Measurement of optic nerve sheath diameter by ultrasound: a means of detecting acute raised intracranial pressure in hydrocephalus.

AIM: To evaluate the utility of measuring the optic nerve sheath diameter in children with shunted hydrocephalus, suspected of having raised intracranial pressure. METHODS: 23 children with shunted hydrocephalus were examined, six had well controlled ICP, 17 however manifested symptoms suggestive of intracranial hypertension. A clinical history was taken from all patients and their parents or carers. The shunt valve was examined clinically, and signs of raised intracranial pressure were sought. Ultrasound examination was performed in both eyes to measure the optic nerve sheath diameters 3 mm behind the globe. These measurements were compared with control data obtained from 102 children who attended the radiology department for unrelated renal ultrasound examination. RESULTS: Control data suggested that the upper limit of normal for optic nerve sheath diameter is 4.5 mm (measured 3 mm behind the globe) in patients over 1 year of age, and 4.0 mm in children less than 1 year of age. Those patients with functioning ventriculoperitoneal shunts had a mean optic nerve sheath diameter of 2.9 (SD 0.5) mm; those with raised intracranial pressure had a mean optic nerve sheath diameter of 5.6 (0.6) mm (p<0.0001). These results confirm that optic nerve sheath diameters in excess of the control data are strongly suggestive of raised intracranial pressure. CONCLUSION: The evaluation of the optic nerve sheath diameter is a simple non-invasive procedure, which is a potentially useful tool in the assessment and monitoring of children with hydrocephalus suspected of having raised intracranial pressure.

Vigabatrin associated visual field loss: a clinical audit to study prevalence, drug history and effects of drug withdrawal.

PURPOSE: To survey clinical visual function including quantitative manual perimetry results in a group of patients taking vigabatrin; to assess the severity of any field defects; to tabulate cumulative and daily doses of medication and to assess possible changes in visual function over time. METHOD: A prevalence study of 100 out of 183 patients currently attending a tertiary referral epilepsy centre who were taking or had recently discontinued vigabatrin (duration 83-3570 days; mean 1885 days) as part of combination anticonvulsant therapy. Complete neuro-ophthalmic examination including Goldmann kinetic perimetry was performed and monocular mean radial degrees (MRD) to the I/4e isopter calculated. Patients were followed up at 6-monthly intervals for not less than 18 months. RESULTS: Acuity and colour vision remained stable in all patients regardless of changes in visual fields. Twenty per cent of patients had significant constriction of their visual field defined as a monocular MRD of 30 degrees or less. Males were significantly more likely to be severely affected than females (P < 0.01). Twenty one patients were followed after discontinuing vigabatrin treatment. Only three of these showed a change in MRD of 10 degrees or more with two deteriorating and one improving. No correlation between treatment duration or cumulative dosage/kg and the severity of defects could be demonstrated. CONCLUSIONS: Earlier reports of a high prevalence of both moderate and more serious field defects were confirmed in patients taking vigabatrin but not in epileptic patients taking other anti-convulsants. We found no evidence of progression or resolution of visual field defects on discontinuing the drug, and no relationship between dose history and visual deficit field loss. An idiosyncratic drug reaction within the neurosensory retina may underlie the pathogenesis of the visual field loss in some patients.

Anterior ischemic optic neuropathy associated with disc drusen.

Anterior ischemic optic neuropathy (AION) is a condition more commonly found in later life. We present a case of unilateral AION in a 13-year-old boy with small discs and ipsilateral optic nerve head drusen.

Pyoderma gangrenosum of the orbit.

Pyoderma gangrenosum is an uncommon chronic ulcerative condition, the aetiology of which is poorly understood. Ophthalmic involvement is rare. The case presented in this paper involves destruction of the orbital contents with subsequent perforation of the eye despite conventional therapy. Evisceration was performed with the patient being subjected to hyperbaric oxygen therapy pre- and post-operatively, with resultant cessation of the disease process.