RESEARCH INTERESTS OF DR. SAYEGH
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The Eye Center continues to pursue a vibrant, active and global research presence to bring you the best eye care available. Here is a sampling of some of our research you may be interested in.
Learning from Giants' Mistakes in Cataract Surgery Fedorov 67 vs Fyodorov 75
Samir I Sayegh, MD, PhD, FACS, FAAO, FASRS
Abstract: One of the most influential papers in the history of cataract surgery is Fedorov and Kolinko’s 1967 paper. All so called third and fourth generation intraocular lens calculation formulas implemented to this day are based on it. We show that the actual expression given in the 1967 article is incorrect and was subsequently corrected by Fedorov and colleagues in 1975. We show the source of error and comment on implications for modern day intraocular power calculations for cataract surgery.
Introduction: Slava Fedorov’s contributions to Ophthalmology are profound and lasting. In a paper with Albina Kolinko in 1967 they attempted a rational theoretical approach to the computation of intraocular lens (IOL) power based on biometry of the patient’s eye1. The paper was written in Russian and was followed by a few similar attempts by mainly European ophthalmologists. In 1975, together with Galin and Linksz, Fedorov (Fyodorov) contributed a similar article and computation to the English literature2. This made the approach more accessible to a wider readership and was followed by the (re)introduction of regression methods exemplified by SRK3,4 and somewhat later, by a realization that theoretical methods were foundational and need be adopted albeit with a grain of tweaking! This is represented by some of the major “third generation” or “vergence based” formulas such as Holladay1, SRKT and HofferQ5,6,7, all of which cite at least one of the Fyodorov and colleague’s papers and are in turn some of the most cited and implemented papers in the IOL power calculation literature. To our knowledge, there is no systematic comparison that has been attempted between the 1967 and 1975 versions of Fedorov and colleagues’ articles. In fact, a number of papers have cited both the 1967 and 1975 articles without mention of any discrepancy4,6,8. Others will cite only one9 or the other3,10,11. Some will mention a date and cite the article from the other date12. Yet others, surprisingly, cite neither13. In the present work we start by a direct comparison of the key formulas and their differences including numeric estimates and clinical implications. We follow with an analysis of the original sources and the sources of errors and draw conclusions as to lessons to be learned. Click here to read the paper, or here to read and download the document.
The Nobel Prize in Physics 2018
The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2018 for groundbreaking inventions in the field of laser physics. Click here to view the highlighted article.
Femtosecond lasers
The use of femtosecond lasers has proven to be a very powerful and versatile tool in the area of ophthalmic surgery. LASIK has benefited from the creation of controlled flaps and all-laser procedures and cataract surgery is contemplating a move to a femtosecond laser platform in the coming years. A Nobel Prize for femtosecond spectroscopy was awarded to Dr. Ahmed Zuwail of Caltech. Leading the effort of femtosecond ophthalmic applications starting in the mid and late 90s, Dr Sayegh pioneered a technology that has and will profoundly impact ophthalmic surgery. His work was in collaboration with Dr. Ron Kurtz and other Intralase and Center for Ultrafast Optical Sciences members at the University of Michigan in Ann Arbor. http://www.engin.umich.edu/research/cuos/
Intraocular Lens Power Calculations for Cataract Surgery
The choice of the correct intraocular lens (IOL) is a critical step that completes the elegance and spectacular results offered by modern cataract surgery. Decades went by when the precise understanding and calculation of such IOL powers eluded the scientific and medical community. The advent of LASIK made the situation more complex and so called “refractive surprises”multiplied. Several ad hoc solutions were proposed but they continued to be unreliable. Dr. Sayegh pioneered a method that established the relationship between the theoretical optics based models and the regression methods used for decades, thus identifying the sources of errors and opening the door to better refractive results for patients undergoing cataract surgery many years following a LASIK procedure. Initial work was performed while Dr. Sayegh was at Washington University in Saint Louis and Barnes Hospital and refinement to the method is ongoing. Dr. Sayegh received an American Society of Cataract and Refractive Surgery best paper award for this work. (link:)
Optical Coherence Tomography(OCT)
A new imaging technique developed at MIT and patented in 1991, OCT has offered a fundamental addition to clinical tools by allowing a layer by layer visualization of delicate ocular tissue in both the front and back of the eye. In addition to offering our patients on a daily basis the most sophisticated OCT tools, our clinic is also involved in several projects related to this novel technology. Novel techniques to extract clinically useful data are being developed. In addition The EYE Center is part of a collaboratory involving the University of Illinois, Texas Instrument, Welch Allyn, Carle Clinic and others, in a 5 year NIH funded project that is implementing hand held devices and developing methods that will facilitate the early diagnosis of diabetic eye disease in addition to other conditions. Dr. Sayegh is leading the clinical ophthalmic applications of the project and is working in close collaboration with Prof. Steve Boppart of the University of Illinois. http://biophotonics.illinois.edu/
Differential Geometry and Corneal Topography
The topography of the cornea is of fundamental importance to the quality of vision and is the main target of LASIK and other refractive corneal surgeries. The exact characterization of such a topography and methods to safely modify it are keys to the delivery of the highest acuity and quality of vision. Methods of differential geometry and of laser physics are brought to bear on the means to achieve these goals. This work is in collaboration with Prof. Franco Nori of the University of Michigan and Prof. Delia Debuc from the Bascom Palmer Institute and former graduate student of Dr. Sayegh. Representative work relating to this research was recently presented at the American Society of Cataract Surgery meeting in San Diego.
EYE Testing: Algorithms and Devices
The determination of the visual acuity and the needed refractive correction (glasses, contacts, laser parameter for LASIK) for a patient is one of the most fundamental tasks performed at an eye clinic. Paper/plastic charts are often used and computer system are becoming more common. We ask the fundamental question of whether traditional methods of presentation and determination of refractive state are optimal and design algorithms and devices to test the different hypotheses and define the future generation of methods. Software developed and refined over the past 12 years is used at out clinic and is evolving into an automated, rapidly convergent algorithm of determining refractive error. Collaboration with Illini Computing, a Champaign based software company is under study.
Matrix Methods in Mathematica for the design and choice of intraocular lenses
An approach based on matrix methods in Mathematica, to allow for the analysis and computation of IOL powers. While the basic matrix approach corresponds to paraxial optics, it can be extended to include astigmatism and other aberrations. We apply our methods to compute lens powers including toric lenses that correct for both defocus (myopia, hyperopia) and astigmatism. We show how the specific use of Mathematica allows an elegant and powerful method for the design and analysis of these intraocular lenses. This work is in collaboration with David Hjelmstad of Arizona State University and Dr. Jean-Phillipe Collliac from Paris, France. The Mathematica software is developed by Wolfram Inc. of Champaign, IL.
Profilometry and Subsurface Imaging in Point of Care Diagnostics in Ocular and Neoplastic Disease
This project is concerned with applying techniques developed and evolving in the realm of ophthalmology to address important issues in breast cancer imaging and therapy. It consists of
Use of topographical techniques analogous to those used in corneal topography
Development of point-of-care lymphedema detection and characterization based on off-the-shelf hardware
Defining and implementing the role of subsurface imaging
Multimodal diagnostics and integration yielding higher sensitivity/ specificity
The project is in collaboration with Prof. Alphonse Taghian of the Massachusetts General Hospital and Harvard University.
Samir I Sayegh, MD, PhD, FACS, FAAO, FASRS
Abstract: One of the most influential papers in the history of cataract surgery is Fedorov and Kolinko’s 1967 paper. All so called third and fourth generation intraocular lens calculation formulas implemented to this day are based on it. We show that the actual expression given in the 1967 article is incorrect and was subsequently corrected by Fedorov and colleagues in 1975. We show the source of error and comment on implications for modern day intraocular power calculations for cataract surgery.
Introduction: Slava Fedorov’s contributions to Ophthalmology are profound and lasting. In a paper with Albina Kolinko in 1967 they attempted a rational theoretical approach to the computation of intraocular lens (IOL) power based on biometry of the patient’s eye1. The paper was written in Russian and was followed by a few similar attempts by mainly European ophthalmologists. In 1975, together with Galin and Linksz, Fedorov (Fyodorov) contributed a similar article and computation to the English literature2. This made the approach more accessible to a wider readership and was followed by the (re)introduction of regression methods exemplified by SRK3,4 and somewhat later, by a realization that theoretical methods were foundational and need be adopted albeit with a grain of tweaking! This is represented by some of the major “third generation” or “vergence based” formulas such as Holladay1, SRKT and HofferQ5,6,7, all of which cite at least one of the Fyodorov and colleague’s papers and are in turn some of the most cited and implemented papers in the IOL power calculation literature. To our knowledge, there is no systematic comparison that has been attempted between the 1967 and 1975 versions of Fedorov and colleagues’ articles. In fact, a number of papers have cited both the 1967 and 1975 articles without mention of any discrepancy4,6,8. Others will cite only one9 or the other3,10,11. Some will mention a date and cite the article from the other date12. Yet others, surprisingly, cite neither13. In the present work we start by a direct comparison of the key formulas and their differences including numeric estimates and clinical implications. We follow with an analysis of the original sources and the sources of errors and draw conclusions as to lessons to be learned. Click here to read the paper, or here to read and download the document.
The Nobel Prize in Physics 2018
The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2018 for groundbreaking inventions in the field of laser physics. Click here to view the highlighted article.
Femtosecond lasers
The use of femtosecond lasers has proven to be a very powerful and versatile tool in the area of ophthalmic surgery. LASIK has benefited from the creation of controlled flaps and all-laser procedures and cataract surgery is contemplating a move to a femtosecond laser platform in the coming years. A Nobel Prize for femtosecond spectroscopy was awarded to Dr. Ahmed Zuwail of Caltech. Leading the effort of femtosecond ophthalmic applications starting in the mid and late 90s, Dr Sayegh pioneered a technology that has and will profoundly impact ophthalmic surgery. His work was in collaboration with Dr. Ron Kurtz and other Intralase and Center for Ultrafast Optical Sciences members at the University of Michigan in Ann Arbor. http://www.engin.umich.edu/research/cuos/
Intraocular Lens Power Calculations for Cataract Surgery
The choice of the correct intraocular lens (IOL) is a critical step that completes the elegance and spectacular results offered by modern cataract surgery. Decades went by when the precise understanding and calculation of such IOL powers eluded the scientific and medical community. The advent of LASIK made the situation more complex and so called “refractive surprises”multiplied. Several ad hoc solutions were proposed but they continued to be unreliable. Dr. Sayegh pioneered a method that established the relationship between the theoretical optics based models and the regression methods used for decades, thus identifying the sources of errors and opening the door to better refractive results for patients undergoing cataract surgery many years following a LASIK procedure. Initial work was performed while Dr. Sayegh was at Washington University in Saint Louis and Barnes Hospital and refinement to the method is ongoing. Dr. Sayegh received an American Society of Cataract and Refractive Surgery best paper award for this work. (link:)
Optical Coherence Tomography(OCT)
A new imaging technique developed at MIT and patented in 1991, OCT has offered a fundamental addition to clinical tools by allowing a layer by layer visualization of delicate ocular tissue in both the front and back of the eye. In addition to offering our patients on a daily basis the most sophisticated OCT tools, our clinic is also involved in several projects related to this novel technology. Novel techniques to extract clinically useful data are being developed. In addition The EYE Center is part of a collaboratory involving the University of Illinois, Texas Instrument, Welch Allyn, Carle Clinic and others, in a 5 year NIH funded project that is implementing hand held devices and developing methods that will facilitate the early diagnosis of diabetic eye disease in addition to other conditions. Dr. Sayegh is leading the clinical ophthalmic applications of the project and is working in close collaboration with Prof. Steve Boppart of the University of Illinois. http://biophotonics.illinois.edu/
Differential Geometry and Corneal Topography
The topography of the cornea is of fundamental importance to the quality of vision and is the main target of LASIK and other refractive corneal surgeries. The exact characterization of such a topography and methods to safely modify it are keys to the delivery of the highest acuity and quality of vision. Methods of differential geometry and of laser physics are brought to bear on the means to achieve these goals. This work is in collaboration with Prof. Franco Nori of the University of Michigan and Prof. Delia Debuc from the Bascom Palmer Institute and former graduate student of Dr. Sayegh. Representative work relating to this research was recently presented at the American Society of Cataract Surgery meeting in San Diego.
EYE Testing: Algorithms and Devices
The determination of the visual acuity and the needed refractive correction (glasses, contacts, laser parameter for LASIK) for a patient is one of the most fundamental tasks performed at an eye clinic. Paper/plastic charts are often used and computer system are becoming more common. We ask the fundamental question of whether traditional methods of presentation and determination of refractive state are optimal and design algorithms and devices to test the different hypotheses and define the future generation of methods. Software developed and refined over the past 12 years is used at out clinic and is evolving into an automated, rapidly convergent algorithm of determining refractive error. Collaboration with Illini Computing, a Champaign based software company is under study.
Matrix Methods in Mathematica for the design and choice of intraocular lenses
An approach based on matrix methods in Mathematica, to allow for the analysis and computation of IOL powers. While the basic matrix approach corresponds to paraxial optics, it can be extended to include astigmatism and other aberrations. We apply our methods to compute lens powers including toric lenses that correct for both defocus (myopia, hyperopia) and astigmatism. We show how the specific use of Mathematica allows an elegant and powerful method for the design and analysis of these intraocular lenses. This work is in collaboration with David Hjelmstad of Arizona State University and Dr. Jean-Phillipe Collliac from Paris, France. The Mathematica software is developed by Wolfram Inc. of Champaign, IL.
Profilometry and Subsurface Imaging in Point of Care Diagnostics in Ocular and Neoplastic Disease
This project is concerned with applying techniques developed and evolving in the realm of ophthalmology to address important issues in breast cancer imaging and therapy. It consists of
Use of topographical techniques analogous to those used in corneal topography
Development of point-of-care lymphedema detection and characterization based on off-the-shelf hardware
Defining and implementing the role of subsurface imaging
Multimodal diagnostics and integration yielding higher sensitivity/ specificity
The project is in collaboration with Prof. Alphonse Taghian of the Massachusetts General Hospital and Harvard University.
