OMS – Ocular motor score : a clinical method for evaluation and follow-up of ocular motor problems in children

Abstract

Background: Eye movements can be a source of valuable information to clinicians. Different classes of eye movements, i.e. saccades, smooth pursuit (SP) and vestibular eye movements can be distinguished on the basis of how they aid vision. They are usually triggered by different well defined anatomical localisations in the brain and brain stem. The Ocular Motor Score (OMS) is a clinical test protocol which comprises 15 subtests regarding ocular motor functions that are important and relevant in clinical practice. The protocol was developed with the aim to create a quantitative measure of a series of combined mostly qualitative assessments today used in the orthoptic clinic in every day practice. In addition, the results of the different subtests will give a specific profile for each child who displays problems in the static or dynamic section of the test.

Aim: The aims of the current studies were to create a reference material for the OMS test protocol, to evaluate OMS according to intrarater and inter-rater agreement and to evaluate the OMS test protocol outcome in children with specific neuropaediatric disorders.

Methods: The OMS test protocol consists of 15 different subtests and are grouped into a static and dynamic section. Since the tests are scored, the overall score from the 15 subtests will give a total OMS (tOMS) score which then can be used as a comparison in the following up of a child. A low tOMS score will indicate a normal ocular motor performance, whereas a high score will indicate a serious ocular motor problem.

Subjects: Study I included a total of 233 neurological healthy children and young adults referred to the department of paediatric ophthalmology, who were divided into four age groups: 0.5-3, 4-6, 7-10 and 11-19. In study II, another 40 children aged 4-10 with and without ocular motor deficiencies were examined. The examinations of the subjects were videotaped to simplify the intrarater agreement procedure and to provide similar conditions for the three raters in the interrater agreement study. Study III involved 13 patients with a mitochondrial disease, Complex I deficiency and study IV 26 patients with congenital cytomegalovirus infection (cCMV). Both groups were included when they came for their ophthalmological examination that formed part of a wider multidisciplinary study.

Results: The findings from study I demonstrated that ocular motor functions tested in the OMS test protocol develop with age. Study II dealt with correlation and showed a high degree of agreement among the raters. However, there was less agreement in the saccades, smooth pursuit (SP) and fusion subtests, especially in the subnormal test results. Study III showed differences in ocular motor performance of children with Complex I deficiency. They showed dysfunctions of the saccades, dysmetric SP and pathological optokinetic nystagmus (OKN). In study IV children with cochlear implants due to cCMV more frequently had pathological Vestibular Ocular Reflex (VOR), which fits in with the balance disturbances reported in the same group.

Conclusion: The OMS test protocol can be of clinical value as a clinical tool in identifying ocular motor problems in children with subtle neuropaediatric disorders and can be used to follow up children with progressive neuropaediatric disorders. Key words: Ocular Motor Score (OMS), children, normative material, agreement, neuropaediatric disorders, ocular motor function, eye movements, strabismus