There are two aims in the management of retinal vein occlusion: the
identification of modifiable risk factors and their medical management
and the recognition and management of sight-threatening complications.
Although the systemic investigation
and treatment in all types of vein
occlusion is similar, the ophthalmological
management of branch and
central retinal vein occlusion differs.
These will therefore be considered
separately.
OPHTHALMOLOGICAL MANAGEMENT
4.1 Central retinal vein occlusion
There
is no proven early treatment that will alter the visual prognosis
in established central retinal vein occlusion. The main management
problem is to differentiate ischaemic from non-ischaemic central retinal vein
occlusion. Patients with ischaemic CRVO are at risk of neovascular glaucoma
for which laser photocoagulation may be beneficial. This risk of iris neovascu-
larisation is higher if the area of retinal ischaemia (retinal non-perfusion as determined by FFA) is >10 disc diameters (CVOS).18 Ischaemic central
retinal vein occlusion is associated with one or more of the following characteristics:-
1. Poor visual acuity (44% of eyes with vision of <6/60There is no evidence as to which combination of the above characteristics
develop rubeosis [CVOS])18
2. Relative afferent pupillary defect
3. Presence of multiple dark deep intra-retinal haemorrhages
4. Presence of multiple cotton wool spots
5. Fluorescein angiography showing greater than 10 disc
areas of retinal capillary non-perfusion (CVOS)18
6. Electrodiagnostic tests (ERG): reduced b wave amplitude,
reduced b:a ratio and prolonged b-wave implicit
time19-23
.
best defines ischaemic CRVO. It is important to note that up to 30% of
patients with initially nonischaemic central retinal vein occlusion will
develop ischaemic transformation.24- 27
This is usually heralded by further rapid visual deterioration and requires
further assessment. CRVO especially of the non-ischaemic type needs to
be differentiated from the ocular ischaemic syndrome and other simulating retinopathies.
.
4.1.1 Management of ischaemic central retinal vein occlusion and
anterior segment neovascularisation
An initial evaluation of risk factors and the appropriate treatment of
the present risks must proceed alongside management of the ocular findings.
The evidence supports the use of laser pan-retinal photocoagulation
when iris new vessels (INV) or angle new vessels (ANV) are visible.
Monthly follow up is advised for six months in all untreated patients with
features of retinal ischaemia and must include undilated pupil examination
and detailed examination of the iris with gonioscopy.18 (However, this
monthly follow up may be impracticable in some UK eye clinics). PRP should
be applied at the earliest sign of INV and or ANV.
.
In circumstances when regular follow-up is impractical, prophylactic
treatment may be appropriate.28
..
4.1.2 Posterior segment neovascularisation
This is an uncommon complication following ischaemic central retinal
vein occlusion in eyes which have not developed neovascular glaucoma or
who have been successfully treated for rubeosis by laser. It has been
reported that this complication does not usually require active therapy.29
..
4.1.3 Pan-retinal Photocoagulation Technique
Pan-retinal photocoagulation for CRVO with INV or ANV requires
1500 - 2000 of 500-micron burns at the retina. This is best applied with
0.05-0.1 seconds applications one burn width apart with sufficient energy
to produce a pale burn in the retina. Treatment is usually placed in the
periphery avoiding areas of retinal haemorrhage. Some cases require further treatment if the iris neovascularisation fails to regress.18
.
There is an alternate view to the management of iris
neovascularisation. There is a suggestion that rubeosis does not inevitably
lead to glaucoma and therefore laser photocoagulation should be withheld because this treatment leads to further contraction of the visual field.30 However, it is our opinion that the weight of evidence supports the recommendations stated above.18,28,31
.
4.1.4 Management of established neovascular glaucoma
The aim of management of this condition in a blind eye is to keep the
eye pain free. This is usually achieved by topical steroids and atropine.
However, if the eye has any visual potential intraocular pressure should
be controlled with topical pressure-lowering agents or cyclo-ablative
procedures. Drainage procedures are of limited value.
.
4.1.5 Macular oedema
Macular oedema following central retinal vein occlusion results from
leakage of perifoveal capillaries. It results in visual loss but there is no
proven treatment for this condition. Randomised controlled trials have
failed to indicate benefit from grid treatment, although a trend in favour
of treatment has been observed in younger patients.32 Although there
was significant reduction in the severity of macular oedema in treated
eyes compared to controls there was no visual acuity benefit.
.
4.2 Recommendations for Further Follow-up
Follow-up after 6 months for ischaemia (> 10DD non-perfusion) should
be every 3 months for 1 year. Non ischaemic eyes should have initial follow
up every 3 months for 6 months. Subsequent follow-up for all patients will
depend upon laser treatment and complications but will not normally be
required after 2 years in uncomplicated cases. The development of disc
collaterals +/- resolution of the CRVO should lead to discharge from
clinical supervision.
.
Experimental treatments
Chorio-retinal anastomosis is an experimental treatment and the results
of randomised trials of this therapy are awaited. However, there are
significant complications associated with laser-assisted chorioretinal venous anastomosis eg choroidal neovascularisation33, retinal and subretinal fibrosis
or traction34,and vitreous haemorrhage.35
.
Trials of other treatments such as radial optic neurotomy with pars plana
vitrectomy, and thrombolytic therapies are under way. These, however, are
only experimental at present and are, therefore, not recommended except
as part of clinical trials.
| Introduction | Methods used | Risk factors | CRVO |
| BRVO | Medical treatment | Cardiovascular problems | Young patient |
| References. | Tables | Main index | Main page. |