Arthur Ho | The University of New South Wales (original) (raw)
Papers by Arthur Ho
Vision research, 2014
Refractive error, higher order aberrations (HOA), axial length (AL), anterior chamber depth (ACD)... more Refractive error, higher order aberrations (HOA), axial length (AL), anterior chamber depth (ACD) and average corneal radius of curvature were measured after cycloplegia from 166 emmetropic participants at the Sydney Myopia Study (SMS, 2004-2005, age 12.63 ± 0.48 years). Measurements were repeated approximately 5 years later at the Sydney Adolescent Vascular and Eye Study (SAVES, 2009-2010, age 17.08 ± 0.67 years). The baseline spherical equivalent (M) did not differ significantly between the participants lost to follow-up (65%) and the participants enrolled in SAVES study (p = 0.932). Refractive error and HOA were measured using a Shack-Hartmann aberrometer for a pupil diameter of 5 mm and AL, ACD and average corneal curvature measured using IOL Master at both visits. Retinal image quality in terms of Visual Strehl ratio (VSOTF) for a 5 mm pupil diameter was determined using on-axis lower and HOA. General linear model was used to determine the association of HOA and retinal image q...
Advances in Experimental Medicine and Biology, 1998
1. Adv Exp Med Biol. 1998;438:835-8. Optimum dry eye classification using questionnaire responses... more 1. Adv Exp Med Biol. 1998;438:835-8. Optimum dry eye classification using questionnaire responses. McMonnies C, Ho A, Wakefield D. School of Optometry, University of New South Wales, Kensington, Australia. PMID: 9634975 [PubMed - indexed for MEDLINE]. ...
Measurement Science and Technology, 1998
The design, construction and performance of a novel optical profilometer based on the laser readi... more The design, construction and performance of a novel optical profilometer based on the laser reading head of a compact disc player is described. The instrument is capable of self-guided scanning along arbitrary contours by utilizing the focus and radial tracking signals from the sensor head. The sensor is mounted on an x , y, θ motorized stage. The radial tracking signal provides the feedback for the angular position of the sensor, ensuring that the optical axis of the sensor is always perpendicular to the profile preventing the signal loss that occurs in conventional profilometers due to deflection of the light beam. The focus signal has a sensitivity in the nanometre range which makes the precision of the stages used to perform the scanning movements the dominant limiting factor for the measuring accuracy. The sensor head intermittently follows the contour, collecting datapoints at a predetermined lateral resolution. The profile is digitized in the form of x , y, and θ coordinates for each scanpoint. The accuracy of the instrument was verified by scanning standard measures with flat and circular cross sections. The mechanical structure of the prototype instrument was purpose built for the measurement of rigid corneal contact lenses. Various lenses have been measured and profile graphs are illustrated.
Publication View. 36144404. The effects of surgery and contact lens wear on the permeability of t... more Publication View. 36144404. The effects of surgery and contact lens wear on the permeability of the corneal endothelium and epithelium (1990). Ho, Arthur. Publication details. Repository, NDLTD Union Catalog (United States). ...
Experimental Eye Research, 1992
ABSTRACT
http://iovs.arvojournals.org/article.aspx?articleid=2336094&resultClick=1
The purpose of this study was to measure the average shape and variability of human corneas and t... more The purpose of this study was to measure the average shape and variability of human corneas and to develop a tool for analyzing, height, curvature, and aberrations based on a conic section model. Fresh Eye Bank Eyes were placed in Dextran until the corneal thickness reached a physiological value. The eyes were placed in a custom made holder and measured
Investigative ophthalmology & visual science, 2015
To determine if the lens volume changes during accommodation. The study used data acquired on 36 ... more To determine if the lens volume changes during accommodation. The study used data acquired on 36 cynomolgus monkey lenses that were stretched in a stepwise fashion to simulate disaccommodation. At each step, stretching force and dioptric power were measured and a cross-sectional image of the lens was acquired using an optical coherence tomography system. Images were corrected for refractive distortions and lens volume was calculated assuming rotational symmetry. The average change in lens volume was calculated and the relation between volume change and power change, and between volume change and stretching force, were quantified. Linear regressions of volume-power and volume-force plots were calculated. The mean (±SD) volume in the unstretched (accommodated) state was 97 ± 8 mm3. On average, there was a small but statistically significant (P = 0.002) increase in measured lens volume with stretching. The mean change in lens volume was +0.8 ± 1.3 mm3. The mean volume-power and volume-...
Ophthalmic Technologies XV, 2005
ABSTRACT The ex vivo accommodation simulator stretches crystalline lenses radially under controll... more ABSTRACT The ex vivo accommodation simulator stretches crystalline lenses radially under controlled conditions, while monitoring the changes in zonular tension and lens diameter. A dual coaxial laser beam system was added for measuring changes in optical power as the lens is stretched. The EVAS instrument was fully characterized and calibrated. The results from 3 porcine eyes will be presented. Several crystalline lenses, similar in shape and size to porcine lenses, were cast molded in silicone gels of different stiffness. These lenses were evaluated using the EVAS instrument and custom made lens holding fixtures. With their well defined shape and material properties, results from these measurements will be useful for cross-validation of finite element models.
Light incident at the temporal limbus of the peripheral anterior eye is focused onto the nasal li... more Light incident at the temporal limbus of the peripheral anterior eye is focused onto the nasal limbus, the usual site of pterygium formation. Parameters which may contribute to observed individual variations in the degree of limbal light focusing were assessed. Computer assisted ray tracing techniques were applied to a human anterior segment model. We varied the angle of incident light
Proceedings of SPIE - The International Society for Optical Engineering
A contact lens (10) for use in controlling or retarding the progression of myopia in an eye has a... more A contact lens (10) for use in controlling or retarding the progression of myopia in an eye has a central optical zone (20) approximating the normal diameter of the pupil of the eye (22) that gives clear central vision at distance for the wearer. An annular peripheral optical zone 24 that is substantially outside the diameter of the pupil is formed around the central optical zone (20) with greater refractive power than that of the central zone (22) so that oblique rays entering the eye through the peripheral optical zone (24) will be brought to focus at a focal plane that is substantially on or anterior to the peripheral region of the retina. Preferably, the rear surface (16) of the lens is shaped to conform to the cornea of the eye and the front surface (18) of the lens (10) is shaped to provide—in conjunction with the rear surface (16)—the desired optical properties of the central and peripheral optical zones. The front surface (18) is also preferably contoured to form a smooth tr...
Ophthalmic Technologies XIV, 2004
ABSTRACT A new instrument was developed to simulate the accommodation of excised human and animal... more ABSTRACT A new instrument was developed to simulate the accommodation of excised human and animal crystalline lenses. The sclera is attached to 8 radially arranged translation stages and dissected into 8 segments. Change in accommodation is simulated by pulling and releasing the scleral segments, varying the load on the zonules and the capsular bag. Each translation stage is equipped with a sensitive force transducer for simultaneous recording of load and displacement. Additionally, changes in optical power, lens diameter, lens thickness and lens shape can be observed and quantified while the lens is stretched and released. The sensitivity and accuracy of the instrument was verified using steel springs and elastic bands. Preliminary results from sensitivity testing and instrument calibration are presented.
Ophthalmic Technologies XIX, 2009
We propose a novel theoretical design of gradient index (GRIN) multifocal contact lens (MFCL) to ... more We propose a novel theoretical design of gradient index (GRIN) multifocal contact lens (MFCL) to compensate presbyopia and make predictions regarding its performance on a schematic model eye and to compare its performance with conventional aspheric progressive MFCL.
Vision research, 2014
Refractive error, higher order aberrations (HOA), axial length (AL), anterior chamber depth (ACD)... more Refractive error, higher order aberrations (HOA), axial length (AL), anterior chamber depth (ACD) and average corneal radius of curvature were measured after cycloplegia from 166 emmetropic participants at the Sydney Myopia Study (SMS, 2004-2005, age 12.63 ± 0.48 years). Measurements were repeated approximately 5 years later at the Sydney Adolescent Vascular and Eye Study (SAVES, 2009-2010, age 17.08 ± 0.67 years). The baseline spherical equivalent (M) did not differ significantly between the participants lost to follow-up (65%) and the participants enrolled in SAVES study (p = 0.932). Refractive error and HOA were measured using a Shack-Hartmann aberrometer for a pupil diameter of 5 mm and AL, ACD and average corneal curvature measured using IOL Master at both visits. Retinal image quality in terms of Visual Strehl ratio (VSOTF) for a 5 mm pupil diameter was determined using on-axis lower and HOA. General linear model was used to determine the association of HOA and retinal image q...
Advances in Experimental Medicine and Biology, 1998
1. Adv Exp Med Biol. 1998;438:835-8. Optimum dry eye classification using questionnaire responses... more 1. Adv Exp Med Biol. 1998;438:835-8. Optimum dry eye classification using questionnaire responses. McMonnies C, Ho A, Wakefield D. School of Optometry, University of New South Wales, Kensington, Australia. PMID: 9634975 [PubMed - indexed for MEDLINE]. ...
Measurement Science and Technology, 1998
The design, construction and performance of a novel optical profilometer based on the laser readi... more The design, construction and performance of a novel optical profilometer based on the laser reading head of a compact disc player is described. The instrument is capable of self-guided scanning along arbitrary contours by utilizing the focus and radial tracking signals from the sensor head. The sensor is mounted on an x , y, θ motorized stage. The radial tracking signal provides the feedback for the angular position of the sensor, ensuring that the optical axis of the sensor is always perpendicular to the profile preventing the signal loss that occurs in conventional profilometers due to deflection of the light beam. The focus signal has a sensitivity in the nanometre range which makes the precision of the stages used to perform the scanning movements the dominant limiting factor for the measuring accuracy. The sensor head intermittently follows the contour, collecting datapoints at a predetermined lateral resolution. The profile is digitized in the form of x , y, and θ coordinates for each scanpoint. The accuracy of the instrument was verified by scanning standard measures with flat and circular cross sections. The mechanical structure of the prototype instrument was purpose built for the measurement of rigid corneal contact lenses. Various lenses have been measured and profile graphs are illustrated.
Publication View. 36144404. The effects of surgery and contact lens wear on the permeability of t... more Publication View. 36144404. The effects of surgery and contact lens wear on the permeability of the corneal endothelium and epithelium (1990). Ho, Arthur. Publication details. Repository, NDLTD Union Catalog (United States). ...
Experimental Eye Research, 1992
ABSTRACT
http://iovs.arvojournals.org/article.aspx?articleid=2336094&resultClick=1
The purpose of this study was to measure the average shape and variability of human corneas and t... more The purpose of this study was to measure the average shape and variability of human corneas and to develop a tool for analyzing, height, curvature, and aberrations based on a conic section model. Fresh Eye Bank Eyes were placed in Dextran until the corneal thickness reached a physiological value. The eyes were placed in a custom made holder and measured
Investigative ophthalmology & visual science, 2015
To determine if the lens volume changes during accommodation. The study used data acquired on 36 ... more To determine if the lens volume changes during accommodation. The study used data acquired on 36 cynomolgus monkey lenses that were stretched in a stepwise fashion to simulate disaccommodation. At each step, stretching force and dioptric power were measured and a cross-sectional image of the lens was acquired using an optical coherence tomography system. Images were corrected for refractive distortions and lens volume was calculated assuming rotational symmetry. The average change in lens volume was calculated and the relation between volume change and power change, and between volume change and stretching force, were quantified. Linear regressions of volume-power and volume-force plots were calculated. The mean (±SD) volume in the unstretched (accommodated) state was 97 ± 8 mm3. On average, there was a small but statistically significant (P = 0.002) increase in measured lens volume with stretching. The mean change in lens volume was +0.8 ± 1.3 mm3. The mean volume-power and volume-...
Ophthalmic Technologies XV, 2005
ABSTRACT The ex vivo accommodation simulator stretches crystalline lenses radially under controll... more ABSTRACT The ex vivo accommodation simulator stretches crystalline lenses radially under controlled conditions, while monitoring the changes in zonular tension and lens diameter. A dual coaxial laser beam system was added for measuring changes in optical power as the lens is stretched. The EVAS instrument was fully characterized and calibrated. The results from 3 porcine eyes will be presented. Several crystalline lenses, similar in shape and size to porcine lenses, were cast molded in silicone gels of different stiffness. These lenses were evaluated using the EVAS instrument and custom made lens holding fixtures. With their well defined shape and material properties, results from these measurements will be useful for cross-validation of finite element models.
Light incident at the temporal limbus of the peripheral anterior eye is focused onto the nasal li... more Light incident at the temporal limbus of the peripheral anterior eye is focused onto the nasal limbus, the usual site of pterygium formation. Parameters which may contribute to observed individual variations in the degree of limbal light focusing were assessed. Computer assisted ray tracing techniques were applied to a human anterior segment model. We varied the angle of incident light
Proceedings of SPIE - The International Society for Optical Engineering
A contact lens (10) for use in controlling or retarding the progression of myopia in an eye has a... more A contact lens (10) for use in controlling or retarding the progression of myopia in an eye has a central optical zone (20) approximating the normal diameter of the pupil of the eye (22) that gives clear central vision at distance for the wearer. An annular peripheral optical zone 24 that is substantially outside the diameter of the pupil is formed around the central optical zone (20) with greater refractive power than that of the central zone (22) so that oblique rays entering the eye through the peripheral optical zone (24) will be brought to focus at a focal plane that is substantially on or anterior to the peripheral region of the retina. Preferably, the rear surface (16) of the lens is shaped to conform to the cornea of the eye and the front surface (18) of the lens (10) is shaped to provide—in conjunction with the rear surface (16)—the desired optical properties of the central and peripheral optical zones. The front surface (18) is also preferably contoured to form a smooth tr...
Ophthalmic Technologies XIV, 2004
ABSTRACT A new instrument was developed to simulate the accommodation of excised human and animal... more ABSTRACT A new instrument was developed to simulate the accommodation of excised human and animal crystalline lenses. The sclera is attached to 8 radially arranged translation stages and dissected into 8 segments. Change in accommodation is simulated by pulling and releasing the scleral segments, varying the load on the zonules and the capsular bag. Each translation stage is equipped with a sensitive force transducer for simultaneous recording of load and displacement. Additionally, changes in optical power, lens diameter, lens thickness and lens shape can be observed and quantified while the lens is stretched and released. The sensitivity and accuracy of the instrument was verified using steel springs and elastic bands. Preliminary results from sensitivity testing and instrument calibration are presented.
Ophthalmic Technologies XIX, 2009
We propose a novel theoretical design of gradient index (GRIN) multifocal contact lens (MFCL) to ... more We propose a novel theoretical design of gradient index (GRIN) multifocal contact lens (MFCL) to compensate presbyopia and make predictions regarding its performance on a schematic model eye and to compare its performance with conventional aspheric progressive MFCL.