Clinical comparison of the optical performance of aspheric and spherical intraocular lenses

[Optical benchtop evaluation of special intraocular lens optics]

Intraocular lenses (IOL) featuring complex optical designs can pose a challenge in understanding their performance, which may hinder making an informed decision when selecting suitable lenses for patients. This underlines the importance of collecting optical quality data of IOLs and making them available. The deployment of benchtop systems for IOL testing offers not only insights into the design features of various IOL solutions but also provides a platform for objective comparisons of special optics designs, including information about their susceptibility to photic phenomena. Recent advances in IOL testing have improved the ability to predict functional effects on visual acuity and contrast sensitivity from objective optical quality metrics. This, for instance, can be used to study monofocal lenses and the impact of asphericity on vision and IOLs tolerance to misalignment. Monofocal-plus IOLs consistently show only a slight improvement in the depth of focus when tested on the optical bench and in clinical settings. Although the pupil dependence found in this technology may limit the advantages of monofocal-plus over standard monofocal technology to extend the range of vision, it is the key to reduce photic phenomena. Refractive and diffractive extended depth of focus (EDOF) IOLs can effectively enhance intermediate vision, with the latter offering a slightly broader depth of focus but potentially increasing the risk of dysphotopsia. However, the limitation of EDOF IOLs is that they often fail to deliver spectacle independence for reading, which can be overcome by trifocal technology. Still, the available trifocal IOLs differ in their location of intermediate and near foci and the susceptibility to produce glare effects. Therefore, the knowledge from optical benchtop testing of IOLs can support optimizing the IOL selection by aligning the patient's visual needs with the IOL's properties, setting the right expectations, and assessing the risk profile for the occurrence of photic phenomena, potentially leading to improved decision-making.

Changes in straylight after cataract surgery

PURPOSE

To investigate straylight in the immediate postoperative period after cataract surgery.

SETTING

Amphia Hospital, Breda, the Netherlands.

DESIGN

Prospective, comparative, single-arm, single-center, single-surgeon study.

METHODS

Patients underwent cataract surgery on both eyes. 1 eye was randomly selected for implantation with a Clareon CNA0T0 intraocular lens (IOL); the fellow eye received a Vivinex XY1 IOL. Straylight was measured with the C-Quant straylight meter.

RESULTS

25 patients were included. Preoperatively, 1 day, 1 week, 1 month, and 3 months postoperatively, eyes with a CNA0T0 IOL had straylight levels (mean ± SD) of 1.48 ± 0.23, 1.26 ± 0.20, 1.06 ± 0.19, 1.11 ± 0.25, and 1.09 ± 0.20 log(s), respectively. For eyes with an XY1 IOL, these values were 1.48 ± 0.21, 1.41 ± 0.41, 1.10 ± 0.20, 1.13 ± 0.20, and 1.16 ± 0.20 log(s), respectively. From 1 week postoperatively, straylight values did not change (1 week vs 3 months: P = .40 and P = .14 and 1 month vs 3 months: P = .74 and P = .50 for CNA0T0 and XY1, respectively). The Pearson correlation coefficient for straylight values between the 2 eyes of individual subjects was 0.80 at 3 months.

CONCLUSIONS

Straylight levels can be considered stable 1 week after cataract surgery. We believe it is safe to use straylight measurements 1 month postoperatively for clinical trials. Straylight is highly correlated between the 2 eyes of an individual postoperatively.

Evaluation of visual quality of spherical and aspherical intraocular lenses by Optical Quality Analysis System

AIM

To evaluate the impact of spherical and aspherical intraocular lenses on the postoperative visual quality of age-related cataract patients using Optical Quality Analysis System (OQAS).

METHODS

Seventy-four eyes with age-related cataracts were randomly divided into spherical and aspherical lens implantation groups. Best-corrected visual acuity (BCVA) was measured preoperatively, one day, one week, two weeks, one month and two months after surgery. A biometric systems analysis using the OQAS objective scattering index (OSI) was performed.

RESULTS

There were no significant differences in visual acuity (P>0.05) before and after spherical and aspheric lens implantation. There was a negative linear correction between the OSI value and BCVA (r=-0.634, P=0.000), and positive corrections between the OSI value and the lens LOCUS III value of nucleus color (NC), nucleus opacity (NO), cortex (C) and posterior lens capsular (P) (r=0.704, P=0.000; r=0.514, P=0.000; r=0.276, P=0.020; r=0.417, P=0.000, respectively). OSI values of spherical vs aspherical lenses were 11.5±3.6 vs 11.8±3.4, 4.1±0.9 vs 3.3±0.8, 3.5±0.9 vs 2.7±0.7, 3.3±0.8 vs 2.6±0.7, 3.2±0.7 vs 2.5±0.8, and 3.2±0.8 vs 2.5±0.8 before and 1d, 1, 2wk, 1 and 2mo after surgery, respectively. All time points varied significantly (P<0.01) between the two groups.

CONCLUSION

Aspherical IOLs does not significantly affect visual acuity compared with spherical IOLs. The OSI value, was significantly lower in the aspherical lens group compared with the spherical lens. This study shows that objective visual quality of aspheric IOLs is better than that of the spherical lens by means of OQAS biological measurement method.

A comparative study on visual and optical performance of Akreos AO and Kontur AB IOLs after phacoemulsification cataract surgery

PURPOSE

Akreos AO and Kontur AB are two commonly used intraocular lenses (IOLs) in Iran. This study was designed to evaluate the visual performance of these lenses.

METHODS

In a comparative interventional study, 35 patients (70 eyes) were recruited, and each IOL was implanted in one eye of the patients, randomly. Best corrected visual acuity (BCVA), contrast sensitivity, aberrometric analysis, and depth of focus were evaluated 1 month and 3 months postoperatively. A visual quality questionnaire was also filled for each eye, and the results were compared.

RESULTS

Mean age of the patients was 60.97 ± 7.00 years. BCVA was not significantly different between the two eyes, before, 1 month, and 3 months postoperatively (p > 0.05 for all). Photopic and mesopic contrast sensitivity was not different between the two lenses instead of photopic 18 cycles per degree, 3 months postoperatively and in mesopic 6 cycles per degree 1 month postoperatively (p = 0.034 and p = 0.002, respectively). Aberrometric factors including HoRMS, Total RMS, and Higher order without Z(4,0) were not significantly different between the two lenses (p > 0.05 for all), but they were slightly lower for Akreos AO. Post-operative distance-corrected visual acuity for intermediate and near vision were not different between the two groups (p > 0.05, respectively).

CONCLUSION

Visual performance of Akreos AO and Kontur AB is similar. However, contrast sensitivity and aberrometric parameters are slightly better for Akreos AO IOL.

Ocular straylight in the normal pseudophakic eye

PURPOSE

To assess normal values for straylight in the pseudophakic eye as a function of age and to develop a model to predict the improvement in straylight after lens extraction based on preoperative straylight levels.

SETTING

Rotterdam Ophthalmic Institute, Rotterdam, the Netherlands.

DESIGN

Review with retrospective cross-study analysis.

METHODS

A literature review was performed to identify relevant papers on straylight and pseudophakia with no patient comorbidities. Sixteen papers met the eligibility criteria and were included in the analysis. The postoperative results were used to define the norm for straylight in pseudophakia. Straylight improvement after lens replacement was assessed by evaluation of preoperative and postoperative values. The age effect was incorporated to determine a model for straylight improvement.

RESULTS

The mean postoperative straylight value derived from 16 studies (1869 eyes) was 1.21 log units ± 0.21 (SD). Age dependence could be assessed from 13 studies (1533 eyes), resulting in the straylight age-norm curve in pseudophakic eyes as follows: Straylight value = 0.0044 × age + 0.89 with ± 0.42 log units of 95% confidence interval. A strong correlation was observed between preoperative straylight and its improvement after lens extraction, yielding the following relationship: Straylight improvement = 1.04 × preoperative straylight value - 0.006 × age - 0.84.

CONCLUSION

A norm for straylight in the pseudophakic eye was developed that is considerably different from the previously published norm for the phakic eye. The new pseudophakic norm can be used clinically to predict the straylight value after lens replacement and as a reference criterion for clinical studies.

FINANCIAL DISCLOSURE

The Netherlands Academy of Arts and Sciences owns a patent on straylight measurement, with Dr. van den Berg as the inventor, and licenses that to Oculus Optikgeräte GmbH for the C-Quant instrument. No author has a financial or proprietary interest in any material or method mentioned.

Comparison of pseudophakic retinal straylight in spherical/aspherical and hydrophobic/hydrophilic intraocular lens

AIM

To study the potential reasons of increased straylight in pseudophakic eyes.

METHODS

Cross-sectional study. Seventy patients diagnosed as bilateral age-related cataract and implanted with Tecnis ZA9003, Sensar AR40e, SA60AT, XLSTABI ZO or Akeros AO intraocular lens (IOL) were enrolled in this research. Straylight was measured by a C-Quant straylight meter three to four weeks postoperatively. Five different modalities of IOL, including spherical/aspherical optics and hydrophobic/hydrophilic material were tested in this study. Normal as well as dilated pupils were used. The main outcome variable for straylight measurement was the logarithmic straylight parameter, log(s).

RESULTS

The straylight parameter increased significantly after pupil dilation (P<0.05). Straylight of aspherical IOL was significantly higher after pupil dilation (P<0.05) compared to spherical IOL. In normal pupil, straylight of hydrophobic IOL was significant higher when compared with hydrophilic IOL (P<0.05).

CONCLUSION

Straylight and visual acuity stand for the different aspects of visual function. Several factors including pupil diameter, optic material, aspherical design of IOL influence intraocular light scattering in pseudophakic eyes. Further investigation was needed to study the impact of optic material and optic surface design on pseudophakic straylight.

Straylight Measurements in Two Different Apodized Diffractive Multifocal Intraocular Lenses

PURPOSE

To evaluate differences in straylight between eyes implanted with a hydrophilic multifocal IOL (Seelens MF; Hanita Lenses, Hanita, Israel) and a hydrophobic multifocal IOL (SN6AD1; Alcon Laboratories, Inc., Fort Worth, TX).

METHODS

In a prospective cohort study, routinely obtained straylight measurements (C-Quant; Oculus Optikgeräte, Wetzlar, Germany) 3 months after standard phacoemulsification for either cataract or refractive lens procedures were compared. Patients were implanted with either the SeeLens MF IOL or the SN6AD1 IOL. Postoperative straylight values, visual acuity, and refractive outcomes were compared.

RESULTS

The SeeLens MF IOL was implanted in 84 eyes and the SN6AD1 IOL in 79 eyes. The difference in straylight was 0.08 (P = .01), with the SeeLens MF IOL having less straylight. Postoperative CDVA was logMAR -0.03 ± 0.06 in the SeeLens MF group, and logMAR -0.02 ± 0.08 in the SN6AD1 group. Mean postoperative refraction was +0.01 ± 0.43 and +0.06 ± 0.35 D, respectively.

CONCLUSIONS

The Seelens MF IOL showed a stray-light of log(s) 0.08 lower than the SN6AD1 IOL. In terms of spherical equivalent and visual acuity the lenses performed equally. More study will aid in understanding the causes and clinical impact of this difference.

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.

High order aberration and straylight evaluation after cataract surgery with implantation of an aspheric, aberration correcting monofocal intraocular lens

AIM

To evaluate the quality of vision in respect to high order aberrations and straylight perception after implantation of an aspheric, aberration correcting, monofocal intraocular lens (IOL).

METHODS

Twenty-one patients (34 eyes) aged 50 to 83y underwent cataract surgery with implantation of an aspheric, aberration correcting IOL (Tecnis ZCB00, Abbott Medical Optics). Three months after surgery they were examined for uncorrected (UDVA) and corrected distance visual acuity (CDVA), contrast sensitivity (CS) under photopic and mesopic conditions with and without glare source, ocular high order aberrations (HOA, Zywave II) and retinal straylight (C-Quant).

RESULTS

Postoperatively, patients achieved a postoperative CDVA of 0.0 logMAR or better in 97.1% of eyes. Mean values of high order abberations were +0.02±0.27 (primary coma components) and -0.04±0.16 (spherical aberration term). Straylight values of the C-Quant were 1.35±0.44 log which is within normal range of age matched phakic patients. The CS measurements under mesopic and photopic conditions in combination with and without glare did not show any statistical significance in the patient group observed (P≥0.28).

CONCLUSION

The implantation of an aspherical aberration correcting monofocal IOL after cataract surgery resulted in very low residual higher order aberration (HOA) and normal straylight.

Comparing the effect of two different intraocular lenses on optical aberrations in bilaterally operated eyes for cataract

OBJECTIVE

To assess high order and spherical aberrations results of hydrophobic acrylic AMO Sensar AR40E and hydrophobic acrylic Alcon AcrySof SA60AT intraocular lenses after implantation in cases with bilateral cataract.

METHODS

Cases diagnosed as bilateral cataract were included in the study and preoperative aberration measurements were recorded by using Nidek OPD SCAN-ARK 1000. Groups were created by implanting AMO Sensar AR40E to one eye of the patients, while Alcon AcrySof SA60AT into the other in a prospective and randomized manner. Aberration measurements were recorded after one and two months of surgery.

RESULTS

Overall, 40 eyes in 20 patients (11 women and 9 men) were included in the study. All patients underwent bilateral phacoemulsification surgery due to cataract. There were 20 eyes in both groups. Mean age was 62.4 (range: 31-82) years. There was no significant difference in aberrations recorded before surgery and one and two months after surgery in both groups. (p<0.05).

CONCLUSION

There was no difference among spherical intraocular lenses used in this study.

The impact on vision of aspheric to spherical monofocal intraocular lenses in cataract surgery: a systematic review with meta-analysis

PURPOSE

To provide a summary of the impact on vision of an aspheric intraocular lens (IOL) compared with a spherical IOL in cataract surgery.

DESIGN

Systematic review with meta-analysis.

PARTICIPANTS

Patients from published randomized controlled trials (RCTs) of cataract surgery with aspheric compared with spherical monofocal IOL implantation.

METHODS

We systematically searched the peer-reviewed literature in MEDLINE, EMBASE, Web of Science, BIOSIS, and the Cochrane Library according to the Cochrane Collaboration method to identify relevant RCTs. The inclusion criteria were RCTs on cataract surgery comparing the use of aspheric versus spherical IOL implantation that assessed visual acuity, contrast sensitivity, or quality of vision. The effects were calculated as mean differences or standardized mean differences (Hedges' g) and pooled using random-effect models.

MAIN OUTCOME MEASURES

Best-corrected visual acuity (BCVA), contrast sensitivity, and subjective perception of the quality of vision.

RESULTS

Forty-three studies provided data and were included, comprising 2076 eyes implanted with aspheric IOLs and 2034 eyes implanted with spherical IOLs. The BCVA showed a significant difference for aspheric IOLs (-0.01 logarithm of the minimum angle of resolution; 95% confidence interval [CI], -0.02 to -0.00). For contrast sensitivity, a significant advantage for aspheric IOLs was found under photopic and mesopic light conditions (photopic: Hedges' g 0.42, 95% CI 0.24-0.61 (3 cycles per degree [cpd]) to 0.53, 95% CI 0.33-0.73 (12 cpd); mesopic: Hedges' g 0.49, 95% CI 0.23-0.75 (1.5 cpd) to 0.76, 95% CI 0.52-1.00 (18 cpd)). Questionnaires targeting the subjective perception of quality of vision yielded less conclusive results.

CONCLUSIONS

Overall, a patient may achieve better contrast sensitivity with an aspheric IOL than with a spherical IOL, especially under dim light. There was no clinically relevant difference in BCVA between aspheric and spherical IOL implantation. The findings on the subjective perception of visual quality were heterogeneous with no clear result favoring either option.

History of ocular straylight measurement: A review

The earliest studies on 'disability glare' date from the early 20(th) century. The condition was defined as the negative effect on visual function of a bright light located at some distance in the visual field. It was found that for larger angles (>1 degree) the functional effect corresponded precisely to the effect of a light with a luminosity equal to that of the light that is perceived spreading around such a bright source. This perceived spreading of light was called straylight and by international standard disability glare was defined as identical to straylight. The phenomenon was recognized in the ophthalmological community as an important aspect of the quality of vision and attempts were made to design instruments to measure it. This must not be confused with instruments that assess light spreading over small distances (<1 degree), as originating from (higher order) aberrations and defocus. In recent years a new instrument has gained acceptance (C-Quant) for objective and controllable assessment of straylight in the clinical setting. This overview provides a sketch of the historical development of straylight measurement, as well as the results of studies on the origins of straylight (or disability glare) in the normal eye, and on findings on cataract (surgery) and corneal conditions.

Effect of interaction of macroaberrations and scattered light on objective quality of vision in pseudophakic eyes with aspheric monofocal intraocular lenses

PURPOSE

To assess the impact of wavefront ocular aberrations on objective vision quality and depth of focus in pseudophakic patients.

SETTING

University Hospital Bretonneau of Tours, Francois Rabelais Medicine Faculty of Tours, France.

DESIGN

Cohort study.

METHODS

Consecutive eyes having implantation of an aspheric monofocal intraocular lens (IOL) (Acri.Smart) were studied. Aberrometry measurements were performed under mesopic conditions with a 6.0 mm pupil using a Wavescan aberrometer. Objective evaluation of optical vision quality was performed using the Optical Quality Analysis System II. The 3 measurements were the modulation transfer function values (MTF cutoff); objective depth of focus, which was computed as the focus range at which Strehl ratio did not fall below 50% of the maximum; and the objective scatter index.

RESULTS

Fifty-four eyes (30 patients) were enrolled. Six months postoperatively, MTF cutoff values were increased with decreasing total ocular spherical aberration, ocular trefoil, and 2nd-order astigmatism (P<.05). Objective depth of focus was positively correlated with 2nd-order astigmatism (r(2) = 0.171, P<.001) and total spherical aberration (r(2) = 0.091, P=.028). Objective scatter was more beneficial for depth of focus, with a significantly positive correlation with this parameter (r(2) = 0.28, P=.002), than compromising of optical quality (no significant correlation with MTF measurements in same multiple regression analysis).

CONCLUSION

Three ocular aberrations (2nd-order astigmatism, trefoil, spherical aberration) seemed to interact with objective contrast sensitivity and depth of focus, whereas residual spherical aberration exerted opposite effects on image quality in individual patients.

Lack of Effect of Intraocular Lens Asphericity on Visual Performance with Acrylic Intraocular Lenses

Purpose.

To determine whether implantation of acrylic intraocular lens (IOL) with aspheric design (Tecnis Z9003, AMO) results in improved visual acuity or contrast sensitivity compared with conventional spherical acrylic IOL (AR40e, AMO).

Methods.

In an intraindividual randomized prospective study of 60 patients with bilateral cataract, the Tecnis Z9003 IOL was compared with the AR40e IOL. Ocular aberrations for a 4.0-mm pupil and 6.0-mm pupil were measured with a Hartmann-Shack aberrometer. Quality of vision was measured using visual acuity and contrast sensitivity under mesopic and photopic conditions.

Results.

Eyes with the Tecnis Z9003 IOL had significantly less spherical aberration and greater Strehl ratio after surgery, showing a better optical quality in comparison with the standard spherical IOL. However, visual acuity and both mesopic and photopic contrast sensitivity were not significantly different between the groups.

Conclusions.

The significantly better optical quality achieved with the aspheric acrylic IOL design did not result in improved visual acuity or contrast sensitivity in comparison with a conventional spherical acrylic IOL.

Effect of residual ocular spherical aberration on objective and subjective quality of vision in pseudophakic eyes

PURPOSE

To determine the level of residual spherical aberration that gives the best objective and subjective quality of image after cataract surgery with intraocular lens (IOL) implantation.

SETTING

Department of Ophthalmology, CHU Bretonneau, Tours, France.

DESIGN

Cohort study.

METHODS

Six months after microincision (1.8 mm) cataract surgery with aspheric IOL implantation, total aberrations were computed using a Wavescan aberrometer. The modulation transfer function (MTF), Strehl ratio, and objective index of scattering were measured using the Objective Quality Analysis System. Objective depth of focus was computed as the focus range at which the Strehl ratio did not fall below 50% of maximum. Subjective depth of focus was calculated as the difference between the vergence of the punctum remotum and that of the punctum proximum.

RESULTS

Thirty patients (54 eyes) were evaluated. The MTF cutoff values were higher with decreasing total ocular spherical aberration (r = 0.56; P < .05). Objective and subjective depth of focus were positively correlated with total spherical aberration (r = 0.26 and r = 0.46, respectively; P < .05).

CONCLUSIONS

A final spherical aberration of zero obtained by compensation of IOL asphericity gave the greatest improvement in objective quality of vision and better MTF contrast. However, a final target ocular spherical aberration between 0.07 μm and 0.10 μm should be considered to be the best compromise between subjective depth of focus and objective contrast sensitivity.

FINANCIAL DISCLOSURE

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

Spherical aberration and other higher-order aberrations in the human eye: from summary wave-front analysis data to optical variables relevant to visual perception

Wave-front analysis data from the human eye are commonly presented using the aberration coefficient c(4)(0) (primary spherical aberration) together with an overall measure of all higher-order aberrations. If groups of subjects are compared, however, the relevance of an observed difference cannot easily be assessed from these summary aberration measures. A method was developed for estimating various optical variables relevant to visual perception from summary wave-front analysis data. These variables were the myopic shift (the difference in the optimal focus between high and low spatial frequencies, a threat to the simultaneous in-focus viewing of fine and coarse patterns), the depth-of-focus (at 8 cpd), and the modulation transfer at high (16 cpd; reading small print) and low (4 cpd; edge detection) spatial frequencies. The depth-of-focus was defined in two ways: using a relative measure (the full width at half-height of the through-focus curve) and an absolute measure (the range where the through-focus curve exceeds a predefined modulation transfer value). The method was shown to be accurate by using previously published contrast sensitivity data and wave-front analysis data. The applicability of the method was illustrated by applying the method to wave-front analysis measurements performed in pseudophakic patients with aspheric and spherical intraocular lenses.