Improving the effectiveness of the infant contrast sensitivity card procedure

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.

The contrast sensitivity of the newborn human infant

PURPOSE

To measure the binocular contrast sensitivity (CS) of newborn infants using a fixation-and-following card procedure.

METHODS

The CS of 119 healthy newborn infants was measured using stimuli printed on cards under the descending method of limits (93 infants) and randomized/masked designs (26 infants). One experienced and one novice adult observer tested the infants using vertical square-wave gratings (0.06 and 0.10 cyc/deg; 20/10,000 and 20/6000 nominal Snellen equivalent); the experienced observer also tested using horizontal gratings (0.10 cyc/deg) and using the Method of Constant Stimuli while being kept unaware of the stimulus values.

RESULTS

The CS of the newborn infant was 2.0 (contrast threshold = 0.497; 95% confidence interval: 0.475-0.524) for vertically oriented gratings and 1.74 (threshold = 0.575; 95% confidence interval: 0.523-0.633) for horizontally oriented gratings (P < 0.0006). The standard deviation of infant CS was comparable to that obtained by others on adults using the Pelli-Robson chart. The two observers showed similar practice effects. Randomization of stimulus order and masking of the adult observer had no effect on CS.

CONCLUSIONS

The CS of individual newborn human infants can be measured using a fixation-and-following card procedure.

A pseudoisochromatic test of color vision for human infants

Despite the development of experimental methods capable of measuring early human color vision, we still lack a procedure comparable to those used to diagnose the well-identified congenital and acquired color vision anomalies in older children, adults, and clinical patients. In this study, we modified a pseudoisochromatic test to make it more suitable for young infants. Using a forced choice preferential looking procedure, 216 3-to-23-mo-old babies were tested with pseudoisochromatic targets that fell on either a red/green or a blue/yellow dichromatic confusion axis. For comparison, 220 color-normal adults and 22 color-deficient adults were also tested. Results showed that all babies and adults passed the blue/yellow target but many of the younger infants failed the red/green target, likely due to the interaction of the lingering immaturities within the visual system and the small CIE vector distance within the red/green plate. However, older (17-23 mo) infants, color- normal adults and color-defective adults all performed according to expectation. Interestingly, performance on the red/green plate was better among female infants, well exceeding the expected rate of genetic dimorphism between genders. Overall, with some further modification, the test serves as a promising tool for the detection of early color vision anomalies in early human life.

Preoperative visual acuity and contrast sensitivity in children with small, partial, or non-central cataracts

BACKGROUND

While there is clear evidence that dense central cataracts >3 mm diameter warrant prompt intervention to prevent deprivation amblyopia, guidelines for management of small, partial and non-central cataracts are not evidence-based. Consensus guidelines advise managing affected infants and preschool children by monitoring for possible progression in size or density and pharmacologic pupillary dilation, if indicated. Extraction is deemed necessary if the cataract progresses sufficiently to obscure the visual axis or if strabismus or nystagmus develops. We evaluated the long-term visual acuity outcome of the consensus guidelines and whether sensory testing during infancy and early childhood may be helpful in guiding treatment.

METHODS

A total of 40 consecutive children diagnosed with small, partial, or non-central cataracts at 1 week to 2.5 years of age were enrolled in a prospective study of forced-choice preferential looking visual acuity and contrast sensitivity development. Long-term visual acuity outcome was assessed by crowded HOTV or ETDRS at 4-11 years.

RESULTS

Of the 40 children managed by consensus guidelines, 24 (60%) had abnormal visual acuity at 4-11 years of age, including 9 (23%) who had moderate to severe visual impairment (20/80 or worse) in 1 or both eyes. Abnormal visual acuity and contrast sensitivity during development were predictive of abnormal long-term visual acuity outcomes.

CONCLUSIONS

Visual acuity and contrast sensitivity tests were sensitive to the effects of visual deprivation on the developing visual system and may be useful in early identification of children with small, partial, or non-central cataracts who could benefit from cataract extraction.

Contrast insensitivity: the critical immaturity in infant visual performance

This is a targeted review of the critical immaturities limiting psychophysical luminance contrast detection in human infants. Three-month-old infants are 50 times less sensitive to contrast than adults are. Rod experiments suggest that early-stage immaturities, like the short length of infant rod outer segments, have only a modest direct effect on infant visual performance. Infant contrast sensitivity may resemble adult extrafoveal sensitivity, because the foveal cones of the neonate are immature and may not generate strong enough responses to mediate visual performance. This use of the extrafoveal retina reduces the high-spatial frequency end of the infant contrast sensitivity function (CSF), contributing to poor infant resolution acuity. The remaining difference between infant and adult CSFs may be a simple overall reduction in infant sensitivity. The maximum of the infant CSF increases proportionately with age, and may be numerically near the infant's age in weeks. Contrast discrimination experiments indicate that the critical immaturity that limits infant contrast sensitivity is a mid-level phenomenon, occurring before the site of the contrast gain control. For example, the infant ascending visual pathway might be limited by large amounts of intrinsic noise. These results suggest that there is little effect of inattentiveness to the psychophysical task by ostensibly alert infant patients or subjects. The clinician or researcher can interpret behavioral measurements of infant visual performance with confidence.

Accuracy of the contrast sensitivity card test for infants: retest variability and prediction of spatial resolution

PURPOSE

We assessed the retest variability of a new contrast sensitivity (CS) card procedure and its ability to predict spatial resolution.

METHODS

Twenty-four 3-month-olds were tested twice with the CS cards and once with the Teller acuity cards (TAC) within a single session.

RESULTS

Coefficient of repeatability (COR) analysis revealed that retest variability of the new cards is superior to that of an earlier prototype at low to mid spatial frequencies. Furthermore, retest variability is comparable to that of infant visual evoked potential studies and the Vistech 6500, a chart commonly used to measure CS in adults. Finally, estimates of visual acuity based on the CS cards were consistent with those provided by the TAC (although CS-based estimates were generally lower overall).

CONCLUSIONS

Given its reliability and accuracy, the new CS card procedure has good potential as a clinical tool for assessing spatial vision in infants and toddlers.