Damian McNamara

April 15, 2013

BOSTON, Massachusetts — A laser scanner that assesses strabismus and amblyopia more accurately identifies preschool children with these conditions, according to a head-to-head comparison of some well-known devices.

"So far the numbers are showing that the Pediatric Vision Scanner is a good screening device," Reed Jost, MS, a researcher at the Retina Foundation of the Southwest in Dallas, Texas, told Medscape Medical News.

The developers of the device known as PVS by REBIScan asked Jost and his team to compare its detection capabilities with those of the SureSight Autorefractor by Welch Allyn and the Randot Preschool Stereoacuity Test by Stereo Optical.

Jost presented the findings here at the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) 39th Annual Meeting.

The researchers enrolled 250 children 2 to 6 years of age in their study; 147 had strabismus and/or amblyopia and 103 served as control subjects. Children were screened at private ophthalmology offices in the Dallas area or at the Retina Foundation of the Southwest. Each child received a comprehensive pediatric ophthalmology examination.

The PVS, developed by David Hunter, MD, from Boston Children's Hospital in Massachusetts, and David Guyton, MD, from the John's Hopkins Children's Center, in Baltimore, Maryland, had a higher a sensitivity and specificity for the detection of strabismus and/or amblyopia.

Table. Performance of Strabismus and Amblyopia Screening Strategies

Screening Device Screening Bayesian Accuracy, % Sensitivity, % (95% CI) Specificity, % (95% CI)
Pediatric Vision Scanner 88 98 (95–100) 87 (79–96)
SureSight (2009 criteria) 68 60 (50–71) 68 (57–80)
SureSight (2013 criteria) 61 70 (60–80) 60 (48–72)
Randot Preschool Stereoacuity Test 77 78 (69–87) 77 (66–88)
CI, Confidence interval


Bayesian analysis was used to detect the accuracy of each test. The PVS correctly identified 144 of the 147 children with strabismus and/or amblyopia and 89 of the 102 control subjects. Depending on the referral criteria used (2009 or 2013), the SureSight Autorefractor misclassified 80 to 85 children, failed to detect 39 to 52 children with strabismus and/or amblyopia, and overreferred 17 to 19 children with astigmatism. The Randot Preschool Stereoacuity Test misclassified 53 children; the split between affected and control children was approximately equal.

The SureSight Autorefractor, which is an indirect measure based on risk factors, "missed a lot of kids and generated overreferral for some others," Jost reported. In contrast, the PVS directly assesses binocular scans for retinal birefringence to measures amblyopia and strabismus.

This study expands on findings from the initial pilot study, which found a sensitivity of 98% and a specificity of 88% for the PVS. Those results were presented last year at the AAPOS annual meeting, as reported at that time by Medscape Medical News.

"The Pediatric Vision Scanner is an exciting development in the area of amblyopia screening. It demonstrated high sensitivity and specificity for the detection of amblyopia and strabismus in a population enriched with these diseases," said Kathy Lee, MD, a pediatric ophthalmologist at St. Luke's Children's Hospital in Boise, Idaho, who was asked by Medscape Medical News to comment on the findings.

"The next step will be to determine how well it works in a population screening setting," said Dr. Lee, who took meeting attendees on a guided poster tour during the AAPOS meeting.

That next step is already underway, Jost reported. "In January, we started testing children 2 to 6 years of age during check-ups at their pediatrician's office." This feasibility study is important, he explained, because the PVS is intended for use in this setting. "It is also meant for vision screening by preschools.... It gives a pass or fail result, which clears kids or determines the need for referral."

This study was funded by a grant from the Thrasher Research Fund. The Pediatric Vision Scanner used was on loan from REBIScan and Children's Hospital Boston. Mr. Jost and Dr. Lee have disclosed no relevant financial relationships.

American Association for Pediatric Ophthalmology and Strabismus (AAPOS) 39th Annual Meeting: Abstract 62. Presented April 6, 2013.