A theoretical study of intraocular lens tilt and decentration on perceptual image quality

Analysis of visual quality improvement after implantation of PanOptix trifocal intraocular lens in cataract patients with different axial lengths

OBJECTIVE

To assess the visual quality, both subjective and objective, of cataract patients with varying axial lengths (AL) after PanOptix trifocal intraocular lens (IOL) implantation and investigated the lens tilt and its correlation with visual outcomes.

METHODS

From July 2020 to June 2022, 70 patients (140 eyes) diagnosed with age-related cataracts and undergoing PanOptix implantation at Chongqing Eye and Vision Care Hospital, Aier Eye Hospital Group, were included. Patients were assigned to either the observation group (35 cases, 70 eyes with PanOptix trifocal IOL) or the control group (35 cases, 70 eyes with bifocal IOL). Patients were further subdivided based on AL into AL < 24 mm (observation group: 23 eyes; control group: 26 eyes) and AL ≥ 24 mm (observation group: 47 eyes; control group: 44 eyes). Postoperative follow-up lasted three months. Visual acuity (distant, intermediate, near), objective visual quality (Strehl ratio: SR, total eye modulation transfer function (MTF)), and visual aberrations were measured preoperatively and at 3 months post-operation.

RESULTS

Postoperatively, all groups saw significant improvements in uncorrected distance visual acuity (UCDVA), uncorrected intermediate visual acuity (UCIVA), and uncorrected near visual acuity (UCNVA) compared to preoperative values (T0) (all P < 0.05). Notably, UCIVA was significantly better in the observation group than in the control group (P < 0.05). At three months (T1), reductions in total high-order aberration (tHOA), internal high-order aberration (iHOA), coma, and trefoil aberrations were observed in both groups compared to baseline, with more significant decreases in the observation group (all P < 0.05). Both SR and MTF cutoff showed marked improvement from T0 to T1, with the observation group experiencing greater enhancements (both P < 0.05). The defocus curve of the observation group showed a gentle slope between +0.5 D and -3.0 D, maintaining superior visual acuity compared to the control group (P < 0.05). Subjective visual quality scores at T1 were significantly higher than at T0 for both groups (P < 0.05), with patients in the observation group scoring higher than those in the control group across all AL categories (P < 0.05). Spearman correlation analysis indicated that the tilt after PanOptix trifocal IOL implantation was associated with tHOA (r = 0.273, P = 0.022), iHOA (r = 0.433, P < 0.001), Trefoil (r = 0.360, P = 0.002) and coma (r = 0.688, P < 0.001).

CONCLUSION

PanOptix trifocal IOL implantation in cataract patients across different AL significantly enhances visual quality compared to bifocal IOLs, suggesting a strong case for its clinical adoption.

Prediction of IOL decentration, tilt and axial position using anterior segment OCT data

BACKGROUND

Intraocular lenses (IOLs) require proper positioning in the eye to provide good imaging performance. This is especially important for premium IOLs. The purpose of this study was to develop prediction models for estimating IOL decentration, tilt and the axial IOL equator position (IOLEQ) based on preoperative biometric and tomographic measures.

METHODS

Based on a dataset (N = 250) containing preoperative IOLMaster 700 and pre-/postoperative Casia2 measurements from a cataractous population, we implemented shallow feedforward neural networks and multilinear regression models to predict the IOL decentration, tilt and IOLEQ from the preoperative biometric and tomography measures. After identifying the relevant predictors using a stepwise linear regression approach and training of the models (150 training and 50 validation data points), the performance was evaluated using an N = 50 subset of test data.

RESULTS

In general, all models performed well. Prediction of IOL decentration shows the lowest performance, whereas prediction of IOL tilt and especially IOLEQ showed superior performance. According to the 95% confidence intervals, decentration/tilt/IOLEQ could be predicted within 0.3 mm/1.5°/0.3 mm. The neural network performed slightly better compared to the regression, but without significance for decentration and tilt.

CONCLUSION

Neural network or linear regression-based prediction models for IOL decentration, tilt and axial lens position could be used for modern IOL power calculation schemes dealing with 'real' IOL positions and for indications for premium lenses, for which misplacement is known to induce photic effects and image distortion.

Femtosecond Laser-Assisted Cataract Surgery versus Conventional Phacoemulsification Surgery: Clinical Outcomes with EDOF IOLs

In this study, we evaluate and compare the outcomes of conventional phacoemulsification cataract surgery (CPS) and femtosecond laser-assisted cataract surgery (FLACS) with the implantation of an extended depth of field (EDOF) intraocular lens (IOL). A prospective, consecutive cohort study was conducted. Patients were given the option to choose FLACS or CPS and were implanted with an EDOF IOL. Refractive data, visual acuity data, ocular aberration measured with a wavefront aberrometer, and optical quality measured with an optical quality analysis system II were collected at one month postoperatively. A total of 92 eyes of 64 patients were enrolled in this study; 35 eyes of 26 patients were treated with FLACS, whereas 57 eyes of 38 patients were treated with CPS. Uncorrected visual acuity at far, intermediate, and near distance and best-spectacle-corrected visual acuity were not statistically significantly different between the groups (all p > 0.05), nor were the mean cylinder and mean spherical equivalent refraction (both p > 0.05). The FLACS group had a lower ocular trefoil than the CPS group (p = 0.033), and there was no significant difference between the two groups considering other aberration parameters, whether ocular or internal (all p > 0.05). Optical-quality-related parameters showed also no significant difference between the two groups (all p > 0.05). In conclusion, there was no significant difference between FLACS and CPS with implantation of EDOF IOLs in postoperative ocular parameters, refractive outcomes, ocular aberration, optical quality, and aberration parameters, except a lower ocular trefoil in the FLACS group. In terms of these indicators, FLACS does not provide an additional clinical benefit for patients over CPS.

Femtosecond Laser-assisted Lens Surgery with Low-energy Pulse versus Conventional Phacoemulsification for Presbyopia Correction: An Intraindividual Study

Background:

Lens surgery with multifocal IOL implantation for presbyopia correction is performed by femtosecond laser-assisted lens surgery or conventional phacoemulsification.

Objective:

To compare the clinical results of femtosecond laser-assisted with low-energy pulse conventional phacoemulsification lens surgery for presbyopia correction intraindividually.

Methods:

Charts from patients who underwent Refractive Lens Exchange (RLE) for presbyopia correction in a single center, with Femtosecond Laser-Assisted Lens Surgery (FLALS) in one eye and Conventional Phacoemulsification (CP) in the other, were retrospectively reviewed. All eyes had the same multifocal Intraocular Lens (IOL) implanted. The clinical outcomes and the results of the level of satisfaction questionnaire were compared between the two groups according to the technique employed (FLALS vs. CP) for a period of up to four years. Stability, efficacy and safety indices were also assessed.

Results:

This study comprised a total of 56 eyes of 28 patients randomly assigned FLALS in one eye and CP in the other. No statistically significant difference was observed between the two techniques regarding postoperative visual acuities, duration of surgical procedure, efficacy or safety indexes (p>0.05). Refraction was stable in all FLALS eyes, whereas a change occurred in 2 eyes (7.1%) operated with CP upon 6 months postoperatively, but without statistical significance (p˃0.05). Satisfaction was slightly better with FLALS but not statistically significant (p=0.134). No immediate myosis or other adverse events after the femtosecond laser were registered.

Conclusion:

The parameters assessed showed no significant differences between the two techniques, in spite of a difference of refraction stability upon 6 months postoperatively.

Comparison of spherical and aspherical intraocular lenses with decentration and tilt error using a physical model of human contrast vision and an image quality metric

PURPOSE

In this study, two intraocular lenses (spherical IOL SA60AT and aspherical IOL SN60WF) are examined in an eye model under conditions of misalignment (defocus, decentration and tilt). The lenses are rated using the contrast sensitivity function (CSF) based on Barten's physical model. The square root integral (SQRI) method is used as a quality criterion comparable to the subjective image quality assessment of the human eye.

METHODS

The IOLs to be tested are decentered from 0 to 1mm and tilted from -5 to +5 degrees in the Navarro eye model (optimized for far-point 6m and pupil aperture 3mm). The defocus of the IOLs is ±0.1mm at the anterior chamber depth (ACD). The optical modulation transfer function (MTF) is simulated with a ray tracing program. The SQRI is calculated using this MTF and the Barten CSF model (for in-focus at aperture 3 and 4.5mm and for defocus at 3mm).

RESULTS

With increasing decentration, the spherical IOL shows a significantly smaller loss of quality for both apertures compared to the aspherical lens. With an aperture of 4.5mm, the image quality of the aspherical IOL is better for small decentration and tilt. The loss of quality of the spherical IOL increases with increasing tilt in both directions. In contrast, the image quality of the aspherical IOL is reduced under decentration for certain tilt values. For ACD-0.1mm, both IOLs behave similarly to the in-focus situation. For ACD+0.1mm, the influence of tilt without decentration is small for both IOLs. With increasing decentration, the quality loss of the aspherical IOL is similar to that in-focus and greater than that of the spherical lens.

CONCLUSION

In general, under the same conditions the spherical SA60AT displays a lower tolerance in loss of quality of subjective vision with lens alignment errors, in comparison to the aspherical SN60WF, limited by certain combinations of decentration and tilt according to this study. This study shows a way to evaluate IOLs based on the subjective visual performance of the eye.

Determinants of intraocular lens tilt and decentration after cataract surgery

Background

To identify the main determinants of intraocular lens (IOL) tilt and decentration after cataract surgery using a novel anterior segment optical coherence tomography (AS-OCT) method.

Methods

Fifty-six patients who underwent phacoemulsification with IOL implantation in one eye were continuously enrolled in this cohort study. Axial length (AL) was measured with IOL Master 700. The tilt and decentration of patients’ preoperative crystalline lenses and postoperative IOLs, as well as crystalline lens thickness (LT), were measured using AS-OCT before surgery and 1 week after surgery.

Results

The mean tilt and decentration of the patients’ preoperative crystalline lenses were 4.90°±1.81° and 0.21±0.02 mm, and the mean tilt and decentration of IOLs were 4.75°±1.66° and 0.21±0.02 mm, respectively. There were no significant differences in magnitude, direction of tilt, or decentration between crystalline lenses and IOLs. The strongest determinant of IOL tilt was preoperative crystalline lens tilt (R²=0.512, P<0.001), followed by AL (R²=0.154, P=0.003). Additionally, crystalline lens decentration and AL explained 54.6% of the variability in IOL decentration. AL was the factor most highly associated with IOL decentration (R²=0.332, P<0.001), rather than crystalline lens decentration (R²=0.214, P<0.001).

Conclusions

The position of the preoperative crystalline lens and AL were the critical determinants of IOL tilt and decentration. The tilt and decentration of IOLs will be greater in patients with larger tilt and decentration of crystalline lenses, or shorter and longer AL.

Simultaneous measurement of displacement, pitch, and yaw angles of a cavity output mirror based on phase measuring deflectometry

Accurate and high dynamic range measurement of the three attitude variations (i.e., displacement, pitch, yaw angles) has been widely researched based on various approaches to meet different application requirements. However, none of the existing methods can detect these three attitude variations at the same time. This paper proposes a method based on a classical phase measuring deflectometry (PMD) system and a double iteration algorithm to simultaneously measure the three variations of the output mirror in a laser resonator. The relationship between the attitude variations and the lateral displacement parameters (LDP) of the imaged structural fringes is derived in the PMD system. Through the established relationship, the attitude variations could be calculated once the LDP are detected. Furthermore, a two-step measuring scheme combining the four-step shifting phase and the color-coded fringe is proposed to effectively detect the LDP. Finally, an experiment is conducted to verify the feasibility of the proposed method.

Keratoconic eyes with stable corneal tomography could benefit more from custom intraocular lens design than normal eyes

We investigated whether eyes with keratoconic corneal tomography pattern could benefit more from aberration correction with custom intraocular lenses (IOLs) than normal cataractous eyes despite the effect of misalignment on the correction of aberrations. Custom IOLs (cIOLs) were calculated for twelve normal and twelve keratoconic eyes using personalized numerical ray tracing models. The Stiles-Crawford weighted root-mean-square spot-size (wRMS) at the virtual fovea was evaluated for cIOLs and aberration-neutral IOLs (nIOLs) in a simulated clinical study with 500 virtual IOL implantations per eye and per IOL. IOL misalignment (decentration, tilt, rotation) and pupillary ectopia (4.5 mm iris aperture) were varied upon each virtual implantation. The nIOLs achieved average wRMS of 16.4 ± 4.3 μm for normal, and 92.7 ± 34.4 μm for keratoconic eyes (mean ± standard deviation). The cIOLs reduced the average wRMS to 10.3 ± 5.8 μm for normal, and 28.5 ± 18.6 μm for keratoconic eyes. The cIOLs produced smaller wRMS than nIOLs in most virtual implantations (86.7% for normal and 99.4% for keratoconic eyes). IOL misalignment resulted in larger wRMS variations in the keratoconus group than in the normal group. Custom freeform IOL-optics-design may become a promising option for the correction of advanced aberrations in eyes with non-progressive keratoconic corneal tomography pattern.

The use of femtosecond lasers in cataract surgery: review of the published results with the LenSx system

PURPOSE

To review the published literature describing the use of the LenSx femtosecond laser technology (Alcon Laboratories, Inc., Fort Worth, TX) in cataract surgery.

METHODS

Literature review.

RESULTS

The LenSx system has been used in more than 200,000 cataract surgery procedures to date. Pre-clinical evaluations have shown that this system produces accurate and reproducible capsulorhexes, and that both the energy required for phacoemulsification and total phacoemulsification time are less than with conventional phacoemulsification. In comparative studies, femtosecond lasers have been shown to produce more precise and reproducible capsulorhexes than manual procedures, and better intraocular lens placement; capsule overlap, circularity of capsulotomy, and centration of the intraocular lens are consistently better with femtosecond lasers than with manual procedures. The improved quality of capsulorhexis and intraocular lens positioning are reflected in favorable visual and refractive outcomes. As with any new technology, there is a significant learning curve: prospective cohort studies have shown that the incidence of intraoperative complications such as suction breaks or anterior capsular tears or tags decreases with experience. In general, the incidence of such complications is within the range (< 2%) considered in recent evidence-based guidelines to be feasible and desirable.

CONCLUSIONS

Although femtosecond laser cataract surgery is in its infancy, the technology is evolving rapidly and offers the potential for more consistent and predictable results after cataract surgery.

Anterior chamber angle evaluation with ultrasound biomicroscopy and optical coherence tomography in eyes implanted with a Crystalens

This study employs optical coherence tomography (OCT) and ultrasound biomicroscopy (UBM) imaging as well as optical aberrometry to examine correlations between the anterior chamber angle aperture and visual acuity for near vision as well as coma along the horizontal and vertical axes in eyes implanted with an accommodative intraocular lens (Crystalens). A retrospective comparative consecutive case series of 22 eyes of 11 patients (5 males) uneventfully implanted with a Crystalens. Eyes with signs of posterior capsular opacification were excluded. All eyes were examined with 40 MHz UBM (Ellex Eyecubed) and spectral-domain OCT (Zeiss Visante). The angle aperture along the horizontal and vertical meridians was recorded based on the software of the systems. The coma root mean square (RMS) scores for the horizontal and vertical meridians were also recorded with the iTrace aberrometer. The anterior chamber angle was significantly wider along the horizontal axis compared with the vertical axis by UBM (46.37° and 44.20°, respectively) and by OCT (46.79° and 43.58°, respectively) (p = 0.02 in both cases, paired-samples t test). The correlations between the logMAR-converted Jaeger near vision score and the horizontal or vertical angle apertures was not statistically significant. Horizontal coma RMS was significantly inversely correlated with the horizontal angle aperture (r = -0.45, p = 0.03 and r = -0.39, p = 0.04 by OCT and UBM, respectively). Measurement of the horizontal angle aperture by the modalities used may represent an anatomical and clinical predictor of the optical aberrations induced by the Crystalens.

Rapid inspection method for measuring interior tilt and decenter in singlet lens

The objective of this study was to present a high-speed, on-line means of measuring interior tilt and decentration in a singlet lens. We propose a noncontact method based on polarized optics, which provides inspection functions for the practical measurement of lenses. The proposed system was used to measure a tilted and decentered lens, and the results of which showed strong agreement with those obtained in theoretical predictions and CodeV simulations. The proposed method provides a wide field of inspection applicable to lenses with a diameter up to 70 mm. Measurement accuracy is of 0.14 deg/pixel in tilt, and 33 μm/pixel in decentration. Inspection time is only 0.78 s.

Clinical and quality of life data correlation with a single-optic accommodating intraocular lens

Purpose

To examine a single-optic accommodating intraocular lens (IOL) visual performance by correlating IOL implanted eyes’ defocus curve with the intraocular aberrometric profile and the impact on the quality of life (QOL).

Methods

Prospective consecutive case series study including a total of 25 eyes of 14 patients with ages ranging between 52 and 79 years old. All cases underwent cataract surgery with implantation of the single-optic accommodating IOL Crystalens HD (Bausch & Lomb). Distance and near visual acuity outcomes, intraocular aberrations, the defocus curve and QOL (NEI VFQ-25) were evaluated 3 months after surgery.

Results

A significant improvement in distance visual acuity was found postoperatively (p = 0.02). Mean postoperative LogMAR uncorrected near visual acuity was 0.44 ± 0.23 (20/30). 60% of eyes had a postoperative addition between 0 and 1.5 diopters (D). The defocus curve showed an area of maximum visual acuity for the levels of defocus corresponding to distance and intermediate vision (−1 to +0.5 D). Postoperative intermediate visual acuity correlated significantly some QOL indices (r ≥ 0.51, p ≤ 0.03; difficulty in going down steps or seeing how people react to things that patient says) as well as with J₀ component of manifest cylinder. Postoperative distance-corrected near visual acuity correlated significantly with age (r = 0.65, p < 0.01).

Conclusions

This accommodating IOL seems to be able to restore the distance visual function as well as to provide an improvement in intermediate and near vision with a significant impact on patient's QOL, although limited by age and astigmatism. Future studies with larger sample sizes should confirm all these trends.

Visual outcomes and optical performance of a monofocal intraocular lens and a new-generation multifocal intraocular lens

PURPOSE

To compare visual acuity outcomes and ocular and intraocular optical quality in patients with a monofocal intraocular lens (IOL) or a multifocal IOL with rotational asymmetry.

SETTING

Vissum Corporation, Alicante, Spain.

DESIGN

Comparative case series.

METHODS

Consecutive eyes of cataract patients were divided into 2 groups. One group received a Lentis Mplus LS-312 multifocal IOL and the other, an Acri.Smart 48S monofocal IOL. Distance and near visual acuities, contrast sensitivity, intraocular aberrations (global minus corneal aberrations), and defocus curves were evaluated preoperatively and postoperatively during a 3-month follow-up.

RESULTS

The study evaluated 52 eyes of 29 patients (age range 36 to 87 years); 24 eyes were in multifocal IOL group and 28 eyes, in the monofocal IOL group. Both groups had a significant improvement in uncorrected and corrected distance visual acuities and in distance-corrected near visual acuity (DCNVA) postoperatively (P ≤ .04). The multifocal IOL group had significantly better uncorrected near acuity and DCNVA (Jaeger [J] 5 versus J2) (both P < .01). The defocus curves showed significantly better visual acuities in the multifocal group at several levels of defocus. The multifocal group had significantly higher amounts of postoperative intraocular primary coma (P<.01), especially in eyes with significant IOL tilt, although there were no significant differences in contrast sensitivity between the 2 IOL groups (P ≥ .25).

CONCLUSIONS

The new-generation multifocal IOL restored distance, intermediate, and near visual function after cataract surgery. The optical quality with this type of IOL was particularly affected by IOL tilt and decentration.

Visual and optical performance with two different diffractive multifocal intraocular lenses compared to a monofocal lens

PURPOSE

To compare the visual acuity outcomes as well as the ocular optical performance of eyes implanted with either a monofocal or one of two diffractive multifocal intraocular lenses (IOLs).

METHODS

One hundred two consecutive eyes of 51 bilateral cataract patients (age 49 to 80 years) were divided into three groups: 22 eyes were implanted with a monofocal IOL (monofocal group), 40 eyes with the Acrysof ReSTOR SN6AD3 IOL (ReSTOR group), and 40 eyes with the Acri.Lisa 366D IOL (Acri.Lisa group). Visual acuity and contrast sensitivity were evaluated pre- and postoperatively. Additionally, ocular optical quality and intraocular aberrations were evaluated postoperatively.

RESULTS

Significant improvement after surgery in uncorrected and corrected distance and near visual acuity was observed in all three groups (P≤.05). Uncorrected near visual acuity was significantly better in eyes from the ReSTOR and Acri.Lisa groups compared to the monofocal group (P≤.01). Photopic contrast sensitivity was significantly better for the spatial frequency of 3 cycles/degree in the monofocal group (P<.01). Significantly higher values of the ocular Strehl ratio and cutoff modulation transfer function spatial frequency were also found in the Acri.Lisa group (P=.01). An acceptable range of vision between near and distance peaks was observed in the defocus curves of the ReSTOR and Acri.Lisa groups.

CONCLUSIONS

The AcrySof ReSTOR and Acri.Lisa 366D IOLs are able to successfully restore near and intermediate visual function after cataract surgery; however, the Acri.Lisa design seems to provide better optical performance. These results need to be confirmed in a randomized, prospective trial.