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Introduction
Stereopsis is the perception of depth and is strictly a binocular phenomenon. It is expressed in seconds of arc (arcsec) and is considered the most developed and complex type of binocular vision.1,2
Stereoacuity depends on both sensory and motor abilities. Eyes are required to make convergent and fixating movements for standard near testing, and cortical fusion mechanisms, sensitive to retinal disparity, are also required.1 Because many factors influence stereopsis, its measurements can provide clinicians with essential information regarding the general health of the visual function, making it a significant vision screening tool.3
Fluctuations in stereoacuity have clinical implications. Improvements in stereoacuity are a key outcome measure after strabismus surgery.4 Deteriorations in stereoacuity are a central factor when monitoring the control of intermittent exotropia and are part of the considerations determining timing for strabismus surgery.1,5 Birch et al.6 reported that postoperatively stereoblind children were 3.6 times more likely to need repeat surgery later in childhood after infantile esotropia surgery. Following accommodative esotropia surgery, odds increased to 17.4 to 32.2-time folds.6 Normal stereoacuity is essential for multiple visuomotor tasks and it has been linked to better reading ability.7,8
Many popular and accessible stereoacuity tests require polarized glasses.1–3 However, testing can be challenging9 in certain populations, particularly patients with short attention spans (eg, children and patients with intellectual disability), which may lead to underestimation or the inability to evaluate “true” stereoacuity. Ciner et al.10 and Birch et al.11 found that testability was high even in young children,10,11 strengthening the notion of variability in compliance in this age group.
This pilot study investigated the new Bernell Evaluation of Stereopsis Test (BEST) (Bernell Corporation, Mishawaka, IN), a filter-free method, and compared it to the Randot Stereotest (Randot) (Stereo Optical, Inc., Chicago, IL) in a pediatric cohort. The BEST uses a lenticular technology for stereoacuity testing.11 Cylindrical lenses refract light from the targets, forming binocular parallax and the illusion of depth without filter glasses.11 The BEST uses colorful animal targets (eg, tiger, cat, dog, bear, bird, bee, and fish) to measure between 400 and 40 arcsec, which may appeal to younger children. Gross stereopsis is tested with a dinosaur target (Figures 1–2).
Patients and Methods
Participants
Children aged 3 to 18 years who were examined at the Center...