We have compared the testability and acuity thresholds achieved with vanishing optotype acuity cards and traditional grating acuity cards when used to examine children with neurological impairment. These children encompass a wide range of ages and abilities and it may be desirable to use the two types of cards for acuity assessment. Subjects were a diverse group of children (n = 91; 8 months-19 years) whose learning ability ranged from normal to severe disability. There was no significant difference between the individual success rates for the two sets of cards (grating 91% (n = 61) vanishing optotype 89% (n = 59)). Over a wide range of acuities (0 to 2.0 LogMAR) the mean difference between acuity thresholds did not differ significantly from zero (p = 0.24). Ninety-three percent of acuity estimates agreed to within +/- 0.50 LogMAR units. The results indicate that the two acuity tests could be used interchangeably in clinical populations of children with neurological impairment.