This document discusses central retinal vein occlusion (CRVO), including distinguishing between ischemic and non-ischemic types. Ischemic CRVO carries a poorer prognosis due to increased risk of neovascularization and vision loss. Features like extensive hemorrhaging and cotton wool spots indicate ischemic occlusion. Non-ischemic CRVO has a milder appearance and course. The document also outlines evaluation, management considerations, and complications like neovascular glaucoma for CRVO.

2.  CRVO
 BRVO
 Hemispheric VO
 Hemicentral VO
 Papillophlebitis
 Macular BRVO

3.  Ischemic CRVO
 Non ischemic CRVO
 Distinction between two varieties is important
becoz it assists the clinician in the following 1.Prediction of the risk of subsequent
neovascularisation.
 2.identification of patients who have poorer
visual prognosis
 3.Determination of the likelihood of
spontaneous visual improvement.
 4.Decision as to appropriate follow up intervals.

4. 





Patients with an ischemic pattern are usually aware of a
sudden, painless decrease in visual acuity. Vision ranges
from 20/200(6/60) to hand movements. The onset,
however, is generally not as rapid or the visual loss as
extensive as in central retinal artery occlusion.
Patients with ischemic occlusion have an average age of
68.5 years.
It represents 20-25% of all CRVOs.
A prominent afferent pupillary defect is common.
Cotton wool spots are usually present and are
numerous.
Characterized by extensive retinal haemorrhages most
notably centerd in posterior pole.

5. Ophthalmoscopic features

6. 
The retina is edematous, particularly in the
posterior pole. Cotton-wool patches (soft
exudates) are often present.
The disc margin is blurred or obscured, and
the precapillary arterioles appear engorged.
Splinter hemorrhages and edema are
present on the disc surface and extend into
the surrounding retina. The physiologic cup
is filled, and the venous pulse is absent.
The arterioles, often overlooked because of
the other more striking pathologic features,
are frequently narrowed.
Sometimes in central retinal vein occlusion
of acute onset, the fundus picture is less
dramatic, and all of the findings previously
discussed may be present, but to a lesser
degree.
Visiondepends on extent of macular
involvement.

7. 





Nonischemic central retinal vein occlusion is a much
milder and more variable disease in appearance,
symptoms, and course compared with ischemic central
retinal vein occlusion.
Patients with nonischemic CRVO are on an average 5
years younger (average age, 63 years) than those with
ischemic vein occlusion.
It represents 75-80% of all CRVOs.
Pupillary testing rarely reveals an afferent defect,which if
present is only slight.
Cotton wool spots if present are few in number and
located posteriorly.
Ophthalmoscopy reveals a variable number of dot and
flame retinal haemorrhages.

8. WITH MINIMAL INTRARETINAL
HEMORRHAGE AND DILATED
BUT NOT TORTUOUS RETINAL
VEINS
CYSTOID MACULAR EDEMA IS
PRESENT ON THE OCT AS BLACK,
HYPOREFL ECTIVE INTRARETINAL
SPACES.

9. VENOUS
DILATATION,TORTUOSITY
AND EXTENSIVE FLAME
SHAPED HGE
FA SHOWS STAINING OF BLD
VESSELS BUT GOOD
CAPILLARY PERFUSION

10. The actual mechanisms
producing the clinical
picture of central retinal
vein occlusion may be
roughly divided into those
conditions that produce a
physical blockage at ,or
posterior to lamina cribrosa,
and those conditions in
which hemodynamic factors
result in an obstruction to
the flow of blood. These
mechanisms probably
coexist in many patients
with central VO.
"Blood and thunder" appearance of a central retinal vein occlusion.

11. Histopathologic evaluation of eyes removed
because of a central retinal vein occlusion
demonstrates an occlusion at or just behind the
level of the lamina cribrosa.
 At this location, there are certain anatomic factors
that predispose the central retinal vein to occlusion.
First, the lumina of the central retinal artery and
central retinal vein are narrower than they are in the
orbital optic nerve, and the vessels are bound by a
common adventitial sheath.


12. 
Green studied 29 eyes that were enucleated 6 hours to 10
years after occlusion. As a result of this study, they
hypothesized that the flow of blood through the central
retinal vein becomes increasingly turbulent as the vein
progressively narrows at the lamina cribrosa, where it also
may be further impinged upon by arteriosclerosis of the
adjacent central retinal artery. This turbulence damages the
endothelium in the retrolaminar vein, which exposes
collagen and initiates platelet aggregation and thrombosis.

Their studies show the evolution of this thrombus. Thrombus
adheres where the endothelium has been severely damaged.

13. 
Recently, color Doppler ultrasound imaging has been used to
examine the blood flow in the orbit, including the optic nerve
head, and has been used to examine patients with central
retinal vein occlusion.

As might be expected, the venous velocity in the eye of a
patient with central retinal vein occlusion is markedly
reduced compared either with the unaffected eye or to
control eyes.

In addition, vascular resistance is slightly higher in the
ophthalmic artery and short posterior ciliary arteries of both
the involved and the clinically healthy fellow eye of patients
with central retinal vein occlusion compared with control
eyes.

15.  Open angle glaucoma is a relatively common
finding in patients who have CRVO.Patients with
a history of glaucoma are five times more likely
to have CRVO than those who do not
,presumably becoz of structural alterations of
lamina cribrosa induced by elevated IOP.
 Acute angle closure glaucoma may precipitate
CRVO.

16. 
All patients with central retinal vein occlusion should have a
comprehensive ophthalmic evaluation, including an appropriate
evaluation for glaucoma. In addition, they should be referred to their
primary care physician for an evaluation of cardiovascular risk factors,
including hypertension and diabetes
GENERAL PRINCIPLES
Maximise Recovery and Vision
Prevent re-occlusion
Detect associated systemic disease
Detect / Prevent Glaucoma
Protect other eye

17.  CBC, PV, ESR
 Urea ,electrolytes,creatinine
 LFT, Protein Electrophoreseis
 Random Glucose, Lipid
 Thyroid function tests.

18.  VA
 Slit lamp examination
 Gonioscopy –to look for angle
neovascularisation
 FFA
 OCT
 CDI (Carotid duplex imaging )

19. Clotting screen
Protein C,S defficiency
Elevated factor V
Actviated protein C resistance
Factor V Leiden a major risk factor in females
(Five percent of European population)
 Dysfibrogenaemia (1/3000)
 Prothrombin
 Antiphopholipid antibodies






20. (A) COLOR PHOTOGRAPH OF
CRVO
(B) FA OF CRVO SHOWING
EXTENSIVE CAPILLARY NON
PERFUSION

23. 


The intravenous fluorescein
angiogram pattern of an
ischemic CRVO is usually
characterized by a delayed
filling time of the venous tree of
the retina, capillary
Also characterized by venous
dilation, and extensive leaking
of fluorescein into the retina,
particularly in the macular area
and in the area adjacent to the
larger venous trunks.
And capillary nonperfusion
may not be noted at the time of
initial occlusion, but usually
manifest shortly thereafter.

24. 



Late-phase photographs
show patchy extravascular
areas of fluorescence and
staining of the retinal veins.
Microaneurysms may not be
noted at the time of initial
occlusion, but are usually
manifest shortly thereafter.
Fluorescence in the macula
indicates capillary leakage and
edema; this not only may
account for much of the initial
visual loss in the acute phase,
but may eventually result in
permanent structural changes.

25. The amount of nonperfusion or
ischemia is determined by
inspecting the fluorescein
angiography negative under
magnification. The photographer
inspects not only the central 30°
or 45°, but as much of the
peripheral retina as possible.
 Another method has been to
classify eyes with less than 10 disc
diameters of perfusion on
fluorescein angiography as
perfused or nonischemic, and
eyes with 10 or more areas of
nonperfusion as nonperfused or
ischemic.


26. 
Fluorescence in the
macula indicates
capillary leakage and
edema; this not only
may account for much
of the initial visual loss
in the acute phase, but
may eventually result in
permanent structural
changes.

27. 



The prognosis for ischemic central retinal vein occlusion is
generally poor because of decreased visual acuity and
neovascularization.
Visual loss occurs because of macular edema, capillary
nonperfusion, overlying hemorrhage (either retinal or
vitreal), or a combination of all of these.
Retinal edema usually gradually subsides except in the
macula, where it may persist for many months or years.
Macular holes or cysts may form.

28. The most serious complication of central retinal vein
occlusion is neovascularization.
 Neovascularization elsewhere (NVE) occurs less
frequently than neovascularization of the iris (NVI),
and usually only in ischemic occlusions.
 The low incidence of retinal surface
neovascularization in ischemic central retinal vein
occlusion is thought to be due to the destruction of
endothelial cells, which provide the source for
endothelial proliferation and neovascularization.


30. Neovascularization of the iris and frequently neovascular glaucoma occurs in
approximately 8%6to 25% of all central retinal vein occlusions and generally only
in those eyes that exhibit an ischemic pattern of occlusion.
 Magargal and co-workers have shown that the incidence of neovascularization
increases dramatically above approximately 50% capillary nonperfusion. The
incidence of anterior segment neovascularization in nonischemic central retinal
vein occlusion is approximately 1%, compared with approximately 35% to 45%
for ischemic central retinal vein occlusion.
 Neovascularization of the iris or angle is significantly correlated with the extent
of capillary nonperfusion on the fluorescein angiogram.
 Rubeosis developed in 80% to 86% of the eyes with severe nonperfusion of three
to four quadrants of the posterior pole or the periphery, but in only 3% to 9% of
those with less capillary nonperfusion.


31. 



Neovascularization of the iris may
develop as early as 2 weeks after
central retinal vein occlusion or as
late as 2½ years.
Neovascularization of the iris will
develop in almost all patients
within the first year, but usually in
the first 3 months.
Symptomatically, patients
complain of tearing, irritation,
pain, and further blurring of vision
as the intraocular pressure in the
affected eye begins to rise.
The pain may become
excruciating. The cornea is hazy
and the pupil dilated, and a
network of fine vessels is seen over
the surface of the iris (rubeosis
iridis) on slit-lamp examination

32. 


By the time gonioscopy reveals
extension of this neovascular
membrane into the trabecular
network and throughout the angle,
the intraocular pressure is usually
markedly elevated.
The angle is initially open, but later
in the disease, peripheral anterior
synechiae develop and the angle
may become irreversibly closed,
resulting in neovascular glaucoma.
Large, extremely irritating bullae
may form on the surface of the
cornea and then break down. Dense
cataracts eventually form, obscuring
the fundus.

33. 
The terms hemicentral retinal vein occlusion and hemispheric
retinal vein occlusion refer to eyes in which approximately half
of the venous outflow from the retina, either the superior or
the inferior, has been occluded. In approximately 20% of eyes,
the branch retinal veins draining the superior and inferior
halves of the retina enter the lamina cribrosa separately
before joining to form a single central retinal vein.
Hemicentral retinal vein occlusion is an occlusion of one of
these dual trunks of the central retinal vein within the nerve.
 Hemispheric retinal vein occlusion is an occlusion involving
the venous drainage from approximately half of the retina,
either the superior or the inferior retina


34. 
In some eyes, the nasal
retina is not drained by a
separate vein, but by a
branch of either the
superior or the inferior
temporal vein. It is the
occlusion of one of these
veins draining both the
nasal retina and the
superior or inferior retina
near the optic disc that
accounts for the majority of
hemispheric retinal vein
occlusions.

The treatment and
classification are similar to
that of branch retinal vein
occlusion.

35. EXTENSIVE HGE
INFERIORLY
FA SHOWING HYPOFLUORESCENCE
DUE TO CAPILLARY NON
PERFUSION& MILD PERI VASCULAR
HYPERFLUORESCENCE

36. Hayreh and associates conducted a prospective but nonrandomized study of
panretinal photocoagulation in ischemic central retinal vein occlusion. They
found no statistically significant difference between the treated and
untreated groups in the incidence of angle neovascularization, neovascular
glaucoma, retinal or optic nerve neovascularization, vitreous hemorrhage, or
visual acuity. The only significant finding was that fewer patients in the treated
group had neovascularization of the iris compared with nontreated controls, but
only if the panretinal photocoagulation was applied within the first 3 months
after the onset of central retinal vein occlusion and panretinal photocoagulation
resulted in a significant loss of the peripheral field.
 Once neovascularization in the anterior segment is detected, panretinal
photocoagulation should be instituted promptly. This will often result in
regression of the iris vessels and prevent complete angle closure; this is also true
in patients with some increase in intraocular pressure but in whom the angle is
not occluded for 360°.


37. 


The Central Retinal Vein Occlusion Study Group performed a
randomized, prospective clinical trial on the effect of macular grid
photocoagulation compared with no treatment on eyes with 20/50 or
worse visual acuity due to macular edema with no capillary nonperfusion
on fluorescein angiography.
Although grid photocoagulation lessens macular edema both
angiographically and clinically, there was no difference in visual
acuity between the treated and untreated patients. For treated
patients, there was a trend toward decreased visual acuity in patients
older than 60 years and visual improvement in patients younger than
this; this effect was not seen in untreated patients.
Although this study suggests a possible benefit to visual acuity in
younger patients with macular edema who are treated compared with
untreated controls, the number of patients in this subgroup is too small
for a statistically valid comparison of treated versus untreated eyes.

38. 



Once developed, neovascular glaucoma responds poorly to any type of
treatment. Cycloplegics, topical pressure-lowering agents, carbonic
anhydrase inhibitors, and corticosteroids, though failing to lower the
intraocular pressure significantly, may make the patient more
comfortable.
Panretinal photocoagulation often cannot be applied in cases of
advanced neovascular glaucoma in which the angle has been
substantially occluded and the cornea may be too cloudy to allow
treatment.
Trans-scleral cyclocryotherapy or trans-scleral laser cyclodestruction,
sometimes combined with 360° of trans-scleral panretinal
cryoablation,has also been used to preserve the globe.
In some cases where visibility is poor and the angle is closed, we have
had some success in the last few years combining pars plana vitrectomy
and endophotocoagulation with a drainage implant

39. Panretinal photocoagulation has been
recommended for the treatment of
neovascularisation secondary to CRVO's. There is
currently debate regarding the timing of this
therapy. Whether delayed intervention (after the
development of iris new vessels) offers as good an
outcome as early laser treatment(at the time of
neovascularisation of the retina alone) needs still to
be shown.
 Grid therapy for macular oedema in CRVO has not
been shown to improve visual acuity.


40.  NO PROVED EFFECTIVE TREATMENT
 PRP if intraocular neovascularisation is
present
 Lower IOP if elevated
 Treat underlying medical conditions
 Macular edema generally does not respond
to grid laser..

42. 
Defn-Obstruction of a branch of a
retinal vein.

Associated features

Macular edema

Macular subretinal fluid

Retinal neovascularisation

Vitreous haemorrhage

Dilated,tortuous retinal vein

Capillary non perfusion

Cotton wool spots

Optico cilliary shunt vessels

Sheathing of vessel

Microaneurysms

43. A.Major at disc
B. major away from disc
C. minor macular
D.
E
periferal not involving
F
macula

45. SHOWS FLAME & BLOT HGE WITH
COTTON WOOL SPOTS AND
VENOUS TORTUOSITY
FA SHOWS BLOCKAGE BY BLOOD
AND AREAS OF CAPILLARY NON
PERFUSION

46. COLOR PHOTO SHOWING VENOUS
SHEATING,COLLATERALS,EXUDATE
S AND RESIDUAL HGES
FA SHOWS CAPILLARY NON
PERFUSION AND TORTUOUS
COLLATERALS EXTENDING ACROSS
HORIZONTAL RAPHE B/W SUP. &
INF. ARCADES

47. (A) THE OCCLUDED VEIN IS
SCLEROTIC
(B) THE VASCULAR CHANGES
DO NOT INVOLVE THE
FOVEA ON FA.

48. (A) INTRARETINAL
HEMORRHAGE
(B) LATE LEAKAGE ON FA

50. Enlargement of the
foveal avascular zone,
causing decreased
vision to 20/100. Note
that there is no
leakage in the macula
as seen .
 Grid laser was not
performed.


51. 
Both fluorescein angiography1and histopathologic examination
confirm that most occlusions occur at an arteriovenous crossing.

Histologically, where the vein and artery cross, they share a
common adventitial sheath, and the venous lumen may be
diminished by as much as a third at this crossing.

The clinical picture of branch retinal vein occlusion is retinal
hemorrhages that are segmental in distribution.



The apex of the obstructed tributary vein almost always lies at an
arteriovenous crossing. Usually some degree of pathologic
arteriovenous nicking is present.
The occlusion is commonly located one or two disc diameters
away from the optic disc. However, the occlusion may lie at a
point near the disc edge or, less frequently, may involve one of the
smaller, more peripheral tertiary or macular branches.

52. 





GENERAL PRINCIPALS
Maximise Recovery and Vision
Prevent re-occlusion
Detect any associated systemic disease
Detect / Prevent Glaucoma
Protect other eye

53. 



Neovascularization of the iris and neovascular glaucoma are uncommon
and occur in only approximately 1% of affected eyes.
More commonly, neovascularization of the disc occurs in approximately
10% of eyes, and neovascularization elsewhere occurs in approximately
20% of eyes. Generally, retinal neovascularization occurs within the
retinal area served by the occluded vessel, but it has been reported to
occur outside in presumably normal retina.
Vitreous hemorrhage due to neovascularization occurs in approximately
half of the eyes with neovascularization.Butner and McPherson239 found
that 11.3% of spontaneous vitreous hemorrhages were due to a branch
retinal vein occlusion, an incidence second only to proliferative diabetic
retinopathy as a cause of vitreous hemorrhage.
Oyakawa and co-workers found that in 38.3% of eyes undergoing a
vitrectomy for a nondiabetic vitreous hemorrhage, the hemorrhaging
was due to a branch retinal vein occlusion.

54. RED-FREE PHOTOGRAPH
FA SHOWING
NEOVASCULARISATION
CAPILLARY NON PERFUSIO

55.  Hypertensive retinopathy
 Diabetic retinopathy
 Ocular ischemic syndrome
 Juxtafoveal telengiectasia
 Combined BRAO and BRVO
 Radiation retinopathy

56. Branch vein obstruction is often associated with preexisting vascular disease. Evaluation for systemic
abnormalities, in particular hypertension, should be
performed.
 Exclusion of diabetes, hyperlipidaemia,
hyperviscosity/coagulation states, antiphospholipid
syndrome, or any other predisposing condition should
be performed.
 Regular review is required until the haemorrhages clear
so that the most suitable treatment option can be
achieved.
 Approximately one third to one half of patients with
BRVO have recovery of visual acuity to 20/40, or better,
without therapy.


57. 




Avoid oral contraceptives
Aspirin
Treat hypercholesterolemia and hypertension
Lower IOP
Anticoagulants if required

58.  For macular edema ,VA of 6/12 or worse
-Wait for clearance of retinal hge to allow
adequate FFA.
-Determine if decreased VA is caused by
macular edema(versus macular nonperfusion)
If macular edema xplains visual loss and no
spontaneous improvement has occurred by 3
mnths,grid macular photocoagulation is
recommended.
If capillary non perfusion explains decreased VA ,
laser treatment is not advised.

59.  Good quality FFA is obtained after retinal hge
has cleared sufficiently.
 If more than 5 Disc diameters of non perfusion
are present,the patient should be followed at 4
mnths interval to seek the development of
neovascularisation.
 If neovascularisation develops PRP to the
involved retinal sector should be applied using
argon laser to achieve “medium”white burns ,
200-500 um in diameter –one burn width apart
to cover the entire involved segment.

60. In patients with neovascularisation treated with
laser ,only 29% developed vitreous
haemorrhage,versus 61% of those untreated.
 The data showed no advantage with treatment
before neovascularisation occurred,even if
extensive capillary non perfusion existed.
 If laser is applied to all non perfused BRVOs a large
% of patients will be treated unnecessarily.


61.  Can photocoagulation improve visual acuity in eyes with


macular edema reducing vision to 20/40 or worse?
Eyes with branch vein occlusion occurring 3 to 18 months
earlier with 20/40 vision or worse because of macular edema
(but not hemorrhage in the fovea or foveal capillary
nonperfusion) were treated with the argon laser in a "grid"
pattern in the area of capillary leakage.
The treatment did not extend closer than the edge of foveal
avascular zone and did not extend outside the peripheral
arcade. At the 3-year follow-up, there was a statistically
significant improvement in the visual acuity of treated eyes
compared with untreated eyes.

62. 

An occlusion limited to a small venous tributary draining a section of the
macula and located between the superior and inferior temporal arcades
is considered a subgroup of branch retinal vein occlusion.Most patients
with macular branch vein occlusion complain of blurring or distortion of
vision. Superior macular vein occlusions are more common than inferior
macular vein occlusions, and some degree of macular edema is present in
approximately 85% of these eyes.
Although small areas of capillary nonperfusion are present in
approximately 20% of eyes, neovascularization is not seen. This type of
macular vein occlusion can be remarkably subtle at times. Joffe and
associates pointed out that clues such as small collateral channels and
microaneurysms often suggest the diagnosis. Treatment of macular
edema in macular vein occlusion by photocoagulation is identical to the
treatment of other branch retinal vein occlusion.

64. 


In 1961, Lyle and Wybar described six young, healthy patients with a
unilateral, relatively benign condition characterized by mild blurring of
vision, essentially normal visual acuity, dilated and tortuous retinal
vessels, a varying amount of retinal hemorrhage, and optic disc edema
All six patients improved spontaneously, but were left with sheathing of
retinal vessels and the formation of vessels on the optic disc. Lyle and
Wybar called this condition "retinal vasculitis" and believed it to be due
to a central retinal vein occlusion secondary to an inflammatory vasculitis
of the venous system.
Lonn and Hoyt agreed with this etiology, but felt that "papillophlebitis"
was a more appropriate descriptive term. Hart and co-workers, however,
pointed out that an inflammatory etiology for this disease is tenuous,
and no well-documented cases have been studied histopathologically.

65. Characteristic features
 Also called optic disc vasculitis.
 These eyes tend to have optic disc edema out of
proportion to the retinal findings,cotton wool
spots that ring the optic disc and occasionally
cilioretinal artery obstructions or even partial
CRAOs.
 Although spontaneous improvement is
common,the course is not always benign.
 Up to 30% of these patients may develop the
ischemic type of occlusion.

67.  THE END