5.1 Treatment of neovascularisation
Disc or retinal neovascularisation is an indication for photocoagulation to the
ischaemic retina (sector photocoagulation), although available evidence
suggests that waiting until vitreous haemorrhage occurs before laser treatment
does not adversely affect the visual prognosis.^6,36 New 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.
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5.1.1 Technique
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
burns.
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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
photocoagulation.³⁷ It will also help to avoid laser to collaterals.
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It is the consensus view of the group that those with severe visual loss (less
than 6/60 vision) and those in whom symptoms have been present for more
than one year are unlikely to benefit from photocoagulation.
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5.2.1 Technique
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.
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5.2.2 Follow-up
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.
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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.
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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 occlusion.