OBJECTIVES: To evaluate the association between obesity and idiopathic intracranial hypertension (IIH) and establish whether there is a relationship with visual outcome. To calculate the prevalence and degree of obesity in a group of patients with IIH. METHODS: 34 patients (31 female and 3 male) were recruited between 1993 ± 1997 with a diagnosis of IIH. Assessment included visual acuity, visual ®eld assessment (Humphrey automated and Goldmann manual perimetry), fundus assessment and measurement of body mass index (BMI). Obesity was de®ned as a BMI of 30 kgam 2 . RESULTS: 70.5% of patients were obese. The relative risk for obesity and IIH was signi®cant at 8 (95%CI: 2,29). This increased to 17 (95%CI: 5,62) for obese females aged 16 to 24 years and 10 (95%CI: 3,35.5) for obese females aged 25 to 34 years. Morbid obesity (BMI b 40) was signi®cantly associated with poor visual outcome. Serial obesity measures showed generally little change in weight over time and there was no correlation between weight change and visual improvement. CONCLUSIONS: This study has documented a relationship between obesity and IIH. A high degree of obesity was associated with a poor visual function and identi®ed as a risk factor for poor outcome. Obesity may be an aetiological factor in this condition although it is unlikely to be the sole cause but more probably a precipitating factor. Weight loss is recommended although failure to lose weight is common. Any weight reduction programme must therefore be actively encouraged and monitored.

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