Pediatric Vision Screening
Pediatric vision screening is intended to identify children with vision disorders including amblyopia (poor vision in an otherwise normal eye), strabismus (misalignment of the eyes), significant refractive error (need for glasses) or other eye abnormalities. Vision screening can be performed in the community setting, such as at health fairs, and at preschools or grade schools, as well as in the medical home, such as at the pediatrician or family doctor’s office.
Amblyopia can be caused by significant refractive error, misalignment of the eyes (strabismus), or deprivation (anything that blocks a clear image from reaching the retina). Causes of deprivation amblyopia include visually significant ptosis (droopy eyelid), cataract, or other media opacities. Amblyopia is potentially reversible with appropriate treatment in childhood, and it is generally believed that the earlier amblyopia risk factors are identified, and the earlier amblyopia treatment is initiated, the more likely the child will develop normal vision. Treatment requires proper identification of the etiology, appropriate treatment, and occlusion therapy. Left untreated, amblyopia can lead to a permanent reduction in vision in one or both eyes and is the leading cause of vision loss in adults under the age of 40.
There are a variety of forms of pediatric vision screening methods available, depending on the age of the child requiring screening, the environment in which screening is being performed, and the amount of money available to invest. Regardless of the type of screening method chosen, one of the keys to a successful pediatric vision screening program is to ensure that children who have been identified as having potential amblyopia risk factors receive a complete pediatric ophthalmology examination including a formal alignment exam, a dilated fundus examination, and a dilated (cycloplegic) refraction .
The American Association for Pediatric Ophthalmology and Strabismus has devised standards for comparing pediatric vision screening methods. These guidelines are set against a child’s cycloplegic refraction performed by a pediatric ophthalmologist in order to determine if the child’s vision screening should have prompted a referral to a pediatric ophthalmologist, or if they should have passed the screening.
Types of Pediatric Vision Screening
Subjective screening requires significant participation from a child to identify optotypes such as letters and shapes. It is most effective in verbal children age 5 and older, but may be attempted in younger verbal children. Subjective screening includes various forms of visual acuity testing, see below.
Pediatric vision screening with acuity measurements is the most widely used method. See Visual acuity assessment in children for more details. This method is inexpensive, but can be difficult to execute properly. The testing distance can vary from 3 – 20 feet and it is critical that the child be tested at the appropriate distance for the chart. It is also important that an appropriate eye chart be selected. Available optotypes include Snellen, Sloan, HOTV, Lea symbols and Patti Pics. The optotypes should be presented in a line, or as single letters with crowding bars, as isolated optotypes often over-estimate vision due to the crowding phenomenon. The child should be seated comfortably in a chair or on their parents lap, and encouraged not to lean forward, if possible. The testing distance should be measured from the child’s face to the eye chart, but even if this distance is imprecise, a subjective screening value can still give useful information, especially in the setting of asymmetry between each eye. A hand should be avoided as a monocular cover, as peeking around the cupped palm, or through fingers is common. The best method is to use a stick on eye patch or large fogged or solid occluder. Regardless of the method of occlusion, it is important that the examiner pay close attention that the child is not peaking from the side of the patch or holding/turning their head sideways. Another alternative is pediatric occlusion glasses, which have a large black plastic over one eye, and large foam animal shapes around the edges making peeking nearly impossible.
Computerized visual acuity testers are also available including: Vision Quest 20/20, Innova and M&S. These devices automate the testing protocol and are performed utilizing a computer monitor. Vision Quest is fully automated and uses crowded HOTV letters in a matching game disguised as a video game.
Objective screening requires less input from children and is faster. With objective screening techniques, the child merely needs to focus on a device long enough for the machine to obtain a measurement.
There are a number of autorefractors which can be used to evaluate for amblyopia risk factors. Most of these tests are done monocularly and therefore do not screen for strabismus. These devices are used on undilated eyes and will give the user an estimation of the child’s refractive error. Based on pre-determined referral criteria, as noted above, the device or examiner can quickly determine if the child passed the screening or should be referred for further evaluation by a pediatric ophthalmologist for a cycloplegic refraction and comprehensive examination. The advantage to autorefractive screening is that it can be performed not only on verbal children, but on pre-verbal and non-verbal children as well. It is also much faster than subjective acuity screening.
Current available autorefractors used for pediatric vision screening include: Grand Seiko binocular autorefractor, Retinomax and the SureSight. While the SureSight is specifically marketed as a vision screening device, both the Retinomax and SureSight auto refractors were validated in the Vision in Preschoolers Study (VIPS).
Photoscreeners take images of the corneal light reflex from a child’s pupil. The test is performed binocularly and is based on the reflexes an examiner or a computer program can analyze to determine if there is strabismus and/or significant refractive error, or anisometropia (unequal refractive error). Photoscreeners can also detect other anatomical abnormalities, including cataract, coloboma or ptosis due to the change in the appearance of the red reflex. Unlike autorefrefractive screening, it can directly screen for manifest strabismus. The test can be performed on both verbal and pre-verbal children, and again, is much faster than acuity screening.
Although hypothetically a photoscreener could also detect leukocoria as a potential sign of retinoblastoma, this would represent a late finding in retinoblastoma as small peripheral tumors would be missed.
Current available photoscreeners include: iScreen, MTI, plusoptiX, Spot, and Visiscreen. The MTI photoscreener, iScreen and Visiscreen use a visible light flash while PlusoptiX and Spot utilize infrared light, which is not visible to the child.
Visual Evoked Potential/Response (VEP/VER)
There is currently one device available from Diopsys which estimates visual acuity, or the difference in visual acuity between two eyes utilizing a sweep VEP. The machine analyzes the results and gives the user a pass/refer result.
Polarized laser scan
In contrast to the above photoscreening devices, a new technology created by Rebion, called the blinq™ pediatric vision scanner, utilizes a polarized laser scan that probes retinal nerve fibers to detect small angle strabismus, and thereby small misalignment of the foveas, which can identify essentially 100% of children who have amblyopia, with fewer false positives compared with photoscreeners. It is an easy to use device, typically held approximately 14 inches from the child’s eyes. While the child fixates on a smiley face, the device simultaneously scans both retinas in 2.5 seconds, with the capacity to detect up to one-degree of misalignment between the foveas, which correlates closely with the presence of amblyopia. A binocularity score is generated inicated the likelihood that the child requires referral to a pediatric ophthalmologist. In a study of this device published summer 2021, an earlier model of the blinq™, the Pediatric Vision Scanner yielded a sensitivity rate of 100% (95% CI, 54%-100%), and a specificity rate of 85% (95% CI, 80%-89%), with a median acquisition time of 28 seconds. The newest model of this scanner, blinq™, has been cleared by the U.S. Food and Drug Administration, and received funding from the National Eye Institute. It was studied in a prospective cross-sectional diagnostic accuracy study of 200 patients age 1-20 years, and found to have 100% sensitivity, and 91% specificity for detecting referral warranted amblyopia and strabismus, with a subanalysis of children age 2-8 years providing similar results.
Artificial intelligence may play a role in vision screening in the future. A smartphone based deep learning system has been shown to identify visual impairment in young children with various etiologies, including anisometropia, strabismus, cataracts, congenital abnormalities, and potentially other structural abnormalities. 
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- American Association for Pediatric Ophthalmology and Strabismus
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