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Instrument Based Vision Screening
Overview and Recommendations
Instrument-based vision screening uses automated devices such as photoscreeners and autorefractors. Photoscreening uses the eye's red reflex to estimate a refractive error as well as identify other factors that put a child at risk for developing amblyopia, such as media opacity, ocular alignment, and ptosis. Autorefraction uses automated technology to estimate the refractive error of each eye. Most auto-refractors measure one eye at a time and, therefore, are limited in their ability to detect strabismus when the refractive error is normal. However, some autorefractors can measure both eyes at the same time. While vision screening devices test for eye conditions or risk factors that may cause decreased vision or amblyopia, they do not test for visual acuity.
Photoscreening and screening with handheld autorefractors may be electively performed on children as young as 6 months, allowing earlier detection of conditions that may lead to amblyopia. These instruments can be used with children unable or unwilling to cooperate with routine visual acuity screening. Photoscreening and handheld autorefraction are recommended as an alternative to visual acuity screening with vision charts from 3 through 5 years of age. Currently, instrument-based vision screening is not recommended for children older than 6 years of age who can be screened using visual acuity charts. Automated photoscreening devices and handheld autorefractors have undergone extensive validation studies in pediatric ophthalmology offices and field settings. The magnitude of refractive error and other risk factors for amblyopia development that should be detected using automated preschool vision screening devices has recently been updated and published.
These recommendations are made with the expectation that vision screening will occur several times during a child's formative years and reflect a desire for high specificity in the youngest children and high sensitivity in older children. Screening with these devices must be combined with a unilateral cover test or stereo test to ensure the most reliable detection of amblyopia risk factors.
Autorefractors and photoscreeners have software and settings that are pre-installed. When the device is turned on, the software version appears on the startup. The referral criteria settings should take into consideration:
- The child's age - younger children have higher passing thresholds.
- Sensitivity - higher detection and referral rates.
- Specificity - fewer false positives but higher chance of missing at risk children.
Screening instrument settings vary from the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) refractive risk factor target numbers used by ophthalmologists to detect refractive errors in the eye care provider office setting.
Many photoscreeners permit the user to select age-specific referral criteria AFTER consulting with a local eye care professional. The settings and software should be kept up to date and can be updated with assistance for a nominal fee, per the manufacturer.
There are no recommendations to determine which method is better for mass screenings. Visual acuity screening with a chart should still be a priority as it may catch conditions not assessed by an automated device. It is ideal to screen for visual acuity as young as possible. It should be performed as soon as a child is able to be screened using a visual acuity chart, or at least by 5 to 6 years of age, to optimize treatment for amblyopia. Visual acuity screening should also be made available upon parent or teacher request or if the child is new to a location that employs instrument-based vision screening.
MDH does not make brand/equipment-specific recommendations. This technology is rapidly evolving, and programs must make careful decisions, including staying up to date on current evidence before purchasing equipment.