Repeatability of Monocular Acuity Testing in Adults with and without Down Syndrome

Abstract

Purpose: Individuals with Down syndrome may experience greater difficulty reliably performing visual acuity (VA) tests because of intellectual disability and limitations in visual quality. This study evaluated the repeatability of acuity (Bailey-Lovie [BL] and HOTV) in subjects with and without Down syndrome.

Methods: High-contrast VA was measured in both eyes of 30 subjects with Down syndrome (mean, 30 years; range, 18 to 50 years) and 24 control subjects without Down syndrome (mean, 29 years; range, 18 to 50 years). In the Down syndrome group, 23 subjects performed BL, and 7 subjects performed HOTV. All control subjects performed both BL and HOTV, but for HOTV analysis, only seven age-matched control subjects were included. For each eye, subjects performed VA three times on different charts (computer controlled, single-line display) until five total letters were missed on each chart. A repeated-measure ANOVA was used to compare the acuity measures between groups.

Results: The average logMAR VA for subjects with Down syndrome was approximately six lines worse than the control subjects (BL: Down syndrome = right eye: 0.51 ± 0.16, left eye: 0.53 ± 0.18; control = right eye: -0.06 ± 0.06, left eye: -0.06 ± 0.08, P < .0001; HOTV: Down syndrome = right eye: 0.47 ± 0.19, left eye: 0.46 ± 0.16; control: right eye = -0.11 ± 0.09, left eye: -0.07 ± 0.07, P < .001). Bailey-Lovie VA repeatability (1.96 * Sw * √2) was 0.13 logMAR (6.5 letters) for Down syndrome and 0.09 logMAR (4.5 letters) for control subjects. HOTV VA repeatability was 0.16 logMAR (eight letters) for both Down syndrome and control subjects.

Conclusions: Despite poorer acuity in individuals with Down syndrome, repeatability of VA measurements was comparable to control subjects for both BL and HOTV techniques.

Figure 1

Average Bailey Lovie visual acuity (BL VA (1A)) with error bars representing ±2 SD for each eye (RE = right eye, LE = left eye) of controls and subjects with Down syndrome (DS). 3B shows the absolute inter-eye difference of the average BL VA for each subject.

Figure 2

Average HOTV visual acuity (2A) for each eye (RE = right eye, LE = left eye) and the absolute inter-eye difference of the average Bailey Lovie visual acuity (BL VA in subjects with Down syndrome (DS) and controls (4B).

Figure 3

The individual standard deviation of three repeated measures of Bailey Lovie (BL) and HOTV visual acuity plotted as a function of average logMAR acuity (A & B) and age (C & D) for both subjects with Down syndrome (DS) and Controls. There is no significant trend with age or average logMAR acuity.

Figure 4

The distribution of unaided spherical equivalent refractive error (A) and cylinder magnitude (B) obtained with distance autorefraction for each eye (Right eye = OD, Left eye = OS) in controls and subjects with Down Syndrome (DS) for those performing BL. Solid lines represent median values, box boundaries represent 25th and 75th percentiles, and whiskers represent 10th and 90th percentiles. Dots represent outliers beyond the 10th and 90th percentiles. *p < 0.001.

Figure 5

The distribution of unaided spherical equivalent refractive error (A) and cylinder magnitude (B) obtained with distance autorefraction for each eye (Right eye = OD, Left eye = OS) in controls and subjects with Down Syndrome (DS) for those performing HOTV. Solid lines represent median values, box boundaries represent 25th and 75th percentiles, and whiskers represent 10th and 90th percentiles. *p≤0.03.