The Experts below are selected from a list of 2058 Experts worldwide ranked by ideXlab platform
Larry N Thibos - One of the best experts on this subject based on the ideXlab platform.
-
Predicting Optical Effects of Tear Film Break Up on Retinal Image Quality Using the Shack-Hartmann Aberrometer and Computational Optical Modeling
Lacrimal Gland Tear Film and Dry Eye Syndromes 3, 2002Co-Authors: Nikole L. Himebaugh, Larry N Thibos, Arthur Bradley, Carolyn G. Begley, Graeme WilsonAbstract:The pre-corneal tear film is the most anterior Refracting Surface of the eye. The large change in refractive index from air to tears makes it the Surface with the greatest optical power. Therefore, a tear film of non-uniform thickness can potentially have a significant impact on the optical quality of the eye. ^1.2 Many clinical studies have shown that, during periods between blinks, the tear film is not stable and does not remain uniform on the Surface of the eye. Instead, it appears to disrupt locally, a phenomenon termed tear film breakup by clinicians, resulting in a tear film which is non-uniform in thickness. Although tear breakup is not usually regarded as an optical phenomenon, there is experimental evidence supporting the hypothesis that local changes in tear film thickness impact the optical quality of the eye. ^3.5 The conclusions from these experimental studies are supported by clinical evidence of “blurry,” ^6.7 “disturbed,” ^8.9and “fluctuating” vision, and reduced visual acuity reported by dry eye patients and contact lens wearers.
-
Spherical Aberration of the Reduced Schematic Eye with Elliptical Refracting Surface
Optometry and vision science : official publication of the American Academy of Optometry, 1997Co-Authors: Larry N Thibos, Xiaoxiao Zhang, Arthur BradleyAbstract:ABSTRACT:We extend the single-Surface schematic-eye model of ocular chromatic aberration to account for spherical aberration of the eye. This extension is accomplished by allowing the model's single Refracting Surface to be a member of the family of ellipses with variable shape parameter (eccentrici
-
Oblique (off-axis) astigmatism of the reduced schematic eye with elliptical Refracting Surface
Optometry and vision science : official publication of the American Academy of Optometry, 1997Co-Authors: Yi-zhong Wang, Larry N ThibosAbstract:The oblique (off-axis) astigmatism of the Indiana Eye, an aspheric reduced-eye model of ocular chromatic aberration and spherical aberration, is computed across the visual field by using Coddington's equations for nonspherical Surfaces of revolution. Our results show that the amount of astigmatism varies significantly with the shape of the Refracting Surface and with the axial location of the pupil. For a pupil located 1.91 mm from the apex of the Refracting Surface (as originally specified for the model), the calculated Sturm's interval was larger than that reported in the literature. However, by moving the model's pupil 0.84 mm axially away from the apex toward the nodal point, a close match was achieved between Sturm's interval of the model eye and published data from human eyes for eccentricities up to 60 degrees. These results demonstrate that the aspheric reduced-eye model is capable of simultaneously accounting for the chromatic, spherical, and oblique astigmatic aberrations typically found in human eyes.
-
the chromatic eye a new reduced eye model of ocular chromatic aberration in humans
Applied Optics, 1992Co-Authors: Larry N Thibos, Xiaoxiao Zhang, Ming Ye, Arthur BradleyAbstract:New measurements of the chromatic difference of focus of the human eye were obtained with a two-color, vernier-alignment technique. The results were used to redefine the variation of refractive index of the reduced eye over the visible spectrum. The reduced eye was further modified by changing the Refracting Surface to an aspherical shape to reduce the amount of spherical aberration. The resulting chromatic-eye model provides an improved account of both the longitudinal and transverse forms of ocular chromatic aberration.
Arthur Bradley - One of the best experts on this subject based on the ideXlab platform.
-
Predicting Optical Effects of Tear Film Break Up on Retinal Image Quality Using the Shack-Hartmann Aberrometer and Computational Optical Modeling
Lacrimal Gland Tear Film and Dry Eye Syndromes 3, 2002Co-Authors: Nikole L. Himebaugh, Larry N Thibos, Arthur Bradley, Carolyn G. Begley, Graeme WilsonAbstract:The pre-corneal tear film is the most anterior Refracting Surface of the eye. The large change in refractive index from air to tears makes it the Surface with the greatest optical power. Therefore, a tear film of non-uniform thickness can potentially have a significant impact on the optical quality of the eye. ^1.2 Many clinical studies have shown that, during periods between blinks, the tear film is not stable and does not remain uniform on the Surface of the eye. Instead, it appears to disrupt locally, a phenomenon termed tear film breakup by clinicians, resulting in a tear film which is non-uniform in thickness. Although tear breakup is not usually regarded as an optical phenomenon, there is experimental evidence supporting the hypothesis that local changes in tear film thickness impact the optical quality of the eye. ^3.5 The conclusions from these experimental studies are supported by clinical evidence of “blurry,” ^6.7 “disturbed,” ^8.9and “fluctuating” vision, and reduced visual acuity reported by dry eye patients and contact lens wearers.
-
Spherical Aberration of the Reduced Schematic Eye with Elliptical Refracting Surface
Optometry and vision science : official publication of the American Academy of Optometry, 1997Co-Authors: Larry N Thibos, Xiaoxiao Zhang, Arthur BradleyAbstract:ABSTRACT:We extend the single-Surface schematic-eye model of ocular chromatic aberration to account for spherical aberration of the eye. This extension is accomplished by allowing the model's single Refracting Surface to be a member of the family of ellipses with variable shape parameter (eccentrici
-
the chromatic eye a new reduced eye model of ocular chromatic aberration in humans
Applied Optics, 1992Co-Authors: Larry N Thibos, Xiaoxiao Zhang, Ming Ye, Arthur BradleyAbstract:New measurements of the chromatic difference of focus of the human eye were obtained with a two-color, vernier-alignment technique. The results were used to redefine the variation of refractive index of the reduced eye over the visible spectrum. The reduced eye was further modified by changing the Refracting Surface to an aspherical shape to reduce the amount of spherical aberration. The resulting chromatic-eye model provides an improved account of both the longitudinal and transverse forms of ocular chromatic aberration.
John E. Greivenkamp - One of the best experts on this subject based on the ideXlab platform.
-
Interferometer and analysis methods for the in vitro characterization of dynamic fluid layers on contact lenses
Optical Engineering, 2012Co-Authors: Brian C. Primeau, John E. GreivenkampAbstract:The anterior Refracting Surface of the eye when wearing a contact lens is the thin fluid layer that forms on the Surface of the contact lens. Under normal conditions, this fluid layer is less than 10 μm thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed by use of a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the Surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. Quantitative analysis beyond typical contact angle or visual inspection methods is provided. Different fluid and contact lens material combinations have been evaluated, and variations in fluid layer properties have been observed. This paper discusses the interferometer design and analysis methods used. Example measurement results of different contact lens are presented.
-
Interferometer for measuring the dynamic Surface topography of a human tear film
Proceedings of SPIE, 2012Co-Authors: Brian C. Primeau, John E. GreivenkampAbstract:The anterior Refracting Surface of the eye is the thin tear film that forms on the Surface of the cornea. Following a blink, the tear film quickly smoothes and starts to become irregular after 10 seconds. This irregularity can affect comfort and vision quality. An in vivo method of characterizing dynamic tear films has been designed based upon a near-infrared phase-shifting interferometer. This interferometer continuously measures light reflected from the tear film, allowing sub-micron analysis of the dynamic Surface topography. Movies showing the tear film behavior can be generated along with quantitative metrics describing changes in the tear film Surface. This tear film measurement allows analysis beyond capabilities of typical fluorescein visual inspection or corneal topography and provides better sensitivity and resolution than shearing interferometry methods. The interferometer design is capable of identifying features in the tear film much less than a micron in height with a spatial resolution of about ten microns over a 6 mm diameter. This paper presents the design of the tear film interferometer along with the considerations that must be taken when designing an interferometer for on-eye diagnostics. Discussions include eye movement, design of null optics for a range of ocular geometries, and laser emission limits for on-eye interferometry.
-
In-vitro interferometric characterization of dynamic fluid layers on contact lenses
Proceedings of SPIE, 2011Co-Authors: Brian C. Primeau, John E. Greivenkamp, John J. SullivanAbstract:The anterior Refracting Surface of the eye when wearing a contact lens is the thin fluid layer that forms on the Surface of the contact lens. Under normal conditions, this fluid layer is less than 10 microns thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens, and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed using a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the Surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. The fluid behavior on the contact lens Surface is measured, allowing quantitative analysis beyond what typical contact angle or visual inspection methods provide. The interferometer system has measured the formation and break up of fluid layers. Different fluid and contact lens material combinations have been used, and significant fluid layer properties have been observed in some cases. The interferometer is capable of identifying features in the fluid layer less than a micron in depth with a spatial resolution of about ten microns. An area on the contact lens approximately 6 mm wide can be measured with the system. This paper will discuss the interferometer design and analysis methods used. Measurement results of different material and fluid combinations are presented.
John P. Frangie - One of the best experts on this subject based on the ideXlab platform.
-
Clinical Pharmacokinetics of Various Topical Ophthalmic Delivery Systems
Clinical Pharmacokinetics, 1995Co-Authors: John P. FrangieAbstract:The eye provides an interesting study in contrasts: it is a delicate structure with a transparent anterior wall as thin as 0.5mm; yet this structure in combination with the ocular adnexa provides a resilient physicochemical barrier. The lids, tears and lacrimal apparatus work in concert to continuously protect the cornea and conjunctiva with a stable tear film, which also serves as the primary Refracting Surface. This elaborate defence system simultaneously prevents ready intraocular access of pharmaceutical agents. Additionally, the trilaminate structure of the cornea has variable permeability to chemical agents, thereby further limiting the passage of highly hydrophobic and hydrophilic moieties. Presenting topical pharmaceutical agents to the eye via different delivery systems allows clinicians to directly affect the profile of drug bioavailability and, ultimately, bioactivity. While achieving optimum bioavailability is therapeutically important, one must simultaneously limit the occurrence of drug-induced adverse effects, both systemic and local. Utilising the different pharmacokinetic properties of drug delivery systems permits clinicians to maximise their therapeutic plans for addressing specific clinical situations while minimising the potential for adverse drug effects.
Brian C. Primeau - One of the best experts on this subject based on the ideXlab platform.
-
Interferometer and analysis methods for the in vitro characterization of dynamic fluid layers on contact lenses
Optical Engineering, 2012Co-Authors: Brian C. Primeau, John E. GreivenkampAbstract:The anterior Refracting Surface of the eye when wearing a contact lens is the thin fluid layer that forms on the Surface of the contact lens. Under normal conditions, this fluid layer is less than 10 μm thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed by use of a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the Surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. Quantitative analysis beyond typical contact angle or visual inspection methods is provided. Different fluid and contact lens material combinations have been evaluated, and variations in fluid layer properties have been observed. This paper discusses the interferometer design and analysis methods used. Example measurement results of different contact lens are presented.
-
Interferometer for measuring the dynamic Surface topography of a human tear film
Proceedings of SPIE, 2012Co-Authors: Brian C. Primeau, John E. GreivenkampAbstract:The anterior Refracting Surface of the eye is the thin tear film that forms on the Surface of the cornea. Following a blink, the tear film quickly smoothes and starts to become irregular after 10 seconds. This irregularity can affect comfort and vision quality. An in vivo method of characterizing dynamic tear films has been designed based upon a near-infrared phase-shifting interferometer. This interferometer continuously measures light reflected from the tear film, allowing sub-micron analysis of the dynamic Surface topography. Movies showing the tear film behavior can be generated along with quantitative metrics describing changes in the tear film Surface. This tear film measurement allows analysis beyond capabilities of typical fluorescein visual inspection or corneal topography and provides better sensitivity and resolution than shearing interferometry methods. The interferometer design is capable of identifying features in the tear film much less than a micron in height with a spatial resolution of about ten microns over a 6 mm diameter. This paper presents the design of the tear film interferometer along with the considerations that must be taken when designing an interferometer for on-eye diagnostics. Discussions include eye movement, design of null optics for a range of ocular geometries, and laser emission limits for on-eye interferometry.
-
In-vitro interferometric characterization of dynamic fluid layers on contact lenses
Proceedings of SPIE, 2011Co-Authors: Brian C. Primeau, John E. Greivenkamp, John J. SullivanAbstract:The anterior Refracting Surface of the eye when wearing a contact lens is the thin fluid layer that forms on the Surface of the contact lens. Under normal conditions, this fluid layer is less than 10 microns thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens, and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed using a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the Surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. The fluid behavior on the contact lens Surface is measured, allowing quantitative analysis beyond what typical contact angle or visual inspection methods provide. The interferometer system has measured the formation and break up of fluid layers. Different fluid and contact lens material combinations have been used, and significant fluid layer properties have been observed in some cases. The interferometer is capable of identifying features in the fluid layer less than a micron in depth with a spatial resolution of about ten microns. An area on the contact lens approximately 6 mm wide can be measured with the system. This paper will discuss the interferometer design and analysis methods used. Measurement results of different material and fluid combinations are presented.