Vision In Preschoolers Study (VIP Study)

To identify whether vision-screening tests can accurately identify preschool-aged children who would benefit from a comprehensive vision examination because of signs of amblyopia, strabismus, and/or significant refractive error.

Vision disorders are the fourth most prevalent class of disability in the United States and the most prevalent handicapping conditions in childhood. Early detection increases the likelihood of effective treatment and allows for actions to decrease the negative impact of the disorders. However, fewer than 15 percent of all preschool children receive an eye examination. Fewer than 22 percent of preschool children receive some type of vision screening. The methods for vision screening vary tremendously and the effectiveness of the methods in appropriately identifying children has not been documented. Amblyopia (2-5%), strabismus (3-4%), and significant refractive error (10-15%) are the prevalent and significant vision disorders of preschool-aged children.

The Vision In Preschoolers (VIP) Study is a multi-phased, multi-center, interdisciplinary, clinical study to evaluate the accuracy of screening tests used to identify preschool-aged children in need of further evaluation for vision disorders. The primary goal of the VIP Study is to determine whether there are tests or combinations of tests that can be used effectively to determine which preschoolers would benefit from a comprehensive eye examination to detect amblyopia, strabismus significant refractive error, and/or reduced visual acuity.

Phase I (Years 1 and 2) was conducted over a two-year period. Phase I activities established which screening tests performed well when administered by licensed eye care professionals (optometrists and ophthalmologists experienced in the care of children) in a population of over 2,500 Head Start preschoolers (at least 1,000 children per year) at high risk for the targeted vision disorders. Year 2 activities included evaluation of the performance of some commercially-available technology-based screening tests when administered by licensed eye care professionals in mobile vans. Year 2 activities also included evaluation of whether a selected set of tests was amenable to administration by lay screeners.

Phase II was conducted over one year. Phase II activities compared pediatric nurses and lay people as screeners in administering screening tests on a high-risk population of nearly 1,500 Head Start preschoolers. Each child was tested twice with each screening test - once by a pediatric nurse and once by a lay screener. Tests selected for Phase II were determined by the outcome of Phase I. Screening was conducted in the Head Start centers.

Phase III activities are currently under development.

Description of Phase I

Phase I of the VIP Study provided estimates of the sensitivity and specificity of each of 11 screening tests and selected combinations of tests for detecting one or more of three targeted conditions (amblyopia, strabismus, and/or significant refractive error) when the tests were conducted by licensed eye care professionals. Further, information on the most appropriate age-specific pass/fail criteria for tests was obtained during this phase.

In addition to completing the screening procedures, each child underwent a comprehensive eye examination by a licensed eye care professional who was masked to the results of the screening. Data collected during this eye examination was used as the gold standard with respect to the absence or presence of the conditions targeted for detection. All screenings and eye examinations were conducted in the mobile vans especially designed for the VIP Study.

The 11 screening tests used in Phase I of the VIP Study were:

• Lea Symbols Visual Acuity Test (Precision Vision)
• HOTV Symbols Visual Acuity Test (Precision Vision)
• Random Dot E Stereoacuity Test (Stereo Optical) Stereo Smile Test II (Stereo Optical)
• Cover-Uncover Test
• Noncycloplegic Retinoscopy
• Retinomax 2 Autorefractor (Nikon)
• iScreen (Digital Vision Screening Technology)
• MTI Photoscreener (Medical Technologies Inc.)
• PowerRefractor II (plusoptiX)
• SureSight Vision Screener (Welch Allyn)

Additional tests administered by lay screeners in Year 2 were:

• Lea Symbols Visual Acuity Test at 3 m or 10 feet (Precision Vision)
• Stereo Smile Test II (Stereo Optical)

The results of Phase I indicated that the proportion of children testable was >99% for the majority of the 11 tests evaluated. Further, screening tests, even when administered by licensed eye care professionals, vary widely in performance. The four best tests, non-cycloplegic retinoscopy, Retinomax Autorefractor, SureSight Vision Screener, and Lea Symbols visual acuity test performed similarly and detected two thirds of children having ≥1 targeted conditions, but nearly 90% of children with the most severe conditions. Two static photoscreeners were less accurate than the 3 tests that assess refractive error in other ways.

In Phase II of the VIP Study, tests in need of further evaluation were used by pediatric nurses and lay screeners to determine if these tests were amenable to administration by personnel with less training than licensed eye care professionals. Screenings took place at the Head Start centers, in more realistic screening environments than the VIP vision van.

The 4 screening tests used in Phase II of the VIP Study were:

• Lea Symbols Visual Acuity Test (2 versions; Good-Lite Company)
• Stereo Smile Test II (Stereo Optical)
• Retinomax 2 Autorefractor (Right Manufacturing Inc.)
• SureSight Vision Screener (Welch Allyn)

Each child was screened on each of these tests twice, once by a pediatric nurse screener and once by a lay screener. As in Phase I, all children completing the screening tests underwent a comprehensive eye examination by a licensed eye care professional masked to the results of the screening. Data collected during the eye examination were used as the gold standard with respect to the absence or presence of the conditions targeted for detection.

The results of Phase II indicated that trained nurses and lay people were able to correctly identify up to 68 percent of children with at least one of the most prevalent vision disorders of childhood: amblyopia, strabismus, refractive errors or reduced visual acuity not associated with any obvious disorder. These results demonstrated that trained lay people and nurses can achieve similar results when using specific tests to screen preschool children for vision disorders. Further, the results demonstrated that trained nurses and lay screeners achieved similar accuracy rates administering the two automated refractors. Nurses correctly identified up to 68 percent of children with vision disorders while lay screeners correctly identified up to 62 percent of these children. Using these hand-held instruments, nurses and lay screeners correctly identified more than 80 percent of children with conditions considered most severe. Using Lea Symbols visual acuity charts displaying several symbols at one time at a distance of 10 feet, nurses and lay screeners were not able to correctly identify as many children with vision disorders. However, when lay screeners administered a simpler version of the symbols visual acuity test at a distance of five feet, they correctly identified 61 percent of children with vision problems. Nurses and lay screeners identified about the same percentage of children with vision problems (45 percent versus 40 percent) using the test of depth perception (Stereo Smile Test II).

Children enrolled in Head Start were eligible to participate in Phases I and II of the VIP Study. All children who had failed a basic Head Start vision screening and a random sample of those children who passed the screening were enrolled.

No longer recruiting. Comments: Recruitment for Phases I and II is complete. Recruitment for Phase III has not yet begun.

Ongoing. Comments: Ongoing. Comments: Phase I and Phase II data collection is complete. In Year 1 of Phase I (2001-2002) 1,379 children were registered into VIP, 1,257 were screened and 1,195 received a comprehensive (Gold Standard) eye examination. In Year 2 of Phase I (2002-2003), 1,724 children were registered into VIP, 1,523 were screened and 1,471 received a comprehensive (Gold Standard) eye examination. In Phase II (2003-2004) 1,635 children were registered into VIP, 1,541 were screened and 1,475 received a comprehensive (Gold Standard) eye examination.

Overview of Findings from Phase I

The study results from Phase I showed that the 11 screening tests, when administered by highly trained personnel in a controlled environment, vary widely in their performance for detecting children who have amblyopia, strabismus, refractive error, and/or reduced visual acuity and who could benefit from a comprehensive eye examination.

With specificity set at 90%, sensitivities for detecting children with any VIP targeted condition were highest, and approximately equivalent for noncycloplegic retinoscopy (64%), Retinomax Autorefractor (63%), SureSight Vision Screener (63%), and Lea Symbols visual acuity testing (61%) among the 11 screening tests evaluated.

Furthermore, when the sensitivity for detecting children with conditions considered the most important to detect was examined, these same 4 tests performed best: noncycloplegic retinoscopy (90%); Retinomax Autorefractor (87%); SureSight Vision Screener (81%); and Lea Symbols visual acuity testing (77%).

Detection of children with amblyopia and detection of children with significant refractive error were most accurate when tests of refractive error were used, while most of the 11 tests showed similar accuracy for detection of children with strabismus.

The tests that use static photorefraction (iScreen and MTI Photoscreener) were less accurate than noncycloplegic retinoscopy, the Retinomax Autorefractor, and the SureSight Vision Screener.

General Summary of Findings from Phase I

When the best tests were used by highly skilled personnel (optometrists and ophthalmologists experienced in working with young children), approximately two thirds of children with one or more VIP targeted disorders and 90% of those children with the most important conditions were identified, while referring 10% of normal children for an eye examination (90% specificity).

Overview of Findings from Phase II

The study results from Phase II showed that pediatric nurse and lay screeners can achieve similar sensitivity for detecting preschool-aged children in need of a comprehensive eye examination when specificity is set at 90%. Results from the Lea Symbols VA test are influenced markedly by test distance and presentation format (isolated symbols vs linear array). Combining the results of Lea Symbols VA testing with those of Stereo Smile II testing did not result in greater sensitivity than for the Lea Symbols VA test alone when specificity was 90%.

With specificity set at 90%, nurse screeners achieved values of sensitivity with the Retinomax Autorefractor, SureSight Vision Screener, and Stereo Smile II test that were slightly higher that those achieved by lay screeners; however, most of the differences were not statistically significant.

Nurse screeners achieved significantly higher sensitivity values with the Linear Lea Symbols VA test than did lay screeners.

The lay screeners achieved higher values of sensitivity with the Isolated Lea Symbols VA test than was achieved by nurse or lay screeners using the Linear Lea Symbols VA test.

Nearly all children (>98%) were testable on each screening test, regardless of type of screener indicating the tests are appropriate for use with preschool-aged children.

Pediatric nurse and lay screeners required similar amounts of time to perform each test.

Combining the results of the Stereo Smile II test with those of the Lea Symbols VA tests did not improve sensitivity over that of the Lea Symbols VA test alone.

General Summary of Findings from Phase II

Specially trained pediatric nurse and lay screeners performed effectively when using selected vision screening tests to identify preschool-aged children in need of a comprehensive eye examination. They performed similarly and were able to detect up to 68% of children with at least one of the most prevalent conditions (with 90% specificity).