Is the Cardiff Acuity Test effective in detecting refractive errors in children?

Refractive error is a common cause of reduced visual acuity in young children. This reduced vision should be detected as soon as possible to avoid development of squinting and educational disadvantage. The Bailey-Lovie Chart (BLC) is based on the logarithm of the minimal angle of resolution (logarithm of the minimum angle of resolution logMAR) and is widely accepted as the clinical standard for visual acuity testing. However, most young children are unable to perform this test because of its symbolic level. The Cardiff Acuity Test (CAT) overcomes these symbolic demands and is the test of choice for young children in most U.K. orthoptic departments. The purpose of this study is to determine how effective the CAT is in detecting reduced visual acuity caused by refractive error in young children.

Visual acuity of the right eye was tested without spectacles in 68 children (mean age, 74 +/- 14.6 months) with known bilateral symmetric refractive error (40 male) using the CAT and the BLC. Subjects were randomized to receive CAT or BLC first in a single assessment using a crossover design. Subjects scoring 0.2 logMAR or better were classified as having passed the test.

The CAT correctly identified reduced vision caused by uncorrected refractive error in 25% (17) of the children compared with a detection rate of 97% (66) for the BLC using the specified pass criteria. Further analysis with an adjusted cut point for the CAT (0.0 logMAR), as used to identify abnormal vision in clinical practice, identified a detection rate of 56% (38 of the children).

This study casts doubt on the current clinical practice used in orthoptic clinics by suggesting that assessment of visual acuity with the CAT alone will underdiagnose reduced acuity caused by refractive errors.