Toxic amblyopia is caused by damage to the optic nerve or retina due to exogenous or endogenous poisons. It can be caused by substances like tobacco, alcohol, methyl alcohol, quinine, and ethambutol. Tobacco and alcohol amblyopia typically affect the central vision and cause fogginess and difficulty with near work. Methyl alcohol amblyopia is usually acute and can cause complete and permanent blindness due to optic nerve damage. Testing is important to differentiate functional and organic amblyopia and guide appropriate treatment.

1. TOXIC
AMBLYOPIA

2. AMBLYOPIA
• Defn
–“A unilateral or bilateral decreaseof visual acuity
causedby pattern vision deprivation or abnormal
binocular interaction for which no obviouscauses
can be detected by physical examination of the
eyeand cannot be corrected by optical or surgical
means but in appropriate casesis reversible by
therapeutic measures.’

3. •
• -
visual lossdue to damage to the opticnerve fibrosis due
to effect of exogenous or endogenouspoisons
• -Its types are asfollows:
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–
–
–
–
tobacco amblyopia
ethyl alcoholamblyopia
methyl alcohol amblyopia
quinine amblyopia
ethambutol amblyopia
Toxic Amblyopia

4. Tobacco amblyopia
Typically occurs in men in pipe smokers, heavy
drinkers ,diet deficiencies in protein &vit.B complex
deficiencies
Pathogenesis:
Toxicagent – cyanide found in tobacco
Excessivetobacco smoking - Excessive
cyanide in blood – degeneration of ganglioncells
particularly in macular lesion–
degeneration of papillomacular bundle in the
nerve - toxic amblyopia

5. •
•
•
•
Characterized by gradually progressive impairment in the
central vision
Patient complains of fogginess &difficulty in doing near
works
V.F.-B/Lcentrocaecal scotoma with diffusemargins,
defects more for red thanwhite
Fundusexamination:normal/slight temporal pallor of the
disc
• ethyl alcohol amblyopia
Usually in association with tobacco amblyopia.
It may also occur in non smokers who are heavy drinkers
and suffering from chronic gastritis.
•
Clinical picture sameastobacco amblyopia

6. MEthyl alcohol amblyopia
Itis typically acute usually resulting in optic atrophy &
permanent blindness
Etiology :
usually occursdue to intake of wood alcohol or
methylated spirit in cheap adulterated/fortified
beverages
- sometimes may be due to inhalation offumes in
industries

7. • Pathogenesis; Metabolized very slowly thus stays in body
for longer period of time – oxidized in to formic acid &
formaldehyde in the tissues -toxic agents causeedema
followed by degeneration of the ganglion cells ofthe retina
resulting in complete blindness due to optic atrophy
•
•
•
•
•
Clinical features:
Symptoms:
In acute poisoning - headache , vomiting ,nausea,dizziness,
abdominal pain
Presenceof characteristic odor
Patient usually brought with complete blindnessnoticed
after 2-3days

8. • Fundus:mild disc edema , markly narrowedblood
vessels
FINALLY:B/L primary optic atrophy

9. • Quinine amblyopia
o May occur evenwith small dosesof the drugs in susceptible
individuals.
• Near total blindness ,deafness & tinnitus
• Pupil –fixed & dilated
• Fundus- retinal edema , marked pallor ofthe disc , extreme
attenuation of retinalvessels
• V.F.-markly contracted

10. • Ethambutol amblyopia
• Causeddue to anti -tubercular drugs
• Usedin dosesof 15mg/kg perday
• usually occurs in patient who haveassociated
alcoholism & diabetes
• Fundus:sign of papillitis

11. • Idiopathic amblyopia
•
•
-unknown etiology
-may be cortical or subcortical

12. • Iscolor vision affected in amblyopia??
– Generally not affected
– Mild abnormalities reported in severeamblyopia,
particularly those with lossof fovealfixation
• Doesamblyopia causea relative afferent
pupillary defect??
– Generally not affected
– Pathologic changeslocated in posterior visual
pathway, not in retina or optic nerve

13. Necessity f o r testiNg
AmblyopiA
• Differential Diagnosis and prognosis.
• Differentiating the functional from theorganic
amblyopia.
• Thedecision , type and extent of theamblyopia
therapy dependson the testresults.
• Guidesthe therapy.