Original article
Visual Acuity Deficits in Children With Nystagmus and Down Syndrome

https://doi.org/10.1016/j.ajo.2013.09.023Get rights and content

Purpose

To investigate the association between visual acuity deficits and fixation instability in children with Down syndrome and nystagmus.

Design

Prospective cross-sectional study.

Methods

setting: Institutional. study population:Sixteen children (aged 10 months-14 years) with Down syndrome and nystagmus, and a control group of 93 age-similar children with unassociated infantile nystagmus. observation procedures: Binocular Teller acuity card testing and eye-movement recordings. Fixation stability was quantified using the nystagmus optimal fixation function (NOFF). An exponential model based on results from the control group with unassociated infantile nystagmus was used to relate fixation stability to age-corrected visual acuity deficits. main outcome measures: Binocular grating visual acuity and NOFF.

Results

Visual acuity was 0.2-0.9 logMAR (20/30-20/174 Snellen equivalent) and corresponded to a 0.4 logMAR (4 lines) mean age-corrected visual acuity deficit. Fixation stability ranged from poor to mildly affected. Although visual acuity deficit was on average 0.17 logMAR larger (P = .005) than predicted by the model, most children had visual acuity deficit within the 95% predictive interval.

Conclusions

There was a small mean difference between the measured visual acuity deficit and the prediction of the nystagmus model. Although other factors also contribute to visual acuity loss in Down syndrome, nystagmus alone could account for most of the visual acuity deficit in these children.

Section snippets

Methods

The research protocol and informed consent form for this cross-sectional study were approved by the Institutional Review Board of the University of Texas Southwestern Medical Center. Written informed consent was obtained from a parent or legal guardian for each participant. This study was performed in accordance with the US Health Insurance Portability and Accountability Act.

Results

Visual acuity in the 16 children with Down syndrome and nystagmus spanned a large range from 0.2-0.9 logMAR or 20/30-20/174 Snellen equivalent (mean 0.58 logMAR, 20/76) with no association with age (linear regression, P = .15). The mean visual acuity deficit with respect to age-matched norms was 0.40 logMAR (Figure 1), or 4 lines poorer than mean normal.

Inspection of the eye-movement recordings obtained under binocular viewing conditions showed infantile nystagmus-type waveforms (pendular [n =

Discussion

Using a behavioral testing method that poses only limited demands on the child's cognitive and motor skills,7, 8 we found mild to moderate visual acuity deficits in this group of children with Down syndrome and nystagmus averaging approximately 4 lines below age-adjusted mean normal; all but 3 scored outside of the normal limits for their age. The number of participants in this sudy was small but spanned a wide age range throughout childhood, thus providing cross-sectional evidence of visual

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