Optometry Commons^™

Preattentive Visual Search (Pavs): A Clinical Tool For Glaucoma, James Loughman

Books/Book chapters

Glaucoma is known to cause peripheral field loss but its impact is often underestimated. The inability to detect a target in an isolated area of the visual field may not be perceived as a significant disability. The determination here however that glaucoma adversely affects an individual’s capacity to deploy attention is an important one. This can be applied to infer the potential impact of the condition on lifestyle, even in the absence of diffuse perimetric field loss. Everyday tasks such as searching for car keys may prove more tedious and require more serial inspection. The ability to guide attention is …

The Statistical Interpretation Of The Coefficient Of Repeatability, James Loughman

Other

No abstract provided.

Macular Pigment And Its Contribution To Visual Performance And Experience, James Loughman, Peter Davison, John Nolan, Mukunda Akkali, Stephen Beatty

Articles

There is now a consensus, based on histological, biochemical and spectral absorption data, that the yellow colour observed at the macula lutea is a consequence of the selective accumulation of dietary xanthophylls in the central retina of the living eye. Scientifi c research continues to explore the function(s) of MP in the human retina, with two main hypotheses premised on its putative capacity to (1) protect the retina from (photo)-oxidative damage by means of its optical fi ltration and/or antioxidant properties, the so-called protective hypothesis and (2) infl uence the quality of visual performance by means of selective short wavelength …

Macular Pigment Optical Density In An Aging Irish Population: The Irish Longitudinal Study On Ageing, John Nolan, Roseanne Kenny, Claire O'Regan, Hilary Cronin, James Loughman, Eithne Connolly, Patricia Kearney, Stephen Beatty

Articles

Purpose: The 3 carotenoids lutein, zeaxanthin, and meso-zeaxanthin, which account for the ‘yellow spot’ at the macula and which are referred to as macular pigment (MP), are believed to play a role in visual function and protect against age-related macular degeneration (AMD) via their optical and antioxidant properties. This study was undertaken to compare MP optical density (MPOD) in a population aged ≧50 years with MPOD values from a normative database of subjects aged 18–60 years. Methods: Seventy-nine subjects were recruited into this pilot study (The Irish Longitudinal Study on Ageing-TILDA). MPOD was measured using heterochromatic flicker photometry. Retinal fundus …

Changes In Intraocular Pressure And Anterior Segment Morphometry After Uneventful Phacoemulsification Cataract Surgery, J. Dooley, S. Charalampidou, A. Malik, James Loughman, L. Molloy, S. Beatty

Articles

Purpose To study changes in anterior segment morphometry after uneventful phacoemulsification cataract surgery, and to investigate whether there is a relationship between any observed changes and intraocular pressure (IOP) reduction after the procedure. Methods The anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), central corneal thickness (CCT), and IOP were measured in 101 non-glaucomatous eyes before and after uneventful phacoemulsification cataract surgery. Results After cataract surgery, the mean ACD, ACV, and ACA values increased by 1.08mm, 54.4mm3, and 13.11, respectively, and the mean IOP (corrected for CCT) decreased by 3.2mmHg. The predictive value of a previously …

Macular Pigment And Its Contribution To Visual Performance And Experience [El Pigmento Macular Y Su Contribución Al Rendimiento Y Experiencia Visuals], James Loughman, Peter Davison, John M. Nolan, Mukunda C. Akkali, Stephen Beatty

Articles

There is now a consensus, based on histological, biochemical and spectral absorption data, that the yellow colour observed at the macula lutea is a consequence of the selective accumulation of dietary xanthophylls in the central retina of the living eye. Scientific research continues to explore the function(s) of MP in the human retina, with two main hypotheses premised on its putative capacity to (1) protect the retina from (photo)-oxidative damage by means of its optical filtration and/or antioxidant properties, the so-called protective hypothesis and (2) influence the quality of visual performance by means of selective short wavelength light absorption prior …

Diagnostic Sensitivity/Specificity Of Preattentive Vision Tests In Glaucoma, James Loughman, Peter Davison, Daniel Ian Flitcroft

Articles

Purpose. Damage to the nerve fiber layer or visual pathway might be expected to reduce the efficiency with which the visual system performs analysis of the ever-changing field of vision. The purpose of this article is to provide a further analysis of previously reported data (Loughman J, Davison P, Flitcroft I, Br J Ophthalmol 2007;91:1493-98.) to: (i) determine the sensitivity and specificity of a test of preattentive vision for glaucoma detection and (ii) provide a cutoff performance level that would serve to distinguish glaucoma in early cases. Methods. Three groups of observers (glaucoma, suspects, and normals) were examined, using computer-generated …

Diagnostic Sensitivity/Specificity Of Preattentive Vision Tests In Glaucoma, James Loughman, Peter Davison, Daniel Ian Flitcroft

Articles

Purpose. Damage to the nerve fiber layer or visual pathway might be expected to reduce the efficiency with which the visual system performs analysis of the ever-changing field of vision. The purpose of this article is to provide a further analysis of previously reported data (Loughman J, Davison P, Flitcroft I, Br J Ophthalmol 2007;91:1493–98.) to: (i) determine the sensitivity and specificity of a test of preattentive vision for glaucoma detection and (ii) provide a cutoff performance level that would serve to distinguish glaucoma in early cases. Methods. Three groups of observers (glaucoma, suspects, and normals) were examined, using computer-generated …

Ocular Aberrations Wavefront Sensor In Clinical Application, Matthew Sheehan

Masters

A versatile Hartmann-Shack (HS) wavefront sensor (WFS) was designed and constructed. Its advantages include simultaneous pupil centre determination, off-axis capability, realtime data displays, and efficient lenslet sampling orientation. The instrument is compact and transportable, making it convenient for use in a clinical setting. Subject alignment is achieved by the use of a parallel channel that is recombined with the sensing channel to simultaneously image the external eye and the HS spots onto a single charge coupled device (CCD). The pupil centre is determined using this image of the eye, rather than the HS spots. Off-axis measurements are possible throughout an …

Open Angle Glaucoma Effects On Preattentive Visual Search (Pavs) Efficiency For Flicker, Motion Displacement And Orientation Pop-Out Tasks, James Loughman, Peter Davison, Daniel Ian Flitcroft

Articles

Background/aim: Preattentive visual search (PAVS) describes rapid and efficient retinal and neural processing capable of immediate target detection in the visual field. Damage to the nerve fibre layer or visual pathway might reduce the efficiency with which the visual system performs such analysis. The purpose of this study was to test the hypothesis that patients with glaucoma are impaired on parallel search tasks, and that this would serve to distinguish glaucoma in early cases. Methods: Three groups of observers (glaucoma patients, suspect and normal individuals) were examined, using computer-generated flicker, orientation, and vertical motion displacement targets to assess PAVS efficiency. …

Open Angle Glaucoma Effects On Preattentive Visual Search (Pavs) Efficiency For Flicker, Motion Displacement And Orientation Pop-Out Tasks, James Loughman, Peter Davison, Ian Flitchcroft

Articles

Background/aim: Preattentive visual search (PAVS) describes rapid and efficient retinal and neural processing capable of immediate target detection in the visual field. Damage to the nerve fibre layer or visual pathway might reduce the efficiency with which the visual system performs such analysis. The purpose of this study was to test the hypothesis that patients with glaucoma are impaired on parallel search tasks, and that this would serve to distinguish glaucoma in early cases. Methods: Three groups of observers (glaucoma patients, suspect and normal individuals) were examined, using computer-generated flicker, orientation, and vertical motion displacement targets to assess PAVS efficiency. …

Population Study Of The Variation In Monochromatic Aberrations Of The Normal Human Eye Over The Central Visual Field, Matthew Sheehan, Alexander Goncharov, Veronica O'Dwyer, Vincent Toal, Christopher Dainty

Articles

Abstract

We present data analysis for ocular aberrations of 60 normal eyes measured with a Hartmann-Shack (HS) wavefront sensor (WFS). Aberration measurements were made on-axis and at 5 degree field angles in the nasal, inferior, temporal and superior semi-meridians. Particular attention is given to aberration distributions and possible strategies for aberration correction are discussed. A versatile HS WFS was designed and constructed with features of simultaneous pupil centre determination, off-axis capability, real-time data displays, and efficient lenslet sampling orientation. The subject alignment is achieved by the use of a parallel channel that is recombined with the sensing channel to simultaneously …

Effects Of Retinal Image Degradation On Pre-Attentive Visual Search (Pavs) Efficiency For Flicker, Movement And Orientation Stimuli, Peter Davison, James Loughman

Articles

Background: Previous research has shown that several clinical conditions cause increased preattentive visual search (PAVS) times, implying reduced parallel search capabilities in glaucoma and DLB dementia. The purpose of the research reported here was to examine for the first time the resistance of PAVS to dioptric blur using targets differing from the background in terms of flicker, vertical displacement, and orientation. Resistance would enhance the applicability of PAVS as a screening method for glaucoma and other clinical conditions affecting performance of a substantial area of the retina. Method: Computer generated flicker, orientation and vertical displacement targets were used to assess …

Effects Of Retinal Image Degradation On Pre-Attentive Visual Search (Pavs) Efficiency For Flicker, Movment And Orientation Stimuli, Peter Davison, James Loughman

Articles

Background: Previous research has shown that several clinical conditions cause increased pre-attentive visual search (PAVS) times, implying reduced parallel search capabilities in glaucoma and DLB dementia. The purpose of the research reported here was to examine for the first time the resistance of PAVS to dioptric blur using targets differing from the background in terms of flicker, vertical displacement, and orientation. Resistance would enhance the applicability of PAVS as a screening method for glaucoma and other clinical conditions affecting performance of a substantial area of the retina. Method: Computer generated flicker, orientation and vertical displacement targets were used to assess …