Optic Neuropathy (Including Nutritional)

BASICS


DESCRIPTION


• Painless, bilateral vision loss including dyschromatopsia and central or centrocecal scotoma


• Exception is unilateral vision loss from phosphodiesterase inhibitors, which are possibly associated with ischemic optic neuropathy


• Typically slowly progressive; less often acute


– Toxins [e.g., methanol, ethylene glycol, toluene, styrene, carbon monoxide, cyanide (from smoking and cassava)]


– Drugs


– Direct (e.g., ethambutol, disulfiram iodochlorohydroxyquinoline, alpha interferon, vincristine, amiodarone, cyclosporine, tacrolimus)


– Indirect (phosphodiesterase inhibitors and infliximab)


– Nutritional deficiencies (e.g., vitamin B12, thiamine, folate)


• System(s) affected: Nervous


EPIDEMIOLOGY


• Affects all ages, races, and economic strata


• Both sexes are equally affected


• Nutritional affects individuals from lower economic status and during times of war and famine


• More common in individuals on certain drugs, occupational exposure, smokers, and alcoholics


Incidence


• Varies on type, yet not known in most cases


– Ethambutol optic neuropathy is 1.5% in 1 Korean study or 100,000 new cases annually (1)


Prevalence


Unknown but varies with type


RISK FACTORS


• Impaired renal disease with ethambutol


• Occupational exposure for toluene and styrene


• Smoking with toxic and nutritional causes


– Pipe and cigar more than cigarettes


• Alcohol intake is often associated with nutritional causes


Genetics


Unknown


GENERAL PREVENTION


• Regular monitoring of patients on ethambutol


• B-complex vitamins and vitamin A reduces incidence in Cuba


PATHOPHYSIOLOGY


• Generally related to interference of mitochondrial function with oxidative stress


– Demyelination of white matter—formic acid, a metabolite of methanol, is a mitochondrial toxin


– Defective mitochondrial oxidative phosphorylation, with buildup of reactive oxygen species in the optic nerve in ethambutol and Cuban epidemic optic neuropathy


– Chelates metal-containing enzymes used in the mitochondria with ethambutol, disulfiram, and penicillamine


– Smoking may cause elevated cyanide


• Vascular changes at optic nerve head with phosphodiesterase inhibitors


ETIOLOGY


Multifactorial with both poor nutrition and toxicity playing roles


COMMONLY ASSOCIATED CONDITIONS


• Smoking and alcohol use are seen often but are not clearly demonstrated


– Tobacco may be a toxin by itself


– Alcohol is not a primary contributor; but is related to poor nutrition


• Pernicious anemia with vitamin B12 deficiency


DIAGNOSIS


HISTORY


• Either acute (some nutritional and toxins) versus gradual progressive loss of color and central vision


– Careful documentation of exposure to drug or toxin or dietary history (2)[B]



ALERT


Methanol and ethylene glycol poisoning presents initially with nausea and vomiting. Vision loss together with respiratory distress is delayed. Coma and death may follow if not recognized (1)[B]

Only gold members can continue reading. Log In or Register to continue

Nov 9, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Optic Neuropathy (Including Nutritional)

Full access? Get Clinical Tree

Get Clinical Tree app for offline access