Fixation preference testing (FPT), the current clinical standard vision test for preverbal children, may not accurately identify either the presence or absence of visual acuity defects, according to a recent study in Ophthalmology.1
As part of the Baltimore Pediatric Eye Disease Study, 1,504 children aged 30 to 71 months were evaluated for decreased visual acuity.2 The researchers employed more than a dozen diagnostic examinations, including FPT, simultaneous prism and cover testing, Hirschberg and modified Krimsky testing, and monocular visual acuity testing in accordance with the Ambylopia Treatment Study protocol. After testing was completed, only 1.2% of the white children and 1.8% of the black children demonstrated decreased visual acuity O.U. when compared to accepted age-based vision standards. The main cause of decreased visual acuity was uncorrected ametropia.
Most importantly, however, the researchers determined that FPT yields unreliable data when compared to results from the other vision examinations; FPT accurately identified only 15% of children with two lines or more of interocular difference in presenting visual acuity. The clinical value of FPT was poor in this study, and its use for diagnosing visual acuity defects in children should be reconsidered, the researchers concluded.
1. Friedman DS, Katz J, Repka MX, et al. Lack of concordance between fixation preference and HOTV optotype visual acuity in preschool children. The
2. Friedman DS, Repka MX, Katz J, et al. Prevalence of decreased visual acuity among preschool-aged children in an American urban population. The Baltimore Pediatric Eye Disease Study, methods and results. Ophthalmology 2008 Jun 4. [Epub ahead of print].