Retinal Vessel Occlusion

Anatomy

The internal carotid artery enters the skull through the carotid foramen and branches into the ophthalmic artery, which further divides into:
- The central retinal artery (occlusion (CRAO); supplies the inner ⅔ of the retina)
- The posterior ciliary arteries (branch retinal vein occlusion (BRAO); supply the outer ⅓ of the retina)
The central retinal vein (occlusion (CRVO))
- Drains either into the superior ophthalmic vein or the cavernous sinus directly

The carotid artery with the ophthalmic artery and branches. Note the central retinal artery and posterior choroidal arteries, which enter the eye around the optic nerve.
Image by BioDigital, edited by Lecturio
Superior view: The internal carotid artery branches into the ophthalmic artery, which further divides into the central retinal artery and the posterior ciliary arteries.
Image by BioDigital, edited by Lecturio
The superior ophthalmic vein and the cavernous sinus, into which the central retinal vein drains.
Image by BioDigital, edited by Lecturio

Embolism (most common cause of ipsilateral CRAO)
- Cardiogenic or atherosclerotic (most commonly of carotid origin)
  - Risk factors include:
    - Hypertension
    - Diabetes mellitus
    - Atrial fibrillation
    - Cardiac valvular problems/patent foramen ovale (leads to clots breaking off)
- Cholesterol embolism; usually occurs after vessel catheterization
- Septic embolism, as a consequence of infective endocarditis
Inflammatory conditions such as temporal arteritis and other forms of vasculitis

Exact causes are not known, although there is an association with the following conditions:

Atherosclerotic conditions
- Hypertension
- Hypercholesterolemia
- Smoking
- Diabetes mellitus
- Obesity
Hypercoagulable state
- Sickle cell anemia
- Antiphospholipid syndrome
- Multiple myeloma
Inflammatory (e.g., systemic lupus erythematosus (SLE))
Pharmacological (e.g., oral contraceptive pills)
CRVO is categorized into 2 types based on etiology: ischemic (hemorrhagic retinopathy) and nonischemic (venous stasis retinopathy)

Image showing a color fundus photograph of the left eye with CRAO; retinal artery attenuation (arrows) and optic disc pallor
Image: “Color fundus photography of the left eye” by Division of Cardiology, Department of Internal Medicine, Pohang St. Mary’s Hospital, Pohang, Republic of Korea. License: CC BY 4.0
Fundus photograph of the right eye indicating CRAO/CRVO: a “blood and thunder” appearance and “cherry red” spot are both seen in this image (a patient with systemic lupus erythematosus)
Image: “Chorea and retinal vessel occlusion” by Department of Neurology, Shariati Hospital, Tehran University of Medical Sciences AND Iranian Center of Neurological Research, Tehran, Iran. License: CC BY 2.0

Central retinal artery occlusion

Sudden, painless, complete monocular vision loss
Patients may recall transient similar episodes (e.g., amaurosis fugax)
Fundoscopic examination reveals:
- Pallor of optic disc due to narrowed arteries
- “Cherry red” spot in the macula (at the fovea centralis)

Central retinal vein occlusion

May be sudden or gradual, painless, monocular vision loss
Fundoscopic examination reveals
- Swollen optic disc (papilledema) and engorged retinal veins with hemorrhage
- “Blood and thunder” appearance due to extensive hemorrhage (ischemic type)
- “Cotton-wool” spots: white deposits on the retina due to swelling of the retinal nerve (ischemic type)

Diagnosis of both conditions is usually clinical but additional investigations may be ordered.

Fluorescein angiography (to differentiate ischemic from non-ischemic forms of CRVO)
Optical coherence tomography (used to assess the progression of retinal vein occlusion or response to treatment)
Carotid doppler
Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP): to rule out vasculitides

Image of a 15-year-old girl with left intraretinal hemorrhaging (CRVO) (patient has a history of systemic lupus and antiphospholipid antibodies)
Image: “Finding of eye fundus” by Department of Pediatrics and Child Neurology, Oita University Faculty of Medicine, Hasama, Yufu, Oita 879-5593, Japan. License: CC BY 2.0
Left eye showing “cherry red” spot with retinal pallor typical of CRAO (arrow)
Image: “Acute central retinal artery occlusion” by James Paget University Hospital NHS Foundation Trust, Lowestoft Road, Gorleston, Great Yarmouth NR31 6LA, Norfolk, UK. License: CC BY 2.0

Vitreous hemorrhage: intraocular bleeding in or around the vitreous body usually from trauma, a retinal tear, or any disease causing neovascularization. Patients present with floaters and cloudy vision. Treatment includes surgery and avoiding anticoagulants. Vitreous hemorrhage is differentiated from a vessel occlusion due to a more gradual onset and the presence of floaters.
Retinal detachment: separation of the neurosensory retina from the retinal pigment epithelium. Classically, the condtion presents as a curtain descending over the eye causing painless vision loss, but can also cause floaters and flashes early on. Most common causes are aging and trauma. Diagnosis is with direct eye exam and ultrasound. Treatment is surgery by laser or freezing.
Cataracts: opacification of the lens in the eye, which leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Risk factors are age and eye injury. Symptoms may include faded colors, blurry or double vision, halos around light, trouble with bright lights, and trouble seeing at night. Cataracts can be visualized as a cloudy lens on eye exam. Curative treatment is surgical replacement of the lens.