Optical and clinical simulated performance of a new refractive extended depth of focus intraocular lens.

OBJECTIVES: The purpose of this study is to evaluate the optical and expected clinical performance of a new refractive Extended Depth of Focus (EDF) intraocular lens (IOL) designed to maintain a monofocal-like dysphotopsia profile. METHODS: Simulated visual acuity (sVA) with varying defocus was calculated using the area under the Modulation Transfer Function measured in an average eye model and from computer simulations in eye models with corneal higher-order aberrations. Tolerance to defocus was evaluated using computer simulations of the uncorrected distance sVA under defocus. To evaluate the dysphotopsia profile, halo pictures obtained using an IOL-telescope, as well as simulated images in a realistic eye model under defocus were assessed. The results of the refractive EDF were compared to those of a diffractive EDF of the same platform. RESULTS: The refractive EDF IOL provides similar range of vision to the diffractive EDF IOL with the same distance, and similar intermediate and near sVA. The refractive EDF IOL provides the same tolerance to hyperopia as the diffractive EDF but more tolerance to myopia. Halo pictures and simulations showed that the refractive EDF provides comparable dysphotopsia profile to the monofocal IOL and better than the diffractive EDF. CONCLUSIONS: The results of this preclinical study in clinically relevant conditions show that the new refractive EDF IOL is expected to provide similar range of vision to the diffractive IOL of the same platform and higher tolerance to refractive errors. The refractive EDF provides a dysphotopsia profile that is better than the diffractive EDF and comparable to that of the monofocal IOL, also in the presence of residual refractive errors.

Optical bench evaluation of the effect of pupil size in new generation monofocal intraocular lenses.

BACKGROUND: A new generation of enhanced monofocal IOLs has been introduced to slightly increase the depth of focus as compared to standard monofocal IOLs. The purpose of this study is to evaluate the effect of pupil size on the through-focus optical performance of three new enhanced monofocal IOLs, designed to improve the range of vision as compared to standard monofocal IOLs. METHODS: Optical bench testing in white light was performed for different pupils, using an average cornea eye. Distance image quality was evaluated using Modulation Transfer Function (MTF) measurements. Through-focus Visual Acuity (VA) was simulated from these measurements (sVA). Three enhanced monofocal IOLs (ICB00, ISOPure, and RayOne-EMV) and three standard monofocal IOLs: two aspheric (ZCB00 and SN60WF) and one spherical (AAB00) were included. RESULTS: The enhanced monofocal IOLs provided an improvement in the intermediate sVA as compared to standard monofocal IOLs. For ICB00, the improvement was independent of the pupil size, while for the ISOPure and RayOne-EMV, the intermediate sVA improved with increased pupil size. Similar to the spherical monofocal IOL, the ISOPure and RayOne-EMV showed a strong correlation between improvement in intermediate sVA and reduction of distance sVA and MTF, and increasing pupil size. ICB00 provided the same distance sVA as the aspheric monofocal IOLs and the lowest variability in MTF with pupil size. CONCLUSION: Optical bench results showed that the ISOPure and RayOne-EMV provide similar performance to a spherical monofocal IOL, with a strong pupil dependency for distance and intermediate vision. The other enhanced monofocal IOL, ICB00, provided a sustained improvement in simulated intermediate VA and maintained distance image quality comparable to that of the standard aspheric monofocal IOLs, even for larger pupils.

Peripheral vision and hazard detection with average phakic and pseudophakic optical errors.

The impact of peripheral optical errors induced by intraocular lenses was evaluated by simulating the average phakic and pseudophakic image qualities. An adaptive optics system was used to simulate the optical errors in 20° nasal and inferior visual field in phakic subjects. Peripheral resolution acuity, contrast sensitivity and hazard detection were evaluated. Pseudophakic errors typical for monofocal designs had a negative effect on resolution acuity and contrast sensitivity and the hazard detection task also showed increased false positive and misses and a longer reaction time compared to phakic optical errors. The induced peripheral pseudophakic optical errors affect the peripheral visual performance and thereby impact functional vision.

Enhancing the Intermediate Vision of Monofocal Intraocular Lenses Using a Higher Order Aspheric Optic.

PURPOSE: To describe and evaluate a new monofocal intraocular lens (IOL) designed to improve intermediate vision using a unique refractive technology. METHODS: The new monofocal lens is based on a higher order aspheric optic and is designed to improve intermediate vision. Simulated visual acuity from far to -2.00 diopters (D) was calculated using optical bench data. The effect of corneal higher order aberrations (HOAs) on simulated visual acuity, pupil size, and decentration was assessed using realistic computer eye models. The susceptibility to photic phenomena was evaluated by measuring preclinically the intensity of the light distribution in the retinal plane. The new lens design was compared to a standard aspheric monofocal IOL that shares the same platform, material, and primary spherical aberration as the new design. RESULTS: Simulated defocus curves showed increased simulated visual acuity in the intermediate range compared to a standard aspheric monofocal IOL with comparable distance vision, independently of the pupil size and corneal HOAs. At -1.50 D, the new IOL design provided a gain of approximately 0.1 logMAR, whereas at distance, the difference was less than 0.05 logMAR. The tolerance to decentration was also similar in both designs. Finally, experimental results indicate that the susceptibility to photic phenomena with the new lens design was similar to that of a standard aspheric monofocal IOL. CONCLUSIONS: Preclinical data showed that the new lens design improves intermediate vision while maintaining comparable distance image quality and keeping the same photic phenomena profile as a standard aspheric monofocal IOL. [J Refract Surg. 2020;36(8):520-527.].

New algorithm for toric intraocular lens power calculation considering the posterior corneal astigmatism.

PURPOSE: To assess the accuracy of toric intraocular lens (IOL) power calculations of a new algorithm that incorporates the effect of posterior corneal astigmatism (PCA). SETTING: Abbott Medical Optics, Inc., Groningen, the Netherlands. DESIGN: Retrospective case report. METHODS: In eyes implanted with toric IOLs, the exact vergence formula of the Tecnis toric calculator was used to predict refractive astigmatism from preoperative biometry, surgeon-estimated surgically induced astigmatism (SIA), and implanted IOL power, with and without including the new PCA algorithm. For each calculation method, the error in predicted refractive astigmatism was calculated as the vector difference between the prediction and the actual refraction. Calculations were also made using postoperative keratometry (K) values to eliminate the potential effect of incorrect SIA estimates. RESULTS: The study comprised 274 eyes. The PCA algorithm significantly reduced the centroid error in predicted refractive astigmatism (P < .001). With the PCA algorithm, the centroid error reduced from 0.50 @ 1 to 0.19 @ 3 when using preoperative K values and from 0.30 @ 0 to 0.02 @ 84 when using postoperative K values. Patients who had anterior corneal against-the-rule, with-the-rule, and oblique astigmatism had improvement with the PCA algorithm. In addition, the PCA algorithm reduced the median absolute error in all groups (P < .001). CONCLUSIONS: The use of the new PCA algorithm decreased the error in the prediction of residual refractive astigmatism in eyes implanted with toric IOLs. Therefore, the new PCA algorithm, in combination with an exact vergence IOL power calculation formula, led to an increased predictability of toric IOL power.

Degradation of Visual Performance With Increasing Levels of Retinal Stray Light.

PURPOSE: To quantify the effect of induced stray light on halo size, luminance threshold, and contrast sensitivity. METHODS: Retinal stray light was induced in five healthy subjects using different photographic filters. The stray light induced ranged from levels observed in intraocular lenses (IOLs) with glistenings (low) to cataract level (high). The visual impact was measured for halo size, luminance detection threshold, and contrast sensitivity with and without a glare source. RESULTS: The amount of retinal stray light induced by the different filters was similar when measured using the psychophysical method and the optical bench method. Low amounts of induced stray light cause the halo size to increase by 21%, the luminance detection threshold to increase by 156%, and contrast sensitivity to decrease by 10% to 21% dependent on spatial frequency and presence of a glare source. The visual impact percentages for high amounts of induced stray light were, respectively, 76%, 2130%, and 30% to 49%. In the presence of a glare source, contrast sensitivity losses were larger and shifted to lower spatial frequencies. CONCLUSIONS: Low levels of retinal stray light can cause significant increases in halo sizes, elevations in luminance detection thresholds, and reductions in contrast sensitivity whether or not a glare source is present.

Preclinical metrics to predict through-focus visual acuity for pseudophakic patients.

This study compares the clinical through-focus visual acuity (VA) in patients implanted with different intraocular lens (IOL) to optical bench testing of the same IOLs to evaluate the suitability of optical metrics of predicting clinical VA. Modulation transfer function and phase transfer function for different spatial frequencies and US Air Force pictures were measured using an optical bench for two monofocal IOLs, three multifocal IOLs and an extended range of vision IOL. Four preclinical metrics were calculated and compared to the clinical through-focus VA collected in three different clinical studies (243 patients in total). All metrics were well correlated (R(2)≥0.89) with clinical data and may be suitable for predicting through-focus VA in pseudophakic eyes.

Effect of the equivalent refractive index on intraocular lens power prediction with ray tracing after myopic laser in situ keratomileusis.

PURPOSE: To determine the impact of the equivalent refractive index (ERI) on intraocular lens (IOL) power prediction for eyes with previous myopic laser in situ keratomileusis (LASIK) using custom ray tracing. SETTING: AMO B.V., Groningen, the Netherlands, and the Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA. DESIGN: Retrospective data analysis. METHODS: The ERI was calculated individually from the post-LASIK total corneal power. Two methods to account for the posterior corneal surface were tested; that is, calculation from pre-LASIK data or from post-LASIK data only. Four IOL power predictions were generated using a computer-based ray-tracing technique, including individual ERI results from both calculation methods, a mean ERI over the whole population, and the ERI for normal patients. For each patient, IOL power results calculated from the four predictions as well as those obtained with the Haigis-L were compared with the optimum IOL power calculated after cataract surgery. RESULTS: The study evaluated 25 patients. The mean and range of ERI values determined using post-LASIK data were similar to those determined from pre-LASIK data. Introducing individual or an average ERI in the ray-tracing IOL power calculation procedure resulted in mean IOL power errors that were not significantly different from zero. The ray-tracing procedure that includes an average ERI gave a greater percentage of eyes with an IOL power prediction error within ±0.5 diopter than the Haigis-L (84% versus 52%). CONCLUSION: For IOL power determination in post-LASIK patients, custom ray tracing including a modified ERI was an accurate procedure that exceeded the current standards for normal eyes.

Explanted multifocal intraocular lenses.

UNLABELLED: We report 2 cases in which single-piece multifocal acrylic intraocular lenses (IOLs) were explanted because of complications related to the presence of glistenings in the bulk of the IOL optic. In both cases, the patients complained about blurry or hazy vision. In vivo slitlamp examinations prior to IOL explantation confirmed the presence of severe glistenings in the IOL optic in 1 case and moderate glistenings in the second case. In the first case, the symptoms resolved and both corrected and uncorrected distance visual acuities improved by 4 lines following IOL exchange with a monofocal IOL. In the second case, the visual symptoms persisted with a hard contact lens. Symptoms resolved following an exchange with a monofocal IOL that was free of glistenings. These findings indicate that straylight caused by IOLs with glistenings may be clinically significant in cases in which multifocal IOLs are implanted and patients require optimized retinal sensitivity. FINANCIAL DISCLOSURE: Mr. van der Mooren, Ms. Langeslag, and Dr. Piers are employees of Abbott Medical Optics, Inc. Drs. Steinert and Tyson are consultants to Abbott Medical Optics Inc.

Extending the range of vision using diffractive intraocular lens technology.

PURPOSE: To describe and to experimentally assess a new intraocular lens (IOL) design using new diffractive technology. SETTING: AMO Groningen b.v., Groningen, Netherlands. DESIGN: Experimental study. MATERIALS AND METHODS: The basic principles of the new diffractive technology are described. The new IOL comprises two diffractive technologies; one is designed to extend the range of vision by elongating the focus, and the other increases the retinal image contrast by correcting chromatic aberration. To assess the potential visual performance, simulations were carried out in clinically verified eye models to predict the clinical defocus curves (visual acuity). The optical performance of the new lens design was evaluated by optical measurements in a model eye. The model eye had a cornea having the spherical aberration and chromatic aberration of an average cataract patient. The measurements were performed in white light and monochromatic light. RESULTS: The simulations suggested an increase in visual acuity of 0.27 logMAR as compared to an aspherical monofocal IOL in the range from -1 to -3 diopter defocus. The white light modulation transfer function in the far focus was identical to that of a monofocal IOL. The new lens demonstrated negative chromatic aberration, therefore showing the capability to actively reduce ocular chromatic aberration. The experiments also show retinal image characteristics of an extended light source that suggest that dysphotopsias (halos) of the new IOL are comparable to those associated with monofocal IOLs. CONCLUSIONS: The application of new IOL diffractive technology enabled optical characteristics that suggested that an extended range of vision can be obtained without compromising distance vision. FINANCIAL DISCLOSURE: All authors are employees of Abbott Medical Optics, Inc.

Impact of intraocular lens material and design on light scatter: In vitro study.

PURPOSE: To determine the typical in vitro straylight levels for intraocular lenses (IOLs) of different materials and designs. SETTING: Abbott Medical Optics, Inc., Groningen, the Netherlands. DESIGN: Experimental study. METHODS: Two optical bench setups were used to determine baseline straylight levels of IOLs placed in a saline-filled cuvette: one for forward scatter positions between 0.6 and 3.0 degrees and one for positions up to 22.0 degrees. Line-spread functions were measured using the small-angle setup, and scattered light intensity was measured using the wide-angle setup. From these measurements, the angular dependent straylight parameter was calculated. Ten IOLs of different materials (hydrophobic and hydrophilic) and designs (monofocal or diffractive multifocal and spheric or aspheric) were studied, and their measured straylight levels were compared with the levels in a 20-year-old and a 70-year-old healthy noncataractous human crystalline lens. RESULTS: Irrespective of the material or design, monofocal IOLs had straylight levels below or close to those of a 20-year-old human crystalline lens. Diffractive multifocal IOLs had straylight levels higher than those of monofocal IOLs but less than those of a 70-year-old human crystalline lens. With increasing angle, hydrophobic IOLs showed a gradual decrease in straylight level. After an initial decrease, hydrophilic IOLs showed an increase in straylight level for larger angles. CONCLUSIONS: The baseline straylight levels of IOLs were design and material dependent (hydrophobic < hydrophilic; monofocal < diffractive multifocal). Most monofocal IOLs had straylight levels below the levels in a 20-year-old human crystalline lens.

Binocular visual acuity for the correction of spherical aberration in polychromatic and monochromatic light.

Correction of spherical (SA) and longitudinal chromatic aberrations (LCA) significantly improves monocular visual acuity (VA). In this work, the visual effect of SA correction in polychromatic and monochromatic light on binocular visual performance is investigated. A liquid crystal based binocular adaptive optics visual analyzer capable of operating in polychromatic light is employed in this study. Binocular VA improves when SA is corrected and LCA effects are reduced separately and in combination, resulting in the highest value for SA correction in monochromatic light. However, the binocular summation ratio is highest for the baseline condition of uncorrected SA in polychromatic light. Although SA correction in monochromatic light has a greater impact monocularly than binocularly, bilateral correction of both SA and LCA may further improve binocular spatial visual acuity which may support the use of aspheric-achromatic ophthalmic devices, in particular, intraocular lenses (IOLs).

Effects of glistenings in intraocular lenses.

Glistenings consist of multiple microvacuoles in intraocular lenses (IOLs) that cause retinal stray light and may affect quality of vision. For four IOL types, the microvacuole particle size distribution and particle volume density was measured using confocal light microscopy and dark field microscopy, and the corresponding extinction coefficient γ was determined. The light scatter contribution induced by microvacuoles was measured as function of both angle and extinction, and was verified by calculations using Mie theory. Two IOL types possessed significant glistenings having stray light levels higher than that of a healthy 20 year old crystalline lens corresponding to γ ≥ 0.08 mm(-1).

Theoretical performance of intraocular lenses correcting both spherical and chromatic aberration.

PURPOSE: To assess the performance and optical limitations of intraocular lenses (IOLs) correcting both longitudinal spherical aberration (LSA) and longitudinal chromatic aberration (LCA) compared to standard spherical and aspheric IOLs. METHODS: Using a set of 46 white light, pseudophakic eye models representing a population of cataract patients, retinal image quality was assessed for three IOL designs-standard spherical IOLs; aspheric IOLs, correcting a fixed amount of LSA; and aspheric refractive/diffractive IOLs, correcting a fixed amount of LSA and LCA. Depth of field and tolerance to IOL misalignments were also assessed. RESULTS: The improvement factor, based on the area under the radial polychromatic modulation transfer function (pMTF) curve of the IOL, correcting both average LSA and LCA over the aspheric IOL was 1.19±0.12, and over the spherical IOL was 1.43±0.29. Within the range of ±1.00 diopter of defocus, pMTF of the IOL correcting both LSA and LCA was equal or higher than both the spherical and aspheric IOLs. The IOL could be decentered up to 0.6 to 0.8 mm before the performance degraded below that of a spherical IOL. CONCLUSIONS: This is the first study that evaluates IOLs correcting both LSA and LCA in the presence of corneal higher order aberrations. Intraocular lenses that correct both LSA and LCA improve simulated retinal image quality over spherical IOLs and IOLs that correct LSA alone, without sacrificing depth of field or tolerance to decentration. Correction of LCA in combination with LSA shows the potential to improve visual performance.

Spherical aberrations of human astigmatic corneas.

PURPOSE: To evaluate whether the average spherical aberration of human astigmatic corneas is statistically equivalent to human nonastigmatic corneas. METHODS: Spherical aberrations of 445 astigmatic corneas prior to laser vision correction were retrospectively investigated to determine Zernike coefficients for central corneal areas 6 mm in diameter using CTView (Sarver and Associates). Data were divided into groups according to cylinder power (0.01 to 0.25 diopters [D], 0.26 to 0.75 D, 0.76 to 1.06 D, 1.07 to 1.53 D, 1.54 to 2.00 D, and >2.00 D) and according to age by decade. Spherical aberrations were correlated with age and astigmatic power among groups and the entire population. Statistical analyses were conducted, and P<.05 was considered statistically significant. RESULTS: Mean patient age was 42.6±11 years. Astigmatic corneas had an average astigmatic power of 0.78±0.58 D and mean spherical aberration was 0.25±0.13 µm for the entire population and approximately the same (0.27 µm) for individual groups, ranging from 0.23 to 0.29 µm (P>.05 for all tested groups). CONCLUSIONS: Mean spherical aberration of astigmatic corneas was not correlated significantly with cylinder power or age (P>.05). Spherical aberrations are similar to those of nonastigmatic corneas, permitting the use of these additional data in the design of aspheric toric intra-ocular lenses.

Combining in vitro test methods for measuring light scatter in intraocular lenses.

Intraocular lenses (IOLs) are designed for implantation for vision correction following cataract removal. The IOL typically replaces a cataractous natural lens that exhibits very high levels of light scattering. The amount of scattering is significantly reduced with an IOL, though it is rarely quantified and both the surface and the bulk of the intraocular lens may contribute to light scatter at some level, and in some cases potentially affecting patients' post-operative quality of vision. The purpose of this paper is to describe two complementary in-vitro quantitative methods for measuring light scatter caused by IOLs. The first method directly measures light scatter from the lens in one plane for angles larger than two degrees. The second method measures light scatter in an eye model including the focal point out to three degrees in the image plane. The measured amount of light scatter from an IOL is typically lower than that found in healthy donor crystalline lenses of various ages that are used as a basis for comparison.