Resolution acuity and spatial summation of chromatic mechanisms in the peripheral retina.

Green stimuli are more difficult to detect than red stimuli in the retinal periphery, as reported previously. We examined the spatial characteristics of chromatic mechanisms using stimuli, modulated from an achromatic background to each pole of the "red-green" cardinal axis in DKL space at 20 deg eccentricity. The "blue-yellow" cardinal axis was also studied for comparison.

Spatiotemporal Summation of Perimetric Stimuli in Early Glaucoma.

Purpose: To investigate achromatic temporal summation under the conditions of standard automated perimetry (SAP), using a Goldmann III (GIII) stimulus and a stimulus scaled to the local area of complete spatial summation (Ricco's area) in open-angle glaucoma (OAG) patients and healthy age-similar control participants.

Methods: Twenty patients with OAG (mean age, 63 years; mean MD, -3.3 dB) and 15 healthy controls (mean age, 64 years) were recruited.

The Effect of Age on the Temporal Summation of Achromatic Perimetric Stimuli.

Purpose: To examine the temporal summation of a Goldmann III-sized stimulus under the conditions of standard automated perimetry in healthy participants of varying age.

Methods: Twenty-seven healthy individuals of varying age (24-80 years) were tested. Achromatic contrast thresholds were measured for seven 0.

Effect of varying CRT refresh rate on the measurement of temporal summation.

Purpose: To quantify the effect of cathode-tube-ray (CRT) monitor refresh rate on the measurement of the upper limit of complete temporal summation (critical duration) in the peripheral visual field of healthy observers.

Methods: Contrast thresholds were measured for seven achromatic spot stimuli (diameter 0.48°) of varying duration (nominal values: 10-200 ms) at an eccentricity of 8.

The Effect of Cataract on Early Stage Glaucoma Detection Using Spatial and Temporal Contrast Sensitivity Tests.

Background: To investigate the effect of cataract on the ability of spatial and temporal contrast sensitivity tests used to detect early glaucoma.

Methods: Twenty-seven glaucoma subjects with early cataract (mean age 60 ± 10.2 years) which constituted the test group were recruited together with twenty-seven controls (cataract only) matched for age and cataract type from a primary eye care setting.

Estimating the critical duration for temporal summation of standard achromatic perimetric stimuli.

Purpose: To estimate the critical duration of temporal summation for achromatic Goldmann III stimuli under the conditions of standard automated perimetry (SAP) and quantify response variability for short-duration stimuli.

Methods: Contrast thresholds were gathered using the method of constant stimuli for seven circular (0.48° diameter) incremental stimuli of varying duration (sum-of-frames equivalent: 8.

Changes in Ricco's area with background luminance in the S-cone pathway.

Purpose: The area of complete spatial summation (Ricco's area) for achromatic stimuli has previously been shown to decrease with increased background luminance. A popular hypothesis is that such a phenomenon reflects increased center-surround antagonism within the receptive field of the retinal ganglion cell. We wished to investigate if similar changes in Ricco's area occur with blue background luminance for the S-cone pathway, guided by the knowledge that the retinal ganglion cells with S-cone input do not display S-cone-mediated center-surround antagonism (S+/S-).

The effect of age on the area of complete spatial summation for chromatic and achromatic stimuli.

Purpose: Previously, an association between the area of complete spatial summation (Ricco's area) and age under scotopic conditions had been found. The authors sought to determine whether Ricco's area is similarly associated with age under photopic achromatic and selective S-cone conditions in peripheral vision and whether any association relates to a loss of ganglion cell density as determined by measurements of peripheral grating resolution acuity.

Methods: Achromatic spatial summation functions were plotted for 68 healthy subjects (aged 20-77 years) in four oblique meridians on a gray background field of 10 cd/m(2).

Sensitivity loss in early glaucoma can be mapped to an enlargement of the area of complete spatial summation.

Purpose: The area of complete spatial summation (Ricco's area) is the largest stimulus size for which area × intensity is constant at threshold. The authors sought to investigate whether Ricco's area changes in early glaucoma to account for the decreased visual signal/noise ratio that may accompany retinal ganglion cell loss.

Methods: Spatial summation functions were measured, and Ricco's area was determined at four 10° retinal locations in 24 patients with early glaucoma (total deviation at test locations, mean, -1.

The robustness of various forms of perimetry to different levels of induced intraocular stray light.

Purpose: To compare directly the robustness of standard automated perimetry (SAP), short-wavelength automated perimetry (SWAP), frequency-doubling perimetry (FDP), and grating-resolution perimetry (GRP) stimuli to different degrees of intraocular stray light induced by commercially available opacity-containing filters.

Methods: Five white opacity filters of increasing density were used to simulate the typical forward light scatter and stray light values associated with age-related lens opacification and significant cataract. The individually induced intraocular stray light value for each filter was quantified with a stray light meter and plotted against individual perimetric thresholds for the right eyes of three normally sighted trained observers for SAP, SWAP, FDP, and GRP.

On the search for an appropriate metric for reaction time to suprathreshold increments and decrements.

Weber contrast, DeltaL/L, is a widely used contrast metric for aperiodic stimuli. Zele, Cao & Pokorny [Zele, A. J.

The effect of age-related lens yellowing on Farnsworth-Munsell 100 hue error score.

Purpose: To investigate the effects of real and simulated age-related changes in crystalline lens yellowing on Farnsworth-Munsell (FM) 100 hue performance.

Methods: FM 100 hue total and partial error scores (PES) were measured in a group of younger (n=10, mean age=22.2+/-2.

How does the short-wavelength-sensitive contrast sensitivity function for detection and resolution change with age in the periphery?

To determine the age-related change in the peripheral short-wavelength-sensitive (SWS) grating contrast sensitivity function (CSF), cut-off spatial frequency (acuity) and contrast sensitivity for both a detection and resolution task were measured at 8 degrees eccentricity under conditions of SWS-cone isolation for 51 subjects (19-72 years). The acuity for both the detection and resolution task declined with age, the detection acuity being significantly higher than the resolution acuity at all ages (p<.01).

Resolution acuity for equiluminant gratings of S-cone positive or negative contrast in human vision.

We measured resolution acuity separately for gratings with positive (+S) and negative (-S) S-cone contrast at different eccentricities in the temporal retina to determine if the resolution performance is limited by a single bipolar opponent mechanism. Gratings were modulated from an achromatic background in either the 90 or 270 deg direction in DKL space. Two additional directions were tested to examine the effects of increased lens yellowing and macular pigment absence in the periphery.

Severity staging by early features of age-related maculopathy exhibits weak relationships with functional deficits on SWS grating acuity.

Purpose: To examine the relationship between short-wavelength-sensitive (SWS) resolution acuity and epidemiologically defined stages of early age-related maculopathy (ARM).

Methods: Subjects consisted of 88 adults aged 51 to 87 years. Psychophysical testing was undertaken in only one eye of each subject (the study eye).

The effect of simulated lens yellowing and opacification on blue-on-yellow acuity and contrast sensitivity.

Short-wavelength-sensitive (SWS) resolution acuity has been reported to be limited by the density of the responding ganglion cells for people without appreciable age-related lenticular change. This study measured the robustness of SWS-cone acuity and contrast sensitivity (CS) to simulated lens yellowing and opacification. Resolution acuity at 8 deg eccentricity proved robust to significant amounts of yellowing and remained lower than detection acuity, indicating that the resolution continued to be limited by ganglion cell density.

Human S-cone vision: relationship between perceptive field and ganglion cell dendritic field.

We measured the S-cone contrast threshold for stimuli of different size modulated along the white -90 deg direction in the isoluminant plane of DKL color space. The stimuli were presented at eccentricities of 5-30 deg in the horizontal temporal retinal meridian. Ricco's area of complete spatial summation was estimated using a bilinear fit of the log threshold/log area function.

Changes in human short-wavelength-sensitive and achromatic resolution acuity with retinal eccentricity and meridian.

Psychophysical measurements using achromatic grating resolution acuity in peripheral vision show a prominent retinal asymmetry in acuity which is consistent with predicted values based on available estimates of midget ganglion cell density. Recent studies have shown that peripheral grating resolution acuity values for short-wavelength-sensitive (SWS) isolating gratings in normal observers are closely related to predicted values based on the underlying small bistratified ganglion cell density. By measuring SWS resolution acuity at different locations across the visual field, we wished to see if any significant acuity asymmetry exists for the short-wavelength system.

Peripheral resolution for achromatic and SWS gratings in early to moderate glaucoma and the implications for selective ganglion cell density loss.

Purpose: To investigate whether there is significant selective reduction in short-wavelength-sensitive (SWS) ganglion cell density in early to moderate glaucoma.

Methods: Peripheral achromatic resolution acuity (an indirect measure of the underlying midget ganglion cell density) and peripheral chromatic resolution acuity under conditions of blue cone isolation (an indirect measure of the underlying small bistratified ganglion cell density) were measured at 13 degrees eccentricity in four oblique meridians in 15 eyes (mean age, 64.6 +/- 9.

Short-wavelength acuity: blue-yellow and achromatic resolution loss with age.

Previous studies have indicated that peripheral resolution for achromatic gratings is sampling limited and directly related to the density of the underlying midget ganglion cell population. Previous studies by the authors have shown that peripheral resolution for blue-cone isolating gratings is also sampling limited, is robust to optical defocus and short-wavelength attenuation, and yields estimates of sampling density which correspond closely with the density of small bistratified ganglion cells. We measured peripheral resolution in a group of normal subjects ranging in age from 12 to 72 years, using both achromatic and blue-cone isolating gratings, to determine how performance (and hence ganglion cell density) changed with age for both systems.

Short-wavelength acuity: optical factors affecting detection and resolution of blue-yellow sinusoidal gratings in foveal and peripheral vision.

Previous studies have indicated that peripheral achromatic grating resolution is limited by the sampling density of the neural array (sampling limited), and largely unaffected by large amounts of optical defocus and significant changes in luminance. Under certain conditions, peripheral short-wavelength sensitive (SWS) grating acuity is also sampling limited. We wished to determine how the sampling-limited nature of SWS-driven grating resolution was affected by changing optical defocus and stimulus luminance.

What limits detection and resolution of short-wavelength sinusoidal gratings across the retina?

Peripheral resolution acuity for achromatic gratings is known to be limited by the density of the underlying ganglion cell sampling array. After confirming isolation of the short-wavelength sensitive (SWS) system using chromatic adaptation methods, we wished to determine if resolution is limited by blue/yellow ganglion cell sampling (evidenced by a superiority of detection over resolution acuity and the perception of aliasing) and thus directly related to SWS-driven ganglion cell density. We measured detection and resolution acuity between 0 degrees and 35 degrees, using blue sinusoidal gratings superimposed on a yellow adapting background which ranged in intensity from 2.