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Vision 101: Instrument-Based Screening for Pre-School Aged Children

The National Center for Children’s Vision and Eye Health (NCCVEH) reports that up to 1 in 17 preschool-aged children, 1 in 5 Head Start children, and an estimated 1 in 4 school-aged children have an undetected and untreated vision disorder that can interfere with their ability to develop properly and perform optimally in school. Conducting vision screening within these age groups will detect amblyopia (wandering eye) and uncorrected amblyopia risk factors such as hyperopia (farsightedness), myopia (nearsightedness), astigmatism (imperfection in the curvature of the eye), and anisometropia (asymmetric vision).

As a result, NCCVEH recommends two options for screening children 3 to 5 years old: optotype-based distance visual acuity screening and instrument-based screening. In this blog we will discuss instrument-based screening.

What is Instrument-Based Screening?

Instrument-based screening uses automated technology to evaluate the structure of the eye for the presence of the following amblyogenic factors in one or both eyes.

  • Refractive errors: when light rays are not focused on the retina, it causes refractive errors such as myopia, hyperopia, or an astigmatism.
  • Eye misalignment: also known as strabismus (crossed eyes), when one eye looks straight while the other eye turns in, out, up or down.
  • Media (ocular) opacities: when eye problems block light from going onto the eye, leading to scarring or clouding of the cornea. In children, cataract (a clouding of the cornea) causes more visual disability than any other form of treatable blindness.

Because instrument-based screening uses automated technology, conducting an exam is easy. The screening device is held approximately 3 feet from the child who looks at an engaging display emitted by the device. Data acquisition is obtained in approximately 2 to 3 seconds and an interpretation of the results is displayed.

Note that instrument-based screening should be used for children 6 years and older only when these children cannot participate in optotype-based screening.

The Results of Instrument-Based Screening

Unlike optotype-based screening methods, instrument-based screening does not provide a measurement of visual acuity (i.e., how the brain interprets the visual signals received from the optic nerve). In other words, you can’t convert instrument-based screening results to an estimated visual acuity value (e.g., +3.00 to 20/40, etc.). Instead, most instruments capture a multitude of measurements of eye health based on an assessment of the structure of the eye. So, it’s important not to compare these approaches to how a child sees.

Early detection of vision issues can lead to an effective intervention and help to restore proper vision. Remember that young children rarely complain when they can’t see well because to them, it’s normal. That’s why screening is so important.

Additional Reading


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