This prospective study found that the Pediatric Vision Scanner (PVS), a binocular retinal birefringence scanning device, had significantly better sensitivity and specificity for detecting strabismus and amblyopia in preschool-aged children than screening for refractive risk factors via the SureSight Autorefractor.
The PVS uses binocular retinal birefringence scans to detect whether fixation of a target is foveal and steady in each eye via the unique polarization signal created by the radially arranged Henle fibers (photoreceptor axons) that emanate from the fovea.
Retinal birefringence scanning with the PVS is a novel approach that provides direct detection of strabismus and amblyopia, rather than the common approach of indirectly assessing refractive risk factors. The authors say it is quick and simple to use, allows a long working distance (40 cm) that is comfortable for preschool children, provides an objective result of “pass” or “refer,” and is more accurate than risk factor assessment.
After a pilot study showing a sensitivity of 97% and specificity of 98% for strabismus and amblyopia, the bulky original version of the PVS was redesigned to be easily incorporated into routine pediatric care, with a reduced size and weight, an enhanced signal-to-noise ratio, and a more child-friendly fixation target.
In this study, the authors used the new PVS and the device currently used by many for preschool vision screening, the SureSight Autorefractor, in 300 consecutive preschool children (age 2 to 6 years). Of the 300 patients, 188 had strabismus only, amblyopia only, or both, and 112 had no strabismus or amblyopia. A masked, comprehensive pediatric ophthalmic examination provided the gold standard for determining sensitivity and specificity for each screening device.
The sensitivity of the PVS to detect strabismus and amblyopia was significantly higher than that of the SureSight Autorefractor (96% vs. 74%), as was the specificity (87% vs. 62%). Furthermore, the SureSight had nearly nine times as many false negatives and more than three times as many false positives as the PVS.
They conclude that the PVS is a simple, quick test that can be used to refer only affected children to eye care professionals or screen children at regular intervals in a primary care setting. This strategy is in keeping with the 2013 AAPOS Vision Screening Committee recommendation that vision “screening should be viewed as a continuous process that occurs throughout visual development, beginning in infancy.”