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Improved Assessment of Visual Field Change is a trial aimed at investigating mechanisms of visual field testing variability. We have found using larger stimulus size substantially lowers short-term variability. In this study, we will determine if larger stimuli detect visual field change at an earlier time. We are also developing a statistical model that accounts for correlations of neighboring test locations.
Disease of the optic nerve, including glaucoma, is the leading cause of blindness in the United States. Treatment decisions for optic nerve diseases are based largely on the changes in visual function that occur mostly as a consequence of disease progression. Unfortunately, the decision as to whether change of visual function has occurred is often difficult because of the high retest variability of conventional visual field testing (perimetry). This variability is so high that with moderate visual loss, a minimum of six tests are often needed in patients with optic nerve damage to reliably distinguish visual field deterioration from random variation. Our preliminary data show that a substantial portion of the variability of perimetry lies in the type of stimulus used and the testing strategy applied.
OBJECTIVES: We propose to test the hypothesis that a large portion of total perimetric variability in patients with visual loss is due to a poor signal-to-noise ratio associated with using a small fixed-size stimulus.
RESEARCH PLAN AND METHODS: To test this hypothesis, we are examining patients with optic nerve diseases with conventional automated perimetry (size III) and tests having large-sized and scaled stimuli (size V, size VI (custom perimeter) and luminance size threshold perimetry - a test where threshold is found by changing stimulus size rather than stimulus intensity). Over four years we will test 100 patients with and glaucoma and 60 normals each eight times. In addition, we are retesting 50 subjects once a week for 5 weeks. We are also studying the associated structural-functional correlations using OCT and developing a statistical model that accounts for correlations of neighboring test locations.
Perimetric variability and the reliable identification of visual field change is the single most difficult problem in visual testing today. We anticipate identifying a method that allows efficient and accurate determination of visual field change. Identification of a superior method would (1) reduce the number of examinations needed, thereby reducing the costs of medical care; (2) minimize misdiagnosis, unnecessary testing and even unnecessary surgery that results from mistakenly interpreting fluctuation of the visual field as progression or improvement; (3) allow earlier disease intervention and (4) reduce the costs of clinical trials.
Observational Model: Case Control, Time Perspective: Prospective
VA Medical Center, Iowa City
Active, not recruiting
Department of Veterans Affairs
Published on BioPortfolio: 2014-07-10T14:09:40-0400
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Partial or complete loss of vision in one half of the visual field(s) of one or both eyes. Subtypes include altitudinal hemianopsia, characterized by a visual defect above or below the horizontal meridian of the visual field. Homonymous hemianopsia refers to a visual defect that affects both eyes equally, and occurs either to the left or right of the midline of the visual field. Binasal hemianopsia consists of loss of vision in the nasal hemifields of both eyes. Bitemporal hemianopsia is the bilateral loss of vision in the temporal fields. Quadrantanopsia refers to loss of vision in one quarter of the visual field in one or both eyes.
Repetitive visual hallucinations experienced mostly by elderly with diminished visual acuity or visual field loss, with awareness of the fictional nature of their hallucinations. It is not associated with delusions and other sensory hallucinations.
A subjective visual sensation with the eyes closed and in the absence of light. Phosphenes can be spontaneous, or induced by chemical, electrical, or mechanical (pressure) stimuli which cause the visual field to light up without optical inputs.
An ocular disease, occurring in many forms, having as its primary characteristics an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function. The consequences of the increased pressure may be manifested in a variety of symptoms, depending upon type and severity, such as excavation of the optic disk, hardness of the eyeball, corneal anesthesia, reduced visual acuity, seeing of colored halos around lights, disturbed dark adaptation, visual field defects, and headaches. (Dictionary of Visual Science, 4th ed)
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