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BMJ Open Ophthalmol
BMJ Open Ophthalmol
bmjophth
bmjophth
BMJ Open Ophthalmology
2397-3269
BMJ Publishing Group BMA House, Tavistock Square, London, WC1H 9JR

39117362
10.1136/bmjophth-2024-001661
bmjophth-2024-001661
Original Research
1506
IOL decentration sensitivity according to spatial frequencies
http://orcid.org/0000-0001-5594-7232
Pieh Stefan 1stefan.pieh@meduniwien.ac.at

Artmayr Cornelia 1cornelia.artmayr@gmail.com

http://orcid.org/0000-0002-5669-3606
Schartmüller Daniel 1daniel.schartmueller@meduniwien.ac.at

Kriechbaum Katharina 1katharina.kriechbaum@meduniwien.ac.at

1 Department of Ophthalmology & Optometry, Medical University of Vienna, Vienna, Austria
Professor; stefan.pieh@meduniwien.ac.at
None declared.

2024
7 8 2024
9 1 e00166130 1 2024
08 6 2024
Copyright © Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.
2024
https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

Abstract

Background/aims

Investigation of the decentration sensitivity of monofocal intraocular implants with a focus on different aberration corrections depending on different spatial frequencies.

Methods

Using an optical bench, the decentration sensitivities of an intraocular lens (IOL) with a high spherical aberration correction of −0.27 µm (ZCB00 Johnson & Johnson), an IOL with an aberration correction of −0.20 µm (Primus HD OphthalmoPro) and an IOL with an aberration neutral design (CT Asphina 409MP Carl Zeiss Meditec) were evaluated for Strehl ratio values and for 25, 50 and 100 lp/mm. Two different corneas with +0.13 µm and +0.28 µm were used. The lenses were tested in the best centration and up to a decentration of 0.5 mm.

Results

Decentration sensitivity affects high spatial frequencies more than lower ones. The possible decentration sensitivity is determined by the amount of spherical aberration of the cornea. The effective decentration sensitivity is determined by the extent to which these spherical aberrations are compensated. If these are not compensated, there is hardly any decentration sensitivity.

Conclusion

High spatial frequencies are more affected by decentration sensitivity. The decentration sensitivity of an IOL is determined by the extent to which the spherical aberration of the cornea is corrected.

Optics and Refraction
Cataract
Cornea
Experimental & laboratory
Medical Scientific Fund of the Mayor of the City of Vienna 15209
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pmcWHAT IS ALREADY KNOWN ON THIS TOPIC

The imaging quality of intraocular lens (IOL) depends on the centration accuracy. The aim was to examine whether the decentration sensitivity of IOLs has a different effect for different spatial frequencies.

WHAT THIS STUDY ADDS

The decentration sensitivity has a stronger effect on the high than on the low spatial frequencies.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

This work shows that the choice of an IOL, taking into account the expected decentration and the existing decentration sensitivity for the respective case, has a particular effect on the detection of fine contrast differences and high spatial frequencies.

Introduction

A prolate lens geometry was introduced for the intraocular market in the early 2000s.1 This lens concept aimed to direct peripheral light rays which are too strongly refracted due to the mostly positive spherical aberration of the cornea into the focal point and thus produce a better imaging quality than achieved with spherical lenses.2 The disadvantage of the concept is a possible higher decentration sensitivity. This refers to the extent of the decrease in image quality in correlation with decentration, which can be expected to be between 0.2 and 0.4 mm.37The decrease is mainly caused by an increase in coma and higher order aberrations with decentration.8 9 The decentration sensitivity depends on the spherical aberration of the cornea and the spherical aberration correction of the lens.1012

This study evaluated the decentration sensitivity for an intraocular lens (IOL) with a high aberration correction, a middle spherical aberration and one with an aberration neutral design. The new aspect of this study is an examination of the comparative effect of decentration sensitivity on low, medium and high spatial frequencies.

Materials and methods

Description of the lenses tested

The ZCB00 (Johnson & Johnson, USA) was designed for a cornea that exhibits spherical aberrations of +0.27 µm.1 This concept is intended to excessively reduce the spherical aberration. The lens’ overall diameter is 13.0 mm and its optic diameter is 6.0 mm. It is made of a hydrophobic acrylate and has a circular sharp edge.

The Primus HD (OphthalmoPro, Germany) corresponds to a modern aspheric lens design, with a moderate compensation of the spherical aberration of the human cornea exhibiting a spherical aberration correction of −0.20 µm. This one-piece lens is made of hydrophobic acrylic material with a C-loop haptic. Its optic diameter is 6.0 mm and its overall diameter is 13.0 mm. Furthermore, it has a continuous circular square edge to impede posterior capsule opacification after surgery.

The CT Asphina 409MP (Carl Zeiss Meditec, Germany) follows an aberration-free concept. The objective of this lens design is not to add or compensate any spherical aberration for a determined incidence of light.13 The lens is made of a hydrophilic acrylate with hydrophobic surface properties and has a plate haptic design with a 6.0 mm optical zone and an overall diameter of 11.0 mm.

Experimental setup

The experimental setup with an optical bench (OptiSpheric IOL PRO 2, Trioptics, Germany) consisted of a laser source (546 nm), a collimation system, two artificial corneas, a wet cell with a saline solution containing an artificial iris and a lens holder. Two different types of artificial corneas corresponding to a human corneal refractive power of 43 dioptres were used. One cornea exhibited a low amount of spherical aberration of +0.13 µm, and the other one a high spherical aberration of +0.28 µm (in both cases related to a diameter of 6.0 mm).1417 All measurements were done with an artificial pupil of 4.5 mm. Measurements were taken with the IOL fixed to the lens holder and immersed in the wet cell. In addition, the lens holder with the lens could be moved by means of a micrometre screw perpendicular to the beam path to generate a lens decentration. The IOL tested focused the projected target at its focal plane, which was captured by an objective microscope lens and a high-resolution charge-coupled device (CCD) camera. The lenses were evaluated in the best centration and in an additional five decentred positions up to 0.5 mm in 100 µm steps.

Optical quality variables

The cross-sectional intensity profile from the line spread function was converted to modulation transfer function (MTF) values using the Fourier transform method.18 In this study, the MTF values at the respective measurement points were calculated for Strehl ratio values and spatial frequencies of 25, 50 and 100 lp/mm. These spatial frequencies correspond in this setup to a visual acuity of Snellen 0.25, 0.5 and 1.0 (logMAR 0.6, 0.3 and 0.0), respectively.

Patient and public involvement

No patients or the public were involved in this work.

Results

Figure 1 shows the results of the Strehl ratio curves with ongoing decentration for the ZCB00, the Primus HD and the CT Asphina 409MP for the two corneas used that have a spherical aberration of +0.13 µm and +0.28 µm.

Figure 1 Strehl ratio in relation to decentration using corneas that exhibit a spherical aberration of +0.13 µm and +0.28 µm. The intraocular lenses examined are the ZCB00, Primus HD and CT Asphina 409MP. All examinations were performed with green light and a pupil opening of 4.5 mm. The grey area from 0.2 mm to 0.4 mm indicates the expandable range of decentration.

Looking at the results with the cornea that has a spherical aberration of +0.13 µm, the Primus HD shows the best result because this IOL only slightly overcompensates the spherical aberration of the cornea. The ZCB00, which achieves the second-best result in the best centration in this overview, overcompensates the spherical aberration of the cornea more than the Primus HD with the spherical aberration correction of −0.27 µm. The CT Asphina 409MP shows the worst result in the best correctioncentration but is equal or superior to the other two lenses with decentration over 0.4 mm.

Regarding the results with the cornea that has a spherical aberration of +0.28 µm, the ZCB00 performs best in the best centration because it only slightly undercorrects the spherical aberration of the cornea.

In the best centration, the Primus HD shows a slight advantage over the CT Asphina 409MP over the entire decentring range because it corrects the spherical aberration of the cornea selected better than the CT Asphina 409MP. However, from a decentration of 0.34 mm, the ZCB00 is inferior to the other two lenses.

Figure 2 displays the results using the +0.13 µm cornea split by spatial frequncies. The results for the ZCB00, for 25, 50 and 100 lp/mm, are shown in green. The ZCB00, which is designed for a +0.27 µm cornea, overcorrects the spherical aberration of the +0.13 µm cornea. The modulation for low spatial frequencies is higher than that for high spatial frequencies. Furthermore, the imaging quality can be seen to deteriorate with ongoing decentration. Considering the results, the Primus HD with its spherical aberration correction of −0.20 µm matches the cornea with a spherical aberration of +0.13 µm better than the ZCB00 with a spherical aberration correction for a cornea with a spherical aberration of +0.27 µm. This leads to better results in relation to all spatial frequencies in the range of decentration examined. The aberration neutral CT Asphina 409MP, which should not influence the spherical aberration of the cornea, performs robustly with respect to decentration. Although the results for this IOL are worse than those of the other two lenses at best centration, it increasingly wins with ongoing decentration due to its robust and de facto horizontal progression for all spatial frequencies.

Figure 2 Modulation/contrast in relation to decentration using the +0.13 µm cornea. The lenses examined are the ZCB00, Primus HD and CT Asphina 409MP. All examinations were performed with green light and a pupil aperture of 4.5 mm. The expected decentration range of 0.2 mm to 0.4 mm is highlighted in grey.

Comparing the course of the spatial frequency for 25 lp/mm with the course of the spatial frequency for 100 lp/mm of the Primus HD, it becomes obvious that the higher spatial frequencies react more sensitively to decentration.

The increase in decentration sensitivity of the ZCB00 is noticeable when using the cornea with a spherical aberration of +0.28 µm, as shown in figure 3. This IOL shows the best imaging quality in the best centration compared with the other lenses as it almost completely compensates for the spherical aberration of the cornea used. When using this cornea, it is also evident that higher spatial frequencies react more sensitively to decentration than the lower ones with the ZCB00. Considering the significantly lower decentration sensitivity of the comparison lenses and the lower decentration sensitivity of the ZCB00 when using the cornea with a spherical aberration of +0.13 µm (figure 2), the decentration sensitivity is shown to correlate positively both to the amount of spherical aberration of the cornea and the extent to which the spherical aberration of the cornea is corrected as long as the IOL actually has an aberration correction. As the CT Asphina 409MP has no correction of spherical aberration, therefore, there is hardly any detectable sensitivity to decentration (figures13). In addition, decentration sensitivity decreases as decentration progresses. Furthermore, high spatial frequencies are more affected by decentration than low spatial frequencies. This is the case up to a decentration of 0.3 mm (see green line and green dashed lines for the ZCB00 in figure 3). With further decentration, this effect fades because the decentration sensitivity decreases. In figurefigure 3 3the Primus HD, with its under correction of the cornea used here, has a lower decentration sensitivity than the ZCB00. The same applies to the CT Asphina 409MP, which images slightly worse than the Primus HD at low and medium spatial frequencies due to its aberration neutral design. At high spatial frequencies, the Primus HD is better than the CT Asphina 409MP only at the beginning of the curve. This is because the differences are less apparent at low resolutions.

Figure 3 Modulation/contrast in relation to decentration using the +0.28 µm cornea. The lenses examined are the ZCB00, Primus HD and CT Asphina 409MP. All examinations were performed with green light and a pupil aperture of 4.5 mm. The expected decentration range of 0.2 mm to 0.4 mm is highlighted in grey.

Discussion

The perception of our environment presents different challenges to the resolution of our vision. In addition, particularly demanding perceptions are presented such as fine black and white contrasts.19 In this study, we especially focused on high spatial frequencies because they are the most likely to reveal differences in imaging quality in the different constellations of the corneas used and the IOL designs investigated. Even if it can be assumed that high spatial frequencies should be more affected by decentration, the extent of such an effect has to be assessed on combinations of a number of parameters in order to draw conclusions for the lens selection in cataract surgery.

Figure 1 shows the two extremes that are considered to be as similar as possible to the condition range of a pseudophakic eye, namely the cornea with a low spherical aberration of +0.13 µm and a lens that has a low spherical aberration correction, here the aberration neutral CT Asphina 409MP. This constellation leads to a very low to barely detectable decentration sensitivity. The other extreme is the cornea with a high spherical aberration of +0.28 µm and an IOL with a high spherical aberration correction, in this case, the ZCB00 with a spherical aberration correction of −0.27 µm. This combination leads to a high decentration sensitivity (figure 1).

All combinations of the corneas and the three implants examined show that low spatial frequencies are generally transmitted better than high spatial frequencies (exemplarily visible in the curves for 25 lp/mm, 50 lp/mm and 100 lp/mm for the Primus HD in figure 2). This is basically due to the diffraction limits of the optics and the imaging errors even in the best centration.

In our setup, the level of image quality in the best centration is a result of the congruence between the spherical aberration of the cornea and the spherical aberration correction of the lens.

The sensitivity of decentration depends on various factors, starting with the level of spherical aberration of the cornea. This is predetermined and determines the range of useful aberration correction by the IOL. The extent of spherical aberration of the cornea correlates with the decentration sensitivity of an aberration correcting IOL. figures2 3 show an example of this, namely the flatter progression of the 100 lp/mm curve for the ZCB00 for a cornea with a spherical aberration of +0.13 μm compared to a cornea with a spherical aberration of +0.28 μm. µm. If, on the other hand, aberration neutral and not aberration correcting optics are used, almost no decentration sensitivity occurs, regardless of the level of spherical aberration of the cornea. This can be seen in figurefigures2 3 2 with the cornea that exhibits a spherical aberration of +0,13 or +0.28 µm from the almost horizontal progression of the curves for 25 lp/mm, 50 lp/mm and 100 lp/mm for the CT Asphina 409MP.

In addition, the degree of aberration correction of the IOL correlates with the decentration sensitivity. This can be seen in figure 3, for example, in the steeper progression of the curves for 50 lp/mm for the ZCB00 compared with the Primus HD in combination with the cornea that exhibits spherical aberration of +0.28 µm. If the IOL does not correct spherical aberrations of the cornea, as in the case of an aberration neutral IOL, the decentration sensitivity is hardly detectable (see again horizontal progression of curves for 25 lp/mm, 50 lp/mm and 100 lp/mm of the CT Asphina 409MP in figures2 3).

The price for the high decentration stability of aberration neutral optics, however, is the relatively poorer imaging quality in good centration (see, eg, the curves for 50 lp/mm of the ZCB00 and the CT Asphina 409MP in figure 3).

Typical for the progression of a decentration sensitivity curve is the gradual self-limitation. The poorer the image quality, the less it can deteriorate. This can be seen, for example, in the 100 lp/mm curve of the ZCB00 in figure 3. Therefore, image quality at best centration determines the extent of the deterioration in image quality dependent on decentration sensitivity.

For completeness, it should be mentioned that decentration sensitivity is pupil dependent and its role is of lesser importance with small pupil apertures.10 20 Also, the refractive power of the cornea as well as the refractive power of the IOL correlate positively with the decentration sensitivity of the IOL.10

IOLs with a higher aberration correction are more sensitive to decentration (figure 1), while, conversely, lenses with a lower aberration correction will image better above a certain decentration. A certain decentration can be assumed for IOLs in the human eye. Therefore, full aberration correction can only make sense assuming a perfect centration. Consequently, in the case of decentration, undercorrection of the spherical aberration of the cornea provides better results than full correction.

As in reality, a decentration of 0.2–0.4 mm can be assumed37 so an under correction of the spherical aberration of the cornea is a prerequisite for good imaging quality in the expected decentration range. This can be seen in figure 3, for example, in the curve for 100 lp/mm for the ZCB00 compared with the Primus HD. Here, the Primus HD, which has a lower spherical aberration correction, performs better than the ZCB00 from a decentration of 0.25 mm. This is all the more true as in reality not only a decentration of the IOL but also a tilt of the IOL of 1°–3° can be assumed.5 6 Thus, the tilt leads to a further deviation from the best IOL position.10 However, there are also rare combinations of decentration and tilt that also allow good imaging qualities.10 In the future, predictability of the IOL position could be improved by using modern OCT (Optical Coherence Tomography) with determination of the preoperative crystalline lens position, as this correlates with the postoperative IOL position.21 22 Additionally, with the knowledge of the respective spherical aberration of the cornea, guidance for lens selection for the specific case can be provided.

The possible extent of decentration sensitivity is determined by the amount of spherical aberration of the cornea. The effective decentration sensitivity is defined by the extent to which the spherical aberration of the cornea is matched by the IOL (figure 1). If the spherical aberration is not compensated, for example, with an aberration neutral lens, there is hardly any decentration sensitivity. If there is a corresponding decentration sensitivity, high spatial frequencies are more affected by the decentration of an IOL than low frequencies (figures2 3). Thus, knowledge of the spherical aberration of the cornea of the eye to be operated on should be a standard in cataract surgery.2326 Likewise, the IOL selected should undercorrect the spherical aberration of the cornea to ensure the result in the expected decentration range.

Data availability statement

No data are available.

Funding: Medical Scientific Fund of the Mayor of the City of Vienna (grant number: 15209).

Patient consent for publication: Not applicable.

Provenance and peer review: Not commissioned; externally peer reviewed.
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References

1 Holladay JT Piers PA Koranyi G et al A new intraocular lens design to reduce spherical aberration of pseudophakic eyes J Refract Surg 2002 18 683 91 10.3928/1081-597X-20021101-04 12458861
2 Yu A-Y Wang Q-M Sun J et al Spherical aberration after implantation of an aspheric versus a spherical Intraocular lens in high myopia Clin Exp Ophthalmol 2009 37 558 65 10.1111/j.1442-9071.2009.02096.x 19702704
3 Langenbucher A Szentmáry N Cayless A et al Prediction of IOL decentration, tilt and axial position using anterior segment OCT data Graefes Arch Clin Exp Ophthalmol 2024 262 835 46 10.1007/s00417-023-06208-9 37658183
4 Wang X Dong J Wang X et al IOL tilt and decentration estimation from 3 dimensional reconstruction of OCT image PLoS ONE 2013 8 e59109 10.1371/journal.pone.0059109 23554982
5 Baumeister M Neidhardt B Strobel J et al Tilt and decentration of three-piece foldable high-refractive silicone and hydrophobic acrylic intraocular lenses with 6-mm OPTICS in an intraindividual comparison Am J Ophthalmol 2005 140 1051 8 10.1016/j.ajo.2005.07.026 16376650
6 Hayashi K Hayashi H Comparison of the stability of 1-piece and 3-piece acrylic intraocular lenses in the lens capsule J Cataract Refract Surg 2005 31 337 42 10.1016/j.jcrs.2004.06.042 15767155
7 Crnej A Hirnschall N Nishi Y et al Impact of intraocular lens haptic design and orientation on decentration and tilt J Cataract Refract Surg 2011 37 1768 74 10.1016/j.jcrs.2011.04.028 21840681
8 Pérez-Merino P Marcos S Effect of intraocular lens decentration on image quality tested in a custom model eye J Cataract Refract Surg 2018 44 889 96 10.1016/j.jcrs.2018.02.025 30055694
9 Xu J Zheng T Lu Y Effect of decentration on the optical quality of monofocal, extended depth of focus, and bifocal intraocular lenses J Refract Surg 2019 35 484 92 10.3928/1081597X-20190708-02 31393986
10 Pieh S Fiala W Malz A et al In vitro strehl ratios with spherical, aberration-free, average, and customized spherical aberration-correcting intraocular lenses Invest Ophthalmol Vis Sci 2009 50 1264 70 10.1167/iovs.08-2187 18978351
11 Tandogan T Son HS Choi CY et al Laboratory evaluation of the influence of decentration and pupil size on the optical performance of a monofocal, bifocal, and trifocal intraocular lens J Refract Surg 2017 33 808 12 10.3928/1081597X-20171004-02 29227508
12 Eppig T Scholz K Löffler A et al Effect of decentration and tilt on the image quality of aspheric intraocular lens designs in a model eye J Cataract Refract Surg 2009 35 1091 100 10.1016/j.jcrs.2009.01.034 19465297
13 Langenbucher A Schröder S Cayless A et al Aberration-free intraocular lenses - what does this really mean Z Med Phys 2017 27 255 9 10.1016/j.zemedi.2017.03.003 28476316
14 Sicam VADP Dubbelman M van der Heijde RGL Spherical aberration of the anterior and posterior surfaces of the human cornea J Opt Soc Am A Opt Image Sci Vis 2006 23 544 9 10.1364/josaa.23.000544 16539049
15 Seiler T Reckmann W Maloney RK Effective spherical aberration of the cornea as a quantitative descriptor in corneal topography J Cataract Refract Surg 1993 19 Suppl 155 65 10.1016/s0886-3350(13)80400-2 8450438
16 Wang L Koch DD Ocular higher-order aberrations in individuals screened for refractive surgery J Cataract Refract Surg 2003 29 1896 903 10.1016/s0886-3350(03)00643-6 14604708
17 Budak K Khater TT Friedman NJ et al Evaluation of relationships among refractive and topographic parameters J Cataract Refract Surg 1999 25 814 20 10.1016/s0886-3350(99)00036-x 10374163
18 Vega F Millán MS Garzón N et al Visual acuity of Pseudophakic patients predicted from in-vitro measurements of Intraocular lenses with different design Biomed Opt Express 2018 9 4893 906 10.1364/BOE.9.004893 30319910
19 Amesbury EC Schallhorn SC Contrast sensitivity and limits of vision Int Ophthalmol Clin 2003 43 31 42 10.1097/00004397-200343020-00006 12711901
20 McKelvie J McArdle B McGhee C The influence of tilt, decentration, and pupil size on the higher-order aberration profile of aspheric intraocular lenses Ophthalmology 2011 118 1724 31 10.1016/j.ophtha.2011.02.025 21665282
21 Hirnschall N Buehren T Bajramovic F et al Prediction of postoperative intraocular lens tilt using swept-source optical coherence tomography J Cataract Refract Surg 2017 43 732 6 10.1016/j.jcrs.2017.01.026 28732605
22 Gu X Chen X Yang G et al Determinants of Intraocular lens tilt and decentration after cataract surgery Ann Transl Med 2020 8 921 10.21037/atm-20-1008 32953721
23 Goto S Maeda N Corneal topography for intraocular lens selection in refractive cataract surgery Ophthalmology 2021 128 e142 52 10.1016/j.ophtha.2020.11.016 33221325
24 Du W Lou W Wu Q Personalized aspheric Intraocular lens implantation based on corneal spherical aberration: a review Int J Ophthalmol 2019 12 1788 92 10.18240/ijo.2019.11.19 31741870
25 Schrecker J Langenbucher A Seitz B et al First results with a new Intraocular lens design for the individual correction of spherical aberration J Cataract Refract Surg 2018 44 1211 9 10.1016/j.jcrs.2018.06.055 30120004
26 Borkenstein AF Borkenstein E-M Luedtke H et al Impact of decentration and tilt on spherical, aberration correcting, and specific aspherical intraocular lenses: an optical bench analysis Ophthalmic Res 2022 65 425 36 10.1159/000522510 35144263
