In this test, paradoxical dilation of the pupil on direct light stimulation indicates a relative afferent pupillary defect (Marcus Gunn pupil) and is pathognomonic of a process that affects the optic nerve, or less commonly the retina, in one eye. The “swinging flashlight test” detects a difference in the visual stimulus from each eye that reaches the efferent limb of the pupillary reflex when the two eyes are stimulated alternately ( Box 1). Unilateral visual impairment: Visual impairment in one eye only localises the abnormality to either the eye or the optic nerve. Pain on eye movement: The presence of pain on eye movement is non-specific but suggests an inflammatory process affecting the globe, optic nerve or orbital contents.ĭiminution of colour intensity: Pale, washed-out vision with relatively little loss of visual acuity is characteristic of processes involving the optic nerve and chiasm. In contrast, a vascular event in the optic nerve would be expected to result in acute symptoms, and a neoplastic process usually evolves more slowly. Subacute history: The evolution of symptoms over days in this case strongly suggests an inflammatory process. No other abnormal neurological findings were detected. Mary’s eye movements were normal, but she found looking to the extremes of gaze painful in the right eye. There were no haemorrhages or other abnormal retinal findings. On ophthalmoscopy, the cornea, anterior chamber, lens and vitreous humour appeared normal in both eyes, as did both optic discs.

The right pupil appeared to paradoxically dilate when the torch was swung alternately from the left to the right eye. Direct and consensual pupillary responses were reduced when light was directed at her right eye. On examination, Mary’s right eye and orbit appeared normal, but her visual acuity was 6/6 in the left eye and 6/12 in the right eye. She had no significant prior medical history. This worsened progressively over the 3 days - vision through her right eye became markedly reduced, grey and blurred. Soon after onset of the headache, she noticed blurred vision in her right eye in particular, coloured objects appeared pale or washed out compared with their appearance through her left eye. The pain was localised to her right periorbital region and forehead, and was made worse by eye movement.

Mary, who is 28 years old, presented to her general practitioner after developing a dull headache and eye pain over 3 days.

Statistics, epidemiology and research design.

Aching pain in eyeball