The document summarizes various causes of sudden vision loss including retinal artery obstruction, retinal vein obstruction, ischemic optic neuropathy, optic neuritis, vitreous hemorrhage, and acute glaucoma. It then describes the blood supply of the eye from the central retinal artery, anterior ciliary arteries, and posterior ciliary arteries. It provides details on retinal vein occlusion including presentation, risk factors, and treatments such as anti-VEGF injections. It also discusses retinal artery occlusion presenting with sudden severe vision loss and visible emboli, as well as treatments focused on underlying causes.

1. Sudden loss of vision
disorders

2. ¡ Retinal artery obstruction
¡ Retinal vein obstruction
¡ ISCHEMIC OPTIC NEUROPATHY
¡ Optic neuritis
¡ Vitreous hemorrhage
¡ Acute glaucoma

4. Blood supply
The blood supply of the globe is
derived from three sources: the
central retinal artery, the
anterior ciliary arteries and
the posterior ciliary arteries.
All these are derived from the
ophthalmic artery, which is a
branch of the internal carotid
artery.
The central retinal artery runs
in the optic nerve to reach the
interior of the eye, and its
branches spread out over the
inner surface of the retina, with
the branching capillaries
supplying the inner half the
neuroretina.

5. Blood supply
¡ The anterior ciliary arteries emerge from
the insertion of the recti muscles and
perforate the globe near the iris root to join
an arterial circle in the ciliary body.
¡ The posterior ciliary arteries are the fine
branches of the ophthalmic artery, which
penetrate the posterior pole of the eye.
¡ Some of these supply the choroid and two or
more larger vessels run anteriorly to reach
the arterial circle in the ciliary body.
¡ The larger vessels are known as the long
posterior ciliary arteries, and those
supplying the choroid arte known as the
short posterior ciliary arteries.

6. Blood supply
The branches of the central
retinal artery are accompanied
by an equivalent vein.
However, the uvea (choroid,
ciliary body, and iris) are all
drained by approximately four
vortex veins in all.
These vortex veins leave the
posterior four quadrants of the
globe.

9. RETINAL VEIN OCCLUSION
¡ In central retinal vein occlusion, the retinal abnormalities
involve all four quadrants of the fundus.
¡ In branch retinal vein occlusion, typically the abnormalities are
confined to one quadrant because the occlusion usually occurs at the
site of an arteriovenous crossing, but they may involve the upper or
lower half (hemispheric branch retinal vein occlusion) or just the
macula (macular branch retinal vein occlusion).
¡

11. Retinal Vascular Occlusions
¡ Retinal vein occlusions (RVO) is due to obstruction of the retinal
veins.
¡ It usually occurs in persons over 50 years old, but can occur
earlier. This is more common in hypertensive patients compared
to normotensives.
¡ It is also associated with diabetes, hyperlipidemia, and other
cardiovascular risks, as well as increased intraocular pressure.
Factors that predispose to increase blood viscosity e.g. leukemia
may also predispose to RVO.

12. RETINAL VEIN OCCLUSION
¡ Retinal vein occlusion is a relatively common and easily diagnosed
retinal vascular disorder with potentially blinding complications.
¡ The patient usually presents with sudden, painless loss of vision at the
time of the occlusion, when the clinical appearance varies from a few
small, scattered retinal hemorrhages and cotton-wool spots to a
marked hemorrhagic appearance with both deep and superficial
retinal hemorrhage, which rarely may result in vitreous hemorrhage.
¡ The presentation may also be with sudden loss of vision due to
vitreous hemorrhage from retinal neovascularization or gradual loss of
vision due to macular edema.

13. ¡ The fundus appearance in CRVO is dramatic with numerous
scattered haemorrhages, cotton wool spots and dilated tortuous
retinal veins in all four quadrants, and swelling of the optic disc,
and the patient experiences sudden blurring of vision in one eye.
The level of vision reduction is dependent on the level of retinal
ischemia.
¡ Ischemic CRVO may progress
to iris revascularization.

14. ¡ Obstruction of a branch of the central retinal vein, called
branch retinal vein occlusions (BRVO) is more common than
central retinal vein occlusion (CRVO).
¡ RVO may be further divided into ischemic and non-ischemic
types.

15. ¡ In BRVO, the venous dilatation, retinal hemorrhages, and cotton wool
spots are confined only to the distribution of the occluded vein.
¡ The obstruction in BRVO usually occurs at an arteriovenous crossing.
¡ Ischaemic BRVO of sufficient size will predispose to retinal or optic disc
revascularization.
¡ Visual loss in RVO is due to ischaemia, macular edema or both.

16. macular edema (OCT)

17. Central retinal vein occlusion
Retinal hemorrhage in all four quadrants, dilated tortuous veins,
and optic disk edema.
¡ Optical coherence tomography shows cystoid macular edema.
Fundus fluorescein angiogram shows late leak with petalloid
appearance of macula.
¡ Patients are usually over 50 years of age, and more than 50%
have associated cardiovascular disease.
¡ The major complications are macular edema, neovascular
glaucoma secondary to iris neovascularization, and retinal
neovascularization.

18. MACULAR EDEMA IN RETINAL VEIN
OCCLUSION
¡ Macular dysfunction occurs in almost all eyes with central retinal vein
occlusion.
¡ Although some will show spontaneous improvement, most will have
persistent decreased central vision due to chronic macular edema,
which is also the main cause of persisting reduction of visual acuity in
branch retinal vein occlusion.

19. treatment
¡ Intravitreal injection of an anti-VEGF agent is the treatment of choice
for macular edema due to central or branch retinal vein occlusion.
¡ Monthly injections of ranibizumab or aflibercept have been shown to
be effective.
¡ Trials are in progress to determine the efficacy of bevacizumab.
Intravitreal steroid, either triamcinolone or Ozurdex (Allergan), which
is an intravitreal sustainedrelease implant containing dexamethasone,
also is effective but may cause increased intraocular pressure and
development or progression of cataract.
¡ Macular edema due to central retinal vein occlusion does not respond
to laser treatment. In branch retinal vein occlusion, grid-pattern
macular argon laser photocoagulation may be indicated when vision
loss due to macular edema persists for several months without any
spontaneous improvement.

20. IRIS AND RETINAL
NEOVASCULARIZATION IN RETINAL
VEIN OCCLUSION
¡ Either initially or subsequently, one-third of central retinal vein
occlusions are ischemic, which is associated with visual acuity
worse than 20/100 and a relative afferent pupillary defect but is
detected best by greater than 10 disk areas of retinal ischemia on
FFA.
¡ One-half of ischemic eyes will develop anterior segment (iris
and/or anterior chamber angle) neovascularization with the risk
of progression to neovascular glaucoma.
¡ The standard treatment for anterior segment neovascularization
is PRP, which may be preceded by an intravitreal anti-VEGF
agent.
¡ In branch retinal vein occlusion, retinal neovascularization
develops in 40% of eyes with more than five disk areas of retinal
ischemia.

21. Management of CRVO
¡ Macular edema in CRVO does not respond to laser
photocoagulation.
¡ Recent clinical trials have shown that the macular edema in CRVO
responds to multiple intravitreal injections of anti-VEGFs and
steroids similar to the situation in diabetic macular edema.

22. ¡ Sectoral retinal laser photocoagulation of the ischemic
retina halves the risk of vitreous hemorrhage.

23. Retinal Artery Occlusions
¡ Retinal artery occlusions result from a s reduction of central
retinal artery perfusion (CRAO) or a branch of the central retinal
artery (BRAO) causing ischemia of the inner retina in the
distribution of the affected blood vessel.
¡ Retinal arterial occlusions are less common and the prognosis is
uniformly worse than vein occlusions.

24. RETINAL ARTERY OCCLUSION
¡ Central retinal artery occlusion causes sudden, severe loss of vision
without pain.
¡ Antecedent transient visual loss (amaurosis fugax) may be reported
and is suggestive of giant cell arteritis or retinal emboli.
¡ Visual acuity ranges between counting fingers and light perception in
90% of eyes at initial examination.
¡ Usually there is permanent extensive loss of visual field.
¡ Twenty-five percent of eyes have cilioretinal arteries that continue to
perfuse the macula, potentially preserving central field and/or visual
acuity.
¡ An afferent pupillary defect can appear within seconds, preceding any
fundus abnormalities, which include opacification of the superficial
retina due to infarction and reduced blood flow in the retinal vessels,
sometimes visible as segmentation (“cattle trucking”) of the blood
column in the retinal arterioles.

25. Retinal Artery Occlusions
¡ On fundoscopy, there is whitening of the affected retina (due to
edema/swelling of the inner retina.
¡ This appears as a cherry red spot in CRAO, whilst in BRAO the whitening
is restricted to the retinal area supplied by the occluded vessel.

27. The retinal whitening disappears at approximately 4 weeks
after the occlusion.
An embolus may be seen
in arterial branch or the
CRA at the optic disc.
The occluded arteriole will
be narrowed, and blood
flow disrupted and seen as
cattle-tracking of the blood
column in the occluded
vessel.

28. In BRAO, a visual field defect corresponding to the distribution of
the occluded vessel is observed.

29. ¡ A foveal cherry-red spot develops due to preservation of the relatively
normal appearance of the choroidal pigment and RPE through the
extremely thin retina overlying the fovea, surrounded by the pale swollen
retina of the rest of the macula.
¡ The fundal abnormalities resolve within 4–6 weeks, leaving a pale optic
disk as the major ocular finding.
¡ Acute central retinal artery occlusion with cherry-red spot
(arrow) and preserved retina due to cilioretinal arterial supply
(arrowheads).

30. Branch retinal artery occlusion
¡ Branch retinal artery occlusion also causes sudden painless visual loss but
usually manifesting as impairment of visual field that usually is
permanent.
¡ Visual acuity is reduced only if there is foveal involvement.
¡ The extent of the fundal abnormalities, primarily retinal opacification as
in central retinal artery occlusion but sometimes accompanied by cotton-
wool spots along its border, is determined by the extent of retinal
infarction.
¡ The cause is often embolic disease,for which clinical evaluation and
investigations need to be undertaken.

31. Imaging
¡ In the acute phase of retinal artery occlusion, OCT shows hyperreflectivity
with thickening of the inner retina extending to include the outer
plexiform layer.
¡ The adjacent outer retinal layers are not clearly discernible and are seen
as a hyporeflective or widened area, probably due to masking of the outer
layers by the cloudy swelling of the inner retina.

32. ¡ Similarly autofluorescence imaging shows reduced autofluorescence due to
masking of the normal autofluorescence of the RPE.
¡ Resolution of the cloudy swelling leads to recovery of normal
autofluorescence, except in areas of very thin inner retina where there may
be increased autofluorescence due to a “window defect.”
¡ FFA in the acute phase shows delayed filling of the involved artery and
prolonged retinal arteriovenous
transit time.

33. ¡ Complete lack of filling of the retinal artery is seen in less than 2% of
cases.
¡ After a variable interval of time, the retinal circulation is reestablished
and may even return to normal.
¡ Thus FFA, which is an invasive procedure with a risk of anaphylactic
reaction, may be indicated in the acute stage, but thereafter, it is
unlikely to be appropriate.
¡ OCT and FAF usually will establish the diagnosis.
¡ FFA and the noninvasive OCT angiography are able to distinguish
between the retinal and choroidal circulation, but only the latter is able
to distinguish between the superficial and deep capillary plexus, thus
providing additional information on the extent of retinal ischemia.
¡ It can be difficult to diagnose long-standing branch retinal artery
occlusion.
¡ However, on OCT, the characteristic thinning of the inner retinal layers
with a well-demarcated junction between the ischemic and normal
retina is a useful sign, and the retinal thickness color map shows the
extent of retinal damage.

34. Investigations
¡ In older patients with central retinal artery occlusion, giant cell arteritis
must be excluded and, if necessary, treated immediately with high-
dose systemic corticosteroids to avoid loss of vision in the other eye.
¡ Investigation for embolic disease by carotid Doppler studies and
echocardiography and assessment of risk factors for arteriosclerosis
are important in both central and branch retinal artery occlusion.
¡ Also vasculitis and congenital or acquired thrombophilia need to be
considered.

35. ¡ In giant cell arteritis, the vascular lumen is obstructed by the
thickened CRA wall due to progressive inflammation.
¡ Similarly, vasculitis from varicella zoster, and orbital infections
in diabetes (e.g. mucormycosis) may lead to CRAO.
¡ Increased blood coagulability may also result in CRAO or BRAO.

36. ¡ Retinal artery occlusions may be caused by arterial wall thickening,
thrombus or emboli.
¡ The potential sources of emboli are similar for CRAO and BRAO
and include calcified emboli cardiac valves and atheromatous
plaques in the carotid arteries.
¡ These emboli are however, seen more frequently in BRAO than
CRAO.

37. Treatment
¡ Irreversible retinal damage occurs within a few hours of retinal artery
occlusion.
¡ Treatment options include ocular massage, anterior chamber
paracentesis, medications to reduce intraocular pressure, vasodilators
(sublingual or transdermal nitroglycerin, oral isosorbide dinitrate,
breathing a mixture of oxygen and carbon dioxide), and intra-arterial
or intravenous thrombolysis.
¡ Intra-arterial thrombolysis is most likely to be effective but is often
difficult to administer quickly enough to be beneficial, and its risks
may not be justifiable especially in branch retinal artery occlusion.
Anterior chamber paracentesis is indicated, particularly when an
embolus is visible on the optic disk.

38. Ischaemic Optic
Neuropathy
¡ Some elderly patients complaining of visual loss in one eye are
found to have a pale swollen optic disc and sometimes evidence of
branch retinal artery occlusion, giving an altitudinal defect of the
visual field.
¡ This appearance should suggest the possibility of temporal arteritis
and an ESR (erythrocyte sedimentation rate) and a temporal artery
biopsy should be considered as
urgent investigations.

39. Retinal Artery Occlusions
¡ There is a group known as ‘nonarteritic’ or idiopathic anterior ischemic
optic neuropathy (AION) which occurs in patients between 50 and 75
years old, individuals who may have diabetes or hypertension, but may
be healthy.
¡ An acute loss of vision occurs.
¡ There may be sectorial optic disc swelling, and a few peripapillary
haemorrhages. An altitudinal visual field defect may be seen.
¡ In these patients retinal arterial occlusion is absent.
¡ About one third of these patients develop
bilateral disease.
There is no known treatment for non-arteritic
AION but giant cell arteritis needs exclusion.

40. ISCHEMIC OPTIC NEUROPATHY
¡ Ischemic optic neuropathy is caused by infarction of the optic
nerve.
¡ Anterior ischemic optic neuropathy is caused by infarction of the
retrolaminar optic nerve (the region just posterior to the lamina
cribrosa) from occlusion (eg, giant cell arteritis), thrombosis, or more
commonly, decreased perfusion (eg, nonarteritic type) of the short
posterior ciliary arteries.
¡ It causes acute loss of vision with optic disk swelling in all cases.
¡

41. ISCHEMIC OPTIC NEUROPATHY
¡ In the rare posterior ischemic optic neuropathy due to infarction of
the retrobulbar optic nerve, there are no optic disk changes in the
acute stage.
¡ Optic atrophy develops after both anterior and posterior ischemic
optic neuropathy.

42. Nonarteritic Anterior Ischemic Optic
Neuropathy
¡ Epidemiology
¡ Usually unilateral but with 15% risk of future fellow eye
involvement
¡ Usually sixth or seventh decade but can occur throughout
adulthood.
¡ Associated with diabetes, hypertension, hyperlipidemia, and end-
stage renal disease
¡ Risk factors:
¡ º Small (crowded) optic disk (“disk at risk”)
¡ º Obstructive sleep apnea
¡ º Nocturnal hypotension including treatment of
hypertension

43. Clinical features
Sudden (occasionally progressive over 2 weeks) loss of vision
¡ • Visual acuity normal or reduced
¡ • Visual field defect (typically inferior altitudinal)
¡ • Color vision normal or reduced
¡ • Reduced pupillary response to light shone in the affected eye
(relative afferent pupillary defect)
¡ • Painless
¡ • Swollen optic disk often with peripapillary splinter hemorrhages
¡ • Recovery of visual acuity in 40% of eyes by 6 months

44. Main differential diagnoses
¡ • Arteritic anterior ischemic optic neuropathy due to giant cell
arteritis
¡ • Optic neuritis
¡ • Papilledema
¡ • Mild, chronic, usually bilateral disk swelling with little change in
visual function
¡ º Diabetic papillopathy
¡ º Amiodarone optic neuropathy

45. Investigations
¡ In most cases, investigation is limited to assessment of vascular risk
factors.
¡ In younger patients, consider systemic vasculitis and acquired or
inherited thrombophilia.
¡ Treatment
¡ No treatment is generally accepted to be beneficial, but systemic
steroids may be used.
¡ Low-dose aspirin therapy may reduce the risk of future fellow eye
involvement.

46. Arteritic Anterior Ischemic Optic
Neuropathy due to Giant
Cell Arteritis (GCA)
¡ Epidemiology
¡ • Age over 50 with increasing incidence with increasing age
¡ • Clinical features
¡ • Usually severe visual loss with risk of complete blindness without prompt
treatment
¡ • Other ocular manifestations of GCA:
¡ º Central retinal artery occlusion
¡ º Cilioretinal artery occlusion
¡ º Retinal cotton-wool spots
¡ º Ophthalmic artery occlusion
¡ º Diffuse ocular ischemia
¡ • Nonocular manifestations of GCA
¡ º Headache
¡ º Swollen, tender, typically pulseless superficial temporal arteries
¡ º Jaw pain on chewing (jaw claudication)
¡ º General malaise, weight loss
¡ º Muscle aches and pains (polymyalgia rheumatica)

47. Investigations
¡ Erythrocyte sedimentation rate (ESR) and C-reactive protein
(CRP) are usually raised.
¡ Temporal artery biopsy for definitive diagnosis (inflammatory cell
infiltration, often but not always including giant cells, and
prominent disruption of the internal elastic lamina) within 2 weeks
after commencement of steroid therapy.
¡ Temporal and other artery ultrasound may be helpful.
¡ Positron emission tomography scans show large vessel arteritis.
Positive temporal artery biopsy with giant
cells (arrows).

48. Treatment
¡ High-dose systemic steroids as soon as a clinical diagnosis is
made.
¡ Oral prednisolone 1–1.5 mg/kg/d Intravenous hydrocortisone,
250–500 mg, if delay of oral therapy
¡ Intravenous methylprednisolone, 500–1000 mg/d for 3 days
¡ Bilateral disease, including transient visual loss in the fellow eye
¡ Progression of visual loss or persistence of systemic
manifestations and/or raised ESR/CRP despite oral therapy
¡ Oral prednisolone usually reduced to 40 mg/d over 4 weeks and
then more gradually tapered and discontinued after 9–12 months
overall as long as no recurrence of disease activity 30% of patients
require long-term steroid therapy

49. Posterior Ischemic Optic
Neuropathy
Sudden visual loss due to optic neuropathy
¡ • No optic disk swelling during the acute stage
¡ • Specific causes
¡ • Massive blood loss, such as from trauma or bleeding peptic ulcer
¡ • Nonocular surgery, particularly lumbar spine surgery in the prone
position or cardiac surgery
¡ • Radiotherapy, usually treatment for skull base or sinus tumors 12–18
months previously with characteristic pattern of gadolinium
enhancement
¡ on MRI and possible benefit from early hyperbaric oxygen therapy
¡ • Giant cell arteritis
¡ • Mucormycosis, which usually occurs in diabetics
¡ • Unless clear precipitating cause, investigation is required, particularly
head imaging (CT or MRI), to exclude optic nerve compression.