This document summarizes retinal artery occlusion, including classifications, epidemiology, clinical features, risk factors, evaluation, treatment, and prognosis for different types. Central retinal artery occlusion typically causes sudden, painless vision loss and has a poor visual prognosis. Branch retinal artery occlusion often causes partial vision loss and has a better prognosis, with vision recovering to 20/40 or better in most cases. Cilioretinal artery occlusion can occur in isolation or with central retinal vein occlusion, and isolated cases typically have a good visual outcome.

1. Retinal Artery Occlusion
Sumit Singh Maharjan

2. classification
• Central retinal artery obstruction
• Branch retinal artery obstruction
• Cilioretinal artery obstruction
• Combined retinal artery and vein obstruction
• Cotton wool spots

3. Central retinal artery obstruction (CRAO)
Epidemiology:
• Larger seen in old adults (60’s)
• M>F
• 1-2% have B/L involvement

4. Clinical features
• Monocular, painless, severe loss of vision which occurs acutely,
possibly over few seconds
• In some cases, premonitory episodes of Amaurosis Fugax may be
present
Risk of CRAO after Amaurosis fugax is estimated to be only 1% per year

5. • VA at presentation – CF to PL+ in 74 – 90% cases
• VA tends only to improve within the 1st week of onset with minimal
chance for appreciable improvement subsequently
• VA recovery after treatment has been shown to correlate with
presenting VA and the duration of visual impairment
• VA may spontaneously improve in 22% with non arteritic CRAO, less
than 10% of pt reports a meaningful recovery of vision
Visual Acquity

6. RAPD and Neovascularization
• Typically afferent pupillary defect develops
within seconds regardless of macular
involvement
• In a majority of cases, ant segment is normal
initially but if rubeosis iridis is present
acutely then ocular ischemia secondary to
presence of a concomitant carotid artery
obstruction should be considered
• Incidence of rubeosis iridis is 16.6 – 18.8%.
• Laser PRP – successful regression in 65% of
cases

7. Findings in Ophthalmoscopy
In acute phase:
• Cherry red spots (90%)
• Post pole retinal opacity or whitening (58%)
• Box carrying of retinal arteries and veins (20%)
• Retinal arterial attenuation (32%)
• Optic disc edema (22%)
• Optic nerve pallor (39%)

8. • Retinal findings predominantly located in the post pole with a normal
appearing periphery
• Retinal whitening corresponds to ischemic damage to the inner half
of the retina and is due to opacification of the retinal nerve fibre and
ganglion cell layer as a result of cessation of axoplasmic transport
caused by the acute ischemic insult
• Opacification is visible ophthalmoscopically where the ganglion cell
layer is more than 1 cell thick i.e. the macula except in the foveal
region where cherry red spot is seen
• Outer nuclear and plexiform layers and photoreceptors remain intact

9. • Size of cherry red spots is variable and depends on the size of foveola
• 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 and as a result does not become hypoxic or opacified
permitting continued visualization of the underlying retinal pigment
epithelium and choroid
• Similarly retinal periphery in CRAO cases appear normal because the
retina is also thinner with a single layer if ganglion cells such that the
nutrition of the inner retinal layers can be maintained by the
choroidal circulation alone

10. • Typically retinal opacification resolves over a period of 4 – 6 weeks,
although at least some retinal whitening is noted in 17% of patient
with complete, non transient CRAO after 1 month
• Pathologically, this evolution corresponds to a resolution of initial
acute ischemia induced intracellular edema with subsequent loss of
neuronal cells and the development of an acellular scar of the inner
retinal cell layer
• Patent cilioretinal artery supplying some or all of the papillomacular
bundle is seen in approx. 1/3rd of cases

11. • Retinal emboli are visible in 20-40% of eyes
• Retinal emboli consists of cholesterol (74%), calcified material (15%),
platelet and fibrin (15%).
• These cholesterol emboli originate from the carotid arteries in
atherosclerotic disease but can also arise from the aortic arch,
ophthalmic artery or proximal CRA.

12. • Cholesterol emboli are frequently small and do not completely
obstruct and frequently found at bifurcation sites
• Emboli can often be asymptomatic and migration and disappearance
of retinal emboli is common
• Calcific emboli are less common, but are larger and cause more
severe or complete obstruction and they mostly originate from
cardiac valves

13. • 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 patient
• In non arteritic CRAO disc may be normal, hyperemic, edematous and
rarely pale

14. Most frequent findings in the chronic stage with CRAO are:
• Optic atrophy (91%)
• Retinal arterial attenuation (58%)
• Cilioretinal collaterals (18%)
• Macular RPE changes (11%)
• Cotton wool spots (3%)

15. • Chronic phase optic nerve pallor is due to optic atrophy and nerve
fiber loss
• In arteritic CRAO, the associated anterior ischemic optic neuropathy
also contributes to the development of pallor
• In chronic CRAO – neovascularization rarely occurs because non
viable tissue is less likely to elaborate angiogenic factors
• Incidence of NVD: 1.8%

16. • Retinal arterial attenuation is more common in chronic phase than in
acute phase
• Months after an acute CRAO, cilioretinal collaterals may develop as a
result of a compensatory enlargement of capillary anastomosis
between retinal capillaries on the surface of the disc and ciliary
capillaries in deeper parts of the optic nerve head
• Probability of developing cilioretinal disc collaterals – 4% in 1 months,
18% in 3 months from onset

17. Ancillary studies
FA:
• Appearance of dye in the CRA is
typically delayed by 5 – 20 sec
• Fluorescence dye lines the arterial wall
in a pattern similar to the laminar flow
filling of normal retinal veins
• In cases with visible intra arterial
emboli, the AV transit time is even
more delayed

18. • Typically, the retinal circulation is re established after an acute CRAO
but the inner retinal tissue has generally already infarcted.
• So every FA return to normal but vision loss, optic nerve atrophy,
arterial narrowing persists.
• In acute stage, OCT shows irregular macular contour with increased
reflectivity of the inner retina
• This reflects the intracellular edema and explains the lack of
intraretinal, hyporeflective fluid spaces in cases of CRAO/BRAO
• Reflectivity of outer retinal layers and RPE is blocked by the highly
reflective inner retinal layer

19. • OCT of chronic CRAO show thinning and atrophy of the inner retina
• OCT may be helpful in chronic cases where fundus may appear
featureless but OCT shows inner retinal atrophy with preservation of
the outer retina.

20. • Central scotoma is the most common defect observed on macular
visual field testing followed by paracentral scotoma
• Patient with cilioretinal sparing show preserved central island of
vision corresponding to the area perfused by the patent cilioretinal
artery
• Preserved temporal island may be seen in some patient, presumably
secondary to choroid derived perfusion of the nasal retina
• Visual field defects improve in approx. 28% of patient, remain stable
in 57% and worsen in 7%.

21. • In CRAO, ERG typically demonstrates more severe attenuation of the
b-wave than a-wave since the inner retinal layer is more affected
• This produces a characteristic negative waveform with the scotopic
white stimulus

22. Systemic associations ocular abnormalities
associated with retinal artery obstruction
Embolic sources
• Systemic arterial hypertension (via atherosclerotic plaque)
• Carotid atherosclerosis
• Cardiac valvular disease
• Left ventricular hypertrophy
• Thrombus after myocardial infarct
• Intravenous drug use
• Lipid emboli (pancreatitis)
• Purtscher’s retinopathy (trauma)
• Deep-vein thrombosis
• Nasal oxymethazoline use

23. Trauma
• Retrobulbar injection
• Orbital floor fracture repair
• Penetrating injury
• Nasal surgery
Coagulopathies
• Sickle-cell disease
• Homocystinuria
• Lupus anticoagulant
• Protein C and/or S deficiency
• Antithrombin III deficiency
• Activated protein C resistance
• Factor V Leiden
• Platelet abnormalities
• Oral contraceptives
• Pregnancy
• Leukemia/lymphoma

24. Ocular conditions
• Prepapillary arterial loops
• Optic disc drusen
• Increased intraocular pressure
• Optic neuritis
Collagen vascular disease
• Giant cell arteritis
• Systemic lupus erythematosus
• Polyarteritis nodosa
• Wegener’s granulomatosis
• Fibromuscular dysplasia

25. Other vasculitides and inflammatory
conditions
• Orbital mucormycosis
• Toxoplasmosis
• Toxocara
• Lyme disease
• Behçet disease
• Cat-scratch disease
Miscellaneous associations
• Susac’s syndrome
• Fabry’s disease
• Sydenham’s chorea
• Migraine
• Hypotension

26. D/D of CRAO
• Single or multiple branch retinal artery obstruction
• Cilioretinal artery obstruction
• Severe commotio retina
• Necrotizing herpetic retinitis

27. Evaluation
Rarely patient presents within first few hours of visual deficit
• These pt should be admitted for observation, treatment and
immediate workup as their risk is higher for cerebral infarction
For pt presenting late
• Etiological work up is recommended on OPD basis
• Only true emergency in such a circumstances would be to rule out
giant cell arteritis in pt > 50 years and start steroid therapy

28. Treatment
• Conservative
• Invasive
• Spontaneous resolution can occur in upto 22% and has been reported
to occur upto 3 days.
• Meaningful visual recovery in < 10%

29. • In experimental study in monkeys,
• Retina suffers no damage till 97 minutes after an acute CRAO but
after 4 hours the retina suffers massive irreversible damage
• Therefore, treatment not instituted after 4 hours from onset.
• However, unlike animal models, humans rarely have complete
obstruction
• As a result, treatment for CRAO has been recommended within 24
hours of onset

30. Current conventional therapy consists of
• dislodging emboli,
• reducing IOP and increasing retinal blood flow,
• vasodilating the ocular blood supply,
• improving retinal circulation,
• decreasing retinal edema,
• maintaining retinal oxygenation until spontaneous reperfusion and
acting on the thrombus.

31. Systematic regimen involving multiple, sequential treatment steps had
better visual outcomes than arbitrary treatment with conservative
measures and protocol includes:
• Ocular massage
• Sublingual isosorbide dinitrate
• IV acetazolamide
• IV mannitol/glycerol
• AC paracentesis
• IV methyl prednisolone
• Streptokinase
• Retrobulbar tolazine

32. Ocular massage
Ocular massage is performed using either a Goldmann contact lens or
digital massage to apply ocular pressure with an in and out movement
to dislodge a possible obstructing embolus
Repeated massage with 10 – 15 sec of pressure followed by sudden
release is recommended
This procedure can produce retinal arterial vasodilatation, thereby
improving retinal blood flow

33. Hyperbaric oxygen
Mixture of 95% oxygen and 5% CO2 can be provided to induce
vasodilatation and improve oxygen
Purpose of hyperbaric O2 is to preserve the retina in an oxygenated
state until recanalization and reperfusion occur typically at 72hrs.
Hyperbaric O2 increases the arterial oxygen pressure and thereby
increases nitric oxide synthesis leading to vasodilation

34. AC paracentesis
• It causes a sudden decrease in IOP, possibly causing the arterial
perfusion pressure behind the obstruction to force an obstructing
embolus downstream.

35. Nd – Yag laser
Nd-Yag laser arteriotomy
Result in extrusion of an embolus
Reopening of the CRA
Return of vision
Laser is focused slightly deep to the vessel wall at the site of embolus
to avoid photodisruption and opacification of the overlying nerve fiber
layer

36. • Steroids 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 pt who have an underlying
systemic disease such as AF, acute internal carotid artery dissection or
hypercoaguable state
EAGLE (European assessment group for lysis in the eye)
• No benefit of using streptokinase, urokinase or T-PA

37. Branch retinal artery occlusion (BRAO)
• Represents 38% of all acute retinal artery occlusion
• RE (60%) > LE (40%)
• Pt presents with monocular vision loss, which may be restricted to
one part of VF
• Initial VA will be 20/40 or better in approx. 3/4th of pt
Presenting visual field defect includes:
• Central scotoma (20%)
• Central altitudinal (13%)
• Sector defect (49%)

38. • These whitening occurs secondary to blocked axoplasmic flow in the
nerve fiber layer as it reaches the hypoxic retinal layer

39. • BRAO typically occurs at the vessel bifurcation and 98% of the time,
temporal vessels are affected
• This may be due to nasal occlusion may be asymptomatic and
undetected
• Emboli are visible in 62% of the time

40. • In chronic stages, sectoral nerve fiber layer loss and arterial
attenuation may be seen
• Rarely in the chronic phase, posterior segment and or iris
neovascularization may be seen particularly in patient with DM
• Artery to artery collaterals may also be seen and are pathognomic of
BRAO

41. • Visual prognosis in eyes with symptomatic BRAO is generally good
and acquity usually improves to 20/40 or better in 80% of eyes
• Risk factor for BRAO are similar to CRAO so similar evaluation is
generally recommended.
• Giant cell arteritis is less common in BRAO
• In cases of an obstruction at a bifurcation, etiology is more often
embolic
• Since visual prognosis is typically good for BRAO, aggressive therapy
is generally not pursed unless significant foveal involvement is seen

42. Cilioretinal artery occlusion
• Accounts for 5% of retinal artery obstruction
• Cilioretinal artery enter the retina from the temporal optic disc,
separate from the CRA and can be seen on examination in 20% of
eyes
• On FA – they are seen 32% of the time and fill concomitantly with the
choroidal circulation

43. When evaluating CLRAO, 3 distinct groups are found:
• Isolated CLRAO
• CLRAO associated with CRVO
• CLRAO in conjunction with anterior ischemic optic neuropathy

44. • Cilioretinal artery occlusion can occur in association with CRVO
Together these occlusion have been hypothesized to constitute a
distinct clinical entity arising from a sudden increase in the intraluminal
capillary pressure due to CRVO
Inducing relative occlusion of the cilioretinal artery whose perfusion
pressure is lower than the central retinal artery

45. • Initial visual field defect include cecocentral scotoma, central scotoma
and central superior or inferior altitudinal defect
• Isolated CLRAO typically have a good prognosis – nearly 90%
achieving 20/40 or better and 60% returning to 20/20.
• Even with severe damage to papillomacular bundle, potential VA can
be quite good, presumably secondary to intact sup and inf nerve fiber
layer bundles supplying the fovea

46. • CLRAO in conjunction with a CRVO comprises 40% of CLRAO
• Venous obstruction are usually non ischemic and tend not to cause
iris neovascularization or neovascular glaucoma
• CLRAO in association with anterior ischemic optic neuropathy is seen
in 15% of eyes with CLRAO and has a poor VA and prognosis ranging
from 20/400 to NPL secondary to optic nerve damage
• Typically hyperemic or pale, edematous optic disc is seen with
superficial retinal whitening along the course of cilioretinal artery

47. • Giant cell arteritis has a selective tendency to involve the post ciliary
artery, resulting in its occlusion, which in turn results in simultaneous
development of both arteritic anterior ischemic optic neuropathy and
CLRAO
• Ocular treatment is generally not pursued unless giant cell arteritis
exists

48. Combined retinal artery and vein occlusion
• CRVO can be seen in association with CRAO,BRAO and CLRAO
• Fundus shows superficial retinal whitening with a cherry red spots
and signs of venous obstruction such as dilated tortous veins,
intraretinal hemorrhage, optic disc edema, cotton wool spots and
marked thickening of the retina

49. • CRAO seen with a CRVO may not be a true CRAO but may be
secondary to the occlusion of the central retinal vein in the region of
the lamina cribrosa
• The blood cannot exists out of the retinal vascular bed as a result of
complete blockage of the central retinal vein and secondarily
compromise entry of blood into the eye
• Visual prognosis is poor with HM range
• After 6 – 8 weeks optic nerve pallor with severe arterial attenuation is
seen
• Rubeosis iris develops in 80% of eyes
• Aggressive treatment with PRP is indicated

50. Cotton wool spots
Ischemic
• Diabetes
• Hypertension
• Retinal vein occlusion
• Ocular ischemic syndrome
• Severe anemia
• Hyperviscosity/hypercoagulable state/dysproteinemia
• Radiation
• Acute blood loss

51. Embolic
Carotid emboli
Cardiac emboli
• Cardiac valvular disease
• Endocarditis
• Rheumatic heart disease
• Deep venous emboli
• White cell emboli/Purtscher and
Purtscher-like retinopathy (head
trauma, long bone fractures, acute
pancreatitis, chest compression injury,
amniotic fluid emboli, fat emboli)
Foreign-body emboli (intravenous drug
abuse, talc)
Collagen vascular disease
• Systemic lupus erythematosus
• Dermatomyositis
• Scleroderma
• Polyarteritis nodosa
• Giant cell arteritis

52. Infectious
• HIV retinopathy
• Fungemia
• Bacteremia
• Rocky Mountain spotted fever
(Rickettsia rickettsii )
• Cat-scratch disease (Bartonella
henselae)
• Leptospirosis
• Onchocerciasis (Onchocerca
volvulus)
Toxic
• Interferon (α2a, β1a)
Neoplastic
• Leukemia
• Lymphoma
• Metastatic carcinoma
Miscellaneous
• Traumatic
• Tractional (epiretinal membrane)
• High-altitude retinopathy
• Papilledema/papillitis
Idiopathic

53. References
• Ryan’s 5th edition
• Myron yanoff 4th edition
• American academy of Ophthalmology-sec 12, 2013,2014
• Kanski’s clinical ophthalmology 8th edition