Development of the spatial contrast sensitivity function (CSF) during childhood: Analysis of previous findings and new psychophysical data

The impact of eye dominance on fixation stability in school-aged children

The aim of the study was to analyze the stability of dominant and non-dominant eye fixations, as well as the influence of development on fixation stability. The study analyzed fixation stability in 280 school-age children, ranging in age from 7 to 12 years old. Fixation stability was determined by calculating the bivariate contour ellipse area (BCEA). During the fixation task, eye movements were recorded using the Tobii Pro Fusion eye tracking device at a 250 Hz sampling frequency. The results indicate that the fixation stability of dominant and non-dominant eyes, as well as the fixation stability of each eye regardless of dominance, improves as children grow older. It was found that for 7 and 8- year-old children, fixation in the dominant eye is significantly more stable than in the non-dominant eye, while in older children, there is no significant difference in fixation stability between the dominant and non-dominant eye.

Empirical validation of QUEST+ in PSE and JND estimations in visual discrimination tasks

One of the most precise methods to establish psychometric functions and estimate threshold and slope parameters is the constant stimuli procedure. The large distribution of predetermined stimulus values presented to observers enables the psychometric functions to be fully developed, but makes this procedure time-consuming. Adaptive procedures enable reliable threshold estimation while reducing the number of trials by concentrating stimulus presentations around observers' supposed threshold. Here, the stimulus value for the next trial depends on observer's responses to the previous trials. One recent improvement of these procedures is to also estimate the slope (related to discrimination sensitivity). The Bayesian QUEST+ procedure (Watson Journal of Vision, 17(3), 10, 2017), a generalization and extension of the QUEST procedure, includes this refinement. Surprisingly, this procedure is barely used. Our goal was to empirically assess its precision to evaluate size, orientation, or temporal perception, in three yes/no discrimination tasks that increase in demands. In 72 adult participants in total, we compared points of subjective equivalence (PSEs) or simultaneity (PSSs) as well as discrimination sensitivity obtained with the QUEST+, constant stimuli, and simple up-down staircase procedures. While PSEs did not differ between procedures, sensitivity estimates obtained with the 64-trials QUEST+ procedure were overestimated (i.e., just-noticeable differences, or JNDs, were underestimated). Overall, agreement between procedures was good, and was at its best for the easiest tasks. This study empirically confirmed that the QUEST+ procedure can be considered as a method of choice to accelerate PSE estimation, while keeping in mind that sensitivity estimation should be handled with caution.

Measures and variability with age of low contrast acuity and near stereoacuity in children

CLINICAL RELEVANCE

Low contrast acuity (LCA) and near stereoacuity (NS) testing are integral to the comprehensive assessment of sensory visual function in children. However, routine ophthalmological evaluations seldom take these measures into consideration. Additionally, there is limited literature regarding the normative values of these parameters in children.

BACKGROUND

This study investigated LCA and NS measures and their variability in children with normal visual acuity. The aim was to provide a benchmark for distinguishing normal measures from abnormal ones.

METHODS

A prospective observational study was conducted in primary and secondary schools across North India. The participants numbered 240 children, aged between 3 and 15 years. They were split into 12 smaller groups of 20 participants in each age group. Only participants with normal monocular uncorrected visual acuity, no refractive error, normal birth history, and no systemic ailments, were recruited. All the participants underwent a complete ophthalmic examination and non-cycloplegic retinoscopy. LCA was measured, using the low contrast Lea number chart at three metres. NS was measured using the Randot® stereo test at 40 cm.

RESULTS

The percentages of males and females, were found to be 55%, and 45%, respectively (p = 0.093). The mean NS was found to be 38.7 ± 11.5 arcsecs in the 3-9-year age group, and 26.7 ± 5.6 arcsecs in the 9-15-year age group (p-value <0.001). The mean NS showed an increasing trend up to 9 years of age. The mean LCA was 64.4 ± 20.1 in the age group of 3-8 years, and 76.38 ± 11.39 in the age group of 8-15 years (p-value <0.001). Considerable variability was noted in the LCA in the younger age group (p-value = 0.000).

CONCLUSIONS

LCA and NS mature gradually during childhood. LCA stabilises after the age of 8, while NS stabilises after the age of 9.

Characteristics and Related Parameters of Quick Contrast Sensitivity Function in Chinese Ametropia Children

PURPOSE

To investigate the characteristics of quick contrast sensitivity function (qCSF) and its related parameters in Chinese ametropia children.

METHODS

This case series study enrolled 106 eyes of 53 children (male/female=29/24, age: 9.04±2.06 years). Examinations included manifest refraction, axial length, corneal curvature, and monocular and binocular qCSF readings without refractive correction (area under log CSF [AULCSF], CSF acuity, and contrast sensitivity [CS] at 1.0 to 18.0 cpd). The subjects were divided into groups according to age and refractive parameters for analysis.

RESULTS

The mean spherical equivalent (SE), AULCSF, and CSF acuity of the test eyes were -0.94±1.53 D, 0.44±0.33, and 8.50±5.97 cpd, respectively. In the monocular qCSF comparison, the refraction sphere (RS) was the major factor correlated with qCSF readings (B=0.186, P =0.009 for AULCSF; B=0.543, P =0.019 for CSF acuity; generalized linear model). The three groups stratified by RS/SE (<-1.00D, -1.00D to 0D, and >0D) showed significant differences in CS at medium spatial frequencies (3.0 and 6.0 cpd; all P <0.05). In the low RS/SE group (within -1 to 0 D), the CS at 12.0 cpd was significantly lower than that in the hyperopia group (all P <0.05). Binocular qCSF readings were significantly correlated with those of the eyes with lower RS (all P <0.05).

CONCLUSION

RS and SE are the major contributing factors of qCSF without refractive correction in children. The CS at medium spatial frequencies decrease significantly as the RS/SE increase. In low myopia children, the CS at medium and high spatial frequencies are significantly decreased, providing practical value in visual function screening in children.

Evaluation of the SpotChecks contrast sensitivity test in children

PURPOSE

The purpose of this study was to determine intrasession repeatability of a worksheet style contrast sensitivity test (SpotChecks) in children and agreement with an established contrast sensitivity test (Pelli-Robson).

METHODS

Forty-three children aged 4 to 12 years participated in this single visit study that included two administrations of the SpotChecks binocularly, a single administration of the Pelli-Robson test and other measures of visual performance such as high-contrast visual acuity. Test order was randomised, and participants wore their habitual correction (39 unaided, 4 wearing glasses) for testing. Bland-Altman plots were used to assess the test-retest repeatability of SpotChecks and its agreement with the Pelli-Robson test. Multiple linear regressions were performed to evaluate whether contrast sensitivity was related to participant characteristics such as age, sex and near binocular visual acuity.

RESULTS

The mean difference in log contrast sensitivity (logCS) between two administrations of the SpotChecks was 0.01, with a coefficient of repeatability (1.96*SD of differences) of 0.14 logCS. The mean difference between SpotChecks and Pelli-Robson was 0.00 logCS with 95% limits of agreement of -0.19 to +0.20. For both tests, a statistically significant increase in logCS was associated with age (slopes were 0.02 logCS/year, p < 0.001 and 0.01 logCS/year, p = 0.02 for the SpotChecks and Pelli-Robson tests, respectively).

CONCLUSIONS

The SpotChecks test shows good intrasession repeatability and excellent agreement with the Pelli-Robson test in children. Contrast sensitivity showed an increase in logCS with age in children for both tests.

Visual Acuity and Contrast Sensitivity in Preterm and Full-Term Children Using a Novel Digital Test

Visual assessment in preverbal children mostly relies on the preferential looking paradigm. It requires an experienced observer to interpret the child's responses to a stimulus. DIVE (Device for an Integral Visual Examination) is a digital tool with an integrated eye tracker (ET) that lifts this requirement and automatizes this process. The aim of our study was to assess the development of two visual functions, visual acuity (VA) and contrast sensitivity (CS), with DIVE, in a large sample of children from 6 months to 14 years (y) of age, and to compare the results of preterm and full-term children. Participants were recruited in clinical settings from five countries. There were 2208 children tested, 609 of them were born preterm. Both VA and CS improved throughout childhood, with the maximum increase during the first 5 years of age. Gestational age, refractive error and age had an impact on VA results, while CS values were only influenced by age. With this study we report normative reference outcomes for VA and CS throughout childhood and validate the DIVE tests as a useful tool to measure basic visual functions in children.

Development of static and dynamic perception for luminance- and texture-defined information from school-ages to adulthood

Few studies have assessed the visual development of static and dynamic information processing at different levels of processing during typical development from the school-age years to adulthood. The implication of non-visual factors on visual development, such as cognitive (e.g., IQ) and attentional abilities, has yet to be systematically assessed with regard to spanning such a large age range. To address these voids, 203 typically-developing participants (aged 6 to 31 years) identified the orientation or direction of a static or moving grating defined by either luminance- or texture-contrast. An adaptive staircase procedure was used to measure contrast sensitivity in all four conditions. Cognitive (Wechsler IQ) and attentional ability (CPT-3) were also measured for all participants. Different developmental rates of contrast sensitivity were found between static and dynamic conditions when defined by more complex, texture-defined information, with the difference in sensitivity starting after the age of 9.71 years. However, static and dynamic profiles for luminance-defined information developed similarly with age. In addition, IQ did not correlate with nor predict the sensitivity across any condition. These results suggest age significantly explains the variance in the developmental profiles of contrast sensitivity above and beyond non-visual factors such as IQ and the CPT-3 attentional scores. Moreover, the neural pathways processing static and dynamic visual information continue to develop through late childhood and adolescence for the processing of texture-defined information only.