Analysis of the optical performance of intraocular lenses using profilometric measurements

PURPOSE

The aim of this study was to develop a methodology, based on profilometer measurements to assess the optical behaviour of Intraocular Lenses (IOls). The "Modulation Transfer Function through-object" (MTF through-object) based on vergence object displacement was calculated for different pupil sizes and pseudophakic eyes. Tilt and decentration were also analysed in a realistic cornea eye model.

METHODS

For comparison between the different IOLs, an optical quality criterion based on a minimum value the MTF through-object and the recognition of simulated vision optotypes was introduced. Five IOLs were used in this study: Tecnis Eyhance, Mini Well, Tecnis Symfony, Tecnis Synergy and RayOne EMV.

RESULTS

The technique was validated with previous methodologies. A general narrowing of the through-object MTF curve compared to the through-focus MTF curve was shown, resulting in greater distances between near and intermediate points and less depth of field around the far peak. The comparison between the IOLs showed that variations in corneal aberrations, pupil size and decentration caused relevant changes in IOL performance. A decrease of the SA produced a hypermetropic shift of the far focus between + 0.3 D and + 0.4 D. Most of IOLs worsen the optical quality as pupil size increased, even the MTF through-object shape changed. Decentration was an important factor in IOL implantation, causing a significant change in MTF through-object shape in most of IOLs.

CONCLUSIONS

This study highlights the need to evaluate pre-operative patients for corneal aberrations and pupillary size to have the best optical success after cataract surgery in multifocal or extended depth of focus IOLs.

KEY MESSAGES

What is known MTF(Modulation Transfer Function) through-focus curves (calculated in image space by moving the detector plane) can be obtained from optical bench assembly or from commercial devices. Recently, some studies proposed to characterize the lens surface design based on the profilometric measurements What is new A novel methodology based on profilometer measurements to assess the optical behaviour of Intraocular Lenses (IOls) was shown. The "Modulation Transfer Function through-object" based on vergence object displacement was introduced in order to analyse five premium IOLs. MTF through-object curve is more appropriate for studying clinical behaviour, as it provides further near and intermediate points distances and lower depth of focus around far peak compare to MTF through-focus curves. The optical behaviour of the five IOLs can vary considerably depending on the eye model and pupil size. The effect of tilt and decentration on the MTF through-object the IOLs was analysed.

Effect of Decentration, Rotation, and Tilt on Objective Optical Quality of Plate Haptic Toric Intraocular Lenses in the Early Postoperative Period

Purpose

This study aimed to determine the influence of decentration, rotation, and tilt on objective optical quality of plate haptic toric intraocular lenses (tIOLs).

Methods

The area ratio of modulation transfer function (MTF), strehl ratio of point spread function (PSF), and higher order aberrations (HOAs) for 3 mm and 5 mm pupil diameter (PD) were evaluated at postoperative 1 month. The retroillumination images pictured by OPD-scan III were used to quantify the degree of decentration and rotation, whereas the tIOL tilt was directly obtained by the tilt aberration. Patients were separated into two subgroups based on tIOL misalignment cutoff values.

Results

There were 29 eyes (24 patients) in the study. The decentration of more than 0.25 mm did not substantially differ from those less than or equal to 0.25 mm. PSF of 3 mm PD and MTF, intraocular HOAs, and trefoil aberration for 3 mm and 5 mm PD significantly deteriorated with a rotation of more than 3 degrees, whereas only intraocular HOAs for 5 mm PD and coma for 3 mm and 5 mm PD were significantly severe with a tilt of more than 0.1 µm and 0.25 µm in corresponding PD. Furthermore, tIOL rotation and tilt were highly correlated with intraocular trefoil aberration and coma, respectively.

Conclusions

The decentration of the monofocal bitoric IOLs is more tolerant to optical quality degradation after 1 month of surgery but more sensitive to intraocular trefoil aberration caused by rotation and coma aberration induced by tilt.

Translational Relevance

As far as we know, this is the first study to investigate the relationship between the plate haptic bitoric IOL misalignment and objective optical quality measured by OPD-scan III in the real world, which may provide reference information for IOL selection to improve surgical outcomes.

Effect of spherical aberration on visual acuity and depth of focus in pseudophakic eyes

PURPOSE

To assess the performance of 4 intraocular lenses (IOLs) in various spherical aberration (SA) conditions, using the VAO adaptive optics simulator.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.

DESIGN

Prospective case series.

METHODS

Distance-corrected visual acuities at distance (CDVA), intermediate (DCIVA), and near (DCNVA) were measured in 42 dilated pseudophakic eyes at baseline and with ocular SA ranging from -0.4 to +0.4 μm in increments of 0.2 μm (6.0-mm pupil). 4 IOL types were assessed: monofocal IOLs with zero-SA, enhanced-monofocal, extended depth-of-focus (EDOF), and continuous range-of-vision.

RESULTS

Compared with SA = 0 μm, significant changes (all P < .05) were: (1) zero-SA monofocal IOLs' DCNVA at high contrast improved by 0.13 logMAR with SA = -0.4 μm and worsened by 0.09 and 0.10 logMAR with SA = +0.2 and +0.4 μm, respectively. DCNVA at low contrast worsened by 0.09 logMAR with SA = +0.4 μm; and (2) with SA = -0.4 μm, the enhanced monofocal IOL lost 0.06 logMAR of CDVA at high contrast and gained 0.09 logMAR of DCNVA at low contrast. There were no significant changes from SA = 0 μm for EDOF and continuous range-of-vision IOLs.

CONCLUSIONS

Zero-SA and EDOF IOLs were the most and least sensitive to SA modulation, respectively. In perfect optical systems where all the optical elements are aligned, induction of targeted amounts of negative SA improved the depth of focus of some IOL types. No benefit was found with positive SA.

Optical Quality and Higher Order Aberrations of Refractive Extended Depth of Focus Intraocular Lenses

PURPOSE

To compare the optical quality and higher order aberrations of four different refractive extended depth of focus intraocular lens (EDOF IOL) models (Lentis Comfort [Teleon Surgical BV], MiniWell (SIFI), LuxSmart [Bausch & Lomb], and AcrySof IQ Vivity [Alcon Laboratories, Inc]) and a monofocal IOL (Tecnis ZCB00; Johnson & Johnson Surgical Vision, Inc).

METHODS

An optical metrology instrument (OptiSpheric IOL PRO2; Trioptics GmbH) was used to study image quality metrics of the different IOLs. The modulation transfer function (MTF) was measured at pupil sizes 1 to 5 mm in 1-mm steps. Area under the MTF and simulated visual acuity were calculated for different pupil diameters. Wavefront aberrations were measured with the SHS Ophthalmic device (Optocraft GmbH), which features a Hartmann-Shack sensor.

RESULTS

All EDOF lenses yielded a simulated far visual acuity of 0.00 logMAR (20/20 Snellen) or better. At the 0.20 logMAR visual acuity level, the EDOF IOLs showed an increased depth of focus of at least 0.75 diopters compared to the monofocal IOL. Pupil dependency was more pronounced with the MiniWell, LuxSmart, and Vivity, whereas the Lentis showed a more consistent behavior at different apertures. The wavefront measurement revealed increased central aberrations for the MiniWell, LuxSmart, and Vivity IOL compared to the monofocal control.

CONCLUSIONS

All EDOF IOLs demonstrated increased depth of focus while maintaining good simulated visual acuity at the far focus. Pupil dependency differed between the IOL models. The wavefront analysis revealed the complex design of the different EDOF IOLs with several zones with varying aberrations. [J Refract Surg. 2023;39(10):668-674.].

Spherical Aberration of Astigmatic Corneas in a Cataract Population

PURPOSE

To study the distribution of spherical aberration (SA) in astigmatic corneas in a cataract population and the relationship between magnitude of corneal astigmatism and fourth-order corneal SA.

METHODS

Data routinely collected using a Scheimpflug camera (Pentacam; Oculus Optikgeräte GmbH) were retrospectively analyzed. Patients with a minimum age of 60 years were included. Total corneal SA (from anterior and posterior corneal surface) was obtained for a 6-mm cor-neal area aligned with the pupil center. Exclusion criteria were insufficient measurement quality, total deviation index (Belin/Ambrósio Deviation) greater than 1.60, and corneal thickness at the thinnest point of less than 490 μm. One eye per patient was chosen randomly. Eyes were divided into low (≤ 1.00 diopters [D]), moderate (> 1.00 to ≤ 2.00 D), and high (> 2.00 D) astigmatism groups according to the Scheimpflug measurements.

RESULTS

A total of 528 eyes were included in this analysis. Low astigmatism was found in 129 patients, moderate astigmatism in 265 patients, and high astigmatism in 134 patients. Mean astigmatism was 0.68 ± 0.24, 1.45 ± 0.28, and 2.91 ± 0.95 D in the low, moderate, and high astigmatism groups, respectively. Mean corneal SA in patients with moderate and high astigmatism was higher than in the low astigmatism group. The difference reached the significance level for the comparison of low and high astigmatism groups (P = .023). The fourth-order SA increased gradually with the magnitude of astigmatism with a slope of 0.015.

CONCLUSIONS

SA was significantly larger in the cataract population with high corneal astigmatism. The increase of positive sign SA with the magnitude of astigmatism suggests that patients with moderate to high astigmatism may benefit more from intraocular lenses with negative sign SA correction. [J Refract Surg. 2023;39(8):532-538.].

Automated and subjective refraction with monofocal, multifocal, and EDOF intraocular lenses: review

Automated refraction (Scheiner principle) is universally used to start a visual examination. Although the results are reliable in eyes implanted with monofocal intraocular lenses (IOLs), they may be less precise with multifocal (mIOL) or extended depth-of-focus (EDOF) IOLs and can even indicate a refractive error that does not clinically exist. Autorefractor results with monofocal, multifocal, and EDOF IOLs were investigated through literature search analyzing the papers reporting the difference between automated and clinical refraction. The average difference ranged between -0.50 diopter (D) and -1.00 D with most mIOL and EDOF IOLs. The differences in astigmatism were generally much lower. Autorefractors using infrared light cannot measure eyes with high technology IOLs precisely because of the influence of the refractive or of the diffractive near add. The systematic error induced with some IOLs should be mentioned in the IOL label to prevent possible inappropriate refractive procedures to treat apparent myopia.

Advanced Optical Wavefront Technologies to Improve Patient Quality of Vision and Meet Clinical Requests

Adaptive optics (AO) is employed for the continuous measurement and correction of ocular aberrations. Human eye refractive errors (lower-order aberrations such as myopia and astigmatism) are corrected with contact lenses and excimer laser surgery. Under twilight vision conditions, when the pupil of the human eye dilates to 5-7 mm in diameter, higher-order aberrations affect the visual acuity. The combined use of wavefront (WF) technology and AO systems allows the pre-operative evaluation of refractive surgical procedures to compensate for the higher-order optical aberrations of the human eye, guiding the surgeon in choosing the procedure parameters. Here, we report a brief history of AO, starting from the description of the Shack-Hartmann method, which allowed the first in vivo measurement of the eye's wave aberration, the wavefront sensing technologies (WSTs), and their principles. Then, the limitations of the ocular wavefront ascribed to the IOL polymeric materials and design, as well as future perspectives on improving patient vision quality and meeting clinical requests, are described.

Analysis and comparison of monofocal, extended depth of focus and trifocal intraocular lens profiles

To test the feasibility of using profilometers to extract information about IOL surfaces design. A standard monofocal IOL (Tecnis 1), a monofocal IOL that provided some depth of focus (Eyhance), an extended depth of focus IOL based on refractive optics (Mini Well) and a trifocal IOL based on diffractive optics were used in this study (Tecnis Synergy). The surface topography of the IOLs was measured by using a multimode optical profilometer. Posterior surface of Tecnis 1 IOL was spherical and the anterior surface aspherical. In the Eyhance IOL, posterior surface was spherical and anterior surface did not fit to any of our reference surfaces, indicating a higher order aspheric surface design. In the Mini Well Ready IOL, a best-fit sphere surface was obtained for the second surface and a high order aspherical surface design was deduced for the first surface. The anterior surface of the Synergy IOL was aspherical and the base curve of the diffractive structure fitted very well to a spherical surface. To consider an aspheric surface as possible best-fit surface provided more information than if only best-fit spherical surface was considered. The high order aspheric surface designs employed in the IOLs studied presented differences, regarding best-fit asphere surface, higher than 1 micron. These differences were correlated with the generation of spherical aberration complex profiles (with Zernike terms higher than 4th order) and with the production of distinct amounts of depth of focus. This method was also useful to deduce the base curve of diffractive surfaces.

Tilt and decentration with various intraocular lenses: A narrative review

We find that tilt and decentration of intraocular lens (IOL) commonly cause visual quality deterioration after cataract surgery. Multiple factors affect IOL tilt and decentration in the pre-, mid-, and post-operation phases. Moreover, the tilt and decentration of 1-piece IOL are less correlated with internal ocular HOAs than those of 3-piece IOL. Aspherical IOLs are more sensitive to decentration or tilt than spherical IOLs. Furthermore, the optical performance of toric IOLs with an accurate axis remains stable irrespective of tilt and decentration. The optical quality of asymmetric multifocal IOLs varies significantly after decentration and tilt in different directions. The image quality enhances or deteriorates in the direction of the decentered IOL. An extended depth of focus IOL can achieve good visual acuity in the distant, intermediate, and near range. Additionally, its tilt and decentration have less impact on the vision than bifocal and trifocal IOL. This is the first review that compares the effect of IOL tilt and decentration on image quality for various IOL designs. The result indicates that a deeper understanding of tilt and decentration of various IOLs can help achieve a better visual effect to visually improve refractive cataract surgery.

[Pseudo-accommodative intraocular lenses]

This article reviews pseudo-accommodative intraocular lenses (IOLs), providing an analysis of the terminology used in this field of ophthalmology and describing the design of modern IOLs, the technological features used to achieve pseudo-accommodation that meets the needs of patients, particularly the new extended depth of focus (EDOF) IOL technology. The article presents the main types of extended depth of focus IOLs, their description, advantages and disadvantages, as well as comparison with multifocal and monofocal IOLs based on clinical studies conducted in different countries.

Spherical aberration for expanding depth of focus

The increase in the depth of focus (DoF) for the treatment of presbyopia or cataracts is a topic of great interest for anterior segment surgeons who have seen how new surgical possibilities to achieve DoF enlargement have emerged. Nowadays, several technologies to extend the DoF are available, from corneal laser refractive surgery procedures in presbyopia to intraocular lens (IOL) implantation in cataract or refractive lens exchange. Some of these procedures are based on aspheric profiles, either in the cornea or in the IOL, which modulate the spherical aberration (SA) and, therefore, extend the light energy on different focal planes. The aim of this narrative review was to give an overall picture about the reasons why there is not a general solution persistent along time of SA induction to extend DoF, especially considering that SA depends on pupil diameter and this decreases with age.

Cataract: Advances in surgery and whether surgery remains the only treatment in future

Background

Cataract is the world's leading eye disease that causes blindness. The prevalence of cataract aged 40 years and older is approximately 11.8%-18.8%. Currently, surgery is the only way to treat cataracts.

Main Text

From early intracapsular cataract extraction to extracapsular cataract extraction, to current phacoemulsification cataract surgery, the incision ranges from 12 to 3 ​mm, and sometimes to even 1.8 ​mm or less, and the revolution in cataract surgery is ongoing. Cataract surgery has transformed from vision recovery to refractive surgery, leading to the era of refractive cataract surgery, and premium intraocular lenses (IOLs) such as toric IOLs, multifocal IOLs, and extended depth-of-focus IOLs are being increasingly used to meet the individual needs of patients. With its advantages of providing better visual acuity and causing fewer complications, phacoemulsification is currently the mainstream cataract surgery technique worldwide. However, patient expectations for the safety and accuracy of the operation are continually increasing. Femtosecond laser-assisted cataract surgery (FLACS) has entered the public's field of vision. FLACS is a combination of new laser technology and artificial intelligence to replace fine manual clear corneal incision, capsulorhexis, and nuclear pre-fragmentation, providing new alternative technologies for patients and ophthalmologists. As FLACS matures, it is being increasingly applied in complex cases; however, some think it is not cost-effective. Although more than 26 million cataract surgeries are performed each year, there is still a gap in the prevalence of cataracts, especially in developing countries. Although cataract surgery is a nearly ideal procedure and complications are manageable, both patients and doctors dream of using drugs to cure cataracts. Is surgery really the only way to treat cataracts in the future? It has been verified by animal experiments that lanosterol therapy in rabbits and dogs could make cataract severity alleviated and lens transparency partially recovered. Although there is still much to learn about cataract reversal, this groundbreaking work provided a new strategy for the prevention and treatment of cataracts.

Conclusions

Although cataract surgery is nearly ideal, it is still insufficient, we expect the prospects for cataract drugs to be bright.

Optical Performance of a Monofocal Intraocular Lens Designed to Extend Depth of Focus

PURPOSE

To test the performance of a new monofocal intraocular lens, intended to extend depth of focus (Tecnis Eyhance, ICB00; Johnson & Johnson Vision, Inc) (ICB-IOL), in comparison to a standard monofocal IOL (Tecnis 1-piece, ZCB00; Johnson & Johnson Vision, Inc) (ZCB-IOL) of the same platform and material.

METHODS

Assessment of the optical performance of the two IOLs was made in vitro using an optical test bench with a model eye. The spherical aberration, modulation transfer function (MTF), and area under the MTF (MTFa) were obtained for pupil sizes ranging from 2 to 5 mm. Through-focus MTFa curves between -3.00 and +1.00 diopters (D) were obtained with three pupil sizes (2, 3, and 4.5 mm). Halo formation was also assessed for both lenses.

RESULTS

The ICB-IOL had slightly worse optical quality at its best focus (ie, lower MTF scores at distance vision) and more negative spherical aberration than the ZCB-IOL for pupils ranging from 2 to 3 mm. The maximum of the through-focus MTFa curve of the ICB-IOL with a 2-mm pupil shifted to a myopic defocus of -0.50 D. For larger pupils (≥ 3.5 mm), there were no differences in spherical aberration, MTF scores, and halo energy between the two lenses.

CONCLUSIONS

The new ICB-IOL is a modified monofocal lens with 0.50 D of additional power in its central 2-mm zone and more negative spherical aberration values, which induce a myopic shift of the maximum of optical quality and could improve intermediate vision. For pupils larger than 3.5 mm, there were no differences between IOLs. The new ICB-IOL design would produce photic phenomena comparable to a standard IOL. [J Refract Surg. 2020;36(9):625-632.].

Extended depth-of-focus technology in intraocular lenses

The extended depth-of-focus (EDOF) intraocular lens (IOL) is an emerging technology that is designed to improve range of vision, especially at intermediate distances. In this review, we describe the clinical performance of 4 emerging EDOF IOL technologies; that is, small aperture, bioanalogic, diffractive optics, and nondiffractive optical manipulations. The American Academy of Ophthalmology generated a consensus statement for EDOF IOLs that provided benchmarks and recommendations for classifying an implant as an EDOF IOL as well as standardized testing criteria for evaluating performance. Although many types of EDOF technologies are being developed, there are important differences in their performance that require further testing and evaluation.

Predictors of Photic Phenomena with a Trifocal IOL

Aim

To assess predictive factors associated with glares and halos in patients undergoing cataract surgery with PanOptix trifocal IOL implantation.

Methods

Single-center retrospective study. One hundred and forty eyes from 70 patients with cataract were bilaterally implanted with a trifocal PanOptix aspherical diffractive lens between 2017 and 2019 and followed-up for six months. All patients were evaluated for refraction, corneal topography, and aberrometry pre- and post-operatively. Patients were assessed at 1 day, 6 days, 1 and 6 months after surgery. One and six months post-operatively patients were asked to complete a satisfaction questionnaire that included photic phenomena assessment. Main outcome measures were photic phenomena at 1 and 6 months of follow-up. Predictors of photic phenomena at 1 and 6 months were also analyzed.

Results

A higher corneal coma was associated with more mild halos at 6 months with no association regarding other degrees of severity. The lower the age the higher the glare or halos, the higher the lens thickness and the lower the anterior chamber depth or chord µ the less halos at 1 month. A significant proportion of patients had more none/mild compared to moderate/severe glare and halos both at 1 and 6 months post-operatively. Baseline BCVA was the only predictor of halos at 1 month and glare and halos at 6 months post-surgery.

Conclusion

On multivariate regression analyses, the only predictor of photic phenomena was baseline visual acuity, suggesting that patients that have a better visual acuity before surgery are more demanding regarding visual outcomes after surgery.

Assessment of the image quality of extended depth-of-focus intraocular lens models in polychromatic light

PURPOSE

The use of monochromatic light in the assessment of intraocular lenses (IOLs) has been criticized for not representing the real-world situation. This study aimed to measure and compare the image quality of 3 extended depth-of-focus (EDOF) IOL models in monochromatic and polychromatic light.

SETTING

David J Apple Laboratory, Heidelberg, Germany.

DESIGN

In vitro study.

METHODS

An optical metrology instrument was used to study image quality metrics of diffractive IOLs with chromatic aberration correction (Symfony and AT Lara) and a refractive lens (Mini Well). The modulation transfer function (MTF) was measured in green and polychromatic light at a 2.0 mm, 3.0 mm, and 4.0 mm aperture. The EDOF IOL's tolerance to defocus was tested against a monofocal lens.

RESULTS

The mean MTF of the EDOF IOL at far distance was decreased in polychromatic compared with monochromatic light. The largest effect was found in the refractive lens; however, at intermediate distance, only small differences occurred. In their tolerance to defocus, the EDOF IOLs were superior to the monofocal IOL. The diffractive IOL had higher MTFs than that of the refractive IOL at 2 primary foci, the refractive IOL's optical quality varied less with defocus at 3.0 mm. The refractive lens was the most susceptible to changes in aperture size.

CONCLUSION

The diffractive EDOF IOL was more resistant to chromatic effects than the refractive IOL. The EDOF IOLs provided an extended through-focus performance compared with the monofocal IOL, but differences in optical design, particularly pupil dependency, should be considered when refining IOL selection for patients.

Optical and visual quality assessment of an extended depth-of-focus intraocular lens based on spherical aberration of different sign

PURPOSE

To assess the optical quality and the visual performance of patients implanted with an extended depth-of-focus (EDOF) intraocular lens (IOL).

METHODS

Thirty-eight eyes underwent implantation of the Mini WELL Ready EDOF IOL and were evaluated at 3-months postsurgery. Higher-order aberrations (HOAs) and modular transfer function (MTF) were measured at 3- and 5-mm pupils. Binocular uncorrected-distance visual acuity (UDVA) and corrected-distance visual acuity (CDVA), uncorrected-distance intermediate visual acuity (UIVA) and corrected-distance intermediate visual acuity (CDIVA) at 80 cm, and uncorrected-distance near visual acuity (UNVA) and corrected-distance near visual acuity (CDNVA) at 40 cm were obtained. Postoperative refraction, binocular defocus curve, halometry and subjective ad hoc patients' questionnaire were also evaluated.

RESULTS

HOAs were 0.171 ± 0.046 µm and 0.406 ± 0.137 µm at 3 and 5 mm, respectively. MTFs decreased as the spatial frequency increased being comparable for both pupils. 92.10% of eyes were within ± 1.00D, and the mean postoperative spherical equivalent was - 0.25 ± 0.65D. Mean UDVA, UIVA and UNVA were 0.06 ± 0.12, 0.05 ± 0.10 and 0.26 ± 0.28 logMAR, respectively. Mean CDVA, CDIVA and CDNVA were - 0.01 ± 0.08, 0.06 ± 0.11 and 0.24 ± 0.12 logMAR, respectively. Defocus curve showed a continuous range of vision, especially at intermediate distances. Mean discrimination index was 0.79 ± 0.04. Questionnaire revealed that about 79% of patients reported a high or moderately high satisfaction with the procedure, and about 95% of patients would undergo the same procedure again.

CONCLUSIONS

The Mini WELL Ready EDOF IOL provided good optical and visual quality with high level of patient satisfaction and seems to be a valuable option to provide unaided vision at different distances minimizing visual disturbances.

Future Intraocular Lens Technologies

The future of intraocular lens (IOL) technology has already begun with a number of recent innovations. The postoperative change of refractive power will lead to a customized fine-tuning that provides patients with the individual vision they expect and with as much spectacle independence as possible. The latest-generation (2.0) Light-Adjustable Lens (RxSight) was recently introduced into clinical practice, with the first results being very encouraging. Other methods of altering the power of an already implanted IOL are under development. The same can be said about the correction of presbyopia, the so-called last frontier in refractive surgery. Extended depth-of-focus IOLs have been introduced, as has the technology of the pinhole IOL. The latter has therapeutic potential beyond the refractive aspect and has already proven helpful in cases of iris defects and irregular corneas. Several technologies are currently being tested to achieve-finally-an accommodative IOL. One such concept uses the (remaining) strength of the ciliary muscle, whereas another is triggered by the pupil reaction when shifting focus from far to near. Not an IOL itself, but rather a high-tech innovation that so far has mostly been implanted during cataract surgery, is a microelectronic sensor that measures habitual intraocular pressure (IOP) at any given time and promises to revolutionize the management of glaucoma patients. The last generation of this device (Eyemate; Implandata Opthalmics Products GmbH) is implanted during small-incision cataract surgery; the latest development is an even smaller sensor that will be inserted suprachoroidally before, in the near future, such a device will be part of a capsular ring. These IOP sensors are a prime example that IOL technology will continue to be a driving force in ophthalmology, with a positive impact far beyond cataract surgery.

Lens-based surgical correction of presbyopia. Where are we in 2020?

INTRODUCTION

Presbyopia is the progressive and irreversible loss of accommodation due to aging. It is one of the main causes of loss of quality of life in people from 45 years of age, due to the, often novel, dependence on spectacles. The eagerness to correct it by ophthalmologists impulsed by the desire of millions of people who suffer from it, has become one of the main drivers for the development of intraocular lens (IOL) technology over the last twenty years.

MATERIAL AND METHODS

This review briefly presents the different alternatives that have allowed us to improve the crystalline lens surgical approach of presbyopia; from monofocal lenses and monovision technique, accommodative, refractive, and diffractive multifocal lenses, and finally the most recent extended depth of focus/field lenses known as EDOFs.

RESULTS

Each IOL has its advantages, limitations and disadvantages. Furthermore, there is no single lens that suits the needs of all patients.

CONCLUSIONS

It is necessary to know the variety of lenses available, and to have an in-depth understanding of their optical properties, as well as the impact that these will have later on their clinical performance and on the visual quality of the patients. This should help us to select the best alternative for each of them.

Optimum Refractive Target in Patients with Bilateral Implantation of Extended Depth of Focus Intraocular Lenses

Purpose

To determine the refractive target of extended depth of focus (EDOF) intraocular lenses in dominant and non-dominant eyes which provides the best binocular vision at all ranges after cataract surgery.

Patients and Methods

This retrospective, single-center, non-comparative study included 47 patients who had undergone bilateral cataract surgery with implantation of EDOF IOLs (Tecnis Symfony or Tecnis Symfony Toric) targeting emmetropia in both eyes. Binocular uncorrected visual acuity at distance (UDVA), near (UNVA), intermediate (UIVA), and manifest refraction spherical equivalent (MRSE) were recorded between 1 and 3 months after the second-eye cataract surgery. Scattergrams for combined binocular UDVA, UIVA, UNVA and postoperative MRSE were plotted and the points of minima of the quadratic regression curve for the dominant and non-dominant eyes were considered as the optimum MRSE corresponding to the best overall visual acuity. Subgroup analysis of patients who achieved UDVA and UIVA ≥20/20 and UNVA ≥20/30 was also performed.

Results

For the overall group, the optimum MRSE was −0.08 D for dominant and −0.63 D for non-dominant eyes. In a subset of 17 patients who achieved excellent acuity at all distances, the mean MRSE for the dominant and non-dominant eyes was −0.07 ± 0.14 D and −0.21 ± 0.24 D, respectively.

Conclusion

Excellent visual acuity at all ranges can be achieved with bilateral EDOF intraocular lenses implanted after cataract surgery. Our results indicate the best results when the dominant eye is targeted at emmetropia and the nondominant eye is targeted between −0.21D and −0.63D, with excellent results shown with mild myopia of −0.21 in the non-dominant eyes. Future studies with larger sample sizes and subjective patient-reported outcomes may validate current study outcomes.

Initial Clinical Outcomes of a New Extended Depth of Focus Intraocular Lens

PURPOSE

To evaluate clinical and patient-reported outcomes of a new extended depth of focus intraocular lens (IOL).

METHODS

Data of patients treated between September 2017 and September 2018 who underwent a refractive lens exchange/cataract surgery with an implantation of the AT LARA 829MP IOL (Carl Zeiss Meditec AG, Jena, Germany) and attended the 1-week, 1-month, and 3-month follow-up visit were reviewed.

RESULTS

At 3 months, the percentage of eyes within ±0.50 diopters (D) of emmetropia was 86.7%. The mean binocular uncorrected distance visual acuity was -0.05 ± 0.09 logMAR and the mean binocular unaided near vision was 0.26 ± 0.14 logMAR. Of all patients, 90.3% were satisfied with their vision. The percentage of patients spectacle-free for near and distance vision was 83.6% and 95.4%, respectively. On a scale from 1 (no difficulty) to 7 (severe difficulty), there was an average 1.2 to 1.4 units increase in glare, halo, and starburst between the preoperative and 1-month visit, and a decrease of 0.2 to 0.3 units between the 1- and 3-month visit.

CONCLUSIONS

The new extended depth of focus IOL provided reasonable unaided near and distance vision, as well as spectacle independence and patient satisfaction. Some optical side effects were reported in the early postoperative period. [J Refract Surg. 2019;35(7):426-433.].

Visualization of Light Propagation with Multifocal Intraocular Lenses Using the Ouzo Effect

The number of presbyopia correcting intraocular lenses (IOLs) is increasing and new technologies are constantly emerging with the aim of correcting the loss of accommodation after cataract surgery. Various optical designs have been proposed to implement multifocality or an extended depth of focus (EDOF). Depending on the optical principle of an implanted lens, the visual performance often is deteriorated by superposition of individual image planes and halos of varying intensity. This experimental study presents a concept to visualize the light fields and especially the halos of mono- and multifocal IOLs using the well known alcoholic beverage “ouzo” in order to obtain qualitative data on the imaging characteristics. We conclude that ouzo is a useful, cost effective, and nonpolluting medium for beam visualization and an alternative to fluorescein or milk, which could find an application for educational purposes.

Clinical and aberrometric evaluation of a new extended depth-of-focus intraocular lens based on spherical aberration

PURPOSE

To compare the refractive, visual, and aberrometric results with a new extended depth-of-focus intraocular lens (EDOF IOL) based on alternating positive and negative spherical aberration in the central 3.0 mm optical zone and an aspheric monofocal IOL of the same platform.

SETTING

Ophthalmology, University Hospital of Verona, Italy.

DESIGN

Prospective case series.

METHODS

Cataract patients free from other ocular disease had bilateral implantation of the EDOF Mini Well IOL or the monofocal Mini IOL. Four to 6 weeks after second-eye surgery, the refraction, visual acuity, defocus curve, contrast sensitivity, and photic symptoms were assessed. Wavefront analysis was performed. The primary endpoint of was the amplitude of the dioptric interval for 0.1 logarithm of the minimum angle of resolution (logMAR) visual acuity. The secondary endpoint was an aberration comparison between the two IOLs.

RESULTS

The study comprised two groups of 25 patients each. The corrected distance visual acuity was better with the monofocal IOL by 0.02 logMAR (P = .03). The 0.1 logMAR dioptric interval was 2.0 diopters (D) for the EDOF IOL and 1.0 D for the monofocal IOL (P < .001). The mean CDVA at -2.0 defocus was 0.15 logMAR ± 0.08 (SD) and 0.52 ± 0.14 logMAR, respectively (P < .001). There was no difference in contrast sensitivity or photic symptoms. The optical aberrations at 4.0 mm and 6.0 mm aperture diameters were similar in the two groups.

CONCLUSION

The EDOF IOL based on spherical aberration provided greater depth of focus than the aspheric monofocal IOL without increasing optical aberrations and with few photic symptoms.

Functional assessment of a new extended depth-of-focus intraocular lens

BACKGROUND/OBJECTIVE

This study aimed to investigate the visual performance of a new extended depth-of-focus intraocular lens (EDOF-IOL).

SUBJECTS/METHODS

In this multicenter, prospective, observational study, we enrolled 97 patients who underwent cataract surgery or refractive lens exchange with implantation of the Mini Well EDOF-IOL (SIFI, Italy). Patients underwent postoperatively the following examinations between 4 and 8 weeks after surgery: corrected distance visual acuity (CDVA), reading speed with Radner's chart, distance-corrected near visual acuity (DCNVA), defocus curve, contrast sensitivity, and haloes quantitative assessment.

RESULTS

In the whole sample, the mean monocular CDVA and DCNVA were, respectively, 0.02 ± 0.07 logMAR and 0.38 ± 0.15 logRAD (logarithm of the reading acuity determination). In the 67 bilaterally implanted patients, binocular CDVA and DCNVA were better (0.00 ± 0.05 logMAR and 0.26 ± 0.13 logRAD) than the corresponding monocular values (p = 0.02 and p = 0.0002, respectively). Ninety-two percent of patients bilaterally implanted reached a binocular reading speed >80 words per minute at a 0.5 logRAD print size (corresponding to the common book print size). The defocus curves showed that the EDOF-IOL provided increased depth of focus through 2.0 D of defocus, with the best performance at 1.0 and 1.5 D. Contrast sensitivity was within normal limits at all spatial frequencies. The mean visual disturbance index was 0.08 ± 0.12, suggesting low night visual disturbances.

CONCLUSIONS

The new EDOF-IOL provided good visual acuity for distance, intermediate, and near vision, with no loss of contrast sensitivity and low risk of night visual disturbances.

Presbyopia: Effectiveness of correction strategies

Presbyopia is a global problem affecting over a billion people worldwide. The prevalence of unmanaged presbyopia is as high as 50% of those over 50 years of age in developing world populations, due to a lack of awareness and accessibility to affordable treatment, and is even as high as 34% in developed countries. Definitions of presbyopia are inconsistent and varied, so we propose a redefinition that states "presbyopia occurs when the physiologically normal age-related reduction in the eye's focusing range reaches a point, when optimally corrected for distance vision, that the clarity of vision at near is insufficient to satisfy an individual's requirements". Strategies for correcting presbyopia include separate optical devices located in front of the visual system (reading glasses) or a change in the direction of gaze to view through optical zones of different optical powers (bifocal, trifocal or progressive addition spectacle lenses), monovision (with contact lenses, intraocular lenses, laser refractive surgery and corneal collagen shrinkage), simultaneous images (with contact lenses, intraocular lenses and corneal inlays), pinhole depth of focus expansion (with intraocular lenses, corneal inlays and pharmaceuticals), crystalline lens softening (with lasers or pharmaceuticals) or restored dynamics (with 'accommodating' intraocular lenses, scleral expansion techniques and ciliary muscle electrostimulation); these strategies may be applied differently to the two eyes to optimise the range of clear focus for an individual's task requirements and minimise adverse visual effects. However, none fully overcome presbyopia in all patients. While the restoration of natural accommodation or an equivalent remains elusive, guidance is given on presbyopic correction evaluation techniques.

Fractal-structured multifocal intraocular lens

In this work, we present a new concept of IOL design inspired by the demonstrated properties of reduced chromatic aberration and extended depth of focus of Fractal zone plates. A detailed description of a proof of concept IOL is provided. The result was numerically characterized, and fabricated by lathe turning. The prototype was tested in vitro using dedicated optical system and software. The theoretical Point Spread Function along the optical axis, computed for several wavelengths, showed that for each wavelength, the IOL produces two main foci surrounded by numerous secondary foci that partially overlap each other for different wavelengths. The result is that both, the near focus and the far focus, have an extended depth of focus under polychromatic illumination. This theoretical prediction was confirmed experimentally by means of the Through-Focus Modulation Transfer Function, measured for different wavelengths.

Visual Performance of a New Extended Depth-of-Focus Intraocular Lens Compared to a Distance-Dominant Diffractive Multifocal Intraocular Lens

PURPOSE

To investigate the clinical performance of a new extended depth-of-focus (EDOF) intraocular lens (IOL) and compare it to that of a distance-dominant diffractive multifocal IOL.

METHODS

Patients implanted with an EDOF IOL (Mini Well; SIFI, Catania, Italy) inducing spherical aberration and with a multifocal IOL (ReSTOR SV25T; Alcon Laboratories, Inc., Fort Worth, TX) were analyzed. The following monocular parameters were investigated: corrected distance visual acuity (CDVA), distance-corrected near visual acuity (DCNVA), reading speed, defocus curve, contrast sensitivity, and halos and glare as quantified by a simulator (Halo & Glare Simulator; Eyeland-Design Network GmbH, Vreden, Germany) and questionnaire.

RESULTS

Twenty patients with the EDOF IOL and 37 with the multifocal IOL were enrolled. No statistically significant difference was observed for CDVA. The defocus curve of the EDOF IOL revealed no gaps for the intermediate range. Statistically significant differences were observed at -1.00 diopter (D) (EDOF IOL: 0.08 ± 0.09 logMAR; multifocal IOL: 0.21 ± 0.12 logMAR; P < .0001) and -1.50 D defocus (EDOF IOL: 0.15 ± 0.11 logMAR; multifocal IOL: 0.24 ± 0.13 logMAR; P = .0122). The reading speed at 40 cm was similar at all print sizes. The mean DCNVA was the same (EDOF IOL: 0.35 ± 0.14 logRAD, multifocal IOL: 0.35 ± 0.13 logRAD). No differences in contrast sensitivity were detected. According to the simulator, halos had a smaller mean size (P = .0439) and a lower mean intensity (P = .0222) with the EDOF IOL. No statistically significant differences were detected for glare size.

CONCLUSIONS

The new EDOF IOL performed similarly to a multifocal IOL at distance and near but was superior at intermediate distances. [J Refract Surg. 2018;34(4):228-235.].

Influence of material and haptic design on the mechanical stability of intraocular lenses by means of finite-element modeling

Intraocular lenses (IOLs) are used in the cataract treatment for surgical replacement of the opacified crystalline lens. Before being implanted they have to pass the strict quality control to guarantee a good biomechanical stability inside the capsular bag, avoiding the rotation, and to provide a good optical quality. The goal of this study was to investigate the influence of the material and haptic design on the behavior of the IOLs under dynamic compression condition. For this purpose, the strain-stress characteristics of the hydrophobic and hydrophilic materials were estimated experimentally. Next, these data were used as the input for a finite-element model (FEM) to analyze the stability of different IOL haptic designs, according to the procedure described by the ISO standards. Finally, the simulations of the effect of IOL tilt and decentration on the optical performance were performed in an eye model using a ray-tracing software. The results suggest the major importance of the haptic design rather than the material on the postoperative behavior of an IOL. FEM appears to be a powerful tool for numerical studies of the biomechanical properties of IOLs and it allows one to help in the design phase to the manufacturers.