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Anterior ischemic optic neuropathy (AION)


It is a segmental or generalized infarction within the pre laminar or laminar portion of optic nerve caused by occlusion of posterior ciliary arteries


  1. Arteritic AION
    1. Etiology -GCA (Giant-Cell-Arteritis)*
    2. Clinical Features
      1. Transient visual obscuration followed by uniocular, sudden and profound loss of vision.
      2. Periocular pain.
      3. Pale, swollen optic nerve head surrounded by small splinter-shaped haemorrhages.
      4. Associated jaw claudication, Polymyalgia Rheumatica.
    3. Treatment: Oral prednisolone,
  2. Non – Arteritic AION< >Etiology
     
    i. Idiopathic                             
     
    ii. Hypertension* is the major risk factor.
    iii. Diabetes                            
     
    iv. Hypermetropic discs and small cups are risk factors
  • Infesun Altitudinal hemianopia*:
  1. Investigations
    1. Serological studies, serum lipids, blood glucose, and factors affecting viscosity.
    2. ESR - To exclude occult GCA and other autoimmune diseases.
Table: Clinical feature distinguishing arteritic from non-arteritic anterior ischemic optic neuropathy (AION)
 
  Features common to both Arteritic AION Non-arteritic AION
Sex ratio
Age
 
> 40 years
Female > male
Usually > 60 years
(Mean 70 years)
Female = Male
Usually 40 – 60 years
(Mean 60 years)
 
Vision loss a. Sudden
b. Reduced colour vision
c. altitudinal or central field defect
Usually severe
Up to 76%
<6/60 (20/200); occasionally progressive
 
Usually moderate
Up to 61% > 6/60 (20/200); non progressive
Ocular pain Usually painless May be present Rare
 
Prior episodes of amaurosis
 
Uncommon Occasional Rare
Laterality Initially unilateral but may become bilateral Fellow eye affected in up to 95% within days to weeks Fellow eye affected in <30% within months to years
 
Optic disc Oedema and pallor of the disc; may be sectoral, flame shaped haemorrhages
 
Pale > hyperemic oedema
Cup normal
Hyperaemic > pale oedema
Cup small
Other symptoms and signs   a. Headache
b. Scalp tenderness; palpable, tender, non-pulsatile temporal artery
c. Proximal muscle and joint aches ‘polymyalgia rheumatica’
d. Anorexia, weight loss, fever
e. Jaw claudication
f. Cranial nerve palsies
a. Associated hypertension in 40% of patients
b. Diabetes in up to 24%
c. Shock (Acute systemic hypotension)
d. Nocturnal hypotension
Investigations
ESR   Usually >40 mm in first hour
 
Mean 20-40 mm in first hour
Temporal artery biopsy   Giant cell glaucomatous vasculitis involving all coats of the vessel wall
 
Not indicated if features do not suggest arteritis
Florescein angiogram   Disc and choroidal filling delay Disc filling delay
Natural history   Improvement rare, fellow eye involvement in up to 95%
 
Improvement in up to 43%, fellow eye affected in <30%
Treatment   Corticosteroids Not proved to be effective
Levodopa-carbidopa combination for 3 weeks
and then double dose for 1 month reported to be beneficial
 
Differential diagnosis Idiopathic optic neuritis, other types of optic nerve inflammation, e.g. syphilis, sarcoidosis, infiltrative optic neuropathy, compressive optic neuropathy, idiopathic disc oedema including diabetic papillopathy & optic disc vasculitis
 
   




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