Perelman School of Medicine at the University of Pennsylvania

Center for Preventive Ophthalmology and Biostatistics (CPOB)

Vision In Preschoolers (VIP) Study

Vision in Preschoolers (VIP) StudyThe Vision in Preschoolers Study (VIP) is a prospective, multi-center, multi-year, multi-phased cross-sectional interdisciplinary clinical study to establish accuracy of tests used to screen for significant and prevalent vision disorders among 3- and 4-year-old preschoolers.  VIP is conducted in 5 clinical centers and in two resource centers and is funded by the National Eye Institute, part of the National Institutes of Health.  The CPOB serves as VIP Coordinating Center.

What is the goal of the VIP Study and why is VIP important?

The goal of the VIP Study is to determine whether a single vision screening test or a combination of tests can be used effectively to determine which 3- and 4-year-old preschoolers would benefit from a comprehensive eye examination to detect VIP-targeted conditions: Amblyopia, Strabismus, and Significant Refractive Error.

The most common handicapping disorders in childhood are vision disorders, including amblyopia, strabismus, refractive error, ocular disease and color vision defects.  Early detection and treatment of the first four of these disorders can potentially prevent vision loss and/or reduce their negative impact during childhood and later in life.  It is estimated that up to 15 percent of all preschool children between the ages of three and five have an eye or vision condition.  Many parents are unaware that their child has an eye problem because vision problems do not hurt and children do not know how they should see.  Eye disease or vision problem if undetected and left untreated can result in reduced vision and hinder child’s ability to learn.

What are Amblyopia, Strabismus, and Significant Refractive Error?

  • Amblyopia is reduced visual acuity in one or both eyes not improved solely with refractive error correction (i.e., prescription glasses) and not attributable to other structural abnormalities.  This condition is also sometimes called lazy eye and occurs when the vision in one of the eyes is reduced because the eye and the brain are not working together properly.  The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye.  Amblyopia is the most common cause of visual impairment in childhood.  The condition affects approximately 2 to 3 out of every 100 children.  Unless it is successfully treated in early childhood, amblyopia usually persists into adulthood, and is the most common cause of monocular (one eye) visual impairment among children and young and middle-aged adults.
  • Strabismus is an “eye misalignment” or inability to direct the two eyes in the same direction simultaneously.  Strabismus (prevalence 3-4%) can result in amblyopia and poor to absent binocular function.  Most strabismus develops in early childhood and some types may not be cosmetically obvious. Detection of strabismus is especially important in young children because of its strong association with amblyopia.  Success rates for treatment of strabismus in young children are 60–90%, depending on the type of strabismus and associated conditions.
  • Refractive Error affecting up to 20% of young children, occurs when light entering the eye is not precisely focused on the retina, causing blurred vision.  Refractive errors are the most easily corrected vision disorder.

Each of the following is the Refractive Error category:

  • Anisometropia is an unequal spherical or cylindrical refractive error between the two eyes, usually defined as more than a 1-diopter difference.
  • Astigmatism is an optical defect in which refractive power is not uniform in all directions (meridians).  Light rays entering the eye are bent unequally by different meridians, which prevent formation of a sharp image focus on the retina due to the presence of an elliptical (egg- or football-shaped) rather than spherical shape of the refracting surfaces of the eye.  Slight uncorrected astigmatism may not cause symptoms, but a large amount may result in significant blurring and headache.
  • Hyperopia (farsightedness) occurs when light enters the eye and the point of focus is behind the retina which results in blurred vision.  The hyperopic eye is not able to see the objects that are nearby.
  • Myopia (nearsightedness) occurs when light enters the eye and the point of focus is in front of the retina which results in blurred vision.  The myopic eye is not able to see the objects that are far away.

Accurate and efficient identification of preschool children with vision disorders has a significant impact on visual outcome.  Healthy vision is an important part of a child’s success in school because a great deal of classroom instruction is conveyed visually through books, computer screens, and chalkboards.

VIP Study Design

VIP is a prospective, multi-center, multi-year, multi-phased cross-sectional interdisciplinary clinical study.  During the Phase I of the Study, licensed optometrists and ophthalmologists compared eleven commercially available screening tests for diagnosing eye disorders in children.  They tested 2,588 children in a mobile van specially designed with four vision screening rooms.  They also gave each child a full eye examination using established diagnostic examination procedures and tests.

For the Phase II of the Study, nurses and lay screeners administered four vision screening tests to 1,452 children at the Head Start centers.  Nurses and lay screeners screened all children who had failed a basic Head Start vision screening and a random sample of those children who passed the screening.  The screening tests included two hand-held automated refractors to measure refractive error (e.g., nearsightedness, farsightedness, or astigmatism), two versions of a test of visual acuity in which the children name or match symbols at a 5 or 10 foot test distance and a test for depth perception in which the children point to 3-dimensional image.  The four tests were selected based on the results from Phase I for their superior performance to detect the VIP-targeted conditions.  All children screened also received a comprehensive eye examination by a licensed eye care professional in a specially equipped vision van at the child’s Head Start Center.

Planning is now underway for the Phase III of the VIP Study.

Study Aims

VIP’s primary outcome measure is the screening test sensitivity and specificity in detecting at least one of the VIP-targeted conditions.

Description of the VIP Procedures  Children between 3 and 5 years of age who were enrolled in Head Start programs, and more than half of whom had failed Head Start vision screening, were screened for the VIP-targeted conditions (Amblyopia, Strabismus, and Significant Refractive Error) using various testing devices.

In Phase I, Licensed Eyecare Professionals (optometrists and pediatric ophthalmologists) completed training and certification procedures for administering commonly used and/or commercially available vision screening tests for preschool children.  In the first year, 1142 children were screened by non-cycloplegic retinoscopy, the Retinomax autorefractor, the Lea Symbols visual acuity test, HOTV visual acuity test, the Random Dot E stereoacuity test, and the unilateral cover test.  In the second year, 1446 children were screened by the SureSight autorefractor, the Retinomax autorefractor, the MTI Photoscreener, the iScreen Photoscreener, the PowerRefractor II video/photoscreener, and the Stereo Smile stereoacuity test.  All children received a standardized, comprehensive eye examination by LEPs who were masked to the screening results.  These results were used to classify children as normal or having one or more of the 4 targeted conditions: amblyopia, strabismus, significant refractive error, and unexplained reduced VA.

In Phase II, Pediatric Nurses and Lay Screeners after formal training and certification, administered the Retinomax Autorefractor, SureSight Vision Screener, Lea Symbols linear visual acuity (VA) test at 10 feet, and Stereo Smile II test, following similar protocols.  Lay screeners also administered an isolated Lea Symbols VA test at 5 feet.  Screening results were compared to results from a standardized eye examination that was used to classify children with respect to 4 conditions: amblyopia, strabismus, significant refractive error, and unexplained reduced VA.

Click on the links to view VIP Phase II protocols and data collection forms.

VIP Publications:

Click here for a list of VIP publications and presentations to date.

CPOB's Role in VIP

CPOB serves as the Coordinating Center for the VIP Study.  Click on the links to learn more about the services of the Coordinating Center.