JRSM >
Volume 95, Number 11 >
Pp. 555-556
Ophthalmology, Norfolk and Norwich Hospital NHS Trust, Colney Lane, Norwich NR4 7UZ, UK
Correspondence to: Mr Gavin Galloway E-mail: gavgal{at}doctors.org.uk
The symptoms of acute glaucoma include ocular pain, decreased vision and epiphora. Associated systemic symptoms are headache, nausea and abdominal discomfort1. We propose a direct relation between the ocular and abdominal symptoms.
CASE HISTORY
A woman of 84 came to the accident and emergency department after five hours of episodic haematemesis, generalized abdominal discomfort and malaise. The abdominal discomfort was a constant dull ache without altered bowel activity; she also had a diffuse headache. On clinical examination the only remarkable finding was a red right eye. Urgent oesophago-gastro-duodenoscopy showed mild gastritis. Clinical review now revealed a changing pattern to her headache, which had become a deep right periorbital pain. An ophthalmological opinion was sought. Best corrected visual acuities were counting fingers (right) and 6/12 (left). The right globe was injected, with an oedematous cornea, a shallow anterior chamber, a fixed oval mid-dilated pupil and significant cataract. On applanation tonometry pressures were 54 mmHg (right) and 19 mmHg (left). Fundoscopy, albeit through hazy media, was normal. Medical management of her glaucoma included 500 mg intravenous acetazolamide, topical pilocarpine 2% to both eyes, topical carteolol 1% twice daily with dexamethasone 0.1% four times daily to the affected eye. Analgesics and antiemetics were provided. Once the intraocular pressure (IOP) had become normal, bilateral laser peripheral iridotomies were performed. After one month her right vision had stabilized at 6/18 with an IOP of 12 mmHg without antiglaucoma medication. The cataract was extracted once the inflammation had settled.
COMMENT
In this patient the acute glaucoma may have been precipitated by enlargement of the cataractous lens, with sudden closure of an already narrow iridocorneal angle. We presume that the haematemesis was secondary to vomiting. The mechanism for abdominal symptoms in acute glaucoma is poorly understood. During squint surgery, manipulation of the extraocular muscles and pressure on the globe can elicit the oculocardiac reflex, causing bradycardia2. Abdominal symptoms, perhaps erroneously attributed to the oculocardiac reflex, are also well documented after squint surgery3. On the basis of early postoperative vomiting associated with squint surgery, Van den Berg suggested a direct oculoemetic reflex4.
The oculocardiac reflex is one of several trigeminal nerve reflexes. Noxious stimulation of trigeminal nerve afferents activates the paratrigeminal nuclei in the medulla with secondary stimulation of the vagus nerve. Orbital trigeminal afferents project via the trigeminal ganglion to the spinal trigeminal nucleus (STN). The STN, extending from the pons to the upper cervical spinal cord, is divided into three subnuclei—subnucleus oralis, interpolaris, and caudalis (SNc). Nociceptive-specific neurons do not respond to tactile input but only to noxious stimuli and are located mainly in SNc, indicating involvement in trigeminal pain processing5. Secondary neural stimulation of the dorsal afferent nucleus of the vagus nerve then occurs. Apart from manipulation of proprioceptive/stretch reflexes in the extraocular muscles6, stimuli to the lids, orbital structures, and, of particular importance, the cornea, have been implicated in the oculocardiac reflex. Perhaps in acute glaucoma, where the pressure rise can be as high as 1 mmHg/minute, corneoscleral stretch may be sufficient to excite an oculo-trigemino-vago-abdominal (oculoabdominal) reflex which directly results in abdominal symptoms such as nausea, vomiting, cramping and pain. This occurs without cardiac involvement and can precede ocular pain or headache.
We propose that there is a direct oculoabdominal reflex triggered via the trigeminal nerve and completed via a loop in the vagus nerve nuclei by way of the visceral motor and visceral sensory branches of the vagus nerve. Abdominal symptoms are seen in other eye conditions with pain derived from the ophthalmic branch of the trigeminal nerve, such as herpes zoster ophthalmicus and migraine. Further studies of the trigeminal-vagus nuclei interface might establish whether there is in fact a separate oculoabdominal reflex.
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