Thomas Raasch | Ohio State University (original) (raw)
Papers by Thomas Raasch
Archives of Ophthalmology, 1986
There is a tendency for the posterior chamber intraocular lens to tilt about the points of insert... more There is a tendency for the posterior chamber intraocular lens to tilt about the points of insertion. This is found clinically and in postmortem studies of eyes that have had intraocular lenses surgically implanted. One end is often located in the lens capsule and the other end is located in the ciliary sulcus. The possibility of anteroposterior displacement also exists. Using a modified Gullstrand schematic model eye, we have computed the amount of spherical and cylindrical errors that are induced due to the tilt and/or displacement of the intraocular lens. If a cylindrical error of approximately 90 degrees from the axis of insertion (lens plus haptic loops) and/or axis of tilt is detected, further careful investigation is warranted.
Current Opinion in Ophthalmology, 1991
This review is a highly selective and personal viewpoint regarding the past year's publicatio... more This review is a highly selective and personal viewpoint regarding the past year's publications in low vision clinical practice and clinical research. This article reviews and provides references on selected aspects of low vision technology, reading, pediatric considerations, visual assessment for the multiply handicapped, and the psychosocial aspects of low vision and rehabilitation. We are impressed that the wealth of current publications underscores that this is an important, productive, and growing area of research and clinical activity.
Investigative ophthalmology & visual science, 2015
Bioptic telescopic spectacles (BTS) consist of a small telescope (or telescopes) mounted high in ... more Bioptic telescopic spectacles (BTS) consist of a small telescope (or telescopes) mounted high in a pair of spectacle lenses. More than 40 states allow for some form of bioptic driving licensure for people with decreased central vision. The purpose of this study was to determine significant associations among previous driving experience, vision, and motor vehicle collisions (MVCs) for bioptic drivers in Ohio. We conducted a retrospective study of patients who received a vision examination and subsequently obtained bioptic licensure. We obtained driving records from the Ohio Bureau of Motor Vehicles in order to determine MVC involvement. Relationships among vision measures, age, sex, previous experience, and MVCs were investigated using time-to-event analysis and the Cox proportional hazards regression model. We identified 237 bioptic drivers (65% male). Age at initial exam ranged from 16 to 81 years, and mean visual acuity was approximately 20/120. The number of MVCs per driver range...
Optometry and Vision Science, 1994
Optometry and Vision Science, 1995
ABSTRACT The term irregular astigmatism has been used to refer to a variety of types of optical i... more ABSTRACT The term irregular astigmatism has been used to refer to a variety of types of optical irregularity, although there are no widely recognized quantitative definitions of irregular astigmatism. This paper proposes a particular approach to defining and quantifying irregular astigmatism, and relates this model to blur disc formation. A model of irregular astigmatism is developed and illustrated using corneal topography data. This method quantifies the variation in dioptric power with meridian by expressing that profile as a series of sinusoidal components. The relation between these components of irregular astigmatism and defocus blur discs is described, as well as the relation between irregular astigmatism and other models used to quantify aberrations. Irregular astigmatism is expressed in diopters, and may predict blur of the retinal image in the same way that spherocylindrical defocus causes blur. This model of irregular astigmatism is an efficient, quantitative means of describing irregular astigmatism.
Optometry and Vision Science
Optometry and vision science : official publication of the American Academy of Optometry, 1997
American journal of optometry and physiological optics, 1982
The magnification properties of several funduscopy techniques are compared. These techniques incl... more The magnification properties of several funduscopy techniques are compared. These techniques include direct and indirect ophthalmoscopy, and slitlamp funduscopy with accessory lenses, such as the Hruby lens and fundus contact lens. Two new approaches are taken in the determination of funduscopic magnification. As a standard, the magnification of direct ophthalmoscopy is assumed to be 1.0X. The magnification provided by other methods is compared to this to yield relative magnification.
ABSTRACT Corneal topographic information is used for a variety of purposes, such as in the fittin... more ABSTRACT Corneal topographic information is used for a variety of purposes, such as in the fitting contact lenses and in monitoring changes in corneal shape. The common presentation formats used to display data derived from commercial photokeratoscopes make the recognition of corneal distortions readily apparent. However, descriptions of these distortions often lack quantitative detail, making interpretation and comparison of irregular corneal topographic data difficult. A method is discribed which uses photokeratoscopic data, and which quantifies specific aspects of corneal shape. Both regular and irregular astigmatisms are well described by this method. The method uses, as input, the power of the cornea as a function of meridian referred to as meridian profile. This profile is decomposed into a series of sinusoidal components, each with a specific amplitude and phase. he regular astigmatism is represented by a specific component, and this component can be fully corrected with a conventional cylindrical lens. Other components represent irregularities that are not correctable optically, but which are described quantitatively by the parameters of the corresponding sinusoids. The meridional profile is completely described by the sum of all the sinusoids, yet we find that relatively few components are needed to accurately describe the irregularities found in keratoconus and in other examplesof abnormal corneal shape. The results demonstrate an efficient and compact means of quantifying different types of corneal distortions, and offer a strategy for conceptualizing irregular astigmatism.
Optometry and Vision Science, 2001
Optometry and Vision Science, 2001
Optometry and Vision Science, 1997
Optometry and Vision Science, 1982
This report describes the design of a variable focus telescopic system for a low vision patient w... more This report describes the design of a variable focus telescopic system for a low vision patient who wanted to be able to see at numerous fixed working distances. A simple and effective means of mounting the telescope onto an existing spectacle lens is described. The discussion presents an analysis of the optical principles used and a formula for determining the equivalent power of a nearpoint telescope.
Archives of Ophthalmology, 1986
There is a tendency for the posterior chamber intraocular lens to tilt about the points of insert... more There is a tendency for the posterior chamber intraocular lens to tilt about the points of insertion. This is found clinically and in postmortem studies of eyes that have had intraocular lenses surgically implanted. One end is often located in the lens capsule and the other end is located in the ciliary sulcus. The possibility of anteroposterior displacement also exists. Using a modified Gullstrand schematic model eye, we have computed the amount of spherical and cylindrical errors that are induced due to the tilt and/or displacement of the intraocular lens. If a cylindrical error of approximately 90 degrees from the axis of insertion (lens plus haptic loops) and/or axis of tilt is detected, further careful investigation is warranted.
Current Opinion in Ophthalmology, 1991
This review is a highly selective and personal viewpoint regarding the past year's publicatio... more This review is a highly selective and personal viewpoint regarding the past year's publications in low vision clinical practice and clinical research. This article reviews and provides references on selected aspects of low vision technology, reading, pediatric considerations, visual assessment for the multiply handicapped, and the psychosocial aspects of low vision and rehabilitation. We are impressed that the wealth of current publications underscores that this is an important, productive, and growing area of research and clinical activity.
Investigative ophthalmology & visual science, 2015
Bioptic telescopic spectacles (BTS) consist of a small telescope (or telescopes) mounted high in ... more Bioptic telescopic spectacles (BTS) consist of a small telescope (or telescopes) mounted high in a pair of spectacle lenses. More than 40 states allow for some form of bioptic driving licensure for people with decreased central vision. The purpose of this study was to determine significant associations among previous driving experience, vision, and motor vehicle collisions (MVCs) for bioptic drivers in Ohio. We conducted a retrospective study of patients who received a vision examination and subsequently obtained bioptic licensure. We obtained driving records from the Ohio Bureau of Motor Vehicles in order to determine MVC involvement. Relationships among vision measures, age, sex, previous experience, and MVCs were investigated using time-to-event analysis and the Cox proportional hazards regression model. We identified 237 bioptic drivers (65% male). Age at initial exam ranged from 16 to 81 years, and mean visual acuity was approximately 20/120. The number of MVCs per driver range...
Optometry and Vision Science, 1994
Optometry and Vision Science, 1995
ABSTRACT The term irregular astigmatism has been used to refer to a variety of types of optical i... more ABSTRACT The term irregular astigmatism has been used to refer to a variety of types of optical irregularity, although there are no widely recognized quantitative definitions of irregular astigmatism. This paper proposes a particular approach to defining and quantifying irregular astigmatism, and relates this model to blur disc formation. A model of irregular astigmatism is developed and illustrated using corneal topography data. This method quantifies the variation in dioptric power with meridian by expressing that profile as a series of sinusoidal components. The relation between these components of irregular astigmatism and defocus blur discs is described, as well as the relation between irregular astigmatism and other models used to quantify aberrations. Irregular astigmatism is expressed in diopters, and may predict blur of the retinal image in the same way that spherocylindrical defocus causes blur. This model of irregular astigmatism is an efficient, quantitative means of describing irregular astigmatism.
Optometry and Vision Science
Optometry and vision science : official publication of the American Academy of Optometry, 1997
American journal of optometry and physiological optics, 1982
The magnification properties of several funduscopy techniques are compared. These techniques incl... more The magnification properties of several funduscopy techniques are compared. These techniques include direct and indirect ophthalmoscopy, and slitlamp funduscopy with accessory lenses, such as the Hruby lens and fundus contact lens. Two new approaches are taken in the determination of funduscopic magnification. As a standard, the magnification of direct ophthalmoscopy is assumed to be 1.0X. The magnification provided by other methods is compared to this to yield relative magnification.
ABSTRACT Corneal topographic information is used for a variety of purposes, such as in the fittin... more ABSTRACT Corneal topographic information is used for a variety of purposes, such as in the fitting contact lenses and in monitoring changes in corneal shape. The common presentation formats used to display data derived from commercial photokeratoscopes make the recognition of corneal distortions readily apparent. However, descriptions of these distortions often lack quantitative detail, making interpretation and comparison of irregular corneal topographic data difficult. A method is discribed which uses photokeratoscopic data, and which quantifies specific aspects of corneal shape. Both regular and irregular astigmatisms are well described by this method. The method uses, as input, the power of the cornea as a function of meridian referred to as meridian profile. This profile is decomposed into a series of sinusoidal components, each with a specific amplitude and phase. he regular astigmatism is represented by a specific component, and this component can be fully corrected with a conventional cylindrical lens. Other components represent irregularities that are not correctable optically, but which are described quantitatively by the parameters of the corresponding sinusoids. The meridional profile is completely described by the sum of all the sinusoids, yet we find that relatively few components are needed to accurately describe the irregularities found in keratoconus and in other examplesof abnormal corneal shape. The results demonstrate an efficient and compact means of quantifying different types of corneal distortions, and offer a strategy for conceptualizing irregular astigmatism.
Optometry and Vision Science, 2001
Optometry and Vision Science, 2001
Optometry and Vision Science, 1997
Optometry and Vision Science, 1982
This report describes the design of a variable focus telescopic system for a low vision patient w... more This report describes the design of a variable focus telescopic system for a low vision patient who wanted to be able to see at numerous fixed working distances. A simple and effective means of mounting the telescope onto an existing spectacle lens is described. The discussion presents an analysis of the optical principles used and a formula for determining the equivalent power of a nearpoint telescope.