The visual acuity test is the most widely used vision screening test, but use of this test alone will underrefer many patients with amblyopia and undiagnosed strabismus. Stereoscopic tests such as the random dot E stereogram are relatively inexpensive, fairly accurate, and easy to use. Stereopsis tests are complementary and offer additional information regarding a patient's visual health.
The use of photorefractive apparatus is relatively new. Reproducible results of photography of the red reflex can screen the nonverbal infant or child. The sensitivity is high (95%) for refractive error in the range of 1.00 to 2.00 diopters. A problem with this technique is that cycloplegia is usually required to prevent obtaining false-positive results, especially for myopia. In addition, two photographs are needed to avoid missing an astigmatic refractive error. The technology offers great promise, but it must be cost-effective. As newer, more rapid and accurate vision tests are developed, these may be incorporated into the screening process.
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