Exploration of the psychophysics of a motion displacement hyperacuity stimulus.
Invest Ophthalmol Vis Sci
; 47(11): 4847-55, 2006 Nov.
Article
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| MEDLINE
| ID: mdl-17065497
ABSTRACT
PURPOSE:
To explore the summation properties of a motion-displacement hyperacuity stimulus with respect to stimulus area and luminance, with the goal of applying the results to the development of a motion-displacement test (MDT) for the detection of early glaucoma.METHODS:
A computer-generated line stimulus was presented with displacements randomized between 0 and 40 minutes of arc (min arc). Displacement thresholds (50% seen) were compared for stimuli of equal area but different edge length (orthogonal to the direction of motion) at four retinal locations. Also, MDT thresholds were recorded at five values of Michelson contrast (25%-84%) for each of five line lengths (11-128 min arc) at a single nasal location (-27,3). Frequency-of-seeing (FOS) curves were generated and displacement thresholds and interquartile ranges (IQR, 25%-75% seen) determined by probit analysis.RESULTS:
Equivalent displacement thresholds were found for stimuli of equal area but half the edge length. Elevations of thresholds and IQR were demonstrated as line length and contrast were reduced. Equivalent displacement thresholds were also found for stimuli of equivalent energy (stimulus area x [stimulus luminance - background luminance]), in accordance with Ricco's law. There was a linear relationship (slope -0.5) between log MDT threshold and log stimulus energy.CONCLUSIONS:
Stimulus area, rather than edge length, determined displacement thresholds within the experimental conditions tested. MDT thresholds are linearly related to the square root of the total energy of the stimulus. A new law, the threshold energy-displacement (TED) law, is proposed to apply to MDT summation properties, giving the relationship T = K logE where, T is the MDT threshold, Kis the constant, and E is the stimulus energy.
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Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Agudeza Visual
/
Glaucoma
/
Técnicas de Diagnóstico Oftalmológico
/
Percepción de Movimiento
Tipo de estudio:
Clinical_trials
Límite:
Adult
/
Humans
/
Middle aged
Idioma:
En
Revista:
Invest Ophthalmol Vis Sci
Año:
2006
Tipo del documento:
Article
País de afiliación:
Reino Unido