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Sensory heterotropia is defined as a secondary deviation following loss or severe reduction in visual function in one eye. We have analyzed the records of 12 1 patients with sensory heterotropias with the purpose of correlating the direction deviation of (eso- or exotropia) with age of onset of visual loss. Esotropia and exotropia were encountered with almost equal frequency when the onset of visual impairment occurred at birth or between birth and 5 years of age and exotropia predominated in older children and adults. We also found a strikingly high incidence of dysfunction of the oblique muscles in patients with sensory eso- and exodeviations. The inferior oblique muscle was the most freq uently involved muscle. Sensory heterotropia is defined as a deviation of one eye following loss or severe impairment of visual acuity. Due to a sensory obstacle to fusion, the fusion reflex innervation becomes suspended and the visually impaired eye changes its position relative to that of the fixating eye and becomes esotropie or exotropic. While most authors agree that the direction of the deviation (esotropia or exotropia) depends on the age at which the visual impairment occurred, there is little agreement on the type of strabismus in the various age groups. For instance, Chavasse1 stated that eyes born blind or having lost vision shortly after birth diverge. Hamburger,J on the other hand, writes that most eyes with congenital unilateral blindness or severe visual impairment in early childhood converge. There is similar disagreement as to the direction of strabismus when the onset of visual impairment is during childhood or adolescence. In view of this discrepancy, and as our preliminary clinical impressions were not in accord with either of the two extreme views stated above,1 we analyzed the records of patients with sensory tropia with the purpose of describing the clinical characteristics of this entity.

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PURPOSE To devise a cost-effective guide for the evaluation of fourth nerve palsies (FNP). METHODS A review of the pertinent English language literature was performed to devise a guide for the evaluation (including neuroimaging) of FNP. The authors report a retrospective review of imaging studies performed on 206 patients with FNP. RESULTS The literature was used to develop the imaging guide. In the retrospective chart review of 206 patients from two tertiary care centers, 28 patients (13.6%) underwent a computed tomography scan and/or a magnetic resonance scan. Of these patients, five had associated neurological symptoms (non-isolated), one was traumatic, five were congenital, four were vasculopathic, eleven were non-vasculopathic, and two were progressive. Following the recommendations of the imaging guide, the five isolated congenital FNP and the four isolated vasculopathic FNP would not have undergone neuroimaging studies. The total costs of these neuroimaging studies in these nine patients were 19,000 dollars. Four patients in the retrospective review with associated neurological deficits (non-isolated) should have undergone neuroimaging according to the guide, but did not. CONCLUSIONS Although the evaluation of FNP can be difficult, the decision to order neuroimaging can be improved by using an imaging guide. An imaging guide for the evaluation of FNP may allow more appropriate and cost-effective imaging of these patients. Isolated congenital, old traumatic, or vasculopathic FNP do not require neuroimaging studies. Patients with non-isolated FNP should have directed neuroimaging studies based upon the results of clinical examination.