Microtropia: clinical findings and management for the primary eye care practitioner

BACKGROUND: Microtropia is a small-angle strabismus with a highly developed degree of binocular cooperation. It is a unilateral comitant horizontal deviation less than 5 prism diopters (PD) in the presence of anomalous retinal correspondence (ARC), amblyopia, some motor fusion, and reduced stereoacuity. CASE REPORT: A 7-year-old white girl presented for a second opinion concerning unexplained vision loss in the left eye. Visual acuities were 20/20 in the right eye and 20/200 in the left eye. Ocular evaluation found normal eye health with a 4-PD constant left esotropia at near and a 3-PD constant left esotropia at distance on unilateral cover test. A diagnosis of steady nasal eccentric fixation microtropia without identity with strabismic amblyopia in the left eye was made. Over the follow-up period, visual acuity improved but the alignment did not. CONCLUSION: Microtropia can defy detection, resulting in a reduced chance of achieving near-normal visual potential in children. It is important for clinicians to understand the possible etiologies, related entities, proper testing, differential diagnoses, and the goals of treatment. This case report reviews the clinical findings, diagnoses, and management of patients with microtropia. Optometry 2011;82:657-661