A clinical evaluation (visual acuity, TNO test, binocular contrast sensitivity and quality of vision questionnaires) and an electrophysiological evaluation (monocular and binocular pattern VEP with multiple spatial frequencies: 60, 30and 15') were performed before and after each correction modality. The P100was significantly wider and slightly earlier after binocular compared to monocular stimulation at T0. The TNO stereopsis score decreased significantly after correction. No other significant differences, either on clinical or electrophysiological criteria, were found between the two modes of correction. Several significant correlations were found between the stereoacuity difference depending upon correction and evoked potentials by binocular pattern at T0. The larger the stereoacuity difference (better stereoacuity with multifocal compensation), the longer the latency of the P100using 60' checks (R=0.82; P=0.004) and the greater the amplitude of the N75using 30' (R=0.652; P=0.04). Our study found no differences between the 2types of correction, but it highlights a benefit of VEP used in current practice and measurement of the P100wave, the best indicator of stereopsis and the most consistent, to predict visual comfort after compensation presbyopia.

ОЦЕНКА КЛИНИКО-ФУНКЦИОНАЛЬНОГО РЕЗУЛЬТАТА МУЛЬТИФОКАЛЬНОЙ КОНТАКТНОЙ КОРРЕКЦИИ У ПАЦИЕНТОВ С ПРЕСБИОПИЕЙ И МИОПИЧЕСКОЙ РЕФРАКЦИЕЙ

The aim of the study was to evaluate the effectiveness of multifocal contact lens correction in patients with presbyopia and myopic refractive error. The study involved 45patients with myopia ranging in age from 43 to 56years in conditions of habitual monofocal contact lens correction, a month after the selection and wearing multifocal contact lenses. Contact correction was carried out according to standard procedures taking into account the accuracy of contact lens fitting, with carrying out functional tests for the “dry eye” syndrome and evaluation of corneal epithelial thickness (Optovue, USA). The as-sessment of the following parameters of visual perception was made: far, near and middle distance (monocular and binocular) visual acuity, the spatial contrast sensitivity, stereovision (I &amp;amp; II Lang test), the area of binocular interaction field (binarymeter), the quality of vision (VF-14 test ). The use of multifocal contact lenses for the correction of presbyopia with the initial myopic refraction ensures high functional results at different distances. Patients with a myopic refraction, previously used contact lenses, easy pass to multifocal correction option. The greatest satisfaction by achieved vision noted in those patients who had achieved refraction (–)0.5diopters. In the selection of contact lenses in older patients the thickness of the corneal epithelium and tear film validity must be taken into account.

Portable simultaneous vision device to simulate multifocal corrections

Multifocal lenses are increasingly used solutions for presbyopia, the age-related loss of crystalline lens focus ability. These lenses work by the principle of simultaneous vision, superimposing focused and defocused images on the retina. Providing the experience of simultaneous vision to a patient before permanent implantation of a multifocal lens is a recognized unmet need to increase the patient’s confidence and optimize the lens selection. We developed a hand-held, see-through multifocal vision simulator based on temporal multiplexing of a tunable lens. The device was calibrated and validated using focimetry and Hartmann–Shack aberrometry revealing high reproducibility of the through-focus multifocal energy distribution and high optical quality. We measured visual acuity and perceptual quality on nine cyclopeged patients with three monofocal, two bifocal, and two trifocal corrections with different far/intermediate/near energy distributions simulated using the device. Visual performance and perceptual quality with multifocal corrections varied across patients, although they were more uniform across distances than monofocal corrections. Among the bifocal and trifocal designs, a trifocal with more energy at far was the most frequently identified as providing better quality. The simultaneous vision simulator proved a promising compact tool to study visual performance with multifocal corrections and to select the lens design best suited for each patient, alternative to costly and bulky adaptive optics based devices.