A 20-year-old, right-handed, female kitchen worker had a sudden onset right neck pain radiating to occipital region, after turning her head to the left whilst in bed. She fell asleep and awoke with vertigo, nausea and vertical diplopia. She vomited on the way to her local hospital. She later admitted to using intrave- nous amphetamines and ‘ecstasy’ [3,4-methylenedioxymethamphetamine (MDMA)] over the past 5 years. On examination, visual acuities were 6 / 6 bilaterally and intraocular examina- tion was normal. Ishihara colour plate testing was 15 / 15 bilaterally. She had a right 1 mm ptosis and mild anisoco- ria (Fig. 1A). A triad of ocular signs were noted: saccadic lateropulsion, Horner’s syn- drome and horizontal-torsional jerk nystagmus (Fig. 1). Hypermetric (over- shoot) ipsilateral (right) and hypometric contralateral (left) saccades were also noted (Fig. 1D–F). Down- gaze (Fig. 1A–C) and upgaze refixations (Fig. 1K–M and N–P) veered ipsilaterally along an oblique rather than a vertical line, indicating a form of saccadic instability. These signs usually indicate infarction of the lateral medulla by occlusion of posterior infe- rior cerebellar artery (PICA; Fig. 2A) or vertebral artery (Fig. 2B), more commonly known as PICA syndrome or Wallenberg’s lateral medullary syn- drome (Meyer et al. 1980; Brazis 1992). Further neurological examination confirmed our suspicions. She had (A) (B) (C) (G) (I) (J) (H) (K) (L) (M) (N) (O) (P) (D) (E) (F) Fig. 1. (A) Right Horner’s syndrome and (B, C) right eye veers to right on downgaze or ‘ipsi- pulsion’. (D) Left to (E) right hypermetric saccade or ‘overshoot’ and (F) refixation. (G–J) Left over right non-commitant skew deviation without torsion. Rotational (anticlockwise) nystagmus in primary gaze, worse on left gaze, fast horizontal phase always and maximal to left. (K) Right eye veers to right on upgaze or right ‘saccadic lateropulsion’ or ‘ipsipulsion’, followed by (L then M) central fixation. Head straightened then (N) vertical saccade with right lateropul- sion, followed by (O then P) central fixation. Diagnosis / Therapy in Ophthalmology Saccadic lateropulsion or ipsipulsion Niaz Islam, 1 Gordon T. Plant 2,3 and James F. Acheson 2,3 1 Department of Medical Retina, Moorfields Eye Hospital, London, UK 2 Department of Neuro-Ophthalmology, Moorfields Eye Hospital, London, UK 3 Department of Neuro-Ophthalmology, National Hospital for Neurology and Neurosurgery, London, UK Acta Ophthalmol. 2008: 86: 688–689 ª 2007 The Authors Journal compilation ª 2007 Acta Ophthalmol Scand doi: 10.1111/j.1600-0420.2007.01040.x Acta Ophthalmologica 2008 688