Induced Tropia Test and Visual Acuity Testing in Nonverbal Children

ABSTRACT

The objective of our study was to compare the Cardiff Acuity Card© test (CAC test) (Kay Pictures Ltd) with the induced tropia test (ITT) in nonverbal children for the detection of monocular vision deficit.

This is a retrospective case note review of 34 nonverbal children, aged 12–48 months, attending the pediatric ophthalmology clinic at Children’s Hospital of Pittsburgh of UPMC between October 2014 and January 2015. 30/34 were included for analysis. Binocular visual acuity and monocular visual acuity were tested at 50cm in 30 and 17 patients, respectively. At 100cm, binocular visual acuity and monocular visual acuity were tested in 16 and 11 patients, respectively. All 30 children had successful induced tropia testing; 21 had no fixation preference and 9 had a fixation preference. Of those that had no difference on monocular visual acuity, five had a fixation preference at 50cm and three at 100cm. Out of 21 that had no fixation preference, 3 had a monocular visual acuity difference, but of only one line.

Our study suggests that to obtain as much information as possible without losing the interest or cooperation of the child, it may be more beneficial to perform the CAC test with both eyes open, followed by ITT, before attempting monocular visual acuity testing with the CAC test. Obtaining visual information using ITT was much more attainable compared to monocular CAC testing. The sensitivity using CAC test to find a visual acuity discrepancy is 40% using ITT as the standard, and the specificity is 63%. If one loses the interest of the child after the ITT, at least some information will have been gleaned rather than none about monocular visual behavior. This provides a more complete, attainable approach to gathering visual information.

KEYWORDS:

• Cardiff acuity cards
• induced tropia test
• fixation preference