CRAO

1. CENTRAL RETINAL
ARTERY OCCLUSION
DR ARPITA

2. ANATOMY

3. • The ophthalmic artery is the first branch of the internal
carotid artery and enters the orbit underneath the optic
nerve through the optic canal.
• The central retinal artery is the first intraorbital branch of
the ophthalmic artery, which enters the optic nerve 8-15
mm behind the globe to supply the retina.
• Short posterior ciliary arteries branch distally from the
ophthalmic artery and supply the choroid.
• Anatomical variants include cilioretinal branches from
the short posterior ciliary artery, which gives additional
supply to the macula from the choroidal circulation
• A cilioretinal artery occurs in approximately 14% of the
population

4. Retinal artery obstructions selectively affect the inner
retina only.

5. • DEFINITION: An abrupt diminution of
blood flow through the central retinal
artery severe enough to cause
ischemia of the inner retina
• A central retinal artery obstruction occurs when the
blockage is within the optic nerve substance itself
and therefore the site of obstruction is generally not
visible on ophthalmoscopy. A branch retinal artery
obstruction occurs when the site of blockage is
distal to the lamina cribrosa of the optic nerve.

6. HISTORY
• In 1859, Van Graefe first described central retinal artery
occlusion (CRAO) as an embolic event to the central
retinal artery in a patient with endocarditis.
• In 1868, Mauthner suggested that spasmodic
contractions could lead to retinal artery occlusion
• In1881 Samelsohn advocated treatment with nitrate
inhalation
• In 1888 Mules did AC paracenteses for CRAO

7. EPIDEMIOLOGY
• Approximately 8.5 CASES PER 100000.
• Similar to other vascular disorders, this condition is
largely seen in OLDER ADULTS but cases in children
and young adults have also been reported.
• The average age at presentation is in the early sixties
• MEN are affected more frequently than women.
• No predilection for one eye over the other has been
reported; however, 1–2% of cases may manifest bilateral
involvement

8. ETIOPATHOGENESIS
• THROMBOTIC-80%
• EMBOLIC -20%

9. CLINICAL FEATURES
• SYMPTOMS
• Monocular
• Sudden loss of vision
• severe
• painless
• Occurs acutely, possibly over the span of a few
seconds.
• In some cases, premonitory episodes of amaurosis
fugax may be reported. Amaurosis fugax represents
transient acute retinal ischemia and typically
suggests an embolic source of occlusion

10. • SIGNS
1) Visual acuity at the time of initial presentation ranges
from counting fingers to light perception
• Central visual acuity may be near normal in patients who
have a transient CRAO or a cilioretinal artery providing
sufficient vascular supply to the fovea.
• The absence of light perception is rare; therefore, in
such cases, concomitant choroidal circulation deficit
(e.g., due to ophthalmic artery occlusion) or optic nerve
involvement should be considered
• Visual acuity tends only to improve within the first week
of onset with minimal chance for appreciable
improvement subsequently
• Visual recovery after treatment has been shown to
correlate with presenting visual acuity and the duration of
visual impairment

11. 2) RAPD
3) INTRAOCULAR PRESSURE is often normal at
presentation but may become elevated in the setting
of rubeosis iridis
4) FUNDUS CHANGES
• Cherry-red spot (90%)
• Posterior pole retinal opacity or whitening (58%),
• Box-carring of retinal arteries and veins (19% and
20% respectively)
• Retinal arterial attenuation (32%)
• Optic disc edema (22%), and optic nerve pallor (39%)
• The retinal findings were predominantly located in the
posterior pole with a normal-appearing periphery

12. • The retinal whitening is due to opacification of the retinal
nerve fiber and ganglion cell layer as a result of
cessation of axoplasmic transport caused by the acute
ischemic insult.
• The opacification is visible ophthalmoscopically where
the ganglion cell layer is more than one cell thick,
i.e., the macula, except in the foveal region, whe cherry-
red spot is seen.

13. • The cherry-red spot is actually normal-appearing retina
and is observed in high contrast against the surrounding
opacified retina because the thin retina in this location is
nourished by the underlying choroidal circulation
• Similarly, the retinal periphery in CRAO cases appears
normal because the retina is also thinner with a single
layer of ganglion cells, such that the nutrition of the inner
retinal layers can be maintained by the choroidal
circulation alone.
• Typically, the retinal opacification resolves over a period
of 4–6 weeks

15. • A patent cilioretinal artery supplying some or all of the
papillomacular bundle is seen in approximately ONE-
THIRD of cases

16. Cilioretinal arteries of varying size are found in about 20 per cent of eyes.
These are part of the posterior ciliary circulation and are therefore spared in a
CRAO. The patch of retina supplied by the artery is left viable; if the patient is
fortunate this will include the macula. A small cilioretinal vessel is seen clearly
in this patient supplying an area of retina temporal to the optic disc. Minute
cholestero emboli can be seen in the inferior and superior temporal arteries
and also in a smal branch artery adjacent to the macula, indicating the
aetiology of the occlusion. Fluorescein angiography demonstrates the slow
rate of filling of the retinal circulation and the normal filling ofthe cilioretinal
artery and choroid.

18. • Box-carring or segmentation of the blood column of both
the arteries and veins occurs secondary to separation of
blood serum from erythrocytes in a stacked or rouleaux
formation

19. • Retinal emboli are visible in 20–40% of eyes with CRAO
.The most common variant is a yellow, refractile
cholesterol embolus (Hollenhorst plaque)

20. • Retinal emboli consist of CHOLESTEROL in 74% of cases,
CALCIFIED MATERIAL in 15.5%, and PLATELET AND FIBRIN in
15.5%
• 1 Cholesterol emboli (Hollenhorst plaques) appear as
intermittent showers of minute, bright, refractile, golden to yellow-
orange crystals, often located at arteriolar bifurcations They rarely
cause significant obstruction to the retinal arterioles and are
frequently asymptomatic.
2 Calcific emboli may originate from atheromatous plaques in
the ascending aorta or carotid arteries, as well as from calcified
heart valves. They are usually single, white, non-scintillating and
often on or close to the disc When located on the disc itself, they
may be easily overlooked as they tend to merge with the disc. They
may cause permanent occlusion of the central retinal artery or one
of its main branches.
3 Fibrin-platelet emboli are dull grey, elongated particles which
are usually multiple and occasionally fill the entire lumen They may
cause a retinal transient ischaemic attack (TIA), with resultant
amaurosis fugax, and occasionally complete obstruction.

26. • Ophthalmologist plays an important role in the
management of these patients by referring them for
prophylactic medical or surgical treatment to forestall the
development of permanent neurological sequelae as
patients with retinal embolization have an increased risk
of developing a permanent stroke over the next few
months and the risk is substantially increased if the
amaurosis fugax is accompanied by signs of transient
cerebral ischaemia or an embolus is visible in the retina
• It should be noted that the leading cause of death in
patients with retinal arterial obstruction is
cardiovascular disease

27. • The optic nerve is acutely edematous in nearly all cases
of arteritic CRAO as a result of the associated anterior
ischemic optic neuropathy that is typically observed in
these patients. In the acute phase of nonarteritic CRAO,
the disc may be normal, hyperemic, edematous, and,
rarely, pale.
• Months after an acute CRAO, cilioretinal collaterals
may develop as a result of a compensatory enlargement
of capillary anastomoses between retinal capillaries on
the surface of the disc and ciliary capillaries in deeper
parts of the optic nerve head.

29. • The most frequent findings in the CHRONIC STAGE of
eyes with CRAO are
• optic atrophy (91%),
• retinal arterial attenuation (58%),
• cilioretinal collaterals (18%),
• macular RPE changes (11%), and
• cotton-wool spots (3%)

31. ANCILLARY STUDIES
• 1) OCT
• In the acute stage, optical coherence tomography (OCT)
shows an irregular macular contour with increased
reflectivity of the inner retina. This corresponds to
intracellular edema and explains the lack of intraretinal,
hyporeflective fluid spaces in cases of CRAO or BRAO.
The reflectivity of the outer retinal layers and RPE is
blocked by the highly reflective inner retinal layer.
• OCT can be helpful in cases of chronic CRAO where the
fundus may appear featureless but the OCT shows inner
retinal atrophy with preservation of the outer retina

33. • 2)FFA
• Initially shows some variable residual retinal circulation
with delayed and sluggish filling of the retinal
vasculature. Complete absence of retinal filling is rare
• Areas of delayed choroidal perfusion, may be seen in
about 11% of eyes with acute CRAO.
• Leakage of fluorescein dye at the level of the RPE is
generally not seen with CRAO unless the choroidal
circulation is involved

35. • 3) ERG
• Typically demonstrates more severe attenuation of the b-
wave than the a-wave since the inner retinal layers are
more affected – this produces a characteristic negative
waveform
• Diminution of the a-wave and b-wave may suggest outer
retinal damage secondary to choroidal vascular
hypoperfusion in the setting of an ophthalmic artery
occlusion in addition to a CRAO

36. 4) AUTOFLUORESCENCE
Imaging in the area supplied by the occluded retinal
artery acutely shows decreased autofluorescence due to
blockage of the normal autofluorescence of the RPE by
the thickened inner retina.
5) VISUAL FIELDS
• Central scotoma is the most common defect observed
on macular visual field testing followed by paracentral
scotoma.
• Patients with cilioretinal sparing show a preserved
central island of vision corresponding to the area
perfused by the patent cilioretinal artery. Peripheral
constriction is the most common visual field deficit noted
in these patients

37. SYSTEMIC ASSOCIATIONS

38. EVALUATION
• The only true emergency in such a circumstance would
be to rule out giant cell arteritis in patients older than 50
years with a positive review of systems. Evaluation for
giant cell arteritis includes compete blood count,
including platelets, erythrocyte sedimentation rate, and
C-reactive protein. If suspicion is high, the patient should
be started on steroid therapy and scheduled for a
temporal artery biopsy.
• In other cases etiologic workup is generally
recommended on an outpatient basis along with a
primary care physician.

39. • The evaluation of embolic source often includes carotid
Doppler imaging and echocardiography since the most
common sources of retinal emboli are from the carotid
artery or the heart and chronic anticoagulation may be
indicated to prevent more serious adverse events.
• Since the cardiac morbidity and mortality are significant
in patients with retinal artery occlusion, a baseline
electrocardiogram is recommended
• A hypercoagulability evaluation should be considered for
patients less than 50 years of age with a suggestive
history (e.g.,prior thrombosis, miscarriage, or family
history) or unknown embolic source
• Other tests for monoclonal gammopathy, cancer,
• infection, and disseminated intravascular coagulation
may be ordered depending on the clinical circumstance

40. TREATMENT
• Adoption of a supine posture might improve ocular
perfusion
• Ocular massage
• sublingual isosorbide dinitrate
• intravenous acetazolamide,
• intravenousmannitol or oral glycerol,
• anterior-chamber paracentesis,
• Intravenous methylprednisolone, streptokinase, and
• Hayreh has shown that irreversible cell injury occurs
after 90-100 minutes of total CRAO in the primate model.
Controversy exists regarding the optimal window of
treatment in humans, but the conservative approach
involves treatment up to 24 hours.

41. • Ocular massage is performed using either a Goldmann
contact lens or digital massage to apply ocular pressure
with an in-andout movement to dislodge a possibly
obstructing embolus.
• Repeated massage with 10–15 seconds of pressure
followed by a sudden release is recommended. This
maneuver can produce retinal arterial vasodilation,
thereby improving retinal blood flow
• A mixture of 95% oxygen and 5% carbon dioxide
(carbogen) can be provided to induce vasodilation and
improve oxygenation, but efficacy has not been proven

42. • Hyperbaric oxygen provides oxygen at levels of
atmospheric pressure. The purpose of hyperbaric
oxygen is to preserve the retina in an oxygenated state
until recanalization and reperfusion occur, typically at 72
hours. The hyperbaric oxygen increases the arterial
oxygen pressure and thereby increases nitric oxide
synthesis, leading to vasodilation
• ‘Rebreathing’ into a paper bag in order to elevate blood
carbon dioxide and respiratory acidosis, as this may
promote vasodilation

43. • Anterior-chamber paracentesis causes a sudden
decrease in intraocular pressure, possibly causing the
arterial perfusion pressure behind the obstruction to
force an obstructing embolus downstream
• Topical timolol 0.5% and intravenous acetazolamide 500
mg to achieve a more sustained lowering of intraocular
pressure
• Hyperosmotic agents. Mannitol or glycerol have been
used for their possibly more rapid IOP-lowering
• Vasodilating medications that have been utilized to
increase retinal blood flow in retinal arterial occlusion
include pentoxifylline, nitroglycerin, and isosorbide
dinitrate

44. • (Nd- YAG) laser arteriotomy in patients with CRAO has
been reported to result in extrusion of an embolus,
reopening of the central retinal artery, and return of
vision. A fundus contact lens is used with the laser in
single-burst mode.
• Pulses are delivered directly to the emboli, beginning
with the lowest power setting and then with increasing
energy until either (1) achieving photofragmentation of
the embolus within the arteriole without creating an
opening in the vessel wall and without vitreous
hemorrhage or (2) creating visible removal of the
embolus from within arteriole into the vitreous cavity,
typically associated with a limited vitreous hemorrhage.
• Digital pressure can be applied to the globe to help stop
bleeding, if it occurs

45. • Corticosteroids should only be used when arteritic
CRAO from giant cell arteritis is suspected.
Anticoagulants should be reserved for secondary
prevention of cerebral and ocular infarction in those rare
patients who have an underlying systemic disease such
as atrial fibrillation, acute internal carotid artery
dissection, or a hypercoagulable condition
• In 2010 the European Assessment Group for Lysis in the
Eye (EAGLE) study group published the results of the
first prospective, randomized clinical trial evaluating the
effect of intra-arterial t-PA compared with conservative
treatment.
• At 1 month, the mean best-corrected visual acuity
improved significantly in both groups but no significant
difference was noted between groups

46. • Iris neovascularization develops after acute CRAO in
approximately 18% of eyes, with a mean time interval of
approximately 4- 5 weeks -typically earlier than in CRVO
3 months), and along with very poor vision may indicate
ophthalmic artery occlusion. Full-scatter PRP is effective
in eradicating the new iris vessels in about two thirds of
cases
• Neovascularization of the disc occurs in 2-3% of
patients. Panretinal photocoagulation is effective for
optic disc neovascularization.
• Intravitreal injection of an anti-VEGF agent is first-line
therapy for iris, trabecular meshwork, or optic disc
neovascularization

47. • Treatment of carotid disease
In patients with a localized stenosis of the artery,
endarterectomy significantly reduces the risk of
subsequent stroke. In experienced hands this operation
carries a mortality of less than 1%, although the
incidence of morbidity is higher.
• If endarterectomy is contraindicated, medical treatment
with drugs that reduce platelet stickiness (aspirin,
dipyridamole) or anticoagulants may be used to reducing
the frequency of transient ischaemic attacks and the risk
of a major stroke.

48. FOLLOW-UP
• The patient should be seen by an ophthalmologist in 3–4
weeks and again a month later in order to detect
incipient neovascularization, particularly of the anterior
segment.
• In the minority of cases where referral to a specialist
vascular team is not indicated, it should be ensured that
the results of systemic investigations have been
reviewed and necessary systemic treatment initiated.

49. PROGNOSIS
• Patients with visualized retinal artery emboli, whether or
not obstruction is present, have a 56% mortality rate
over 9 years, compared to 27% for an age-matched
population without retinal artery emboli.
• Life expectancy of patients with CRAO is 5.5 years
compared to 15.4 years for an age-matched population
without CRAO