Independence of optokinetic nystagmus asymmetry and binocularity in infantile esotropia
A. Aiello, K. W. Wright and M. Borchert
Division of Ophthalmology, Childrens Hospital Los Angeles.
OBJECTIVE: Children with congenital esotropia, amblyopia, or early visual
deprivation have persistent asymmetric monocular pursuit, as measured by
optokinetic nystagmus (OKN), and favor targets moving in a temporal to
nasal direction. Previous studies suggest that binocular visual development
is necessary for the development of symmetric monocular OKN. We recently
treated patients with congenital esotropia with unconventionally early
surgery to establish good binocularity. We wished to determine if mature
symmetric OKN responses could develop in patients with congenital esotropia
following the acquisition of good stereopsis. METHODS: Electro-oculographic
recordings documented horizontal eye movements in response to an electronic
OKN stimulus. PATIENTS: The recordings of three patients with congenital
esotropia that had been surgically aligned before age 20 weeks and who had
achieved high-grade stereopsis with random dot and Titmus stereographic
testing were studied. We compared this group of children with groups of
age-matched controls, including the following: (1) three patients with
congenital esotropia who underwent surgical alignment after age 6 months
and who had no amblyopia but poor stereopsis; (2) three children with
accommodative esotropia, good ocular alignment when wearing spectacles, and
good stereopsis; and (3) three normal children. RESULTS: The normal
children and those with accommodative esotropia demonstrated normal
symmetrical OKN. The patients with congenital esotropia showed poor nasal
to temporal OKN regardless of the degree of stereopsis or timing of
surgery. CONCLUSIONS: Our results indicate that good binocularity, as
measured by stereopsis, is not sufficient for the development of symmetric
OKN in patients with congenital esotropia.
