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Ocular System

Retinal artery occlusion

Ocular emergency caused by occlusion of retinal artery with resultant infarction of the retina resulting in profound, usually monocular vision loss, and is associated with significant functional morbidity

Ocular emergency caused by occlusion of retinal artery with resultant infarction of the retina resulting in profound, usually monocular vision loss, and is associated with significant functional morbidity

  • Ophthalmic emergency

Etiopathogenesis

Non-arteritic CRAO:

Result of thrombosis or emboli inducing severe vision loss
  • Carotid artery atherosclerosis
  • Cardiogenic emboli
  • Hypertension
  • Smoking
  • Diabetes
  • Thromboembolic disease

Arteritic CRAO (< 5% of CRAO cases)

Attributed to a vasculitic etiology
  • Giant cell arteritis (GCA): Idiopathic vasculitis that primarily affects an elderly population with granulomatous inflammation of the intima of the small to medium-sized arteries of the upper body and head resulting in stenosis and occlusion of flow
  • Other less common vasculitic etiologies:
    • Polyarteritis nodosa
    • Granulomatosis with polyangiitis (formerly Wegener’s)
    • Churg-Strauss syndrome
    • Behcet’s disease
CRAO

Classification

  • Central Retinal Artery Occlusion (CRAO) (60%): Due to obstruction at the level of Lamina Cribrosa
  • Branched Retinal Artery Occlusion (35%)
  • Cilioretinal Artery Occlusion (1-2%)

Presentation

CRAO typically presents with painless, sudden (within seconds), and profound unilateral vision loss.

  • Sudden painless loss of vision

Complications:

  • Irreversible damage to neural tissue (after 90 minutes of occlusion)
  • Neovascular glaucoma (2-6%)
  • Vision loss (due to optic atrophy)

Diagnosis

Fundus examination:

  • Marked narrowing of retinal arteries
  • Retina becomes milky white
  • Cherry-red spots on macula centre + pale surroundings
  • Cattle tracking: segmentation of blood columns
  • Atrophic changes
  • Hollenhorst plaques (cholesterol emboli in retinal arteries)
Funduscopic appearance of the classic cherry red spot against the background of retinal whitening in central retinal artery occlusion
Funduscopic appearance of the classic cherry red spot against the background of retinal whitening in central retinal artery occlusion. | Olson, E. A., & Lentz, K. (2016). Central Retinal Artery Occlusion: A Literature Review and the Rationale for Hyperbaric Oxygen Therapy. Missouri medicine, 113(1), 53–57.

FFA (Fundus fluorescein angiography):

  • Delay in arterial filling
  • Masking of chorioretinal vasculature due to retinal oedema

Optical coherence tomography (OCT):

Non-invasive, non-contact imaging technology that allows in vivo evaluation of the inner and outer retinal architecture
  • Incomplete CRAO: Minimal disruption of the retinal architecture and inner layer hyper-reflectivity without retinal edema
  • Subtotal CRAO: Inner macular thickening and loss of organization of the inner retina
  • Total CRAO: Marked inner retinal thickening and subfoveal choroidal thinning.
98-year-old female presenting with reperfused central retinal artery occlusion
98-year-old female presenting with reperfused central retinal artery occlusion. A. Color fundus photograph shows the classic cherry–red spot. B. Fundus autofluorescence show diffuse pigment alterations and obscuration of the macular details due to retinal edema. C. Red-free imaging highlights the whitening of the retina. D. Fluorescein angiography demonstrates reperfusion of arterial flow with staining of the arterial wall. E. Optical coherence tomography demonstrates thickening of the inner retinal layer with marked hyperreflectivity and posterior shadowing in the entire macular area with sparing of the fovea. | Mehta, N., Marco, R. D., Goldhardt, R., & Modi, Y. (2017). Central Retinal Artery Occlusion: Acute Management and Treatment. Current ophthalmology reports, 5(2), 149–159. https://doi.org/10.1007/s40135-017-0135-2

Management

Treatment is unsatisfactory as retinal tissues cannot survive ischemia beyond 90-100 minutes.

A. Aggressive Treatment (within 24 hours)

  • Immediate lowering of IOP:
    • Intermittent ocular massage: Help facilitate the outflow of aqueous fluid which lowers IOP
    • Topical glaucoma drops
    • Anterior chamber paracentesis
    • Diuretics (acetazolamide or mannitol)
  • Improve blood flow and/or oxygenation:
    • Hyperbaric oxygen (HBO) therapy
    • Vasodilators and inhalation of 5% CO+ 95% O2
  • Fibrinolytic therapy
  • IV Steroids
  • Laser photodisruption

B. Work-up for associated systemic conditions

  • Systemic steroids: Administered when vasculitic/arteritic aetiology suspected
  • Smoking cessation and blood pressure control: Indicated for all
  • Carotid endarterectomy: Cases with significant carotid disease
  • Long-term anticoagulation: Cases with cardiogenic emboli

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