Guidance
2 The procedure
2 The procedure
2.1 Indications
2.1.1 Age-related macular degeneration (AMD) is characterised by damage to the central part of the retina (the macula) resulting in progressive loss of central vision. Peripheral vision is not affected so individuals retain some useful vision. The prevalence of macular degeneration increases with age.
2.1.2 Ninety percent of people with age-related macular degeneration have dry (atrophic) macular degeneration, characterised by thinning of the macular retina. The other 10% have wet (exudative or neovascular) macular degeneration, characterised by the growth of abnormal new blood vessels in the choroid layer underneath the retina. These new vessels can leak fluid and cause scarring, which can threaten vision. The vessels can be classified using fluoroscein angiography into 'classic' if they can be seen clearly and 'occult' if they cannot. Wet macular degeneration usually occurs in people who already have dry macular degeneration. Of these two conditions, wet macular degeneration progresses more quickly and vision loss is more severe.
2.1.3 Laser therapy is used to coagulate new vessels in wet macular degeneration. However, the procedure itself may permanently impair vision, especially if the vessels are very close to the fovea. Recurrence is common. Standard laser therapy appears to work only in people with classic neovascular macular degeneration.
2.1.4 Other new treatments for macular degeneration include surgery to remove new vessels, macular translocation, photodynamic therapy and new drugs that suppress new vessel formation (antiangiogenic drugs).
2.2 Outline of the procedure
2.2.1 This procedure involves the use of radiotherapy to destroy the new vessels formed in patients with wet neovascular AMD. The beam of radiotherapy is angled to avoid damage to the optic nerve and structures in the other eye.
2.3 Efficacy
2.3.1 Three randomised controlled trials (RCTs) reported radiotherapy as having no significant benefit on visual acuity when compared with sham treatment or observation. Two RCTs found that radiotherapy reduced loss of visual acuity when compared with very low dose (effectively sham) radiation or observation only. However, the dose of radiation used varied among the studies, ranging from 2 Gy to 20 Gy. For more details, refer to the Sources of evidence section.
2.3.2 The Specialist Advisors considered trials to have shown little or no benefit from using radiotherapy, and that any effect was likely to be modest. One Specialist Advisor also noted that all patients in the UK being treated with this procedure were enrolled in clinical trials.
2.4 Safety
2.4.1 In the RCTs identified, the main complication reported was cataract which ranged from 2% (1/51 eyes) to 67% (28/42 eyes). Other potentially serious complications reported were: vitreous haemorrhage (1/42 eyes) and retinal detachment (1/42 eyes). For more details, refer to the Sources of evidence section.
2.4.2 One Specialist Advisor considered the main safety concerns of this procedure to be radiation retinopathy, dry eyes and cataract.