Through-focus Modulation Transfer Function Research Articles

In vitro optical assessment of three types of non-diffractive extended depth-of-focus intraocular lenses

Objective: To evaluate the in vitro optical performance of three types of non-diffractive extended depth-of-focus (EDoF) intraocular lenses (IOLs). Methods: Experimental study. Three Vivity IOLs, three Eyhance IOLs, and three ES60 IOLs were included. The professional optical bench OptiSpheric® IOL PRO 2 and an ISO-2 corneal model were applied. The through-focus modulation transfer function (MTF) and predicted visual acuity (logarithm of the minimum angle of resolution) of different spatial frequencies and different focuses under apertures of 3.0 mm and 4.5 mm were recorded. The aspheric monofocal (Tecnis ZCB00), diffractive EDoF (Tecnis Symfony), and trifocus (STF1) IOLs, as well as the lowest visual requirement criteria of EDoF IOLs of American Academy of Ophthalmology served as assessment controls. Results: For the 3.0-mm aperture, the peak value of the MTF was highest with ZCB00, followed by Eyhance, ES60, Vivity, Symfony, and STF1. All experimental non-diffractive EDoF IOLs had two MTF peaks, and the distance between both peaks was longest with Vivity (1.76 D), followed by ES60 (1.43 D) and Eyhance (1.36 D). Among the control IOLs, Symfony had two MTF peaks, and the peak MTF of the intermediate focus was highest. STF1 had three MTF peaks, and the peak MTF of the near focus was highest. For the 4.5-mm aperture, the ranking of the MTF peak of the six types of IOLs was the same as that for the 3.0-mm aperture. Vivity had an increased MTF peak of the distance focus, but a decreased intermediate focus MTF peak, while the MTF peaks of the distance, intermediate, and near focuses in the other IOLs decreased, compared to those for the 3.0-mm aperture. The predicted visual acuity of the distance focus of the three types of non-diffractive EDoF IOLs was all better than 0.0. The predicted visual acuity of the intermediate focus of the Vivity IOL and the ES60 IOL was 0.11 and 0.05 better than that of the Eyhance IOL, respectively. Based on the predicted visual acuity of 0.2, Vivity and ES60 had a depth of focus of at least 0.50 D exceeding ZCB00, while Eyhance had a depth of focus of 0.40 D exceeding ZCB00. Conclusion: In the experiments in vitro, the three types of non-diffractive EDoF IOLs exhibited varying degrees of intermediate to near focus optical performance while maintaining distance focus optical performance. The Eyhance IOL showed better distance focus optical performance than ES60 and Vivity IOL. The Vivity IOL and the ES60 IOL showed better depth of focus extensions than the Eyhance IOL and met the lowest visual requirement criteria of EDoF IOLs of American Academy of Ophthalmology.

Effect of decentration and tilt on the in vitro optical quality of monofocal and trifocal intraocular lenses.

To evaluate and compare the effect of decentration and tilt on the optical quality of monofocal and trifocal intraocular lenses (IOL). Optical quality of a monofocal IOL (AcrySof IQ SN60WF; Alcon Laboratories, Inc., USA) and a trifocal IOL (AcrySof IQ PanOptix; Alcon Laboratories, Inc., USA) was assessed using an in vitro optical bench (OptiSpheric IOL R&D; Trioptics GmbH, Germany). At apertures of 3.0mm and 4.5mm, modulation transfer function (MTF) at spatial frequency of 50 lp/mm, MTF curve and the United States Air Force (USAF) resolution test chart of the two IOLs were measured and compared at their focus with different degrees of decentration and tilt. Optical quality at infinity, 60cm and 40cm and the through-focus MTF curves were compared when the two IOLs were centered at apertures of 3.0mm and 4.5mm. Spectral transmittance of the two IOLs was measured by the UV-visible spectrophotometer (UV 3300 PC; MAPADA, China). The SN60WF and the PanOptix filtered blue light from 400 to 500nm. Both IOLs at the far focus and the PanOptix at the intermediate focus showed a decrease in optical quality with increasing decentration and tilt. The PanOptix demonstrated enhanced optical quality compared to the previous gradient at the near focus at a decentration range of 0.3-0.7mm with a 3.0mm aperture, and 0.5mm with a 4.5mm aperture, whereas other conditions exhibited diminished optical quality with increasing decentration and tilt at the focus of both IOLs. When the two IOLs were centered, the SN60WF had better optical quality at infinity, while the PanOptix had better optical quality at 60cm and 40cm defocus. The optical quality of the SN60WF exceeded that of the PanOptix at far focus, with a 3mm aperture decentration up to 0.7mm and a 4.5mm aperture decentration up to 0.3mm; this observation held true for all tilts, irrespective of aperture size. As both decentration and tilt increased, the optical quality of the SN60WF deteriorated more rapidly than that of the PanOptix at the far focal point. The SN60WF showed a decrease in optical quality with increasing decentration and tilt. Optical quality of the PanOptix at the near focus increased in some decentration conditions and decreased in some conditions, while it showed a decrease at the other focuses with increasing decentration. While tilt only had a negative effect on optical quality. When both IOLs were centered, the PanOptix provided a wider range of vision, while the SN60WF provided better far distance vision. At the far focus, the SN60WF has better resistance to tilt than the PanOptix, but the optical quality degrades more quickly when decentered and tilted.

Tolerance to decentration of biaspheric intraocular lenses with refractive phase-ring extended depth of focus and diffractive trifocal designs.

This study aimed to investigate the in vitro tolerance to decentration of biaspheric intraocular lens (IOLs) with refractive phase-ring extended depth-of-focus (EDOF) and diffractive trifocal designs. This experimental study was carried out at the Department of Optics and Optometry and Vision Science, University of Valencia, Spain. The modulation transfer function (MTF) of the ETLIO130C EDOF and the TFLIO130C trifocal IOLs (AST Products Inc., Billerica, MA, USA) were determined at different levels of decentration for a given wavelength and pupil diameter using the PMTF optical bench (Lambda-X Ophthalmics, Nivelles, Belgium). The modulation transfer function (MTF) curves, the through-focus MTF curves, and the Strehl ratios were measured at 3-mm pupil aperture for 0.25-, 0.50- and 0.75-mm decentration. The optical design of the trifocal TFLIO130C IOL is robust to small decentrations, with virtually no change in MTF response for 0.25 mm decentration. For greater decentration levels, the MTF response is slightly reduced with increasing decentration. The ETLIO130C EDOF design is robust to decentration, as the MTF response is only minimally affected when increasing the decentration up to 0.75 mm. MTF responses are slightly reduced with greater levels of decentration, but the range of focus provided by both trifocal and EDOF designs are preserved. The effects for average levels of decentration reported in the literature are minimum for both IOL designs.

Real-time assessment of spectrometer alignment using modulation transfer function (MTF) measurement

The effective spectral resolution of a spectrometer that utilizes dispersive optics is normally limited by either the size of the sensor pixels or the optical resolution of the focusing optics. Therefore, achieving optimal optical alignment is crucial to maximize the spectrometer's effective spectral resolution. In this paper, we introduce a laboratory method for real-time assessment of spectrometer alignment by measuring the modulation transfer function (MTF). The modulation on spectral signal is generated using an interferometer, allowing control of the modulation frequency by adjusting the optical path difference. The results show that the proposed technique can provide useful information about the alignment of the spectrometer, which can be used to obtain the optimum alignment of the spectrometer. The accuracy of the proposed method was confirmed by comparing the MTF measurement, and hence the resolution evaluation, with the specifications of a commercial spectrometer. In addition, we demonstrate the use case of the proposed method by performing a through-focus MTF measurement on a custom-built spectrometer with known misalignments.

Optical Performance of a Segmented Extended-Depth-of-Focus Intraocular Lens under the Influence of Different Values of Spherical Aberration Generated by Refractive Surgery.

Corneal refractive surgery induces high-order aberrations, specifically spherical aberration (SA). These aberrations can have implications when patients later develop cataracts and require the implantation of multifocal intraocular lenses (MIOLs). MIOLs with asymmetric designs pose challenges in predicting outcomes, particularly in these cases. The aim of this study was to evaluate how different values of SA, resulting from various types of refractive surgeries, affect the optical performance of the FEMTIS Comfort intraocular lens. The through-focus modulation transfer function (TF-MTF) curve and high-contrast images of tumbling E were used as parameters to assess the optical performance of the MIOL. These parameters were measured using an adaptive optics visual simulator. Increasingly negative values of SA make the MIOL more bifocal, moderating its extended-depth-of-focus characteristic. Conversely, higher positive SA values cause the TF-MTF curve to shift towards positive vergences, leading to worsened distance vision in the +1.00 to +2.00 D range, but improved vision in the +0.50 D to +1.00 D range. Assessing SA in patients prior to implanting MIOLs with asymmetric designs is necessary for predicting outcomes and making informed decisions based on the visual requirements of patients.

Comparison of the Polychromatic Image Quality of Two Refractive-Segmented and Two Diffractive Multifocal Intraocular Lenses.

Evaluating chromatic aberration for a multifocal intraocular lens (MIOL) in vitro is essential for studying its performance because it helps determine the most appropriate lens for each patient, enhancing surgical outcomes. While refractive MIOLs with angular power variation have shown positive clinical outcomes, studies of these MIOLs on optical benches primarily employed monochromatic green light, neglecting the impact of longitudinal chromatic aberration (LCA) on MIOL performance. To address this gap, we evaluated the through-focus modulation transfer function (TF-MTF) and the point spread function (PSF) of two refractive segmented extended depth of focus intraocular lenses (IOLs) (Femtis Comfort and Precizon Presbyopic), comparing the results with those obtained with two widely known diffractive multifocal intraocular lenses (AcrySof IQ ReSTOR and FineVision Pod F). Measurements of the TF-MTF were conducted using both monochromatic and polychromatic light in a customized optical bench. The refractive designs exhibited distinct haloes in the PSFs. When comparing the refractive and diffractive designs, opposite signs of LCA were observed at near foci. These findings emphasize the influence of the optical design of IOLs on their performance under polychromatic light, providing valuable information for vision care professionals when selecting the most suitable lens for each patient.

Peripheral optical anisotropy in refractive error groups.

This study investigated differences in peripheral image quality with refractive error. Peripheral blur orientation is determined by the interaction of optical aberrations (such as oblique astigmatism) and retinal shape. By providing the eye with an optical signal for determining the sign of defocus, peripheral blur anisotropy may play a role in mechanisms of accommodation, emmetropisation and optical myopia control interventions. This study investigated peripheral through-focus optical anisotropy and image quality and how it varies with the eye's refractive error. Previously published Zernike coefficients across retinal eccentricity (0, 10, 20 and 30° horizontal nasal visual field) were used to compute the through-focus modulation transfer function (MTF) for a 4 mm pupil. Image quality was defined as the volume under the MTF, and blur anisotropy was defined as the ratio of the horizontal to vertical meridians of the MTF (HVRatio). Across the horizontal nasal visual field (at 10, 20 and 30°), the peak image quality for emmetropes was within 0.3D of the retina, as opposed to myopes whose best focus was behind the retina (-0.1, 0.4 and 1.5D, respectively), while for hyperopes it lay in front of the retina (-0.5, -0.6 and -0.6D). At 0.0D (i.e., on the retina), emmetropes and hyperopes both exhibited horizontally elongated blur, whereas myopes had vertically elongated blur (HVRatio=0.3, 0.7 and 2.8, respectively, at 30° eccentricity). Blur in the peripheral retina is dominated by the so-called "odd-error" blur signals, primarily due to oblique astigmatism. The orientation of peripheral blur (horizontal or vertical) provides the eye with an optical cue for the sign of defocus. All subject groups had anisotropic blur in the nasal visual field; myopes exhibited vertically elongated blur, perpendicular to the blur orientation of emmetropes and hyperopes.

Beam-Shaping Extended Depth of Focus Intraocular Lens: Optical Assessment With Corneas of Increasing Spherical Aberration.

To assess the optical quality and halo formation of a beam-shaping extended depth-of-focus (EDOF) intraocular lens (IOL) (AcrySof IQ Vivity; Alcon Laboratories, Inc) with corneas of long-range spherical aberration (SA) such as those resulting from myopic laser ablations. The optical quality of the EDOF IOL and a reference monofocal IOL was evaluated with three corneas (A, B, and C, with SA =+0.135, +0.290, +0.540 µm, respectively, for a 5.15-mm pupil at the IOL plane). The through-focus modulation transfer function area (MTFa) curves were obtained between -5.00 and +2.00 diopters (D) defocus range. The halo was also assessed with the three corneas. Through-focus MTFa curves for a 4.5-mm IOL pupil showed a slight decrease in the maximum MTFa value provided by the EDOF IOL compared to the monofocal IOL in the three corneal situations (A: 45.9 vs 38.6 units; B: 41.1 vs 33.1 units, and C: 26.9 vs 23.8 units). For the 3.0-mm pupil, the EDOF IOL also had lower maximum MTFa than the monofocal IOL; however, the depth-of-focus increased to -2.20 D. With corneas A and B, the halo induced was of low energy with both IOLs. With cornea C, the EDOF IOL created a much larger and intense halo. The EDOF IOL provided a good distance optical performance and an extended range of focus of approximately 2.00 D, with a halo of low intensity when evaluated with a corneal SA similar to the one induced by a low to moderate myopic ablation. With a high myopic ablation, the halo induced would be of considerable size and energy. [J Refact Surg. 2023;39(2):95-102.].

Optical Assessment and Expected Visual Quality of Four Extended Range of Vision Intraocular Lenses.

To assess the optical performance of four extended range of vision (ERV) intraocular lenses (IOLs) and predict the visual quality of the average pseudophakic patient. Four ERV IOLs (LuxSmart, Bausch & Lomb; Vivity, Alcon Laboratories, Inc; Tecnis Eyhance, Johnson & Johnson Vision; and Isopure, PhysIOL) were inserted in an on-bench model eye. Their performance was assessed using through-focus modulation transfer function (MTF)-based metrics, through-focus point spread function, and halo analysis for three pupils (2.0, 3.0, and 4.5 mm). The expected visual acuity and the range of vision was estimated from the through-focus area under the MTF curve. A monofocal IOL (Tecnis ZCB00; Johnson & Johnson Vision) was included as reference. The Tecnis ZCB00 showed the highest image quality at far for all pupil conditions, closely followed by the Tecnis Eyhance. The LuxSmart and Vivity performed similarly in the intermediate range (-1.00 to -2.00 diopters [D]) with a 3.0-mm pupil and showed better performance than the other ERV IOLs for that range. All ERV lenses presented pupil dependent performance. All lenses reached normal expected visual acuity (0.0 logMAR) at far distance. The Tecnis ZCB00, Tecnis Eyhance, and Isopure decreased their expected visual acuity with defocus (0.1 logMAR at 66 cm) faster than the LuxSmart and Vivity (0.0 logMAR at 66 cm). The LuxSmart and Vivity produced greater halos than the Tecnis ZCB00, but they showed little change with larger pupils. The Isopure lens showed a pupil-dependent halo. The expected visual acuity decreased with the object distance differently, depending on the ERV design. The Vivity and LuxSmart lenses showed an expanded imaging capability (⩾ 0.50 D) with respect to a monofocal lens that may benefit intermediate vision. The Tecnis Eyhance and Isopure lenses showed more modest extensions that mainly rely on pupil constriction. [J Refract Surg. 2022;38(11):688-697.].

Laboratory Evaluation of Halos and Through-Focus Performance of Three Different Multifocal Intraocular Lenses.

To compare the halo features and through-focus performance of three different multifocal intraocular lenses (MIOLs) that provide distance, intermediate, and near vision in a clinical trial. A trifocal diffractive MIOL (AT LISA tri 839MP; Carl Zeiss Meditec), a diffractive extended depth-of-focus MIOL (TECNIS Symfony ZXR00; Abbott Laboratories, Inc), and a rotational asymmetric refractive MIOL (SBL-3; Lenstec, Inc) were assessed in a modified International Organization for Standardization eye model. The modulation transfer function (MTF) at the IOLs' foci was obtained using aperture sizes of 3 and 4.5 mm. Through-focus MTF curves were compared among all MIOLs. Images of the slit pattern were used to assess halo formation and characteristics. The AT LISA tri and Symfony IOLs showed symmetric halos. The halos of the AT LISA tri IOL were larger but weaker in distance and near foci, whereas the halos of the Symfony IOL were smaller and fainter in intermediate focus. The halos of the SBL-3 IOL were asymmetric and appeared as tangentially downward weaker halos. The optical performance of diffractive MIOLs gradually deteriorated as the aperture increased. The distance foci of the AT LISA tri and SBL-3 IOLs were of similar superior optical quality, the intermediate focus of the Symfony IOL showed the best optical quality, and the near focus of the SBL-3 IOL outperformed the near foci of the remaining IOLs. The differences in the design of the MIOLs translate to differences in optical performance at their foci, through-focus expressions, and halo features, which can provide further information to surgeons when selecting what IOL to implant. [J Refract Surg. 2022;38(9):552-558.].

Optical and Clinical Outcomes of an Enhanced Monofocal Intraocular Lens for High Hyperopia.

To evaluate the optical and clinical performance of an enhanced monofocal intraocular lens (IOL) (TECNIS Eyhance ICB00; Johnson & Johnson Vision) in patients with high hyperopia and a short axial length. Power mapping, wavefront analysis, and the through-focus modulation transfer function area (TF-MTFa) were measured in vitro for three IOL powers (10.00, 20.00, and 30.00 diopters [D]). The clinical study included 22 patients with an axial length of less than 22.5 mm. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity and binocular defocus curve were evaluated 6 months postoperatively. For the three IOL powers, the power mapping revealed an increase in positive power from the periphery to the center of the lens, providing an extra positive correction of 1.00 D for a 2-mm pupil size. The TF-MTFa curves showed only a peak of maximum MTFa at the distance focus. As the pupil size became smaller, there was a focus extension effect, providing an extended depth of focus of up to -1.50 D for a 2-mm pupil size. No significant dependency of the IOL base power on the power profile, wavefront, or optical quality was found. The clinical outcomes showed that all patients achieved a binocular CDVA of 0.1 logMAR or better. The mean visual acuity was better than 0.1 logMAR between +0.50 and -1.50 D of defocus. At a vergence of -2.00 D, the visual acuity was 0.11 ± 0.13 logMAR. The monofocal enhanced IOL provided good distance optical and visual quality and optimal visual acuity up to an intermediate-near vision distance of 50 to 40 cm in patients with high hyperopia and a short axial length. [J Refract Surg. 2022;38(9):572-579.].

In vitro optical performance of multifocal and extended depth-of-focus intraocular lenses in spherical aberration conditions.

To evaluate and compare the optical performances of 4 different types of intraocular lenses (IOLs) in various spherical aberration (SA) conditions. POSTECH, Pohang, South Korea. In vitro laboratory study. A custom optical bench system with adaptive optics was used. A monofocal IOL, a bifocal IOL, a trifocal IOL, and an extended depth-of-focus (EDoF) IOL from Zeiss were evaluated by measuring through-focus modulation transfer function (MTF) as a function of vergence. MTF changes with SA from -0.1 to +0.1 with 0.05 μm step size were analyzed and compared. In aberration-free conditions, the 4 IOLs showed different MTF curves consistent with their designs. In SA conditions, all the IOLs showed MTF value decreases and the decrease rates at the far focus varied from 28% to 38% per 0.1 μm SAs. The trifocal IOL had low MTF values at the intermediate focus in the noise level with ±0.1 μm SAs. All tested IOLs showed MTF decreases with SA in different levels. The trifocal and EDoF IOLs were the most and least sensitive to SA among the evaluated IOLs. The study results might be useful in the selection of IOLs for cataract patients with SA.

Polychromatic Assessment of a Refractive Segmented EDOF Intraocular Lens.

This study aimed to evaluate in vitro performance refractive segmented EDOF intraocular lenses under polychromatic light using an optical bench that complies with the ISO 11979-2 Norm. The through focus modulation transfer function (TF-MTF) of the Femtis Comfort LS-313 MF15 (Oculentis GmbH, Berlin, Germany) IOL was evaluated for IOLs with three different base powers. The effect of the asymmetry of the segmented designs was evaluated with 3 different wavelengths and with polychromatic light at a 3.0 mm and 5.0 mm pupil diameter. It was demonstrated that the TF-MTF curves exhibit a bifocal profile that, in practice, results in an EDOF design. As a consequence of the LCA, the TF-MTF values in white light were lower than in monochromatic light. Images of the USAF test chart were obtained to confirm the prediction of the TF-MTFs. We found that Femtis Comfort is a bifocal low-addition IOL and this fact can result in an EDOF effect which was obtained previously in clinical trials. Moreover, we showed that the base power influences the IOL optical quality, which results as more effective for high powers (hyperopic eyes) than for low powers (myopic eyes). The LCA of the segmented refractive design was very low and presumably not clinically relevant.

Optical and Clinical Outcomes of an Extended Range of Vision Intraocular Lens.

To assess the in vitro optical quality and halo formation of the AcrySof IQ Vivity intraocular lens (IOL) (Alcon Laboratories, Inc) and to evaluate the clinical outcomes in patients who had bilateral implantation of this IOL. The optical quality was evaluated with the PMTF optical bench (Lambda-X). Through-focus modulation transfer function area (MTFa) curves between -5.00 and +2.00 diopters (D) were obtained for 3- and 4.5-mm pupil apertures. The halo was assessed in vitro with a test bench. The clinical study included 30 patients. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity and binocular defocus curve were evaluated 6 months postoperatively. The through-focus MTFa curve for the 4.5-mm pupil size showed only one peak at distance focus (38.4 units). For the 3-mm pupil size, the through-focus MTFa showed a lower peak of MTFa (28.9 units), located at -0.70 D, and an extended depth of focus up to -2.20 D. The halo formed was larger and more intense compared to a standard monofocal IOL. The clinical outcomes at 6 months revealed satisfactory visual acuity outcomes. All patients achieved a binocular CDVA of 0.1 logMAR or better. The mean visual acuity was better than 0.2 logMAR between +1.00 and -2.00 D of defocus. At a vergence of -2.50 D, the visual acuity was 0.31 ± 0.09 logMAR. The AcrySof IQ Vivity IOL provided good distance optical and visual quality and an extended range of focus of approximately 2.00 D, obtaining an optimal or functional visual acuity up to 50 to 40 cm. The halo formed was low intensity overall, but higher intensity than a monofocal IOL. [J Refract Surg. 2022;38(3):168-176.].

Changes in Optical Quality Induced by Tilt and Decentration of a Trifocal IOL and a Novel Extended Depth of Focus IOL in Eyes With Corneal Myopic Ablations.

To assess the effect of decentration and tilt combined with prior myopic ablations on the optical performance of a trifocal intraocular lens (IOL) and a novel IOL with an extended depth of focus (EDOF) design. The XACT Mono-EDOF ME4 (Santen Pharmaceutical Co Ltd) and the trifocal FineVision (PhysIOL) IOLs were analyzed with and without simulated previous myopic ablations. The optical quality of the IOLs was evaluated with the PMTF optical bench (LAMBDA-X). The through-focus modulation transfer function (MTF) curves were recorded. Measurements were done for three situations: centered, 0.4 mm decentered, and 4 degrees tilted. The trifocal IOL showed three peaks of vision and the EDOF IOL showed a far distance peak with intermediate addition. When decentration or tilt were induced, the trifocal IOL showed negligible changes but the EDOF IOL showed a -0.50 diopters (D) shift of the overall curve. With simulated myopic ablation, the trifocal IOL showed a -0.50 D shift of the curve. When tilt or decentration were also induced, the better optical results were found at -1.00 D. With myopic ablations, the EDOF IOL showed a -0.50 D shift of the optical quality and when decentration or tilt were then induced, negative shifts over -1.00 D were found. The trifocal IOL was less affected by mis-alignments. When myopic ablations were induced, both lenses decreased their optical quality and the effects of misalignments were higher. In patients who have undergone corneal myopic ablation procedures, proper alignment of the implanted IOL and obtaining effective emmetropia becomes even more critical. [J Refract Surg. 2021;37(8):532-537.].

Total Depth of Focus of Five Premium Multifocal Intraocular Lenses.

To compare the in vitro optical performance of five premium multifocal intraocular lenses (IOLs), including a single-valued metric that shows the total range of distances where a multifocal IOL generates an acceptable image quality. Through-focus modulation transfer function (MTF) and the image of a United States Air Force target were obtained for a 3-mm pupil and a wavelength of 546 nm in five multifocal IOLs (Tecnis Symfony [Johnson & Johnson], FineVision Micro F [PhysIOL], Acrysof IQ PanOptix [Novartis], and Artis Symbiose Mid and Plus [Cristalens Industrie] multifocal IOLs). Total depth of focus (TDOF) is computed by adding the vergence intervals where the through-focus MTF at 50 cycles/mm is 0.15 or greater. Due to their different optical designs (bifocal, trifocal, or extended depth of focus), energy is distributed differently between far, intermediate, and near focus for each multifocal IOL. The light distribution of the Symbiose Mid and Plus multifocal IOLs was similar, concentrating the energy into far focus and the intermediate into near focus, but extending the intermediate focus more (Plus) or less (Mid) toward the near focus. TDOFs were: 1.58 diopters [D] (FineVision); 1.71 D (Tecnis Symfony); 1.73 D (Artis Symbiose Plus); 1.74 D (Artis Symbiose Mid); and 1.90 D (Acrysof IQ PanOptix). TDOFs were similar between multifocal IOLs with a maximum difference of 0.32 D and mean value of 1.73 D. The combination of the Symbiose Mid and Plus IOLs can theoretically provide a TDOF of 2.90 D in case one is implanted in one eye and the other in the fellow eye. [J Refract Surg. 2020;36(9):578-584.].

Optical tolerance to rotation of trifocal toric intraocular lenses as a function of the cylinder power.

The aim was to assess the impact of 5- and 10-degree rotations in the optical quality of a trifocal toric intraocular lens with different amounts of cylinder. Two Physiol Toric intraocular lenses with 1.5 and 3.0 D of cylinder were analysed in three different positions: centred, 5 and 10 degrees rotated. The optical quality of the intraocular lenses was evaluated with the PMTF optical bench through specific perpendicular targets. The analysis was performed by the through-focus modulation transfer function curves and the modulation transfer function corresponding to distance vision (0 D of vergence). For a centred situation, the through-focus modulation transfer function curves of both intraocular lenses showed the classical three peaks corresponding to the powers of the two principal meridians of the intraocular lenses. When 5 and 10 degrees of rotation were induced, the three peaks were attenuated in both cases. The case with the intraocular lens with 3.0 D of cylinder and 10 degrees of rotation showed the worst optical quality and a significant loss of trifocality. The modulation transfer function values obtained for distance vision also showed the worst optical quality for the intraocular lens with 3.0 D of cylinder and 10 degrees of rotation. Rotations over 5 degrees decreased the optical quality of trifocal toric intraocular lenses, being this reduction moderate from 5 to 10 degrees for low levels of cylinder (≤1.5 D). For mid-high levels of cylinder (≥3.0 D), rotations over 5 degrees cause a significant loss of optical quality at all object distances.

Laboratory evaluation of the optical properties of two extended-depth-of-focus intraocular lenses

BackgroundTo experimentally compare the optical performance of two different Extended-Depth-of-Focus (EDOF) intraocular lenses (IOLs) using a standardized optical bench set-up.MethodsIn this experimental study, following IOLs were assessed: the TECNIS® Symfony ZXR00 (Johnson&Johnson, Santa Ana, USA) and the AT LARA 829MP (Carl Zeiss Meditec, Jena, Germany) IOLs. The through-focus modulation transfer function (MTF) values were measured at a spatial frequency of 50 lp/mm and at aperture sizes of 2, 3, and 4.5 mm. Each IOL was measured while centered using ISO 11979-2 Model 1 (aberration-free) and Model 2 (+ 0.28 μm spherical aberration) corneas. United States Air Force (USAF) target images were also recorded for a qualitative evaluation.ResultsAt 2 mm pupil with ISO1 cornea, the primary and secondary foci of both IOLs appeared to merge, providing an elongated depth of focus. At 3 and 4.5 mm pupil sizes, the through-focus MTF curves of both IOLs showed a bifocal-like V-pattern. While the Symfony IOL showed an overall superior MTF values when measured with the ISO2 cornea, the opposite propensity could be observed with the AT LARA IOL. This optical behavior could be qualitatively confirmed by the USAF target images.ConclusionsAlthough the two EDOF IOLs share similarities in their optical properties, the main difference lies in their optical design and performance with respect to spherical aberration. Such characteristics should be taken into account during IOL and patient selection.

Topography and longitudinal chromatic aberration characterizations of refractive–diffractive multifocal intraocular lenses

Most optical systems present chromatic aberration quantified along the optical axis by the longitudinal chromatic aberration (LCA). LCA is controlled by the biomaterial Abbe number combined with diffractive effects, driven by the intraocular lens (IOL) topography. This study experimentally aimed at describing the effect invitro of LCA in diffractive multifocal IOLs, with the help of dedicated optical benches and topographic characterization. Centre Spatial de Liège, Belgium. Optical and topology analysis of various multifocal diffractive IOLs. Seven diffractive multifocal IOLs, available on the market and exhibiting different diffractive profiles, made from various biomaterials, were characterized under different wavelengths. Through-focus modulation transfer function (MTF) curves and IOL diffraction efficiency depends on the incident light wavelength. In this study, the topology properties of various multifocal IOLs were investigated and their characteristics were correlated to their optical behavior for various wavelengths. Chromatic properties and their origins were then compared. As expected, diffractive and refractive effects were found to act in opposite ways, and could be partially or completely compensated. The LCA of each of the IOLs was evaluated invitro. In most of the multifocal IOLs studied, some of the foci were found to be refractive, whereas others were diffractive. Although the results were not extrapolated to clinical relevance, it was shown, in some of the cases, that LCA could be fully compensated.

Effects of decentration and tilt at different orientations on the optical performance of a rotationally asymmetric multifocal intraocular lens

To assess the effects of decentration and tilt at different orientations on the optical quality of a rotationally asymmetric multifocal intraocular lens (IOL). Shandong Eye Institute, Qingdao, China. Experimental study. A rotationally asymmetric multifocal IOL (SBL-3) was tested using standardized optical bench testing. The optical quality was quantified using the modulation transfer function (MTF), through-focus MTF, and images of the United States Air Force Target test at apertures of 3.0mm and 4.5mm. The multifocal IOL was measured while it was centered, decentered by 0.3mm and 0.5mm, and then tilted by 3 degrees and 5 degrees at near-horizontal (near vision zone), distance-horizontal (distance vision zone), and vertical orientations of the long axis of the multifocal IOL. The optical performance was better at the aperture of 4.5mm than at 3.0mm for the centered multifocal IOL. The optical quality was improved at near focus and decreased at distance focus for the near-horizontal decentration, contrary to the status for the distance-horizontal decentration, with a more obvious tendency at the 3.0mm aperture than at 4.5mm. For the near-horizontal tilting, the optical quality at near focus was more significantly deteriorated than distance focus, opposite to that for the distance-horizontal tilting, with a more distinct tendency at a 4.5mm aperture than at 3.0mm. The optical quality of the asymmetric multifocal IOL was sensitive to and varied significantly after decentration and tilt at specific directions. The decentration induced increased or decreased optical quality, whereas tilt just yielded decreased optical quality.