The Effect of Stimulus Size on the Reliable Stimulus Range of Perimetry.

PURPOSE: Automated perimetry uses a 3.5 log unit (35dB) range of stimulus contrasts to assess function within the visual field. Using 'Size III' stimuli (0.43°), presenting stimuli within the highest 15dB of available contrast may not increase the response probability at locations damaged by glaucoma, due to retinal ganglion cell response saturation. This experiment examines the effect of instead using 'Size V' (1.72°) stimuli. METHODS: Luminance increment thresholds for circular spot stimuli of each stimulus size were measured in 35 participants (mean deviation -20.9 to -3.4 dB, ages 52-87) using the method of constant stimuli, at four locations per participant. Frequency-of-seeing curves were fit at each size and location, with three free parameters: mean, standard deviation, and asymptotic maximum response probability. These were used to estimate the contrasts to which each participant would respond on 25% of presentations (c25). RESULTS: Using segmented orthogonal regression, the maximum observed response probabilities for size III stimuli began to decline at c25 = 25.2 dB (95% confidence interval 23.3-29.0 dB from bootstrap resampling). This decline started at similar contrast for the size V stimulus: c25 = 25.0dB (22.0-26.8 dB). Among locations at which the sensitivity was above these split-points for both stimulus sizes, c25 averaged 5.6 dB higher for size V than size III stimuli. CONCLUSIONS: The lower limit of the reliable stimulus range did not differ significantly between stimulus sizes. However, more locations remained within the reliable stimulus range when using the size V stimulus. TRANSLATIONAL RELEVANCE: Size V stimuli enable reliable clinical testing later into the glaucomatous disease process.

Assessment of the reliability of standard automated perimetry in regions of glaucomatous damage.

PURPOSE: Visual field testing uses high-contrast stimuli in areas of severe visual field loss. However, retinal ganglion cells saturate with high-contrast stimuli, suggesting that the probability of detecting perimetric stimuli may not increase indefinitely as contrast increases. Driven by this concept, this study examines the lower limit of perimetric sensitivity for reliable testing by standard automated perimetry. DESIGN: Evaluation of a diagnostic test. PARTICIPANTS: A total of 34 participants with moderate to severe glaucoma; mean deviation at their last clinic visit averaged -10.90 dB (range, -20.94 to -3.38 dB). A total of 75 of the 136 locations tested had a perimetric sensitivity of ≤ 19 dB. METHODS: Frequency-of-seeing curves were constructed at 4 nonadjacent visual field locations by the Method of Constant Stimuli (MOCS), using 35 stimulus presentations at each of 7 contrasts. Locations were chosen a priori and included at least 2 with glaucomatous damage but a sensitivity of ≥ 6 dB. Cumulative Gaussian curves were fit to the data, first assuming a 5% false-negative rate and subsequently allowing the asymptotic maximum response probability to be a free parameter. MAIN OUTCOME MEASURES: The strength of the relation (R(2)) between perimetric sensitivity (mean of last 2 clinic visits) and MOCS sensitivity (from the experiment) for all locations with perimetric sensitivity within ± 4 dB of each selected value, at 0.5 dB intervals. RESULTS: Bins centered at sensitivities ≥ 19 dB always had R(2) >0.1. All bins centered at sensitivities ≤ 15 dB had R(2) <0.1, an indication that sensitivities are unreliable. No consistent conclusions could be drawn between 15 and 19 dB. At 57 of the 81 locations with perimetric sensitivity <19 dB, including 49 of the 63 locations ≤ 15 dB, the fitted asymptotic maximum response probability was <80%, consistent with the hypothesis of response saturation. At 29 of these locations the asymptotic maximum was <50%, and so contrast sensitivity (50% response rate) is undefined. CONCLUSIONS: Clinical visual field testing may be unreliable when visual field locations have sensitivity below approximately 15 to 19 dB because of a reduction in the asymptotic maximum response probability. Researchers and clinicians may have difficulty detecting worsening sensitivity in these visual field locations, and this difficulty may occur commonly in patients with glaucoma with moderate to severe glaucomatous visual field loss.

Correlating perimetric indices with three nerve fiber layer thickness measures.

PURPOSE: To determine which of three estimates of retinal nerve fiber layer thickness (RNFLT) correlate best with visual field sensitivity measured using standard automated perimetry (SAP). METHODS: Data were collected from 400 eyes of 209 participants enrolled in the Portland Progression Project. These individuals ranged from high-risk suspects to having non-end-stage glaucoma. In each eye, three measures of average RNFLT (spectral domain optical coherence tomography [SDOCT], scanning laser polarimetry [SLP], confocal scanning laser tomography [CSLT]) and SAP (Humphrey HFAII) were performed on the same day. Mean deviation (MD), mean sensitivity (MS), and pattern standard deviation (PSD) were linearized using the equations MD(Lin) = 10(MD*0.1), MS(Lin) = 10(MS*0.1), and PSD(Lin) = 10(PSD*-0.1). Correlations between each of the estimates of RNFLT and each of the functional metrics were calculated (nine total). Pearson correlations and generalized estimating equations (GEE) were used to calculate the strength and significance of the correlations. RESULTS: Linearized MS had the strongest correlation with SDOCT (r = 0.57), intermediate with SLP (r = 0.40), and weakest with CSLT (r = 0.13). When multiple RNFLT measures were included in a GEE model to predict MS(Lin), SDOCT was consistently predictive (p < 0.001) whereas CSLT was never predictive in these multivariate models. Similar findings were observed for MD(Lin) and PSD(Lin). CONCLUSIONS: Average RNFLT estimated from SDOCT predicts SAP status significantly better than average RNFLT estimated from SLP or CSLT.

Looking while unhappy: mood-congruent gaze in young adults, positive gaze in older adults.

Recent findings that older adults gaze toward positively valenced stimuli and away from negatively valenced stimuli have been interpreted as part of their attempts to achieve the goal of feeling good. However, the idea that older adults use gaze to regulate mood, and that their gaze does not simply reflect mood, stands in contrast to evidence of mood-congruent processing in young adults. No previous study has directly linked age-related positive gaze preferences to mood regulation. In this eye-tracking study, older and younger adults in a range of moods viewed synthetic face pairs varying in valence. Younger adults demonstrated mood-congruent gaze, looking more at positive faces when in a good mood and at negative faces when in a bad mood. Older adults displayed mood-incongruent positive gaze, looking toward positive and away from negative faces when in a bad mood. This finding suggests that in older adults, gaze does not reflect mood, but rather is used to regulate it.

Age-related positivity enhancement is not universal: older Chinese look away from positive stimuli.

Socioemotional selectivity theory postulates that with age, people are motivated to derive emotional meaning from life, leading them to pay more attention to positive relative to negative/neutral stimuli. The authors argue that cultures that differ in what they consider to be emotionally meaningful may show this preference to different extents. Using eye-tracking techniques, the authors compared visual attention toward emotional (happy, fearful, sad, and angry) and neutral facial expressions among 46 younger and 57 older Hong Kong Chinese. In contrast to prior Western findings, older but not younger Chinese looked away from happy facial expressions, suggesting that they do not show attentional preferences toward positive stimuli.

Is flicker-defined form (FDF) dependent on the contour?

Flicker-defined form (FDF) is a temporally driven illusion within which randomly positioned background elements are flickered in counterphase to stimulus elements, creating the illusion of a contour in the region between the background and the stimulus dots. It has been proposed that FDF is dependent on the boundary region between the counterphase flickering dots. Is the stimulus area or the illusory contour itself (region between stimulus and background) paramount to the FDF percept? Circular stimuli were compared to ring stimuli to determine the relative importance of area and contour. The rings were tested in the following configurations: constant maximum diameter/variable area; constant area/variable contour; and constant contour/variable area. For rings with constant diameter, no effect of ring thickness was found. No effect of contour was found for rings of a constant area. For rings of constant contour, the smaller the area the greater the threshold. These results suggest a greater dependence on the area of a stimulus rather than its contour. Area dependence suggests that the theory of contour dependence by a fast extraction system is unlikely. This temporally defined magnocellular-dependent illusion is influenced by slow surface perception mechanisms of the parvocellular system.

Is there an age-related positivity effect in visual attention? A comparison of two methodologies.

Research suggests a positivity effect in older adults' memory for emotional material, but the evidence from the attentional domain is mixed. The present study combined 2 methodologies for studying preferences in visual attention, eye tracking, and dot-probe, as younger and older adults viewed synthetic emotional faces. Eye tracking most consistently revealed a positivity effect in older adults' attention, so that older adults showed preferential looking toward happy faces and away from sad faces. Dot-probe results were less robust, but in the same direction. Methodological and theoretical implications for the study of socioemotional aging are discussed.

Selective preference in visual fixation away from negative images in old age? An eye-tracking study.

Recent studies have suggested that older individuals selectively forget negative information. However, findings on a positivity effect in the attention of older adults have been more mixed. In the current study, eye tracking was used to record visual fixation in nearly real-time to investigate whether older individuals show a positivity effect in their visual attention to emotional information. Young and old individuals (N = 64) viewed pairs of synthetic faces that included the same face in a nonemotional expression and in 1 of 4 emotional expressions (happiness, sadness, anger, or fear). Gaze patterns were recorded as individuals viewed the face pairs. Older adults showed an attentional preference toward happy faces and away from angry ones; the only preference shown by young adults was toward afraid faces. The age groups were not different in overall cognitive functioning, suggesting that these attentional differences are specific and motivated rather than due to general cognitive change with age.

Quantifying facial expression recognition across viewing conditions.

Facial expressions are key to social interactions and to assessment of potential danger in various situations. Therefore, our brains must be able to recognize facial expressions when they are transformed in biologically plausible ways. We used synthetic happy, sad, angry and fearful faces to determine the amount of geometric change required to recognize these emotions during brief presentations. Five-alternative forced choice conditions involving central viewing, peripheral viewing and inversion were used to study recognition among the four emotions. Two-alternative forced choice was used to study affect discrimination when spatial frequency information in the stimulus was modified. The results show an emotion and task-dependent pattern of detection. Facial expressions presented with low peak frequencies are much harder to discriminate from neutral than faces defined by either mid or high peak frequencies. Peripheral presentation of faces also makes recognition much more difficult, except for happy faces. Differences between fearful detection and recognition tasks are probably due to common confusions with sadness when recognizing fear from among other emotions. These findings further support the idea that these emotions are processed separately from each other.

Configural masking of faces: evidence for high-level interactions in face perception.

The perception of a stimulus can be impaired when presented in the context of a masking pattern. To determine the timing and the nature of face processing, the effect of various masks on the discriminability of faces was investigated. Results reveal a strong configural effect: the magnitude of masking depends on the similarity between mask and target. Masking is absent for non-face masks (noise, houses), modest for scrambled and inverted faces and strongest for upright faces, even when they differ in size, gender or viewpoint from the targets. This suggests an extra-striate location for the masking (possibly FFA). Reduced but significant masking for isolated face parts (internal features or head shape) is consistent with holistic computations in face perception. The duration over which a face mask can impair face discrimination (130 ms) is markedly longer than previously assumed and is sufficient for iterative and feedback computations to be part of face processing.