Use of Lea symbols in young children
- Johns Hopkins University School of Medicine, 233 Wilmer, Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287–9028, USA
Clinicians must continue to refine as well as develop new visual acuity tests for preschool children
A ccurate measurement of visual acuity is fundamental to ophthalmological care for all ages. This measure is used for diagnosis, for documentation of clinical outcomes, for qualification for special education or disability programmes, and for permission to drive a motor vehicle. More than 20 years ago the importance of ensuring that such a measure be scientifically rigorous was recognised with the development of the Bailey-Lovie visual acuity test1 and the Early Treatment of Diabetic Retinopathy Study (ETDRS) test derived from it.2 The ETDRS test incorporated important design elements including letter selection, proportional optotype spacing, standard illumination, methods of administration, and scoring. Despite the quality of this test for school age children and adult patients, it is too difficult for preschool children.
Clinicians testing visual acuity of preschool children have not yet found a single best test. An accurate, reproducible, and highly testable measure is needed by the paediatric eye care community for screening and office testing. Practitioners have utilised an assortment of test chart configurations with letter, number, and picture optotypes. Letter optotypes have generally been too difficult for preschool children, while traditional picture optotypes, like the Allen pictures, though much more testable, substantially reduce the sensitivity of the test for the detection of amblyopia.3,4 This is a critical drawback since amblyopia is the most common reason to test visual acuity in this age group. In addition, the practitioner has individualised most testing with plenty of room for the art of administration, including the judicious use of second chances.
An ideal test of visual acuity in early childhood should include as many of the design features of the ETDRS as possible. Using the same test optotypes and presentation strategy throughout …
