Measuring visual function in age-related macular degeneration with frequency-doubling (matrix) perimetry.

Purpose: To determine the agreement between the Humphrey Matrix perimeter 10-2 test and the 10-2 Humphrey Field Analyzer (HFA) test when assessing visual function in patients with age-related macular degeneration (AMD).

Methods: Forty-two eyes of 42 subjects with AMD (average 75.0 years, SD=6.

Appearance of the frequency-doubling stimulus at threshold.

Purpose: It has been argued that the threshold for detecting frequency-doubling (FD) technology perimeter stimuli differs from the threshold for perceiving spatial structure (pattern) in the same targets. Thresholds for perceiving spatial structure have typically been assessed using orientation-identification experiments. The authors investigated the influence of orientation, edge profile, and psychophysical method on the origin of the reported differences in detection and orientation-identification thresholds for FD gratings.

Quantifying adaptation and fatigue effects in frequency doubling perimetry.

Purpose: The second eye tested in frequency doubling perimetry has higher thresholds (reduced sensitivity) than the first. The authors investigated how this "second-eye effect" evolves over time and studied systematic changes in threshold in the first eye.

Methods: Thresholds were measured in four subjects for 5 degrees -square, 0.

Characteristics of the normative database for the Humphrey matrix perimeter.

Purpose: The Humphrey Matrix (Carl Zeiss Meditec, Dublin CA; Welch-Allyn, Skaneateles, NY) is a high-spatial-resolution perimeter that uses frequency-doubling stimuli. It incorporates an efficient test strategy that assumes that age, eccentricity, and test procedure type have only small effects on sensitivity. The results used to create the normative database for the perimeter were examined, to see whether these assumptions were met and to examine the form of the normative data.

Anatomy of a supergroup: does a criterion of normal perimetric performance generate a supernormal population?

Purpose: To interpret individual results from automated perimeters, a normative database must be developed. Typically, a set of criteria determines those subjects that may be included in the database. This study examined whether a criterion of normal performance on an established perimeter generates a subgroup with supernormal perimetric performance.

Frequency-doubling technology perimetry and optical defocus.

Purpose: The frequency-doubling technology (FDT) perimeter has no provision for introducing corrective lenses, save for the patient's spectacles, and so patients are sometimes tested in the presence of moderate levels of defocus. The effect of defocus on frequency-doubling (FD) sensitivity was determined for both the commercially available instrument and for smaller targets that may be useful in spatially localizing visual field defects. In addition, whether stimulus artifacts may be detectable in the presence of defocus was assessed.

Effect of eccentricity on luminance-pedestal flicker thresholds.

We investigated the effect that spatially coincident luminance increments (luminance pedestals) have on flicker thresholds at several eccentricities and target sizes. Luminance pedestals elevated flicker amplitude-thresholds more when stimuli were presented eccentrically, both at low (4 Hz) and high (20 Hz) temporal frequencies. Altering the size of the eccentric stimulus failed to equate central and eccentric thresholds at all pedestal amplitudes.

Effect of dichoptic adaptation on frequency-doubling perimetry.

Background: In frequency-doubling technology (FDT) perimetry, the second eye tested has reduced sensitivity. We investigated the cause of this sensitivity reduction.

Methods: Contrast sensitivity was measured for frequency doubling (0.

Mechanisms isolated by frequency-doubling technology perimetry.

Purpose: The frequency-doubling (FD) phenomenon describes the increase in apparent spatial frequency occurring when low-spatial-frequency sine wave gratings undergo rapid counterphase flicker. It is unclear whether the visual mechanisms isolated when pattern appearance is used as a threshold criterion are the same as when a simple detection criterion (as in FD perimetry) is used. It is also unclear whether the FD stimulus isolates mechanisms that differ from those isolated by spatially uniform flicker.