Take-Home Message: Physicians should focus on referral criteria in screening technology rather than the instrument itself.
Nashville—New screening technologies have revolutionized the early detection of amblyopia, by allowing children to be screened long before they are able to cooperate with reading an eye chart.
These instruments—photoscreeners and autorefractors—work by detecting risk factors for amblyopia (anisometropia, high bilateral hyperopia and astigmatism, and strabismus) rather than amblyopia itself.
Another advantage is that the instrument software can be customized based on the age of the patient or the desired sensitivity or specificity, by altering the referral criteria the package uses.
The most important factor, according to Sean P. Donahue, MD, PhD, is not what instrument should be purchased but the referral criteria put into the instrument in order to appropriately refer children. Dr. Donahue is professor of ophthalmology, neurology, and pediatrics, Vanderbilt University Medical Center, and chief, Pediatric Ophthalmology, Vanderbilt Children’s Hospital, Nashville.
Four types of refractive screening instruments are available:
- Off-axis photoscreeners,
- Automated refractors,
- Retinal birefringence, and
- Visual-evoked potentials.
Of these, the first two devices are the most commercially available.
MTI (Medical Technologies & Innovations, Inc.), the oldest and the primary example of these instruments, was based on an analogue picture. The fundamental concept was a linear flash away from the visual axis. By evaluating how the flash returned from the retina, clinicians were able to interpret the possible refractive error and strabismus because the flash was out of focus in a nonemmetropic eye, Dr. Donahue explained.