diagnosis of branch retinal vein occlusion is clinical, as described before.
doubtful cases, especially small
BRVO, fluorescein angiography may be indicated to confirm the diagnosis.
Fluorescein angiography is particularly useful in determining the extent
of macular oedema and ischaemia. Approximately 50% of untreated eyes with
BRVO retain vision of 6/12 or better whilst 25% will have vision of <6/60.
Macular oedema and neovascularisation
of the retina or disc are the two major
complications which may require
therapy. Retinal neovascularisation occurs in 36% eyes with >5 DD6
and 62% with >4DD 36
area of non-perfusion.
5.1 Treatment of neovascularisation
Disc or retinal neovascularisation is an indication for photocoagulation
ischaemic retina (sector photocoagulation),
although available evidence
suggests that waiting until vitreous
haemorrhage occurs before laser treatment
does not adversely affect the visual
vessels occur only when
there is at least a quadrant of
capillary closure and commonly after six months
following the occlusion. Follow
up visits at 3- 4 monthly intervals are
recommended in patients with one
quadrant or more retinal ischaemia. It is
recommended that sector laser photocoagulation
is applied once retinal or optic
disc neovascularisation occur. Fluorescein
angiography is not usually necessary
prior to laser because the area
of ischaemia is visible clinically.
Photocoagulation for neovascularisation is applied to the sector of retinal
capillary closure. 500-micron burns
at the retina are used and are applied in a
scatter pattern to the affected
sector, one burn width apart are appropriate with
sufficient energy to create a gentle
burn. A quadrant usually requires 400-500
5.2 Treatment of macular oedema
Randomised clinical studies in the laser treatment of macular oedema have
demonstrated that a grid pattern
of photocoagulation in the distribution of
leaking capillaries is beneficial
but it is recommended only after a period of
three to six months following the
initial event and following absorption of the
majority of haemorrhage.5,37
Fluorescein angiography should be carried out
prior to this therapy usually at
> 3 months if visual acuity is 6/12 or less. 5,38
This has two functions. Firstly
it identifies the leaking capillaries and secondly
will indicate the degree of macula
ischaemia, which may limit the value of
It will also help to avoid laser to collaterals.
It is the consensus view of the group that those with severe visual loss
than 6/60 vision) and those in whom
symptoms have been present for more
than one year are unlikely to benefit
Laser photocoagulation for macular oedema requires gentle burns of 100-200
microns. The power depends on the
individual patient. An average of between
20 to 100 applications (depending
on the area of vascular leakage) are required
in a grid pattern to the areas of
vascular leakage but avoiding the foveal
avascular zone (i.e the burns must
not approach the foveal centre by less than
1/2 DD). Collaterals should be avoided.
Initial follow-up in all patients
should be at three months following the occlusion.
Subsequent follow-up at three to
six monthly intervals will depend on complications and laser treatment,
and will not normally be required after two years in uncomplicated cases.
5.3 New treatments
Vitrectomy and sheathotomy as treatment
for BRVO are currently under evaluation.
No recommendations on these new
treatments are possible at present.
5.4 Hemisphere vein occlusion
The risk of rubeosis in ischaemic
hemi-central vein occlusion is greater than that of BRVO but less than
that of CRVO.24 The risk of disc neovascularisation appears
greater for hemispheric vein occlusion
than either ischaemic CRVO or BRVO.39 The
management of hemispheric vein occlusion
is similar to that described for branch
retinal vein occlusion, the guidelines
for laser treatment being those described above for retinal branch vein