A New Contrast Sensitivity Test for Pediatric Patients: Feasibility and Inter-Examiner Reliability in Ocular Disorders and Cerebral Visual Impairment.

Purpose: Assess feasibility and interexaminer reliability of a new test of contrast sensitivity (CS) for pediatric populations. Methods: The Double Happy (DH) measures CS using a method similar to the Teller Acuity Cards. The schematic DH face is 16 degrees in diameter with features of 0.3 c/d and a channel frequency of 0.8 c/d. DH log10 CS is in 0.15 log unit steps, 0.05 to 2.1. Participants were 43 unselected patients, ages 2 to 18 years: 23 were diagnosed with ocular disorders only; 20 were diagnosed with cerebral visual impairment (CVI). Two examiners measured DH log10 CS. Visual acuity (VA) was also measured. Results: All 43 participants were tested for binocular DH log10CS. Cohen's kappa values for interexaminer reliability were fair. The between examiner ICC was +0.92 (P < 0.001). The mean difference between examiners was near zero, and the 95% CI was -0.44 to 0.45 log10CS. DH log10CS was near normal in the ocular disorder group and reduced in the CVI group. VA was reduced in both groups. DH log10 CS and VA were correlated (r = -0.65). DH log10 CS was a marginally better predictor of diagnosis than VA. Conclusions: DH log10CS test was successful in a diverse pediatric population diagnosed with ocular disorders or CVI. Interexaminer reliability was comparable to that of adults tested previously using the same stimuli and methods. Both CS and VA are reduced in CVI. Translational Relevance: CS and VA both should be tested in pediatric clinical populations, especially in those at risk of CVI.

Sensitivity to S-Cone Stimuli and the Development of Myopia.

Purpose: Longitudinal chromatic aberration (LCA) is a color signal available to the emmetropization process that causes greater myopic defocus of short wavelengths than long wavelengths. We measured individual differences in chromatic sensitivity to explore the role LCA may play in the development of refractive error. Methods: Forty-four observers were tested psychophysically after passing color screening tests and a questionnaire for visual defects. Refraction was measured and only subjects with myopia or hyperopia without severe astigmatism participated. Psychophysical detection thresholds for 3 cyc/deg achromatic, L-, M-, and S-cone-isolating Gabor patches and low-frequency S-cone increment (S+) and decrement (S-) blobs were measured. Parametric Pearson correlations for refractive error versus threshold were calculated and nonparametric bootstrap 95% percentage confidence intervals (BCIs) for r were computed. Results: S-cone Gabor detection thresholds were higher than achromatic, L-, and M-cone Gabors. S-cone Gabor thresholds were higher than either S+ or S- blobs. These results are consistent with studies using smaller samples of practiced observers. None of the thresholds for the Gabor stimuli were correlated with refractive error (RE). A negative correlation with RE was observed for both S+ (r = -0.28; P = 0.06; BCI: r = -0.5, -0.04) and S- (r = -0.23; P = 0.13; BCI = -0.46, 0.01) blobs, although this relationship did not reach conventional statistical significance. Conclusions: Thresholds for S+ and S- stimuli were negatively related to RE, indicating that myopes may have reduced sensitivity to low spatial frequency S-cone stimuli. This reduced S-cone sensitivity might have played a role in their failure to emmetropize normally.

On the number of perceivable blur levels in naturalistic images.

Blur is a useful cue for depth. Natural images contain objects at a range of depths whose depth can be signaled by their perceived blur. Here, to evaluate the usefulness of blur as a depth cue, we estimate the number blur levels that observers can perceive simultaneously. To estimate this value, observers discriminated and classified dead leaves patterns that contained a controlled distribution of blur levels but are more complex or naturalistic than stimuli typically used in blur research. We used a 2-IFC discrimination task, in which observers reported the interval that contained more blur levels and a classification task, in which observers reported the number of perceived blur levels. In both tasks, observers could not discriminate or classify more than four levels of blur in the stimulus reliably. In isolation from other cues, blur may provide only a coarse cue to depth and add limited depth information when present in natural scenes with complex distributions of blur and multiple depth cues.

Characterization of field loss based on microperimetry is predictive of face recognition difficulties.

PURPOSE: To determine how visual field loss as assessed by microperimetry is correlated with deficits in face recognition. METHODS: Twelve patients (age range, 26-70 years) with impaired visual sensitivity in the central visual field caused by a variety of pathologies and 12 normally sighted controls (control subject [CS] group; age range, 20-68 years) performed a face recognition task for blurred and unblurred faces. For patients, we assessed central visual field loss using microperimetry, fixation stability, Pelli-Robson contrast sensitivity, and letter acuity. RESULTS: Patients were divided into two groups by microperimetry: a low vision (LV) group (n = 8) had impaired sensitivity at the anatomical fovea and/or poor fixation stability, whereas a low vision that excluded the fovea (LV:F) group (n = 4) was characterized by at least some residual foveal sensitivity but insensitivity in other retinal regions. The LV group performed worse than the other groups at all blur levels, whereas the performance of the LV:F group was not credibly different from that of the CS group. The performance of the CS and LV:F groups deteriorated as blur increased, whereas the LV group showed consistently poor performance regardless of blur. Visual acuity and fixation stability were correlated with face recognition performance. CONCLUSIONS: Persons diagnosed as having disease affecting the central visual field can recognize faces as well as persons with no visual disease provided that they have residual sensitivity in the anatomical fovea and show stable fixation patterns. Performance in this task is limited by the upper resolution of nonfoveal vision or image blur, whichever is worse.

Spatial frequency summation in visual noise.

Kersten [Vision Res. 27, 1029 (1987)] reported that absolute efficiency for the detection of static, one-dimensional bandpass noise was high and approximately constant for stimulus bandwidths ranging from 1 to 6 octaves. This result implies that human observers integrated information efficiently across a wide range of spatial frequency. One interpretation of this result--and similar results obtained with auditory stimuli [J. Acoust. Soc. Am. 32, 121 (1960)]--is that human observers, like ideal observers, can detect stimuli using an internal filter that has an adjustable bandwidth. The current experiments replicate Kersten's findings, extend them to the case where observers are uncertain about stimulus bandwidth, and use the classification image technique to estimate the filter used to detect noise stimuli that differ in bandwidth. Our results suggest that observers do not adjust channel bandwidth to match the stimulus and that detection thresholds are consistent with the predictions of a multiple-channel model.