The developmental eye movement (DEM) ratio fails to detect fixation and saccade abnormalities among children with nystagmus, and cannot be used to detect true eye movement disorders, according to a study published in Optometry and Vision Science. However, it is instrumental in diagnosing cerebral visual impairment (CVI), according to the report.
Investigators enrolled 157 participants in the analysis consisting of children with (n=28) and without (n=129) nystagmus. Among participants without nystagmus, 94 were normally sighted, 13 had ocular visual impairment, and 22 had CVI. The cohort of children with nystagmus consisted of patients with infantile nystagmus syndrome ([INS]; n=20), CVI (n=2), or fusion maldevelopment nystagmus syndrome ([FMNS]; n=6). A total of 5 children with ocular visual impairments and nystagmus had albinism. All participants underwent DEM testing, and values were compared between children with and without pathological nystagmus.
Presenting visual acuity (VA) varied among the groups. Normally sighted children had a mean VA of -0.23±0.08 logarithm of the minimum angle of resolution (logMAR), children with ocular visual impairments had a VA of 0.38±0.23 logMAR, and those with CVI had a VA of 0.17±0.25 logMAR.
The report shows that vertical times for the DEM were significantly influenced by age (t, -6.32; P <.001), ocular visual impairments (t, 3.32; P =.001), and CVI (t, 5.83; P <.01). Horizontal times were also influenced by age (t, -7.87; P <.001), ocular visual impairments (t, 2.17; P =.03), and CVI (t, 6.18; P <.001).
The findings also reveal that children with cerebral visual impairments need more time (21 ms) to complete horizontal subsets than children with ocular visual impairments (t, 2.76; P =.007). Nystagmus, however, could not be distinguished using either vertical or horizontal times.
Compared with normally sighted children, the DEM ratio was 0.03±0.07 larger among children with INS and 0.02±0.10 larger among participants with FMNS. These findings indicate no clinical utility for discriminating normal sight from INS (t, 0.41; P =.68) or FMNS (t, 0.17; P =.86). The DEM ratio was also not influenced by ocular visual impairment (t, -0.95; P =.34) or CVI (t, 1.36; P =.17) status.
The only significant variable for the DEM ratio was age, which decreased the ratio by 0.022 per year (t, -2.46; P =.02).
“[W]e believe that the vertical and horizontal subtests are useful in the diagnosis of cerebral visual impairments and in the detection of delayed visual processing speed or number naming skills,” according to the researchers. “However, we found no evidence that the ratio has predictive power concerning visual impairment or the presence of involuntary drifts and saccades.”
Study limitations include the removal of a small subset of participants who found the horizontal test too difficult to perform.
Tanke N, Barsingerhorn AD, Goossens J, Boonstra FN. The developmental eye movement test does not detect oculomotor problems: evidence from children with nystagmus. Optom Vis Sci. Published online August 1, 2022. doi:10.1097/OPX.0000000000001930