Theoretical Comparison of Aberration-correcting Customized and Aspheric Intraocular Lenses

The Influence of Accommodative Demand on Ocular Aberrations: A Study of Zernike Coefficients Repeatability and Variability

PURPOSE

To evaluate the repeatability of the Zernike coefficients in healthy eyes when monocular accommodation was stimulated at different vergences demands.

METHODS

A total of 36 right eyes from healthy volunteers were prospectively and consecutively recruited for this study. Wavefront aberrometry was conducted to objectively characterize the ocular optical quality during accommodation, from the individual's far point to a 5 D accommodation demand in steps of 0.5 D. The repeatability of Zernike coefficients up to the fourth order was assessed by calculating the within-eye repeatability (Sw), the coefficient of repeatability (CR), the coefficient of variation (CV), and the intraclass correlation coefficient (ICC) as an indicator of measurement reliability.

RESULTS

Correlation among repeated measurements showed high reliability (ICC > 0.513) for all parameters measured except some fourth-order Zernike coefficients, C(4, -4) (ICC < 0.766), C(4, -2) (ICC < 0.875), C(4, 2) (ICC < 0.778) and C(4, 4) (ICC < 0.811). Greater repeatability and less variability were obtained for high-order Zernike coefficients (CR < 0.154), although an increase in CR in the coefficients analyzed was observed with increasing accommodative demand. No clear trend was evident in CV; however, it was observed that the low-order Zernike coefficients exhibit lower CV (CV < 1.93) compared to the high-order Zernike coefficients (CV > 0).

CONCLUSIONS

The reliability of Zernike coefficients up to the fourth order in healthy young individuals demonstrated a strong consistency in measuring terms up to the fourth order, with more variability observed for high-order terms. The Zernike coefficients up to the third order exhibited the highest level of repeatability.

Rotational stability and capsular bag performance of a hydrophobic acrylic open-loop single-piece intraocular lens

PURPOSE

To evaluate the rotational stability and capsular bag performance of a blue light-absorbing hydrophobic acrylic open-loop single-piece intraocular lens (IOL) with a blast-finished anchor wing haptic design during the first 6 postoperative months.

METHODS

In this prospective clinical study, patients with age-related cataract and potential postoperative corrected distance visual acuity (CDVA) of 0.2 logMAR or better were included. The patients received a non-toric hydrophobic acrylic single-piece IOL with an axis mark (YST0.00; Nidek Co. Ltd, Japan). Surgeries were video-taped. Retroillumination images were acquired 1 h, 1 week and 6 months postoperatively. Rotational stability was assessed by precise image overlay. At 6 months, Purkinje meter measurements were performed to evaluate tilt and decentration.

RESULTS

In total, 100 eyes of 77 patients were included in the analysis. Mean absolute rotation was 2.1 ± 1.7° (median 1.7, range: 0-7.9) at 6 months (1 h - 6 months postoperatively). IOL rotation was ≤3° and ≤6° in 74 (74%) and 98 (98%) eyes, respectively. Mean absolute IOL rotation from the end of surgery to 6 months was 2.5 ± 2.2° (median 2.3, range: 0-15.6; n = 78). Mean tilt (pupillary axis) and decentration were 4.1 ± 1.9° (median 4.0, range: 0.5-8.2) and 0.35 ± 0.17 mm (median 0.32, range: 0.06-0.91) respectively (n = 84). Postoperatively, 98 (98%) eyes achieved a CDVA of 0.2 logMAR or better, 95 (95%) of ≤0.1 and 81 (81%) of ≤0.0.

CONCLUSIONS

This hydrophobic acrylic single-piece IOL showed an excellent rotational stability and capsular bag position with low tilt and decentration values.

Comparison of Automated Keratometer and Scheimpflug Tomography for Predicting Refractive Astigmatism in Pseudophakic Eyes

PURPOSE

To analyse the correspondence between refractive astigmatism and corneal astigmatism in pseudophakic eyes with non-toric intraocular lenses.

SETTING

Yeouido St. Mary hospital, Seoul, Republic of Korea.

DESIGN

Evaluation of a diagnostic test instrument.

METHODS

This retrospective study included 95 eyes of 95 patients. Corneal astigmatism was measured with an automated keratometer (RK-5, Canon) and Scheimpflug tomography (Pentacam HR, Oculus). Refractive astigmatism was compared to keratometric astigmatism (based on anterior corneal measurements only), equivalent K-reading, and total corneal astigmatism (both based on anterior and posterior corneal measurements). Vector analysis was carried out by Næser's polar value method. The accuracy was defined as the average magnitude of the vectorial difference in astigmatism (DA). Each corneal measurement was optimized in retrospect by a multiple linear regression equation between refractive and corneal astigmatism.

RESULTS

Keratometric astigmatism overestimated with-the-rule (WTR) refractive astigmatism and underestimated against-the-rule (ATR) refractive astigmatism. Several measurements based on both corneal surfaces' values did not show any statistically significant difference with respect to refractive astigmatism. The mean corneal astigmatism by total corneal refractive power (TCRP) at 4.0 mm (zone/pupil) produced the lowest mean arithmetic DA and the highest percentage of eyes with a DA ≤ 0.50 dioptre. After optimization, the accuracies of automated KA and TCRP 4.0 mm (zone/pupil) were similar.

CONCLUSIONS

Total corneal astigmatism measured by Scheimpflug tomography at a 4.0 mm zone centered on the pupil accurately reflects the refractive astigmatism in pseudophakic eyes. However, the accuracy of total corneal astigmatism is not different from automated KA after optimization.

Influence of decentration and tilt of Tecnis ZCB00 on visual acuity and higher order aberrations

BACKGROUND/OBJECTIVES

To determine the influence of decentration and tilt of a pseudophakic aspheric intraocular lens (IOL) on visual acuity (VA) and higher-order aberrations (HOAs), and to analyze the agreement between pupil center/axis and iridocorneal angles center/axis when assessing IOL decentration and tilt.

SUBJECTS/METHODS

A prospective interventional case series study including thirty-three patients undergoing Tecnis ZCB00 (Abbott Medical Optics) implantation. IOL decentration and tilt with respect to two reference systems (pupil and iridocorneal angles centers/axes), in cartesian (X,Y) and polar (radius/tilt, polar angle/azimuth) coordinates, were assessed with optical coherence tomography. VA and internal and ocular HOAs were evaluated. Multiple linear regression models and intraclass correlation coefficient (ICC) were computed.

RESULTS

IOL decentration only showed a significant effect on internal HOAs for [Formula: see text] (R2 = 0.20, P = 0.04). IOL decentration with respect to the pupil center showed a significant effect on ocular [Formula: see text] (R2 = 0.18, P = 0.05), [Formula: see text] (R2 = 0.36, P = 0.001) and [Formula: see text] (R2 = 0.24, P = 0.02); and with respect to the center of iridocorneal angles, on ocular [Formula: see text] (R2 = 0.21, P = 0.03), [Formula: see text] (R2 = 0.32, P = 0.003), primary coma (R2 = 0.41, P < 0.001), and coma-like (R2 = 0.40, P = 0.001). Poor agreement between both reference systems was found for IOL decentration measurements (ICC ≤ 0.41), except for the polar angle coordinate (ICC = 0.83). Tilt measurements showed good agreement (ICC ≥ 0.75).

CONCLUSIONS

Tecnis ZCB00 decentration and tilt values after uneventful implantation appear not to have influence on VA, and their effect on HOAs are not high enough to clinically affect quality of vision. Pupil and iridocorneal angles used as reference systems may be interchangeable for IOL tilt measurements, but not for decentration.

Effects of tilt and decentration of Visian Implantable Collamer Lens (ICL V4c) on visual quality: an observational study

Background

The central hole of the Visian Implantable Collamer Lens (ICL V4c) provides a reference to observe its tilt or decentration. This study aimed to investigate the tilt and decentration effects of ICL V4c on visual quality after implantation.

Methods

A total of 135 eyes from 69 patients who underwent ICL V4c implantation were included in this study. Evaluation of uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and aberrations were performed 6-months postoperatively. The anterior segment parameters were collected using CASIA2 anterior segment-optical coherence tomography, tilt and decentration of ICL V4c were analyzed using MATLAB software. All patients received questionnaires to investigate the visual quality postoperatively.

Results

The safety and effectiveness were 1.18 ± 0.17 and 1.11 ± 0.18, respectively. No significant changes were observed regarding higher-order and spherical aberrations after the operation; however, coma and trefoil significantly increased compared to preoperative values. The average total decentration and tilt was 0.21 ± 0.12 mm and 2.54 ± 1.00°, respectively. Horizontal, vertical, and total values of tilt and decentration were not significantly associated with postoperative CDVA, UDVA, and aberrations. The most common visual symptom was halo, and 97.04% of patients had a satisfaction score ≥ 8. The total or horizontal tilt was significantly positively correlated with the frequency, severity, and bothersome scores from the questionnaires.

Conclusions

ICL V4c implantation can obtain high visual quality and patient satisfaction. Although the degree of tilt and decentration after ICL V4c implantation was small, a positive effect on subjective visual quality was observed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02499-4.

The relationship between angle kappa and astigmatism after phacoemulsification with implanting of spherical and aspheric intraocular lens

Purpose:

To determine the significance of any association between either change in angle kappa (K°) or the rectilinear displacement (L, mm) of the first Purkinje image relative to the pupil center and unexpected changes in astigmatism after phacoemulsification.

Methods:

Orbscan II (Bausch and Lomb) measurements were taken at 1, 2, and 3 months after unremarkable phacoemulsification in patients implanted with spherical (group 1, SA60AT, Alcon) or aspheric (group 2, SN60WF, Alcon) nontoric IOLs. The outputs were used to calculate L. Astigmatism, measured by autorefractometry and subjective refraction, was subjected to vector analysis (polar and cartesian formats) to determine the actual change induced over the periods 1–2 and 2–3 months postop.

Results:

Chief findings were that the mean (n, ±SD, 95%CI) values for L over each period were as follows: Group 1, 0.407 (38, ±0.340, 0.299–0.521), 0.315 (23, ±0.184, 0.335–0.485); Group 2, 0.442 (45, ±0.423, 0.308–0.577), 0.372 (26, ±0.244, 0.335–0.485). Differences between groups were not significant. There was a significant linear relationship between (A) the change in K (ΔK = value at 1 month-value at 2 months) and K at 1 month (x), where ΔK =0.668-3.794X (r = 0.812, n = 38, P = <0.001) in group 1 and ΔK = 0.263x -1.462 (r = 0.494, n = 45, P = 0.002) in group 2, (B) L and the J₄₅ vector describing the actual change in astigmatism between 1 and 2 months in group 2, where J₄₅ (by autorefractometry) =0.287L-0.160 (r = 0.487, n = 38, P = 0.001) and J₄₅ (by subjective refraction) =0.281L-0.102 (r = 0.490, n = 38, P = 0.002), and (C) J₄₅ and ΔK between 2 and 3 months in group 2, where J₄₅ (by subjective refraction) =0.086ΔK-0.063 (r = 0.378, n = 26, P = 0.020).

Conclusion:

Changes in the location of the first Purkinje image relative to the pupil center after phacoemulsification contributes to changes in refractive astigmatism. However, the relationship between the induced change in astigmatism resulting from a change in L is not straightforward.

Clinical Outcome of Lentis Comfort Intraocular Lens Implantation

PURPOSE

To evaluate visual outcome and patient satisfaction following Lentis Comfort intraocular lens (IOL) implantation.

METHOD

This retrospective case series examined 68 eyes of 41 patients (mean age 72.0 ± 8.1 years) who underwent Lentis Comfort (LS-313 MF15, Oculentis GmbH, Berlin, Germany; Santen, Osaka, Japan) implantations. Patients were evaluated for visual acuity (VA) at several distances (0.3, 0.5 and 5 meters), refractive error, defocus curve and contrast sensitivity, in addition to answering a questionnaire on photic phenomena, visual discomfort and patient satisfaction.

RESULTS

Uncorrected visual acuity was 0.05 ± 0.13 (logMAR) for distance, 0.23 ± 0.17 (logMAR) for intermediate, and 0.52 ± 0.20 (logMAR) for near. Defocus curve showed the binocular visual acuity attained was almost 20/20 within the range of +0.5 D to -1.5 D. Contrast sensitivity was within the normal range. The Lentis Comfort IOL tolerated astigmatism to some extent. Patient age could potentially be related to uncorrected visual acuity. Questionnaire results showed almost all patients were satisfied with Lentis Comfort IOL implantation.

CONCLUSION

Lentis Comfort IOLs provided better visual function at far and intermediate distances.

[Performance of a new 7 mm intraocular lens with follow-up over 1.5 years]

BACKGROUND

Good visibility over the entire fundus is mandatory for optimal diagnostics and treatment of retinal pathologies. If an IOL implantation is planned in the context of retinal pathologies, a model with an enlarged optic diameter offers various advantages. The two most important benefits are an enhanced view at the fundus periphery and an improvement of the IOL positional stability especially with combined vitrectomy and the use of gas or silicone oil tamponades. The purpose of this study was to evaluate the performance and positional stability of a new 7 mm IOL.

MATERIAL AND METHODS

This prospective study included 55 eyes of 39 patients who were scheduled for standardized cataract surgery and received a monofocal 7.0 mm optic IOL (Aspira-aXA, HumanOptics). An incision size of 2.0 mm was chosen. Follow-up visits were performed 1 week (1W), 1 month (1M), 4 months (4M) and 1.5 years (1.5J) postoperatively. Measurements included subjective refraction, uncorrected and corrected distance visual acuity (UDVA and CDVA) as well as IOL stability regarding decentration, tilt and rotation (IOLs had a pseudomarking on the periphery of the optics).

RESULTS

Except for the postoperative occurrence of an Irvine-Gass syndrome in one eye, no intraoperative or postoperative complications were reported. The CDVA did not change significantly (p = 0.40) within the postoperative course from 1 month (median 0.00 logMAR; -0.10 to 0.22 logMAR) to 1.5 years (median 0.00 logMAR; -0.10 to 0.10 logMAR). The IOL was found to be stable over the postoperative course as decentration was < 0.02 mm and tilt < 5.5°. There was a median rotation of 1.8° (0.0-13.4°) within the first postoperative week, which was not significantly different from the rotation between surgery and 1.5 years (median 1.4°; 0.0-10.9°).

CONCLUSION

With comparable functional performance and the same small incision size as with usual 6.0 mm IOLs, the Aspira-aXA offers the advantages of a 7.0 mm optic in the diagnostics and treatment of peripheral retinal pathologies. In addition, the lens shows good position stability in the capsular bag.

Pre-clinical estimation of the intraocular lens A-constant, and its relationship to power, shape factor, and asphericity

Calculating the intraocular lens power for a particular patient requires an empirical "lens constant" to estimate the final axial location after surgery. This is normally calculated from clinical results for each new lens style, but it can also be estimated without clinical data by comparing a new style to an existing style. The lenses are axially positioned in a model eye at comparable locations, and image distances are used to estimate the change in lens constant. The A-constant used by the SRK/T calculation method is evaluated here, but this can be easily converted for other calculations using an average eye. Raytrace calculations demonstrate the method, and also illustrate the effects that refractive index, shape factor, and asphericity have on the refractive error. Actual lens measurements at 35°C in saline are preferable if details of the reference lens are uncertain.

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.].

Stability of Various Types of Aspheric Intraocular Lenses After Implantation: A One-Year Retrospective Study

Objective

The aim of the present study was to evaluate the stability of four different types of aspheric intraocular lenses (IOLs) after implantation.

Methods

This retrospective study included 124 eyes implanted with four different types of aspheric IOLs including a one-piece four-loop fixed hydrophilic acrylic IOL, a one-piece flat fixed acrylic IOL, a one-piece two-loop fixed acrylic IOL, and a three-piece two-loop fixed silicone IOL. IOL decentration, tilt, and ocular coma-like aberration (coma) at one-week, one-month, three-month, and one-year time points were evaluated postoperatively.

Results

IOL decentration, tilt, and coma in the AO, 36A, IQ, and KS-AiN implantation groups were statistically significantly different one week and one year postoperatively (p < 0.01). There were significant differences between each of the pairs of groups (p < 0.01), except for coma between the AO and 36A implantation groups one week postoperatively (p > 0.05). When comparing the different time points (ie, one week, one month, three months, and one year postoperatively), IOL decentration, tilt, and coma were significantly different in each group (p < 0.05). IOL decentration, tilt, and coma in each group increased over the period from one week to one year postoperatively. A positive linear correlation was observed between IOL decentration or tilt and coma one year postoperatively (p < 0.01).

Conclusion

One-piece multi-point fixed acrylic IOLs demonstrate better stability when compared with three-piece two-point fixed silicone IOLs. IOL decentration, tilt, and coma increase gradually over time. Ocular coma-like aberrations are influenced by the stability of IOLs.

Stability and Visual Outcomes of the Capsulotomy-Fixated FEMTIS-IOL After Automated Femtosecond Laser-Assisted Anterior Capsulotomy

PURPOSE

To evaluate stability and performance of a new monofocal anterior capsulotomy-fixated intraocular lens (IOL) (FEMTIS; Teleon Surgical B.V., Spankeren, Netherlands) after femtosecond laser-assisted cataract surgery (FLACS).

DESIGN

Prospective, multicenter, interventional, noncomparative case series.

METHODS

FLACS with FEMTIS IOL was performed in 336 eyes of 183 cataract patients with fixation of the IOL to the anterior capsulotomy followed up for 12 months. Examination included uncorrected distance visual acuity (UDVA), best-corrected visual acuity (CDVA), subjective refraction, IOL centration, posterior capsule opacification (PCO), and investigators' satisfaction questionnaire.

RESULTS

At 12 months, mean IOL rotation was 1.50 ± 1.76 degrees and decentration 0.14 ± 0.14 mm from baseline (day of surgery). Mean horizontal IOL tilt was 0.70 ± 0.60 degrees and vertical 1.15 ± 1.06 degrees relative to the baseline (crystalline lens). Mean distance between IOL and iris was 0.32 mm to 0.36 mm for all measured meridians. Mean UDVA was 0.12 ± 0.14 logMAR (range -0.20 to 0.54 logMAR), mean CDVA -0.01 ± 0.09 logMAR (range -0.30 to 0.20 logMAR). Mean spherical equivalent was 0.35 ± 0.53 diopter (D) and 98% of eyes (n = 235) were within ±1.0 D. Median PCO score was 1 with an Nd:YAG laser rate of 3.1% after 12 months. Most surgeons were very satisfied (median score: 1) with surgery and implanted IOL.

CONCLUSIONS

Implantation of FEMTIS IOL provided excellent visual and stable refractive outcomes. IOL decentration was very low compared to other published studies and showed an exceptional high in-the-bag stability over a 12-month period. This lens benefits from femtosecond laser capsulotomies. It can be positioned very predictably and offers an optimal platform for toric and multifocal IOL optics.

On the Chromatic Dispersion of Hydrophobic and Hydrophilic Intraocular Lenses

SIGNIFICANCE

There is a high variation of chromatic dispersion with contemporary intraocular lens (IOL) materials. It is well known that chromatic aberration limits the optical performance especially with high-power lenses. Lens manufacturers, however, rarely provide data on the chromatic dispersion of their materials, limiting the comparability of available materials.

PURPOSE

This study aimed to analyze chromatic dispersion of hydrophobic and hydrophilic IOLs without prior knowledge of the IOLs' geometries.

METHODS

We adapted Bessel's method for measuring focal length by placing the IOL in a wet cell. The chromatic dispersion of several hydrophobic and hydrophilic IOLs was characterized by measuring their focal lengths at multiple wavelengths. From the measured focal lengths, the refractive indices and the Abbe numbers were obtained. We measured four hydrophobic and two hydrophilic IOL models with a nominal power of 21 to 29.5 D.

RESULTS

The hydrophobic IOLs had lower Abbe numbers (Abbe numbers <41) than did the hydrophilic IOLs (Abbe numbers >50). Most Abbe numbers were in agreement with the values provided by the IOL manufacturers, and the measurements were independent from IOL power. The repeatability for the Abbe number was better than ±3.5% for all lenses and better than ±2% for lenses between 21 and 26.5 D. The dispersion could be described by a Conrady model (R > 0.997).

CONCLUSIONS

The hydrophobic materials showed larger dispersion than did the hydrophilic IOL materials resulting in increased chromatic aberration. The method allowed for an estimation of the IOL's Abbe number without prior knowledge of IOL geometry.

Clinical evaluation of a new monofocal IOL with enhanced intermediate function in patients with cataract

PURPOSE

To evaluate the effectiveness and safety of 2 enhanced monofocal intraocular lenses (IOLs). The TECNIS Eyhance IOL (Model ICB00) was compared with a standard monofocal IOL (TECNIS Monofocal, Model ZCB00).

SETTING

European multicenter study.

DESIGN

Prospective, bilateral, randomized, comparative/evaluator-masked, controlled study.

METHODS

Adult subjects scheduled to undergo bilateral, primary phacoemulsification cataract extraction and posterior IOL implantation were randomized to receive the enhanced monofocal ICB00 IOL or the monofocal ZCB00 IOL in both eyes. Monocular endpoints at 6 months included distance-corrected intermediate visual acuity (DCIVA), photopic corrected distance visual acuity, and uncorrected intermediate visual acuity (UIVA). Binocular visual acuities, monocular corrected distance contrast sensitivity (first eyes), patient-reported outcomes, and safety were assessed at 6 months.

RESULTS

Overall, 139 patients were bilaterally implanted with the enhanced monofocal IOL (n = 67) or standard monofocal IOL (n = 72) and available for the 6-month visit. The enhanced monofocal IOL significantly improved mean monocular and binocular DCIVA and UIVA by at least 1-line logarithm of the minimum angle of resolution vs the standard monofocal IOL (all P ≤ .0001). Distance vision for the enhanced monofocal IOL was 20/20 or better and comparable with that of the standard monofocal lens at 6 months. Contrast sensitivity, photic phenomena outcomes, and rates of adverse events were similar between the 2 groups.

CONCLUSIONS

In patients undergoing cataract surgery, TECNIS Eyhance IOL Model ICB00 provided enhanced intermediate vision and similar distance performance and photic phenomena compared with a standard monofocal IOL, along with improved functional performance in daily life.

Misalignment and tilt effect on aspheric intraocular lens designs after a corneal refractive surgery

PURPOSE

To numerically evaluate and compare the tolerance to misalignment and tilt of aspheric intraocular lenses (IOLs) designed for three eyes: with standard cornea and with simulated corneas after myopic and hyperopic laser ablation surgery.

METHODS

Three aspheric IOLs of +20.00 diopter (D) with different spherical aberration (SA) ([Formula: see text]) values have been designed using a theoretical model eye. Drastic changes on the theoretical eye anterior corneal asphericity have been performed to simulate myopic and hyperopic refractive surgeries. The effect of IOL misalignment and tilt on the image quality has been evaluated using a commercial optical software design for the three eye models. Image quality was assessed from the modulation transfer function (MTF), root mean square (RMS) values of defocus, astigmatism, coma and spherical aberration ([Formula: see text]), and retinal images obtained from a visual simulator using an aleatory optotype of 0.00 LogMar visual acuity (VA).

RESULTS

IOL misalignment and tilt reduced MTF values in general, and increased wavefront aberrations errors. Aberration-free IOLs maintained best the MTF values when misalignments were applied, together with good on-axis optical quality. IOLs with negative SA ([Formula: see text]) correction decreased the MTF value under 0.43 for misalignments values higher than 0.50 mm with the three corneas. The effect of misalignment on RMS astigmatism and coma was correlated with the IOL SA ([Formula: see text]) and with the three corneas.

CONCLUSIONS

This theoretical study shows that the largest degradation in image quality arises for the IOL with the highest amount of spherical aberration ([Formula: see text]). Moreover, it has been found that the aspherical design has a more influential role in misalignment tolerance than in tilt tolerance.

Comparison of Post-Cataract Surgery Visual Outcomes and Quality of Life in Patients Bilaterally Implanted with Multifocal Intraocular Lenses

Introduction

The present study compared visual outcomes in eyes with bilateral implantation of two multifocal intraocular lenses (MFIOLs)—the Eyecryl™ ACTV diffractive multifocal IOL (group 1) and AcrySof^® IQ ReSTOR^® multifocal IOL (group 2).

Methods

This was a prospective, two-group observational longitudinal study of 118 eyes from 59 patients conducted at Laxmi Eye Institute, Panvel, India. We evaluated the patients at 1, 3, and 6 months. We assessed visual acuity, contrast sensitivity, higher-order aberrations, reading speed, defocus curve, stereopsis, quality of life (QOL), and adverse events in these participants.

Results

The median (interquartile range) best-corrected distance visual acuity was 0.18 (0, 0.18) in group 1 and 0.18 (0, 0.18) in group 2 at 1, 3, and 6 months; the difference was not statistically significant (p = 0.48). The binocular defocus curve in both groups showed two peaks at 0.0 to −0.5 D and at −2.5 D. The mean (95% confidence interval) critical print size was significantly different between groups 1 and 2 at low illumination (0.918 [0.905, 0.931] vs 1.154 [1.128, 1.180]; p = 0.004). Contrast sensitivity was significantly better in group 1 under mesopic conditions but not under scotopic conditions. Though total QOL did not differ significantly between groups, the psychosocial quality of life was significantly better in group 1. About 23% of patients in group 2 reported unwanted images, compared with 0% in group 1 (p = 0.01).

Conclusion

We found that the Eyecryl and AcrySof groups were comparable for best-corrected visual acuity, photopic contrast sensitivity, defocus curve, reading parameters, stereopsis, and quality of vision. However, the Eyecryl group had better mesopic contrast and a lower proportion of unwanted images. Psychosocial quality of life was significantly better in the Eyecryl group; however, satisfaction was similar between groups. The cost of one of the lenses is less than the other. Thus, individuals with limited resources may opt for the Eyecryl™ ACTV, with similar visual outcomes.

Biomechanical Stability of Three Intraocular Lenses With Different Haptic Designs: In Silico and In Vivo Evaluation

PURPOSE

To assess the biomechanical stability of three different marketed intraocular lenses (IOLs) with different haptic designs (four-loop IOL [Micro F FineVision model] and double C-loop IOL [POD F and POD FT models], all manufactured by PhysIOL), in silico (computer simulation) and in vivo (in the context of lens surgery).

METHODS

An in silico simulation investigation was performed using finite element modeling (FEM) software to reproduce the compression test defined by the International Organization for Standardization and in vivo implantation in patients in the context of lens surgery was evaluated 1 day and 3 months postoperatively. IOL decentration and rotation were tested. In addition, the stress and strains were analyzed with the finite element method.

RESULTS

In the in silico evaluation, the compression force for the POD F IOL was slightly lower than for the POD FT IOL and Micro F IOL for all compression diameters. The axial displacement was maximum for the POD FT IOL and the tilt, rotation, and lateral decentration were substantially lower than the acceptable tolerance limits established in ISO 11979-2. In the in vivo evaluation, a total of 45 eyes from 45 patients were selected, 15 eyes for each IOL model under assessment. Statistically significant differences were found between the Micro F and POD F IOLs for lateral decentration in x-direction (in absolute value) at 3 months postoperatively (P = .03).

CONCLUSIONS

Although statistically significant differences have been found when comparing the displacement, tilt, and rotation between the different lenses, these differences cannot be considered clinically relevant, which would suggest that all three IOL models yield excellent stability in those terms. FEM appears to be a powerful tool for numerical studies of the biomechanical properties of IOLs. [J Refract Surg. 2020;36(9):617-624.].

Static and Dynamic Factors Associated With Extended Depth of Focus in Monofocal Intraocular Lenses

PURPOSE

To analyze factors affecting depth of focus (DOF) and near vision functionality in eyes implanted with aspheric monofocal intraocular lenses (IOLs).

METHODS

This prospective study included 111 eyes of 74 patients that underwent phacoemulsification with monofocal IOL implantation. Ninety-one normal eyes were randomized to receive aberration-free (n = 30) or negative-spherical aberration (SA) IOLs (n = 61). Twenty post-hyperopic femto-LASIK eyes received aberration-free IOLs. Corneal higher-order aberrations (SA, coma, trefoil, and corneal asphericity) for a 6 mm pupil were measured by Scheimpflug tomography. Ray-tracing metrics (visual Strehl optical transfer function [VSOTF], effective range of focus [EROF], sphere shift [SS], EROF-SS), pupil size measurements at far and near, and ocular and corneal SA were obtained using ray-tracing aberrometry. Distance-corrected near visual acuity (DCNVA) and subjective defocus curves up to ±4.0 diopters were evaluated.

RESULTS

Multivariable logistic regression found corneal profile and IOL type to be determinants of extended DOF with monofocal IOLs. The aberration-free IOL group showed significantly better DCNVA and higher total SA than the negative-SA group. Post-hyperopic LASIK eyes showed significantly better DCNVA; higher negative SA, coma, and Q value (P < .05), and smaller pupil size (P = .05) than normal eyes implanted with aberration-free IOLs.

CONCLUSION

Corneal profile and type of IOL implanted were the most important factors influencing near vision functionality with aspheric monofocal IOLs. Higher positive SA in the aberration-free group potentially led to better DCNVA than the negative-SA group in normal eyes. Hyperprolate corneas had better DOF curves and DCNVA than normal corneas. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Evaluation of the optical performance for aspheric intraocular lenses in relation with tilt and decenter errors

PURPOSE

To evaluate and compare the effect of misalignment and tilt on the optical performance of different aspheric intraocular lens (IOL) designs.

METHODS

Three aspheric IOLs with a different quantity of spherical aberration (SA) have been designed and the effect of IOL misalignment and tilt on the imaging quality of an eye model has been numerically assessed using a commercial optical design software. The prototypes have been manufactured by lathe turning and tested in vitro using the same optical bench (PMTF, Lambda-X) that complies with International Organization for Standardization standard 11979-2 requirements. Image quality was evaluated from the modulation transfer functions (MTFs), through-focus modulation transfer functions (TF-MTFs), root mean square (RMS) values of defocus, astigmatism and coma, and images of the United States Air Force (USAF) target were taken. A comparison with the optical performance of spherical IOLs has also been performed.

RESULTS

Intraocular lens misalignment and tilt increased wavefront aberrations; the effect of misalignment on root mean square (RMS) astigmatism and coma was positively correlated with the spherical aberration of the IOL. Aberration-free IOLs showed the highest MTF for all misalignment values and for IOLs with negative SA correction the MTF decays below 0.43 when they are decentered 0.50 mm.

CONCLUSIONS

Aspherical IOLs are more sensitive than spherical IOLs to misalignment or tilt, depending on their SA correction. The optical degradation caused by IOL misalignment had a greater effect on IOL designs with a higher amount of negative spherical aberration. In contrast, the effect of tilt on the optical performance was less sensitive to the IOL design.

The Influence of Decentration on Higher-Order Aberrations in Artisan Aphakic Intraocular Lens Implantation Eyes

Purpose

To characterize the influence of decentration on higher-order aberrations of Artisan aphakic intraocular lens implantation eyes. Setting. Department of Ophthalmology and Vision Science, Eye and ENT Hospital of Fudan University, Shanghai, China.

Design

Retrospective case series.

Methods

Twenty-three eyes of 18 patients were retrospectively examined. Location of the IOL was imaged using a slit-lamp, and decentration (the distance from the center of a pupil to the geometric center of the IOL) was measured using the AutoCAD 2007 software. Ocular and internal higher-order aberrations were measured using the wavefront analyzer KR-1W (Topcon) and their correlation with decentration were analyzed. Coma, spherical, 3rd-, 4th-order, trefoil, tetrafoil aberrations, ocular, and internal higher-order aberrations were calculated for a 4.0 mm pupil diameter.

Results

The mean age of patients was 33.6 ± 21.4 years (ranging from 7 to 72 years). The mean follow-up period was 28.2 ± 10.5 months (ranging from 12 to 52 months). The mean postoperative best-corrected visual acuity (BCVA) was 0.19 ± 0.19 logMAR (range −0.18–0.52). The mean decentration was 0.57 ± 0.28 mm (range 0.15–1.21 mm). There was no correlation between Artisan IOL decentration and ocular higher-order aberrations, internal higher-order aberrations, coma, spherical, 3rd-, 4th-order, trefoil, and tetrafoil aberrations, respectively. There was a positive correlation between Artisan IOL decentration and 2nd-astig aberrations when 2nd-astig aberrations were less than 0.1.

Conclusions

The position of Artisan IOLs showed slight decentration and the amounts of decentration were not large enough to influence higher-order aberrations.

Bifocal nondiffractive intraocular lens for enhanced depth of focus in correcting presbyopia: Clinical evaluation

PURPOSE

To assess the clinical outcomes and patient satisfaction after bilateral cataract surgery with implantation of a bifocal refractive enhanced depth of focus intraocular lens (IOL) with a low near addition (add).

SETTING

Department of Ophthalmology, Ludwig-Maximilians-University Munich, Munich, Germany.

DESIGN

Prospective longitudinal case series.

METHODS

Eyes with bilateral age-related cataract and corneal astigmatism of less than 1.0 diopter (D) had standard microincision cataract surgery with implantation of a bifocal nondiffractive shape-segmented enhanced depth of focus IOL (Lentis Comfort, LS-313 MF15). The corrected and uncorrected (UDVA) distance visual acuities, uncorrected intermediate (UIVA) and near (UNVA) visual acuities, defocus, corneal astigmatism, spectacle independence, contrast sensitivity, rotational stability, photic phenomena, and patient satisfaction were evaluated over a 3-month follow-up.

RESULTS

The study comprised 22 patients (44 eyes). The mean postoperative manifest spherical equivalent was -0.10 D ± 0.58 (SD), resulting in a mean UDVA of 0.07 ± 0.10 logMAR, mean UIVA of 0.21 ± 0.15 logarithm of minimum angle of resolution (logMAR), and mean UNVA of 0.53 ± 0.15 logMAR. Binocular UDVA was 0.01 ± 0.08 logMAR. The best reading distance was 0.46 ± 0.09 m. More than 95% of patients were satisfied with their visual acuity, and less than 10% reported photic phenomena. The IOL showed an excellent rotational stability.

CONCLUSIONS

The enhanced depth of focus IOL with 1.5 D of near add showed excellent intermediate and far visual performance and acceptable near visual restoration. Patient satisfaction was very high, and few patients reported disturbing photic phenomena.

Comparative Analysis of Clinical and Functional Results and Position of Intraocular Lens after Femtolaser-Assisted and Standard Cataract Phacoemulsification

Modern surgical treatment of cataracts provides effective results. The study of the position of the intraocular lens (IOL) in the capsule bag can be considered as one of the most important factors influencing the final visual and refractive result of the operation.

Aim: comparative analysis of clinical and functional results and position of the IOL in the capsular bag, namely decentration and tilt, when performing femtolazer-assisted phacoemulsification (FLACS) and standard phacoemulsification (CPCS). 

Materials and methods. We surveyed 57 patients (57 eyes). FLACS was performed in 27 patients, CPCS – in 30 patients. Standard methods of research were used, determination of the position of the IOL (decentration and tilt) in the capsular bag on the device OCT-Casia2 (TOMEY, Germany) and study of wave front were conducted.

Results. Comparative analysis of the obtained results showed no significant difference between groups in postoperative visual acuity, however, there was the trend towards higher performance corrected distance visual acuity and uncorrected distance in the group FLACS (0.68 ± 0.18 and 0.74 ± 0.2) compared to the group CPCS (0.58 ± 0.28 and 0.65 ± 0.24). Internal higher order aberrations were significantly low in the group with femtolazer accompaniment: in 3 mm zone almost 2 times (p = 0.041), in 5 mm zone 1.3 times (p = 0.047). Vertical decentration in a CPCS group made 0.217 ± 0.26 mm, in FLACS group – 0.118 ± 0.05 mm, the vertical tilt – 0.75 ± 0.37° and 0.54 ± 0.36 respectively. 

Conclusion. Decentralizations and IOL tilt tended to lower indices in the FLACS during the observation period up to 2 months after the operation, which was accompanied by lower values of higher order internal aberrations.

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.

Comparison of refractive predictability and endothelial cell loss in femtosecond laser-assisted cataract surgery and conventional phaco surgery: prospective randomised trial with 6 months of follow-up

Objective

Femtosecond laser-assisted cataract surgery (FLACS) decreases the use of energy and provides a more precise capsulorhexis compared with conventional phaco surgery (CPS). The purpose of this study was to examine if the lower energy use in FLACS caused less endothelial cell loss compared with CPS and if there was a difference in refractive predictability between CPS and FLACS.

Methods and analysis

This was a randomised controlled study of 96 patients with a 6-month follow-up comparing one eye surgery by FLACS and the contralateral eye operated by CPS (divide and conquer technique). Both eyes had intraocular aspheric lenses implanted. Uncorrected distance visual acuity, corrected distance visual acuity (CDVA), central corneal endothelial cell count and hexagonality (non-contact endothelial cell microscope) were assessed preoperatively at 40 and at 180 days postoperatively.

Results

The mean phaco energies were 6.55 (95% CI 5.43 to 7.66) and 9.77 (95% CI 8.55 to 10.95) U/S (p<0.0001) by FLACS and CPS, respectively. At day 40, the mean endothelial cell loss (ECL) was 344 cells/mm² (95% CI 245 to 443) by FLACS (12.89%) and 497 cells/mm² (95% CI 380 to 614) by CPS (18.19%) (p=0.027). At day 180, ECL was 362 cells/mm² (95% CI 275 to 450) in FLACS (13.56%) and 465 cells/mm² (95% CI 377 to 554) in CPS (17.03%) (p=0.036).

The mean absolute difference from the attempted refraction was 0.43 (95% CI 0.36 to 0.51) dioptres (D) at day 40 and 0.46 D (95% CI 0.39 to 0.53) at day 180 by FLACS compared with 0.43 D (95% CI 0.36 to 0.51) at day 40 (p=0.95) and 0.46 D (95% CI 0.37 to 0.52) at day 180 (p=0.91) with CPS.

Conclusion

ECL was significantly lower in FLACS compared with CPS at both day 40 and day 180. ECL was correlated to the energy used. We found no difference in refractive predictability or CDVA between the groups.

Stability and visual outcomes yielded by three intraocular trifocal lenses with same optical zone design but differing material or toricity

PURPOSE

To compare rotational stability, centration and visual outcomes provided by three trifocal lens models that have the same optical zone design but different material, composition, and/or toricity.

METHODS

The study included 78 patients with symmetric bilateral intraocular lens implantation. The lenses under evaluation were trifocal intraocular lenses made of hydrophilic acrylic material: a spherical lens 26% hydrophilic acrylic (POD FineVision), a similar lens but having a toric design (POD Toric FineVision), and a trifocal lens 25% hydrophilic acrylic material (FineVision/MicroF). Moreover, the lenses share the same optical zone design. The lenses' rotational stability and centration were measured by means of the PIOLET software, which relies on recording and image processing techniques to determine lens rotation and centration based on slit-lamp images. We also assessed patients' visual quality by means of 25, 40, and 80 cm VA tests.

RESULTS

The best centration results were achieved with the POD Toric FineVision model, although the differences were not statistically significant. As for lens rotation, it was below 5° in all cases under study. Regarding VA, all subjects attained at least 0.3 logMAR for far distance uncorrected VA, at 80 cm VA was about 0.2 logMAR, at 40 cm it was above 0.15 logMAR, and at 25 cm it was about 0.3 logMAR for both lens types.

CONCLUSION

All three intraocular lens models yield excellent visual results at far, near as well as intermediate distances. The POD FineVision and POD Toric FineVision models, with double C-loop design, yielded the best results centration-wise and rotation-wise. Differences had no clinical relevance.

Suturing technique for scleral fixation of toric intraocular lens in the traumatic aphakic eye with corneal astigmatism

PURPOSE:

To describe the clinical outcomes of traumatic aphakic eyes with corneal astigmatism after using a novel technique for toric intraocular lens suture fixation.

METHODS:

In total, 12 eyes of 12 patients who underwent a new scleral suture fixation technique of one-piece toric intraocular lens (SN6AT series, Alcon Inc., TX, USA) were included in our retrospective study. Preoperative patient status, postoperative visual acuity and refractive outcomes, postoperative intraocular lens rotation, tilt, decentration, and complications were analyzed.

RESULTS:

The mean follow-up was 11.6 ± 1.0 months. The mean preoperative best-corrected visual acuity was 0.55 ± 0.32 in the logarithm of minimum angle of resolution equivalent; the postoperative best-corrected visual acuity was 0.45 ± 0.34. The mean preoperative total corneal astigmatism was 2.51 ± 1.67 D. The mean postoperative residual astigmatism was 0.77 ± 0.54 D. The mean intraocular lens rotation was 3.33° ± 1.37° (range, 1°-6°). The mean intraocular lens tilt in horizontal direction was 3.64° ± 1.02° (range, 2.6°-6.3°) and in vertical direction it was 3.19° ± 1.07 ° (range, 1.6°-5.2°). The mean intraocular lens decentration in horizontal direction was 0.14 ± 0.03 mm (range, 0.089-0.192 mm) and in vertical direction it was 0.15 ± 0.02 mm (range, 0.113-0.181 mm). One patient had mild vitreous hemorrhage and two other patients had high postoperative residual sphere and astigmatism, respectively. But no other serious complications were observed.

CONCLUSION:

Scleral suture fixation of foldable toric intraocular lens to correct corneal astigmatism can be a safe and effective alternative technique to manage traumatic aphakic eyes that lack adequate capsular support.

Clinical outcome and higher order aberrations after bilateral implantation of an extended depth of focus intraocular lens

Purpose:

The purpose of this study was to assess the clinical outcome after a bilateral implantation of an extended depth of focus intraocular lens in comparison to a monofocal intraocular lens.

Setting:

Department of Ophthalmology, Charité—Medical University Berlin, Germany.

Patients and Methods:

A total of 60 eyes of 30 patients were enrolled in this prospective, single-center study. The cataract patients underwent phacoemulsification with bilateral implantation of a TECNIS® Symfony (Abbott Medical Optics, Santa Ana, CA, USA, 15 patients) or a TECNIS Monofocal ZCB00 (Abbott Medical Optics, Santa Ana, CA, USA, 15 patients). Postoperative evaluations were performed after 1 and 3 months, including visual acuities at far, intermediate, and near distance. Mesopic, scotopic vision, and contrast sensitivity were investigated. Aberrometry was performed using an iTrace aberrometer with a pupil scan size of 5.0 mm.

Results:

After 3 months, the TECNIS Symfony group reached an uncorrected visual acuity at far distance of −0.02 logMAR compared to −0.06 logMAR in the TECNIS Monofocal group ( p = 0.03). Regarding the uncorrected vision at intermediate and near distance the following values were obtained: intermediate visual acuity −0.13 versus 0.0 logMAR (TECNIS Symfony vs TECNIS Monofocal, p = 0.001) and near visual acuity 0.11 versus 0.26 logMAR (TECNIS Symfony vs TECNIS Monofocal, p = 0.001). Low-contrast visual acuities were 0.27 versus 0.20 logMar (TECNIS Symfony vs TECNIS Monofocal, p = 0.023).

Conclusion:

The TECNIS Symfony intraocular lens can be considered an appropriate alternative to multifocal intraocular lenses because of good visual results at far, intermediate, and near distance as well as in low-contrast vision.

The efficiency of aspheric intraocular lens according to biometric measurements

Purpose

To analyze internal spherical aberration in pseudophakic eyes that underwent aspheric intraocular lens (IOL) implantation, and to investigate the relationships between biometric data and the effectiveness of aspheric IOL implantation.

Methods

This retrospective study included 40 eyes of 40 patients who underwent implantation of an IOL having a negative spherical aberration of -0.20 μm (CT ASPHINA 509M; Carl Zeiss Meditec Inc., Germany). The IOLMaster (version 5.0; Carl Zeiss AG, Germany) was used for preoperative biometric measurements (axial length, anterior chamber depth, central corneal power) and the measurement of postoperative anterior chamber depth. The spherical aberrations were measured preoperatively and 3 months postoperatively using the iTrace (Tracey Technologies, Houston, TX, USA) at a pupil diameter of 5.0 mm. We investigated the relationships between preoperative biometric data and postoperative internal spherical aberration, and compared biometric measurements between 2 subgroups stratified according to internal spherical aberration (spherical aberration ≤ -0.06 μm vs. spherical aberration > -0.06 μm).

Results

The mean postoperative internal spherical aberration was -0.087 ± 0.063 μm. Preoperative axial length and residual total spherical aberration showed statistically significant correlations with internal spherical aberration (p = 0.041, 0.002). Preoperative axial length, postoperative anterior chamber depth, IOL power, and residual spherical aberration showed significant differences between the 2 subgroups stratified according to internal spherical aberration (p = 0.020, 0.029, 0.048, 0.041 respectively).

Conclusion

The corrective effect of an aspheric IOL is influenced by preoperative axial length and postoperative anterior chamber depth. Not only the amount of negative spherical aberration on the IOL surface but also the preoperative axial length should be considered to optimize spherical aberration after aspheric IOL implantation.

Comparative Analysis of the Clinical Outcomes With a Monofocal and an Extended Range of Vision Intraocular Lens

PURPOSE

To evaluate and compare the clinical outcomes with an aspheric monofocal intraocular lens (IOL) and an extended range of vision (ERV) IOL based on achromatic diffractive technology.

METHODS

This was a prospective comparative study including 80 eyes undergoing cataract surgery with implantation of the monofocal Tecnis ZCB00 IOL (Abbott Medical Optics Inc., Santa Ana, CA) (monofocal group: 30 eyes of 15 patients) or the ERV Tecnis Symfony IOL (Abbott Medical Optics, Inc.) (ERV group: 50 eyes of 25 patients). Visual, refractive, contrast sensitivity, defocus curve, ocular optical quality (Optical Quality Analysis System; Visiometrics SL, Terrassa, Spain), and quality of life (National Eye Institute Refractive Error Quality of Life Instrument 42 Questionnaire) outcomes were evaluated during a 3-month follow-up.

RESULTS

Significantly better postoperative uncorrected monocular and binocular distance (UDVA), intermediate (UIVA), and near (UNVA) visual acuities were found in the ERV group (P ≥ .013). Postoperative spherical equivalent was within ±1.00 diopters in 94% and 100% of eyes in the ERV and the monofocal groups, respectively. Binocular UIVA and UNVA of 0.20 or better (Snellen 20/30) were observed in all cases in the ERV group and in 13.3% and 6.7% of eyes of the monofocal group, respectively. No significant differences among groups were observed in contrast sensitivity (P ≥ .156) or ocular optical quality parameters (P ≥ .084). In the monocular defocus curve, all visual acuities were better in the ERV group (P ≤ .002), except for the +0.50-diopter defocus level (P = .367). Significantly better scores were obtained for dependence on correction (P = .003) and suboptimal correction (P = .038) subscales in the ERV group.

CONCLUSIONS

The extended range of vision IOL provides better distance, intermediate, and near visual acuity than the aspheric monofocal IOL, while maintaining the same level of visual quality. [J Refract Surg. 2016;32(7):436-442.].

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.

In vivo subjective and objective longitudinal chromatic aberration after bilateral implantation of the same design of hydrophobic and hydrophilic intraocular lenses

PURPOSE

To measure the longitudinal chromatic aberration in vivo using psychophysical and wavefront-sensing methods in patients with bilateral implantation of monofocal intraocular lenses (IOLs) of similar aspheric design but different materials (hydrophobic Podeye and hydrophilic Poday).

SETTING

Instituto de Optica, Consejo Superior de Investigaciones Cientificas, Madrid, Spain.

DESIGN

Prospective observational study.

METHODS

Measurements were performed with the use of psychophysical (480 to 700 nm) and wavefront-sensing (480 to 950 nm) methods using a custom-developed adaptive optics system. Chromatic difference-of-focus curves were obtained from best-focus data at each wavelength, and the longitudinal chromatic aberration was obtained from the slope of linear regressions to those curves.

RESULTS

The longitudinal chromatic aberration from psychophysical measurements was 1.37 diopters (D) ± 0.08 (SD) (hydrophobic) and 1.21 ± 0.08 D (hydrophilic). From wavefront-sensing, the longitudinal chromatic aberration was 0.88 ± 0.07 D and 0.73 ± 0.09 D, respectively. At 480 to 950 nm, the longitudinal chromatic aberration was 1.27 ± 0.09 D (hydrophobic) and 1.02 ± 0.13 D (hydrophilic). The longitudinal chromatic aberration was consistently higher in eyes with the hydrophobic IOL than in eyes with the hydrophilic IOL (a difference of 0.16 D and 0.15 D, respectively). Similar to findings in young phakic eyes, the longitudinal chromatic aberration from the psychophysical method was consistently higher than from wavefront-sensing, by 0.48 D (35.41%) for the hydrophobic IOL and 0.48 D (39.43%) for the hydrophilic IOL.

CONCLUSION

Longitudinal chromatic aberrations were smaller with hydrophilic IOLs than with hydrophobic IOLs of the same design.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Evaluation of the SVOne: A Handheld, Smartphone-Based Autorefractor

Purpose

The SVOne is a portable Hartmann-Shack wavefront aberrometer that can be attached to a smartphone to determine the refractive error of the eye objectively. The aim of the present study was to compare the findings of the SVOne with retinoscopy, subjective refraction, and two commercially available autorefractors (Topcon KR-1W and Righton Retinomax-3).

Methods

Refractive error was assessed both with and without cycloplegia in 50 visually normal, young adults using the five techniques described above. Further, to assess repeatability of the instruments, the entire procedure was repeated in a subgroup of 10 subjects. All data were analyzed in terms of power vectors (M, J₀, and J₄₅).

Results

No significant difference was observed between the mean values of M (spherical equivalent) for the different techniques. However, a significantly higher mean value of precyclopegic J₀ was recorded for the SVOne, which also had the highest limits of agreement for both the J₀ and J₄₅ astigmatic components. Retinoscopy and subjective refraction showed the best repeatability (in terms of M values) for precycloplegic and postcycloplegic measurements, respectively. High and significant linear correlations were observed between the subjective findings and the other four techniques.

Conclusions

The results indicate that the SVOne handheld aberrometer provides measurements of refractive error in normal, young individuals that are not significantly different from other subjective and objective procedures. This instrument is valuable for vision screenings, as well as examinations taking place outside the clinical office. It may also serve as an adjunct in the standard optometric examination.

Image Quality Analysis of Eyes Undergoing LASER Refractive Surgery

Laser refractive surgery for myopia increases the eye’s higher-order wavefront aberrations (HOA’s). However, little is known about the impact of such optical degradation on post-operative image quality (IQ) of these eyes. This study determined the relation between HOA’s and IQ parameters (peak IQ, dioptric focus that maximized IQ and depth of focus) derived from psychophysical (logMAR acuity) and computational (logVSOTF) through-focus curves in 45 subjects (18 to 31yrs) before and 1-month after refractive surgery and in 40 age-matched emmetropic controls. Computationally derived peak IQ and its best focus were negatively correlated with the RMS deviation of all HOA’s (HORMS) (r≥-0.5; p<0.001 for all). Computational depth of focus was positively correlated with HORMS (r≥0.55; p<0.001 for all) and negatively correlated with peak IQ (r≥-0.8; p<0.001 for all). All IQ parameters related to logMAR acuity were poorly correlated with HORMS (r≤|0.16|; p>0.16 for all). Increase in HOA’s after refractive surgery is therefore associated with a decline in peak IQ and a persistence of this sub-standard IQ over a larger dioptric range, vis-à-vis, before surgery and in age-matched controls. This optical deterioration however does not appear to significantly alter psychophysical IQ, suggesting minimal impact of refractive surgery on the subject’s ability to resolve spatial details and their tolerance to blur.

Effects of intraocular lenses with different diopters on chromatic aberrations in human eye models

BACKGROUND

In this study, the effects of intraocular lenses (IOLs) with different diopters (D) on chromatic aberration were investigated in human eye models, and the influences of the central thickness of IOLs on chromatic aberration were compared.

METHODS

A Liou-Brennan-based IOL eye model was constructed using ZEMAX optical design software. Spherical IOLs with different diopters (AR40e, AMO Company, USA) were implanted; modulation transfer function (MTF) values at 3 mm of pupil diameter and from 0 to out-of-focus blur were collected and graphed.

RESULTS

MTF values, measured at 555 nm of monochromatic light under each spatial frequency, were significantly higher than the values measured at 470 to 650 nm of polychromatic light. The influences of chromatic aberration on MTF values decreased with the increase in IOL diopter when the spatial frequency was ≤12 c/d, while increased effects were observed when the spatial frequency was ≥15 c/d. The MTF values of each IOL eye model were significantly lower than the MTF values of the Liou-Brennan eye models when measured at 555 nm of monochromatic light and at 470 to 650 nm of polychromatic light. The MTF values were also found to be increased with the increase in IOL diopter.

CONCLUSION

With higher diopters of IOLs, the central thickness increased accordingly, which could have created increased chromatic aberration and decreased the retinal image quality. To improve the postoperative visual quality, IOLs with lower chromatic aberration should be selected for patients with short axial lengths.

From corneal shape to ocular wavefront in eyes with aspheric IOLs: the feasibility of IOL customisation

PURPOSE

To determine if it is possible to predict the ocular wavefront aberrations of eyes with an aspheric IOL from the corneal shape and other readily available eye characteristics. A reliable prediction is a prerequisite for future IOL customisation.

METHODS

Sixty pseudophakic eyes with aspheric IOLs of 60 patients were included. The corneal shape and the ocular wavefront aberrations were measured postoperatively with a Scheimpflug camera and an aberrometer, respectively. The elevation data of the anterior corneal surface were fitted by Zernike polynomials. Linear regression models for the Zernike coefficients describing the ocular wavefront aberrations up till the fourth order were determined, with as independent variables the Zernike coefficients describing the corneal shape, the eye (right/left), IOL power, and axial length.

RESULTS

Linear regression equations with an explained variance (adjusted R-square) above 0.50 were found for five Zernike aberration terms: defocus (z(2,0); adjusted R-square 0.90), the astigmatism terms (0.81 for oblique astigmatism [z(2,-2)] and 0.88 for regular astigmatism [z(2,2)]), vertical coma (z(3,-1); 0.52), and spherical aberration (z(4,0); 0.71).

CONCLUSION

The defocus, astigmatism, vertical coma, and spherical aberration terms of the ocular wavefront are strongly associated with the corneal shape in pseudophakic eyes and may thus be predicted from the corneal shape and other eye characteristics.

Describing the corneal shape after wavefront-optimized photorefractive keratectomy

PURPOSE

To develop a procedure for describing wavefront-optimized photorefractive keratectomy (PRK) corneas and to characterize PRK-induced changes in shape.

METHODS

We analyzed preoperative and postoperative corneal elevation data of 41 eyes of 41 patients (mean [±SD] age, 38 [±11] years) who underwent a myopia-correcting (preoperative spherical equivalent refraction -3.9 [±1.5] diopters) wavefront-optimized PRK, assessed with Scheimpflug imaging. Zernike polynomials were fitted to the elevation data. The diameter of the greatest corneal zone that could be analyzed and the number of Zernike orders needed to make a reliable fit were determined, based on the fitting error. The PRK-induced changes in corneal shape were studied.

RESULTS

All subjects could be included for analysis of zones up to 6 mm in diameter. This was 90, 83, and 44% for 7, 8, and 9 mm, respectively. The number of Zernike orders (terms) needed for an accurate fit ranged from four (15) for a 4-mm analyzed zone diameter to eight (45) for 8 mm. For the anterior surface, the spherical aberration term decreased significantly (p < 0.01) after PRK for the 4-mm analyzed zone diameter (-0.09 μm), remained unchanged for 5 mm (+0.01 μm; p = 0.56), and increased significantly for 6 mm (+0.40 μm) and above (p < 0.01). There was no significant change in any other higher-order Zernike term, but the square root of the sum of the squares of all higher-order terms increased significantly for all analyzed zone diameters. Photorefractive keratectomy did not influence the posterior corneal shape.

CONCLUSIONS

The cornea after wavefront-optimized PRK can be described as accurately as a healthy cornea and with a similar number of Zernike polynomials. The anterior corneal shape changes significantly after treatment, whereas the posterior corneal shape remains unchanged. The observed effect of wavefront-optimized ablation on the spherical aberration term depends on the diameter of the analyzed zone.

Computational aspects of the through-focus characteristics of the human eye

Calculating through-focus characteristics of the human eye from a single objective measurement of wavefront aberration can be accomplished through a range of methods that are inherently computationally cumbersome. A simple yet accurate and computationally efficient method is developed, which combines the philosophy of the extended Nijboer-Zernike approach with the radial-basis-function-based approximation of the complex pupil function. The main advantage of the proposed technique is that the increase of the computational cost for a vector-valued defocus parameter is practically negligible in comparison to the corresponding scalar-valued defocus parameter.

Registration tolerance of a custom correction to maintain visual acuity

PURPOSE

To present a predictive model of the registration tolerance for wavefront-guided correction to maintain acuity within fixed limits and demonstrate the potential utility using two typical keratoconic eyes.

METHODS

Change in log visual Strehl was plotted as a function of translation error for a series of rotations of a wavefront-guided correction. Contour lines were added at Δlog visual Strehl levels predicted to induce one- and two-line losses of logMAR visual acuity. The model was validated by regressing measured acuity loss from subjects viewing acuity charts that were degraded by the residual wavefront error resulting from the movement of wavefront-guided correction against the model's predicted acuity.

RESULTS

The model's predicted change in acuity can be substituted for measured change in acuity (R² = 0.91) within measurement error (±0.1 logMAR). Translation and/or rotation of a wavefront-guided correction induced asymmetric optical tolerance to movement. Induced errors depended on the wavefront error being corrected, the wavefront-guided correction design, and the amount of registration error.

CONCLUSIONS

Change in log visual Strehl can be used to determine the registration tolerance necessary to keep the variation in acuity within user-defined limits. This tolerance is unique for each wavefront error and wavefront-guided correction design.

Multifocal IOL Implant with or without Capsular Tension Ring: Study of Wavefront Error and Visual Performance

Purpose

To evaluate visual performance and wavefront error after multifocal intraocular lens (MIOL) implant with or without capsular tension ring (CTR).

Methods

Sixty eyes of 60 candidates for phacoemulsification and MIOL implantation were included in the study and were randomly divided into 2 groups. Thirty eyes (group 1) were implanted with the AcrySof ReSTOR® SN60D3 MIOL and Corneal® ACPI 11 CTR and 30 eyes (group 2) received the same MIOL with no CTR.

Results

Twenty days and at 360 days after surgery, the uncorrected and corrected distance visual acuity at high and low contrast were not significantly different between the 2 groups. The root mean square (RMS) of ocular and internal wavefront error was significantly different in the 2 groups early after surgery and did not modify significantly over the 1-year follow-up period. The RMS of total and internal high-order aberrations and ocular and internal trefoil and coma aberrations were significantly lower in group 1 compared to group 2 (p<0.05). Ocular, corneal, internal modulation transfer function at high and low spatial frequencies and ocular, corneal, internal Strehl ratio were not significantly different between the groups. The IOL decentration and tilt were higher in group 1 compared to group 2.

Conclusions

ReSTOR MIOL was effective in improving visual performance and provided a good quality of vision due to a significant reduction of high-order spherical aberration. The implant of CTR additionally reduced the ocular wavefront error related to a reduction of third-order aberration related to better IOL position.

Effect of a single-piece aspheric hydrophobic acrylic intraocular lens design on centration and rotation

PURPOSE

To assess the rotation and centration stability of the new design features of a 1-piece aspheric hydrophobic acrylic intraocular lens (IOL).

SETTING

National Eye Hospital, Cairo, Egypt.

DESIGN

Randomized clinical trial.

METHODS

Patients in this study had implantation of a 1-piece Tecnis 1 ZCB00 IOL or a 3-piece Sensar AR40e IOL. Decentration and rotation were recorded immediately postoperatively, and 2 to 3 days and 8 weeks postoperatively. This was done using 2 slitlamp eyepieces and referring to constant corneal landmarks (ie, the limbus and the phaco incision).

RESULTS

Thirty-two 1-piece IOLs and 30 3-piece IOLs were implanted. Although the 1-piece IOLs moved toward the corneal center more than the 3-piece IOLs between 3 days and 8 weeks postoperatively (P=.054), the difference was not statistically significant between 0 day and 3 days or during the entire follow-up (P=.546 and P=.367, respectively). There were no statistically significant differences in the horizontal or vertical components of this movement between the 2 groups (P=.883 and P=.636, respectively). The mean rotation was 2.5 degrees ± 9.1 (SD) in the 1-piece IOL group and 0 ± 6.5 degrees in the 3-piece IOL group, with no statistically significant difference between the groups (P=.521).

CONCLUSION

The new 1-piece design showed relatively good centration and stability in the horizontal, vertical, and rotational aspects.