Ocular side effects

Systemic administration

Certain

1. Decreased vision

2. Diplopia

3. Horizontal nystagmus

4. Postsurgical visually induced ‘emergence reactions’

5. Extraocular muscles

a.Abnormal conjugate deviations

b.Random ocular movements

6. Lacrimation

7. Visual hallucinations

8. Distortion of visual perception

Probable

1. Increased intraocular pressure – minimal (deep level of ­anesthesia)

Conditional

1. Optic neuritis

2. Blindness – transient

Clinical significance

All ocular side effects due to ketamine are transient and reversible. After ketamine anesthesia, diplopia may persist for up to 30 minutes during the recovery phase and may be particularly bothersome to some patients. ‘Emergence reactions’ occur in 12% of patients and may consist of various psychological manifestations from pleasant dream-like states to irrational behavior. The incidence of these reactions is increased by visual stimulation as the drug is wearing off. El’kin et al (2000) showed inadequate evaluation of size, shape and velocity in visual perception for the first 24 hours post anesthesia. Fine et al (1974) report three cases of transient blindness following ketamine anesthesia lasting about half an hour with complete restoration of sight and no apparent sequelae. This is thought to be a toxic cerebral-induced phenomenon or an anoxic insult. The effect of ketamine on intraocular pressure is somewhat confusing, with various authors obtaining different results. Intraocular pressure is probably not elevated in the first 8–10 minutes after the drug is administered; however, after this there may be increased muscle tone with a resultant increase in intraocular pressure. Fantinati et al (1988) reported a case of bilateral optic neuritis after a general anesthesia induced by ketamine. Ketamine is also used as a recreational drug for its psychedelic effect, and abusers may develop visual hallucinations, coarse horizontal nystagmus, abnormal conjugate eye deviations and diplopia.

Shaw IH, Moffett SP. Ketamine and video nasties. Anaesthesia 45: 422, 1990.

Whitwam JG. Adverse reactions to intravenous agents: side effects, Thorton JA (ed), Adverse Reactions to Anaesthetic Drugs, Elsevier, New York, pp 47–57, 1981.

Generic name: Methoxyflurane.

Proprietary name: Penthrane.

Primary use

This methyl ether is used as an inhalation anesthetic with good analgesic and muscle relaxant properties.

Ocular side effects

Systemic administration

Certain

1. ‘Flecked retinal syndrome’

2. Fluorescein angiography – window defects

Probable

1. Decreased intraocular pressure

2. Myasthenia gravis

a.Diplopia

b.Ptosis

c.Paresis of extraocular muscles

Clinical significance

Ocular side effects due to methoxyflurane are rare, but a unique adverse ocular reaction has been reported. Oxalosis occurs for unknown reasons, with calcium oxalate crystal deposits throughout the body. These deposits have a pre­ dilection for the retinal pigment epithelium and around retinal arteries and arterioles. They may be found in any ocular tissue, but mainly in vascularized tissue. Seldom does this interfere with vision. The deposition of these crystals in the retina gives the clinical picture of an apparent ‘flecked retinal syndrome’. With time the crystals become less prominent, but may remain visible for many years. There is no known effective treatment. This drug can also aggravate or unmask myasthenia gravis.

References and Further Reading

Ausinsch B, et al. Ketamine and intraocular pressure in children. Anesth Analg 55: 773, 1976.

Crandall DC, Leopold IH. The influence of systemic drugs on tear constituents. Ophthalmology 86(1): 115–125, 1979.

Drugs that cause psychiatric symptoms. Med Lett Drugs Ther 28: 81, 1986. El’kin IO, Verbuk AM, Egorov VM. Comparative characterization of changes in visual perception after ketamine and brietal anesthesia in children.

Anesteziol Reanimatol 1: 17–19, 2000.

Fantinati S, Casarotto R, et al. Bilateral retrobulbar neuritis after general anesthesia. Ann Ophthalmol 114: 649, 1988.

Fine J, Weissman J, Finestone SC. Side effects after ketamine anesthesia: Transient blindness. Anesth Analg 53: 72, 1974.

MacLennan FM. Ketamine tolerance and hallucinations in children. Anaesthesia 37: 1214, 1982.

Meyers EF, Charles P. Prolonged adverse reactions to ketamine in children. Anesthesiology 49: 39, 1979.

References and Further Reading

Albert DM, et al. Flecked retina secondary to oxalate crystals from methoxyflurane anesthesia: Clinical and experimental studies. Trans Am Acad Ophthalmol Otolaryngol 79: 817, 1975.

Argov Z, Mastaglia FL. Disorders of neuromuscular transmission caused by drugs. N Engl J Med 301: 409, 1979.

Bullock JD, Albert DM. Flecked retina. Arch Ophthalmol 93: 26, 1975.

Kaeser NE. Drug-induced myasthenic syndromes. Acta Neurol Scand 70(Suppl. 100): 39, 1984.

Novak MA, Roth AS, Levine MR. Calcium oxalate retinopathy associated with methoxyflurane abuse. Retina 8: 230–236, 1988.

Schettini A, Owre ES, Fink AI. Effect of methoxyflurane anesthesia on intraocular pressure. Can Anaesth Soc J 15: 172, 1968.

Sweetman SC (ed). Martindale: The Complete Drug Reference, 34th edn, Pharmaceutical Press, London, p 1304, 2004.