Retinal Vein Occlusions
Morphology
CRVO
 BRVO
 Hemispheric VO
 Hemicentral VO
 Papillophlebitis
 Macular BRVO
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CENTRAL RETINAL VEIN
OCCLUSION
» 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 the
level of the 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.
PATHOLOGY
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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.
Anatomical Studies
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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. Initially, the
thrombus adheres where the endothelium has been severely damaged.
Doppler Studies
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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.
There is evidence, however, that the central retinal artery blood flow is
also impaired in eyes with acute central retinal vein occlusion.
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.
There is also a trend toward higher vascular resistance of the central
retinal artery in the clinically healthy eyes of patients with central
retinal vein occlusion compared with control eyes.
Risk Factors
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An increased risk of central retinal vein occlusion
was found in patients with systemic hypertension,
diabetes mellitus, and open-angle glaucoma; the
risk of central vein occlusion was decreased for
patients with increasing levels of physical activity
and increasing levels of alcohol consumption.
For women, the risk decreased with the use of
postmenopausal estrogen and increased with a
higher erythrocyte sedimentation rate.
The Eye Disease Case-Control Study Group: Risk factors for
central retinal vein occlusion.
Arch Ophthalmol 114:545, 1996
Risk Factors for Central Retinal
Vein Occlusion
Investigations

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 PRINCIPALS
Maximise
Prevent
Recovery and Vision
re-occlusion
Detect
associated systemic disease
Detect
/ Prevent Glaucoma
Protect
other eye
Standard Investigations
FBC, PV, ESR
 U+E, Creatinine
 LFT, Protein Electrophoreseis
 Random Glucose, Lipid
 Urine analysis

Ophthalmic Investigations
FFA
 CDI (Color doppler )
 Carotid disease-Using digital subtraction angiography, Brown and
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associates studied 37 patients with central retinal vein occlusion; they found
that significant ipsilateral stenosis (greater than 50%) was not higher in these
patients compared with historically matched controls. They did find, however,
that patients with ischemic central retinal vein occlusion had a higher
incidence of overall carotid atherosclerotic obstruction (ipsilateral and
contralateral) than patients with nonischemic central retinal vein occlusion
Thrombophilic Screen ( less than 50
years )
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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 G20210A
Antiphopholipid antibodies
Ischemic Central Retinal Vein
Occlusion

Patients with an ischemic pattern are usually
aware of a sudden, painless decrease in visual
acuity. Vision ranges from 20/400 to hand
movements. The onset, however, is generally not
as rapid or the visual loss as extensive as in central
retinal artery occlusion. Exceptional cases have
been noted in which patients with an acute onset
had reasonably good vision and yet demonstrated
a picture of ischemic central retinal vein
occlusion. Patients with ischemic occlusion have
an average age of 68.5 years.
Nonischemic Central Retinal
Vein Occlusion

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 central
retinal vein occlusion are an average of 5
years younger (average age, 63 years) than
those with ischemic vein occlusion
Ophthalmoscopic features
Confluent hemorrhages are the most prominent ophthalmoscopic feature of an acute ischemic central retinal vein occlusion These hemorrhages
occur in a wide variety of shapes and sizes; they are usually concentrated in the posterior pole, but may be seen throughout the retina. Hemorrhages
in the superficial retina may be so prominent about the posterior pole that the underlying retina is obscured. Many hemorrhages are flame shaped,
reflecting the orientation of the nerve fibers. Dot and punctate hemorrhages are interspersed and indicate involvement of the deeper retinal layers.
Bleeding may be extensive, erupting through the internal limiting membrane to form a preretinal hemorrhage or extending into the vitreous. Small
dot hemorrhages may be seen either isolated or clustered around small venules. The entire venous tree is tortuous, engorged, dilated, and dark. The
retina is edematous, particularly in the posterior pole; some of this edema may obscure portions of the retinal vessels. 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. Vision depends on extent of
macular involvement.
Angiography
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The intravenous fluorescein angiogram pattern of an
ischemic central retinal vein occlusion is usually
characterized by a delayed filling time of the venous
tree of the retina, capillary and 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 are usually manifest shortly thereafter.
Late-phase photographs show patchy extravascular
areas of fluorescence and staining of the retinal
veins. The intravenous fluorescein angiogram pattern
of an ischemic central retinal vein occlusion is
usually characterized by a delayed filling time of the
venous tree of the retina, capillary and 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
Microaneurysms may not be noted at the time of
initial occlusion, but are usually manifest shortly
thereafter.
Late-phase photographs show patchy extravascular
areas of fluorescence and staining of the retinal
veins. 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.
Classifying ischaemia
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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.
Macular Oedema
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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.
Prognosis CRVO
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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.
Neovascularization
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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.
Percentage of Ocular Neovascularization
in Venous Occlusion
Neovascularization of the Iris.
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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.
Neovascularization of the Iris
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Neovascularization of the iris may develop as early
as 2 weeks after central retinal vein occlusion or as
late as 2½1/2 years Neovascularization of the iris
will develop in almost all patients within the first
year, but usually in the first 3 months.89
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. 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.
HEMICENTRAL AND HEMISPHERIC
RETINAL VEIN OCCLUSION
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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
Hemispheric retinal vein
occlusions
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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.
BRANCH RETINAL VEIN
OCCLUSION
PATHOLOGY
Leber was probably the first investigator to note the
connection between branch retinal vein occlusion and the
arteriovenous intersection. Koyanagi found that the majority
(77.7%) of his cases of temporal vein occlusion involved the
superior retina. He attributed this to the preponderance of
arteriovenous crossings in this region compared with other
quadrants.Others later confirmed this anatomic observation,
noting that branch retinal vein occlusion always occurs at an
arteriovenous intersection.Both fluorescein angiography1and
histopathologic examination confirm that most occlusions
occur at an arteriovenous crossing and that the few that do
not are in the vicinity of a retinal artery. 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.
Morphology
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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.
Risk Factors for Branch Retinal
Vein Occlusion
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Systemic hypertension
History of cardiovascular
disease
 Increased body mass index at
20 years of age
cholesterol
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History of glaucoma
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High serum levels of
a2-globulin
Management of BRVO
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Branch vein obstruction is often associated with
pre-existing 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.
An important complication of branch
retinal vein occlusion is
neovascularization
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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.
Branch Vein Occlusion Study
Group –Vitreous Hemorrhage
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Of patients with ischemic vein occlusion who
were treated before neovascularization occurred,
12% developed a subsequent vitreous hemorrhage,
whereas only 9% of ischemic eyes treated after
neovascularization occurred developed a vitreous
hemorrhage. Although the study was not designed
to determine the optimal time for treatment, the
data suggest (but do not prove) that there may be
no advantage to treatment before the development
of neovascularization. The study was not able to
draw conclusions about the effect of
photocoagulation on the prevention of visual loss.
Branch Vein Occlusion Study
Group- Macular Oedema
 Can photocoagulation improve visual acuity in eyes with
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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 to the fovea than the
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.
MACULAR BRANCH
RETINAL VEIN OCCLUSION
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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.
Macular Oedema- FFA
PAPILLOPHLEBITIS
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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.
Investigations and therapy
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GENERAL PRINCIPALS
Maximise Recovery and Vision
Prevent re-occlusion
Detect any associated systemic disease
Detect / Prevent Glaucoma
Protect other eye
General Therapy
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Avoid oral contraceptives
Aspirin
Treat hypercholesterolemia and hypertension
Lower IOP
Anticoagulants if required
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If vision drops consider re-occlusion.
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Panretinal photocoagulationSummary
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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 to be
shown. Grid therapy for macular oedema in
CRVO has not been shown to improve visual
acuity.
Central Retinal Vein Occlusion
Study Group - Photocoagulation
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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°.
Central Retinal Vein Occlusion
Study Group- Macular Oedema
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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.
Chorioretinal anastomosis in patients with
nonischemic central retinal vein occlusion.
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McAllister and Constablereported a surgical technique to create a chorioretinal anastomosis in
patients with nonischemic central retinal vein occlusion. Their current technique is to rupture Bruch's
membrane first in an area adjacent to the edge of a vein located at least three disc diameters from the
optic disc with the argon laser; they then use a YAG laser to create a small opening in the sidewall of
the adjacent vein.
In their study there was an average of 2.1 attempts to create an anastomosis, which was successful in
only 42% of the patients in the first series171 and 67% of patients in the second series.172 In the first
series, ischemic central vein occlusion did not develop in any of the patients in whom a successful
anastomosis was produced, but it did develop in 31% of patients in whom such an anastomosis could
not be created.171 It should be noted, however, that this is not a control group, and they have not
reported on a controlled clinical trial of this procedure. All the patients with a successful anastomosis
had an improvement in final visual acuity compared with pretreatment visual acuity. In the group of
patients with an unsuccessful anastomosis, 38% had an improvement in visual acuity, 44% had a
worse visual acuity, and 19% had no change.
There were some minor complications, such as vitreous and retinal hemorrhages, that tended to clear
fairly well. However, there were some major complications, including a major fibrovascular
proliferation at 14% of the sites where surgery was attempted.This complication can lead to serious,
nonclearing vitreous hemorrhages and/or traction retinal detachment and may require a vitrectomy
for treatment.
Lacking a controlled clinical trial for this new treatment, there is no way to know whether laser
chorioretinal anastomosis is more effective for nonischemic central retinal vein than no treatment.
Neovascular Glaucoma
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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
Contact Us
Author : John G. O'Shea MD
Illustrations: Robert Harvey
FRCSEd (from Practical
Ophthalmology, 2002
Palmtrees Publishing)
Rob Harvey
E-mail Address :
rob_harvey@msn.com
Correspondence
Birmingham and Midland Eye
Centre, Dudley Rd,
Birmingham B18 7QH, U.K