Younger kids may benefit from photoscreening

October 15, 2005

Orlando—Photoscreening in younger elementary school children was more sensitive than patched surround HOTV acuity, according to a study conducted in a school setting among nearly 1,700 children.

Orlando-Photoscreening in younger elementary school children was more sensitive than patched surround HOTV acuity, according to a study conducted in a school setting among nearly 1,700 children.

Robert W. Arnold, MD, a pediatric ophthalmologist in private practice in Anchorage, AK, and chairman of the American Academy of Pediatric Ophthalmology and Strabismus (AAPOS) Vision Screening Committee, discussed the study at the AAPOS annual meeting.

Acuity testing, sometimes combined with stereopsis, is the current standard for screening young children. While objective testing was better at finding what screeners were looking for in the recent study, primarily children who were not focusing well or misaligning their eyes, acuity testing remains a valid screening tool, Dr. Arnold said.

Ideally, amblyopia and other vision problems will be detected through a series of age-appropriate tests before children start school. However, not all children undergo these tests, and some who do may have problems that escape detection, Dr. Arnold said. As a result, schools inherit the task of identifying children with vision problems and are interested in the most effective method of screening young elementary students.

"The school question is really saying we were hoping to have caught these by now, but if we haven't, can we do a better job in the schools," Dr. Arnold explained. "School nurses are frustrated with the younger kids because many of them don't do very well on acuity testing."

Some lack the language skills to complete the test successfully, while others have never been tested and are too nervous or frightened to do well.

To explore which forms of testing would be most effective with younger elementary children, the Anchorage School District and Alaska Blind Child Discovery (a charitable project to photoscreen every Alaskan preschooler; http://www.abcd-vision.org/) instituted a study. School nurses performed patched HOTV surround acuity testing and two types of photoscreening (MTI and Gateway DV-S20) on 696 children in first grade, 710 kindergartners, and 271 children in a special-needs pre-K program.

All children were patched during screening in accordance with protocols established for childhood vision screening in the Amblyopia Treatment Studies conducted by the Pediatric Eye Disease Investigator Group.

Both students and screeners tolerated the patching well, and visual acuity data were obtained for children at all three grade levels.

After the screening images were obtained, Dr. Arnold interpreted the photos and subsequently determined positive PPVs. The PPV for total HOTV acuity was 75%, while the PPV was 83% for Gateway photoscreening and 91% for MTI photoscreening. Of the approximately 1,700 students screened, data were collected for only 234 (14%) on whom confirmatory exams had been done.

"This limits estimations of validity because very few kids who tested 'normal' on the screening were likely to have a good eye exam given no indication from the screening result," Dr. Arnold said.

To obtain a fairly reliable larger sample of outcomes from which to estimate validation statistics, the investigators devised two categories.

"We call validation estimates from the complete exams Gold Standard Exams, while we coined the term Silver Standard Exams for those with no actual comprehensive exam but rather the combination of very normal sensory and objective tests combined with the Gold Standard Exams," Dr. Arnold explained.

Testing times

Cost and time estimates for screening were also developed. The average time to test with HOTV was 143 ± 58 seconds per child (SD), 82 ± 27 seconds with MTI, and 41 ± 10 seconds with the Gateway DV-S20. The estimated cost to screen with patched HOTV was 12 cents, compared with 11 cents for Gateway and $3.75 for MTI. These costs did not include interpretation or mailed notification to parents.