An out-of-hours GP phones the Emergency Department for urgent advice about a 61-year-old woman with sudden severe unilateral eye pain, blurred vision, frontal headache, nausea, and seeing haloes around lights. Symptoms began 2 hours earlier while she was in a dark cinema.

The GP reports a red eye, a mid-dilated poorly reactive pupil, and marked ocular discomfort. The local ophthalmologist has been delayed on the motorway, and immediate transfer to specialist eye care is being arranged. Before the patient is moved, the GP asks which initial positioning advice should be given in primary care if immediate admission is not possible.  

What is the most appropriate immediate advice?