Impact of Decentration and Tilt on Spherical, Aberration Correcting, and Specific Aspherical Intraocular Lenses: An Optical Bench Analysis

Abstract

Introduction The human eye is not optically symmetrical, and very few IOLs are perfectly centered in the eye. That is why contrast sensitivity can degrade in some conditions, especially in low light. In an optical bench analysis, we compare spherical (A), aberration correcting (B) and specific aspherical lenses (C) in terms of impact of decentration and tilt on the modulation transfer function as well as the simulated overall quality with USAF test targets. Material and Methods: The OptiSpheric IOL PRO2 was used to measure the optical performance of IOLs (A,B,C). In order to assess the optical quality of the IOLs, the optical quality parameters for the aperture size of 3.0 mm and 4.5 mm at the IOL plane were assessed. Through Frequency Modulation Transfer Function (MTF) and Strehl Ratio (SR) values, as well as the “US Airforce 1951 resolution test chart images” as qualitative simulation, were analyzed. All measurements (ISO) were repeated and done for centered, decentered (1mm) and tilted (5°) IOLs. Results: Centered: The MTF (mean) at 50 lp/mm (IOL A, B, C) with 3.0 mm aperture was 0.794/0.716/0.797 (ISO 1 cornea) and 0.673/0.752/0.723 (ISO 2 cornea) and with 4.5 mm aperture 0.728/0.365/0.751 (ISO 1) and 0.276/0.767/0.505 (ISO 2). The Strehl ratio (mean) with 3.0 mm aperture was 0.763/0.829/0.898 and with 4.5 mm aperture 0.228/0.386/0.432. Decentered by 1mm: The MTF (mean) at 50 lp/mm with 3.0 mm aperture was 0.779/0.459/0.726 (ISO 1) and 0.695/0.381/0.662 (ISO 2). The MTF (mean) at 50 lp/mm with 4.5 mm aperture was 0.732/0.348/0.653 (ISO 1) and 0.355/0.069/0.346 (ISO 2). The Strehl ratio (mean) with 3.0 mm aperture was 0.829/0.543/0.397 and with 4.5 mm aperture 0.259/0.145/0.192. Tilted by 5 degree: The MTF (mean) at 50 lp/mm with 3.0 mm aperture was 0.731/0.705/0.751 (ISO 1) and 0.623/0.727/0.732 (ISO 2). The MTF (mean) at 50 lp/mm with 4.5 mm aperture was 0.579/0.406/0.701 (ISO 1) and 0.277/0.512/0.429 (ISO 2). The Strehl ratio (mean) with 3.0 mm aperture 0.539/0.478/0.514 and with 4.5 mm aperture 0.262/0.136/0.201. Conclusion: Aberration correcting IOLs perform best when perfectly centered. The optical performance of aberration correcting IOLs can be markedly downgraded by misalignment. The examined ZO optic performed well in decentration and tilt. The ZO concept seems to be a good alternative to aspheric lenses, as it achieves to combine benefits of spherical and aspheric intraocular lenses. There is no perfect IOL, but fitting and choosing the right one for the individual case seems to be crucial to take advantage of benefits and minimize disadvantages. This is why knowledge of optical properties is also mandatory for the surgeon.

Automated and Subjective Refraction With Monofocal, Multifocal and Extended Depth of Focus Intraocular Lenses – A Review

“…However, we have information about their profile, confirming slight changes in the central anterior surface, and we know that even minor decentration affects the optical result when measured at the optical bench. 49,50 However, the difference between the automated refraction outcome and the subjective refraction outcome is expected to be low and similar to that of monofocal IOLs.…”

Die Rostocker Methode zur qualitativen und quantitativen Bewertung von Intraokularlinsen

“…In general, the light sheet method also makes it possible to infer chromatic properties [11], but since fluorescein cannot be excited with red light, another dye or a scattering medium would have to be used in the case of red light. In addition, measurements on optical benches can provide accurate information about decentering and tilt of the IOL and its intensity distribution as a function of pupil diameter, as shown by Borkenstein and colleagues [24]. Both the light sheet method and the optical bench measurement methods present the scientific standard for the determination of cross-sectional images in this research area, however, there may always be a reduction in the image quality of the cross-sectional images; in the case of the fluorescein bath this is due to the dependence of the light sheet thickness, and in the case of the optical bench this is due to the width of the extracted volume from the 3-D PSF.…”

“…Generell erlaubt auch die Lichtblattmethode, Aussagen über chromatische Eigenschaften abzuleiten [11], da aber Fluorescein nicht mit rotem Licht angeregt werden kann, müsste für die Verwendung von rotem Licht ein anderer Farbstoff oder ein streuendes Medium verwendet werden. Darüber hinaus können Messungen an optischen Bänken genaue Aussagen über Dezentrierung und Verkippung der IOL und deren Intensitätsverteilung in Abhängigkeit des Pupillendurchmessers treffen, wie von Borkenstein und Kollegen gezeigt [24]. Sowohl die Lichtblattmethode als auch die Messmethoden an optischen Bänken präsentieren den wissenschaftlichen Standard für die Bestimmung von Querschnittsbildern in diesem Forschungsgebiet, wobei es jedoch immer, im Falle des Fluoresceinbades durch die Abhängigkeit der Lichtblattdicke und im Falle der optischen Bank durch die Breite des extrahierten Volumens aus der 3-D-PSF, zu einer Verringerung der Bildqualität der Querschnittsbilder kommen kann.…”

4-Point scleral fixation technique using Gore-tex® sutures for cut-out plated haptic intraocular lenses

“…Aspheric aberration neutral IOLs are the preferred choice for fixation in this case due to their lower incidence of spherical aberrations induced postoperatively 10 and their tolerance to some degree of tilt and decentration. 11 , 12 …”