drug induced optic neuropathy

8/13/2019 Drug Induced Optic Neuropathy

1/23


2/23

Optic Neuropathy

0Disorders of optic nerve involving

degeneration of the nerve.

0

Causes:1. Hereditary

2. Acquired: a) Ischemic

b) Nutritional

c) Toxic (DRUG INDUCED)


3/23

Mechanisms of DION

0Mitochondrial dysfunction

0Disruption of blood flow to the optic nerve

0 Imbalance in ionic photoreceptor metabolism

0Unknown mechanisms


4/23

Drugs Causing Optic Neuropathy


5/23

Drugs Causing Optic Neuropathy

0Most supporting information available for:1. Ethambutol (antitubercular drug)

2. Amiodarone (antiarrthymic drug)

3. Sildenafil (PDE-5 inhibitor)4. Topiramate (anticonvulsant drug)

5. Linezolid (anti-MRSA antibiotic)

6. Vigabatrin (antiepileptic drug)7. Isoniazid (antitubercular drug)


6/23

ETHAMBUTOL

0 First line agent in the treatment of Tuberculosis

0 Its toxicity is dose and duration dependent

0 Dose > 25mg/kg/day

0 Duration > generally 3-6months

0

Earlier toxicity at a lower dose in renal disease

0 Mechanism: Chelation of Copper in retinal cells.


7/23

Ocular Side Effects

0Optic Neuritis with abrupt visual impairment

0Dyschromatopsia (colour vision

abnormalities) with patient c/o fading of

some colours in vision:

1. Red-green or

2. Blue-yellow dyschromatopsia


8/23

Ocular Side effects(contd.)

0Visual field Defects:1. Central type:

a) Decreased Visual Acuity

b) Central or centrocaecal scotomas

c) blue-green colour dyschromatopsia

2. Peripheral type:

a) Peripheral Visual Field constriction

b) Red-green dyschromatopsia


9/23

Treatment and Follow-Up

0 Prompt ophthalmic evaluation (disc may be normal or

slightly swollen with splinter shaped hemorrhages)

0 Immediate discontinuation of the drug

0 Follow-up every 4 weeks for doses > 15mg/kg/day

0 Prognosis: is good with early cessation of treatment

but recovery may take up to 12 months

0 Few patients do develop permanent visual

impairment due to optic atrophy


10/23

AMIODARONE

0 Class III antiarrthymic drug used for ventricular

arrrhythmias

0 Causes reversible Vortex keratopathy in cornea,

conjuctival effects and optic neuropathy

0 Not dose related optic neuropathy

0 Slow onset over years


11/23

Ocular Side Effects

0 Insiduous unilateral or bilateral visual impairment

0 Bilateral disc swelling which may persist for months

after cessation of therapy

0 Visual field defects usually peripheral constriction

(unlike Ethambutol which causes usually central

scotomas)


12/23

D/D

Optic Neuropathycaused by

Amiodarone

Non ArteriticIschemic Optic

Neuropathy

0 Slow onset

0 Mild visual loss

0 Prolonged disc

edema

0 Usually bilateral

0 Slow resolution

0 Relatively quick

onset

0 More visual loss

0 Shortened disc

edema

0 Usually unilateral

0 Rapid resolution

VS


13/23

Treatment and Follow-Up

0Cesssation of drug

0Prognosis: variable and slow

0 Screening: Baseline at the start of start of

treatment and every 6 months but not very

helpful


14/23

VIGABATRIN

0 Second line antiepileptic drug for

uncontrolled partial seizures and infantile

spasms

0 Idiosyncratic toxicity and not dose related

0Presentation of symptoms over months oryears


15/23

Ocular Side Effects

0 Bilateral concentric or binasal visual field defect

0 Ophthalmoscopy may show:

0Peripheral atrophy

0Nasal optic disc atrophy

0Arteriolar narrowing

0Abnormal macular reflex

0 Surface wrinkling


16/23

Follow Up

0Baseline visual field examination before

starting treatment

0Reassessment after 6 months for 3 years and

then annually if no abnormality seen


17/23

Sildenafil

0 PDE-5 inhibitor used for erectile dysfunction in males

0 Mechanism: causes inhibition of PDE-6 in rods and

cones leading to visual disturbances

0 Most common cause of drug associated ocular

toxicities in US


18/23

Ocular side efffects

0 Causes Non Arteritic Ischemic Optic Neuropathy by

causing hypotension in peripheral small arteries

supplying optic nerve0 NAION characterized by sudden, painless, unilateral,

partial, sectoral loss of vision

0 Occurs in individuals already on risk with DM, HTN,

IHD, hyperlipidemia, sleep apnea etc.


19/23

Recommendations

0 Avoid using these drugs in patients with small,

crowded discs

0 Basline ophthalmic examination may be done in at

risk patients to rule out small discs


20/23

LINEZOLID

0 Anti-MRSA antibiotic

0 Optic neuropathy with long term use > 5-11 months

0 Causes gradual, painless, bilateral loss of vision

0 Withdrawal of drug aids recovery

0

Baseline and periodic eye evaluations arerecommended


21/23

ISONIAZID

0 First line antitubercular drug

0 Can produce optic neuropathy in patients with concurrent

hepatic or renal disease

0 Causes mild vision loss, scotomas, and dyschromatopsia

0 Since given with ethambutol, it is recommended to stop

ethambutol first and if symptoms do not resolve then stop

isoniazid

0 Treatment: stop the drug, give pyridoxine

0 Periodic eye examinations to see optic disc swelling.


22/23

Updates!

0 ROLE OF OCT IN ETHAMBUTOL OCULAR TOXICITY:

0 In ethambutol toxicity, early changes are not clinically

apparent on fundoscopy.

0 With OCT we can see loss of retinal nerve fibre layer

as a sign of early toxicity of the drug which would not

be apparent on fundoscopy

0 So OCT is an additional way to objectively monitor

patients on ethambutol in addition to VF testing.

Zoumalan CI, Agarwal M, Sadun AA. Optical coherence tomography can measure axonal loss in patients with

ethambutol-induced optic neuropathy. Graefes Arch Clin Exp Ophthalmol. May 2005;243(5):410-6.


23/23

Thank You!

drug induced optic neuropathy

Documents