Dr. Mengchan Sun, PhD - Johnson and Johnson Vision - Optical Scientist

Dr. Mengchan Sun

PhD

Johnson and Johnson Vision

Optical Scientist

Groningen, Groningen | Netherlands

Main Specialties: Ophthalmology


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Dr. Mengchan Sun, PhD - Johnson and Johnson Vision - Optical Scientist

Dr. Mengchan Sun

PhD

Introduction

Mengchan Sun is currently an optical scientist in Johnson & Johnson Vision since 2017, in Groningen, the Netherlands. She was an Early Stage researcher to the Instituto de Optica, CSIC since 2012, in Madrid, Spain. She also is the fellow of OpAL which is an Initial Training Network (ITN) funded by the European Commission's Seventh Framework Programme (FP7) under the Marie Curie Actions. Prior to this, she was a master student in the Department of Information Communication Techniques, KTH - Kungliga Tekniska högskolan (Royal Institute of Technology) in Stockholm, Sweden. Her previous professional experience includes Optical Engineer to develop a low-cost multi-functional fundus camera in MECAL Company in 2010, in Eindhoven, the Netherlands. Ms. Mengchan Sun also worked as part of the project the Energy research Centre of the Netherlands in 2009.

Primary Affiliation: Johnson and Johnson Vision - Groningen, Groningen , Netherlands

Specialties:


View Dr. Mengchan Sun’s Resume / CV

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Number of Publications

14

Publications

Number of Profile Views

111

Profile Views

Number of Article Reads

3

Reads

Number of Citations

13

Citations

Education

Apr 2017
UVa
PhD
Sep 2012
KTH
MSc
Aug 2008
HZ
BSc

Experience

Mar 2012
Marie Curie Fellowship
Fellow

Publications

14Publications

3Reads

13PubMed Central Citations

Impact of residual astigmatism on optical and visual performance for toric intraocular lenses

ESCRS

Purpose: The purpose of this study is to evaluate the effect of residual astigmatism in toric intraocular lenses (IOL) on optical and visual performance using realistic eye models Methods: An average eye model based on the Liou-Brennan eye model and 46 realistic eye models that contain higher order corneal aberrations were used in the calculations. Simulations were performed in two toric IOLs with two different Abbe numbers and levels of corneal spherical aberration (SA) correction (model ZCT that fully compensates corneal SA, and model SN6AT that provides a partial correction) and three different toric powers (1.50, 2.25 and 3.00D). Residual astigmatism was induced by rotating the toric IOL with respect to the astigmatism axes of the cornea, from 0 to 20 degrees. The modulation transfer function (MTF) and the simulated visual acuity (sVA), calculated using the area under the MTF from 0 to 50 cycles per mm, were calculated using ray-tracing for 3 and 5mm pupil in white light. Results: Residual astigmatism increased by 0.04, 0.06 and 0.08D per degree of IOL rotation for toric powers of 1.5, 2.25 and 3.0D respectively. The amount of residual astigmatism induced by toric IOL rotation depended on the power of the toric IOL and the rotation, not on the IOL design or the pupil size. Simulations in the computer eye models predicted a loss of sVA between 0.7 and 1.8 lines per diopter of residual astigmatism depending on the pupil size, corneal HOAs and design.Image quality was also reduced by toric IOL rotation for all IOL models and conditions. For up to 0.8D of residual astigmatism, ZCT IOLs provided significantly higher MTF than the SN6AT IOLs for 3 and 5 mm pupil (p<0.05). The average improvement in MTF for eyes implanted with the ZCT IOLs with respect to the SN6AT IOLs was 18, 17 and 14% for residual astigmatism below 0.5, 1 and 1.5D respectively for 3mm pupil. For 5mm pupil, ZCT provided an improvement of 15 % for astigmatism below 0.5 and 1D and 12% for astigmatism below 1.5D. Conclusions: Simulations in computer eye models were able to predict the VA losses due to residual astigmatism found in clinical data. Residual astigmatism degraded MTF and the impact depended on pupil size, corneal aberrations and IOL design. MTF was significantly higher for the ZCT IOLs than for the SN6AT IOLs for up to 0.8D of residual astigmatism.

View Article
April 2018
7 Reads

The effect of angle kappa in visual performance in diffractive intraocular lenses

ARVO

Purpose: The purpose of this study is to evaluate the effect of the angle kappa on the visual performance provided by diffractive intraocular lenses (IOL) using a realistic eye model. Methods: The through focus modulation transfer function (MTF) was calculated by ray tracing for 0, 5 and 10 degrees of angle kappa using a computer eye model with average ocular dimensions and corneal aberrations (Liou and Brennan 1997). Induced astigmatism was calculated as the relative defocus between best foci MTF positions for the two main meridians. The area under the MTF from 0 to 50 cycles per mm (MTFa) and the simulated VA (sVA) were calculated from the MTF data for the average pupil size of the pseudophakic eye (Alarcon, Canovas et al. 2016). Results: Calculations in the eye model showed that angle kappa was mostly related to IOL tilt rather than IOL decentration. For example, 10 degrees of angle kappa induced 10 degrees of IOL tilt and 0.13 mm of decentration respect to the center of the pupil. An average angle kappa of 5 degrees induced 5 degrees of IOL tilt and 0.07 mm of decentration. Induced astigmatism increased with the angle kappa due to the oblique incidence of the rays on the cornea. The induced astigmatism was 0.1D for 5 degrees and 0.4D for 10 degrees angle kappa. The increase of the astigmatism was correlated with the reduction in MTF at distance (R2=0.98). For the multifocal IOL, relative to 0 degrees, the MTF was reduced by 5 and 30% for 5 and 10 degrees of angle kappa respectively. Simulated VA did not change for 5 degrees angle kappa and was reduced by 0.02 logMAR for 10 degrees. Conclusions: Simulations in computer eye models showed that a large angle kappa may induce low amounts of astigmatism (up to 0.5D for 10 degrees) determining an MTF reduction. Simulated VA was not affected even for large amounts of angle kappa.

View Article
April 2018
5 Reads

Full shape crystalline lens quantification from 3-D OCT images and its application to predict the post-operative IOL position.

Investigative Ophthalmology & Visual Science

Purpose: Full shape crystalline lens quantification is critical to improve state-of-the-art intraocular lens (IOL) selection in cataract surgery. We estimated lens volume (VOL), surface area (SA), diameter (DIA) and equatorial plane position (EPP) in patients before cataract surgery, and we evaluated the EPP as an estimator of post-operative IOL position (ELP). Methods: The anterior segment of 7 eyes (76±8 y.o, range, 66-87 y.o) from 6 patients before cataract surgery and 1 eye (80 y.o) post-operatively (Aspheric monofocal Asphina IOL, Zeiss) were imaged and quantified using a customdeveloped 3-D Optical Coherence Tomography (OCT) system provided with distortion correction algorithms. Whole crystalline lens 3-D models were constructed from the information visible through the pupil (Martinez-Enriquez et al. IOVS 2016), and VOL, SA, DIA, lens thickness (LT) and EPP (distance from the anterior lens apex to the equatorial plane) were estimated pre-operatively. EPP was used as estimator of ELP. The estimation error was compared with state-of-the-art methods, namely: ELP=LT/2; Rosen et al. (2006) constant: ELP=0.41LT; and the intersection approach, where the ELP is estimated as the plane of intersection between anterior and posterior lens best fitting conicoid surfaces. Results: Mean VOL, SA, DIA, LT and EPP across subjects (±SD) was 208±27 mm3, 186±14 mm2, 9.27±0.32 mm, 4.76±0.42 mm & 2.16±0.22 mm, respectively. The ratio EPP/LT was patient-dependent (0.44-0.47) indicating the importance of individual anatomical measurements for ELP proper estimation. The ELP estimation error was 62 μm (equivalent to -0.07 D) using the newly proposed metric EPP, whereas using other metrics was: +202 μm (-0.27 D) using LT/2, -204 μm (+0.29 D) using Rosen constant, and -168 μm (+0.24D) using the intersection approach. Conclusions: 3-D OCT measurements with dedicated algorithms allow full quantification of the crystalline lens in-vivo. The estimated parameters (EPP in particular) provide valuable information for improving the estimation of the postoperative IOL position and thus the IOL selection. Improvements by 0.25 D in IOL power calculations resulting from accurate ELP accumulate to those arising from patient-specific measurements of posterior corneal surface, 3-D biometry and 3-D ray tracing analysis.

View Article
June 2017
3 Reads

Crystalline lens volume, diameter and equator estimates from OCT images: impact on future paradigms of cataract surgery

Investigative Ophthalmology & Visual Science

Purpose: Measurement of crystalline lens geometry in-vivo is critical to optimize performance of state-of-the-art cataract surgery. To date, in-vivo accurate estimation of crystalline lens whole shape parameters is missing. In this study we estimate lens volume (VOL), equatorial diameter (Ø) and equatorial plane position (EPP). The method was validated ex-vivo and demonstrated in-vivo. Methods: 27 ex-vivo human lenses (19-71 y.o) were measured and whole lens 3-D volumes were constructed from custom-developed OCT images provided with distortion correction and analysis tools. In-vivo conditions were simulated for these volumes, assuming that only the information within a given pupil size (PS) was available. A parametric model was used to estimate the whole lens shape from PS-limited data. The accuracy of the estimated shape parameters was evaluated comparing estimates from the whole lens data and PS-limited data ex-vivo. Finally, the proposed models were applied to in-vivo lens measurements in 2 young accommodating (0D-6D in 1.5D steps, PS 5mm) and 2 cataract (PS 4 mm) eyes. Results: Crystalline lens VOL was estimated within 96 % accuracy (mean errors across lenses ranging from 8.67±6.62 to 6.88±5.98 mm3 , for 4-5 mm PS). EPP was estimated with <50 µm (errors of 42±37 to 36±32 µm). Errors in Ø were 0.24±0.20 to 0.20±0.22 mm. VOL of the ex-vivo lenses increased at rates of 1.16 mm3 /year, r=0.74, P<0.001; Ø increased at 8 µm/year, r=0.39, P=0.10; and relationship EPP/ thickness slightly shifts forward. Lens VOL in-vivo remained almost constant with accommodation (S#1=155±1.3, S#2=180±0.7 mm3 ), Ø decreased at 0.03 mm/D, r=-0.95, P=0.009 and EPP shifts backward 2.5 µm/D, r=0.94, P=0.01. In the cataract eye, the estimated lens values were VOL=200.3 and 215.7 mm3 , Ø=9.50 and 9.70 mm, and EPP=2.076 and 2.229 mm (distance from anterior lens) in S#1 and S#2 respectively. Conclusions: Quantitative OCT with dedicated image processing algorithms allows accurate estimation of whole shape human crystalline lens parameters, as demonstrated from ex-vivo measurements, where entire lens images are available. Patientspecific eye models that include the information on lens VOL and EPP are critical for better IOL selection (based on ray tracing instead of traditional regression formulas), and will help in presbyopiacorrecting paradigms including crystalline lens refilling and accommodative IOLs.

View Article
September 2016
31 Reads

Unraveling eye crystalline lens optics, structure and function

Latin America Optics and Photonics Conference

The young eye's crystalline lens is tuned to optimize optical quality and can reshape to focus. Custom-developed imaging, i.e. 3D quantitative OCT, allows its understanding, serving as inspiration for novel multifocal & accommodating IOLs.

View Article
August 2016
3 Reads

Three-dimensional biometry and alignment in eyes implanted with Accommodative IOLs as a function of accommodative demand

Investigative Ophthalmology & Visual Science

Purpose Accommodative intraocular lenses (A-IOLs) appear as a promising solution for the correction of presbyopia. We used custom spectral Optical Coherence Tomography (sOCT) to fully image and quantify in 3D the anterior segment of the eye in patients implanted with A-IOLs designed to move axially inside the eye. Methods Custom sOCT provided with quanti뾠⪀cation tools (automatic image analysis and fan an optical distortion correction algorithms) was used to fully image in 3D the ocular anterior segment in 20 eyes from 10 patients (73-82 years old) implanted with single-optic A-IOLs (Crystalens AO, B&L). Measurements were performed pre-operatively, and post-operatively for 0, 1.25 and 2.5 D accommodative demands, under phenilephrine. The following parameters were extracted from the images: anterior and posterior corneal and lens (natural and A-IOL) surface 3D geometry, preand post- anterior chamber depth (ACD), and lens and A-IOL tilt. ACD and lens alignment were estimated from 3D data, from the distances between surface apices, and from the vectors normal to the pupil and lens planes, respectively. Results Data were obtained from fully registered pre/post-operative images, and from images corresponding to di erent accommodative demands (see Figure). The average ACD pre-op was 2.67±0.25 mm, and post-op (relaxed accommodation) was 3.84±0.39 mm, with high left/right eye symmetry. Most lenses moved axially backward upon an accommodative demand (up to 0.4 mm), opposite from the expected shift by design. Only five lenses moved forward (up to 0.11 mm). Natural lens tilt ranged from -2.14 to 1.84 (superior). The absolute tilt of the implanted A-IOLs was on average higher than the natural lens’ tilt; in 5 eyes the A-IOL tilt exceeded by more than x2.5 the pre-op tilt, and changed orientation. A-IOLs tilts generally occurred in the superior/nasal orientation. Most lenses changed tilt with accommodative demand (from 0 to 9 deg/D, on average across eyes). Conclusions Quantitative sOCT imaging of the pre- and post-operative anterior segment of the eye appear essential to understand the mechanisms by which current A-IOLs operate and advance towards new developments. The tested A-IOL did not work as expected in most eyes, indicating that potential improvements in near vision are unlikely resulting from e ective change in paraxial power, but may be associated to induced lens tilt.

View Article
June 2016
4 Reads

Full 3-D OCT-based pseudophakic custom computer eye model

Biomedical optics express

We compared measured wave aberrations in pseudophakic eyes implanted with aspheric intraocular lenses (IOLs) with simulated aberrations from numerical ray tracing on customized computer eye models, built using quantitative 3-D OCT-based patient-specific ocular geometry. Experimental and simulated aberrations show high correlation (R= 0.93; p< 0.0001) and similarity (RMS for high order aberrations discrepancies within 23.58%). This study shows that full OCT-based pseudophakic custom computer eye models allow understanding the relative contribution of optical geometrical and surgically-related factors to image quality, and are an excellent tool for characterizing and improving cataract surgery.

View Article
March 2016
4 Reads

Advances in Anterior Segment OCT: Crystalline and Intraocular Lens Applications

Frontiers in Optics

We quantified anterior-segment geometry in young eyes and eyes implanted with IOLs using quantitative custom-developed sOCT. Crystalline lens curvature and high-order surface-elevation terms changed with accommodation. OCT-based computer eye-models predicted optical aberrations in pseudophakic eyes.

View Article
October 2015
4 Reads

OCT 3-D surface topography of isolated human crystalline lenses.

Biomed Opt Express 2014 Oct 11;5(10):3547-61. Epub 2014 Sep 11.

Instituto de Óptica "Daza de Valdés", Tel: + 34 915616800; Consejo Superior de Investigaciones Científicas. Serrano 121, 28006, Madrid, Spain.

View Article
October 2014
2 Reads
9 Citations
3.650 Impact Factor

Intraocular lens alignment from an en face optical coherence tomography image Purkinje-like method

Optical Engineering

Measurement of intraocular lens (IOL) alignment implanted in patients in cataract surgery is important to understand their optical performance. We present a method to estimate tilt and decentration of IOLs based on optical coherence tomography (OCT) images. En face OCT images show Purkinje-like images that correspond to the specular reflections from the corneal and IOL surfaces. Unlike in standard Purkinje-imaging, the tomographic nature of OCT allows unequivocal association of the reflection with the corresponding surface. The locations of the Purkinje-like images are linear combinations of IOL tilt, IOL decentration, and eye rotation. The weighting coefficients depend on the individual anterior segment geometry, obtained from the same OCT datasets. The methodology was demonstrated on an artificial model eye with set amounts of lens tilt and decentration and five pseudophakic eyes. Measured tilt and decentration in the artificial eye differed by 3.7% and 0.9%, respectively, from nominal values. In patients, average IOL tilt and decentration from Purkinje were 3.30±4.68  deg and 0.16±0.16  mm, respectively, and differed on average by 0.5 deg and 0.09 mm, respectively, from direct measurements on distortion-corrected OCT images. Purkinje-based methodology from anterior segment en face OCT imaging provided, therefore, reliable measurements of IOL tilt and decentration.

View Article
January 2014
12 Reads

3-D biometry and alignment in eyes implanted with A-IOLs as a function of accommodative demand

Investigative Ophthalmology & Visual Science

Purpose Accommodative intraocular lenses (A-IOLs) appear as a promising solution for the correction of presbyopia. We used custom spectral Optical Coherence Tomography (sOCT) to fully image and quantify in 3D the anterior segment of the eye in patients implanted with A-IOLs designed to move axially inside the eye. Methods Custom sOCT provided with quantification tools (automatic image analysis and fan an optical distortion correction algorithms) was used to fully image in 3D the ocular anterior segment in 20 eyes from 10 patients (73-82 years old) implanted with single-optic A-IOLs (Crystalens AO, B&L). Measurements were performed pre-operatively, and post-operatively for 0, 1.25 and 2.5 D accommodative demands, under phenilephrine. The following parameters were extracted from the images: anterior and posterior corneal and lens (natural and A-IOL) surface 3D geometry, pre-and post- anterior chamber depth (ACD), and lens and A-IOL tilt. ACD and lens alignment were estimated from 3D data, from the distances between surface apices, and from the vectors normal to the pupil and lens planes, respectively. Results Data were obtained from fully registered pre/post-operative images, and from images corresponding to different accommodative demands (see Figure). The average ACD pre-op was 2.67±0.25 mm, and post-op (relaxed accommodation) was 3.84±0.39 mm, with high left/right eye symmetry. Most lenses moved axially backward upon an accommodative demand (up to 0.4 mm), opposite from the expected shift by design. Only five lenses moved forward (up to 0.11 mm). Natural lens tilt ranged from -2.14 to 1.84 (superior). The absolute tilt of the implanted A-IOLs was on average higher than the natural lens’ tilt; in 5 eyes the A-IOL tilt exceeded by more than x2.5 the pre-op tilt, and changed orientation. A-IOLs tilts generally occurred in the superior/nasal orientation. Most lenses changed tilt with accommodative demand (from 0 to 9 deg/D, on average across eyes). Conclusions Quantitative sOCT imaging of the pre- and post-operative anterior segment of the eye appear essential to understand the mechanisms by which current A-IOLs operate and advance towards new developments. The tested A-IOL did not work as expected in most eyes, indicating that potential improvements in near vision are unlikely resulting from effective change in paraxial power, but may be associated to induced lens tilt.

View Article
June 2013
2 Reads

Design of the image optics of a Retina Microscope

Authors:
Mengchan Sun

KTH, School of Information and Communication Technology (ICT)

Abstract [en] Human today stress more and more importance on their health due to social welfare and advanced medical equipment. Ophthalmological device design already creates healthy living patterns around it. In the design process, effect quality of design and cost manufacturing is the objects which is necessary to be considered. The project itself was commissioned by the well-known Eye-care clinic [confidential] in High-end market. Therefore, a low-cost multi-functional fundus camera medical system, called the Retina Microscope is under developing. The whole process of the optimization of a Retina Microscope and designing aspherical lens instead of the old model will be described. The purpose is to be able to inspect the eye (the inside retina and outside cornea) and prevent needless blindness. Using a low-cost LED-based point illumination and a ring-light solution provides more flexibility for integrating refractometry. By using Zemax is to optimize the solution for the integration of a non-mydriatic fundus camera and a cornea camera. Two prototypes are already built, which are under testing and optimizing. Design and optimization is run by optical design software ZEMAX. The simulation analysis, setting parameters, the results of comparison and the controlling of optimization programming is the core of the design. My final design about plastic aspherical doublet lens is adopted by the company, and began to manufacture commercially.

View Article
April 2011
2 Reads

Full OCT-based pseudophakic custom computer eye

M Sun, P Pérez-Merino, A De Castro, J Birkenfeld, S Ortiz, S Marcos

We compared experimental wave aberrations in pseudophakic eye implanted with an aspheric accommodative intraocular lens (IOL) with simulated aberrations from numerical ray tracing on a customized computer eye model, built using quantitative all OCT-based geometry. Experimental and simulated aberrations show high correspondence (r= 0.79; p< 0.05). Full OCT-based pseudophakic custom computer eye models allow understanding of the relative contribution of optical geometrical and surgically-related factors to image quality. Quantitative OCT proves an excellent technique for pre-operative 3D biometry and post- cataract surgery evaluation.

View Article
April 2011
10 Reads