From suppression to stereoacuity: a composite binocular function score for clinical research

Abstract

Purpose: This study aimed to validate a binocular function score that is based on common clinical measures of visual function, providing a more complete analysis of binocular outcomes, against laboratory-based dichoptic tests of threshold stereoacuity and depth of suppression. Methods: Scores on a composite binocular function (BF) score derived from clinical stereoacuity measures (Randot Preschool Stereoacuity Test and Randot Butterfly) and the Worth 4 Dot test were determined in adults (n = 20; age 24.8 ± 7.2 years) and children (N = 77; age 8.3 ± 1.7 years) with abnormal binocular vision from strabismus or amblyopia. Adults had threshold stereoacuity measured with a novel, computerised dichoptic psychophysical test of stereopsis. Depth of suppression (dichoptic eye chart inter-ocular contrast balance test) was determined in both adults and children. Results: Clinical Randot stereoacuity was measurable in 50% of adult and 61% of child participants. Threshold stereoacuity was measurable in 65% of the adult participants. The presence of suppression or simultaneous perception (flat fusion or diplopia) was measurable in all participants, enabling assignment of a BF score to all participants in both groups. In adults, the BF score was highly correlated with the psychophysical threshold stereoacuity measure (ρ = 0.71; p < 0.001). In both adults and children, there was also a high correlation between the BF score and inter-ocular contrast balance (adult ρ = 0.90; child ρ = 0.86; p < 0.001). Conclusions: The composite BF score is a convenient and valid scale of binocularity that can be used to extend the stereoacuity measure in cohorts where nil stereoacuity is common and thus could be considered as an outcome measure in clinical trials.

Suppression Rather Than Visual Acuity Loss Limits Stereoacuity in Amblyopia

“…In the amblyopic group, depth of suppression clearly emerged as the most important factor impacting on stereoacuity, even though the strength of this relationship relied on the results of our two most severe cases, because we have no independent reason for doubting their validity. The strong relationship between the contrast balance ratio and the clinically derived BF score in binocularly abnormal observers with deepest suppression, previously reported 35 and seen in the current data, supports the inclusion of these more severe examples.…”

“…Bangerter filters are known to degrade VA, vernier acuity and will also reduce contrast sensitivity at higher spatial frequency. 30,35 Although Bangerter filters degrade vision mainly by a loss of contrast at high spatial frequencies possibly as a consequence of light scatter, it has been suggested that there is also a phase scrambling of image features as a consequence of their microelement composition. 31 In agreement with previous reports, the filters had progressive, profound consequence on optotype acuity, probably by a combination of amplitude and phase filtering.…”

“…With the advent of polarized or three-dimensional monitors, new dichoptic tests have been developed that measure stereoacuity to threshold, 3,25,34 and tests can also be used to quantify the relative contrast balance required for binocular perception (a measure of the depth of suppression). 19,35,36 The contrast of stimulus can be modified in the dichoptic displays to attenuate presentations to either eye so the factors influencing stereoacuity threshold can be investigated. With this method contrast is equally reduced across all spatial frequency components.…”

Factors Associated with Impaired Motor Skills in Strabismic and Anisometropic Children

“…Depth of suppression using a computerized dichoptic eye chart that determines the non-preferred eye/preferred eye contrast ratio (i.e., balance point) at which the child can overcome interocular suppression and report letters presented to each eye with equal likelihood (Contrast Balance Index, CBI). 2,39 Movement Assessment Battery for Children, Second Edition. Each child was tested during binocular viewing with the MABC-2 40 (administered by KRK or SEM), a standardized test used to identify children with delay or impairment in motor development that is administered in three age bands (3-6, 7-10, and 11-16 years) and consists of Manual Dexterity, Aiming and Catching, and Balance subscales with eight tasks in total ( Table 1).…”

Disrupted neural signals in patients with concomitant exotropia

“…The Worth 4‐dot Test was used to assess binocularity and the Titmus test for stereoacuity. We combined both binocularity and stereoacuity measurements to capture a broad range of binocular function using a modified binocular function score derived from the log value of the Titmus test and the Worth 4‐Dot Test at near (see Table ) 23 …”