European guest lecture subfoveal new vessels in age related macular degeneration

Abstract

Age-related macular degeneration (AMD) is a major cause of blindness in the Western World. While only 10% of AMD patients have the exudative form of the.disease, 88% of legal blindness, attributable to AMD, is due to this type. 1 This exudative form is characterised by the presence of subretinal new vessels which leak serum, blood and lipids. Eventually, this exudative process leads to an organised scar tissue and the cica­ tricial disciform lesion results in significant and permanent loss of central vision. Clinically, the wide spectrum of the exuda­ tive form comprises many different and varied patterns including choroidal neovascularisa­ tion, retinal pigment epithelium detachment and tears, fibrovascular disciform response and even vitreous haemorrhage. The initial location of the subretinal new vessels (SNV) is probably the most important risk factor and will induce, more or less severe, clinical symptoms. Previously published randomised control­ led trials have brought evidence that for patients referred at an early stage there is a beneficial effect on visual outcome from focal laser treatment. However, less than 20% of patients with new vessels, presenting in referral centres ful­ fill the criteria of these studies.2,3,4 Most of the patients (58%) present with late stages of the disease process, involving not only the subfoveal area but the entire mac­ ular area. Even newly symptomatic patients may have new vessels within the foveal avascular zone by the time they consult an ophthalmologist. The most important concern is about these subfoveal new vessels (Fig. 1). They were, until recently, considered not to be amenable to laser treatment: complete obliteration was likely to result in an immedi­ ate and severe loss of vision. 5 A precise diagnosis and classification system of subretinal neovascularisation in AMD is needed in order accurately to eval­ uate the natural history and to select appro­ priate management. On fluorescein angiography, major types of new vessels are, at present, identifiable: -visible or well defined SNV (that fill early with dye and leak profusely to the late phase). (Fig. 2a) -occult or poorly defined SNV (that have less precise features on the early frames but give rise to late leakage). (Fig. 2 b) -visible SNV can be surrounded or can occur during the natural course, within an area of occult new vessels. (Fig. 2 c) -vascularised pigment pigment epithelial detachments can contain either visible or, more frequently, subretinal neovascular membranes (which may be partially obscured by turbid or haemorrhagic fluid). (Fig. 2d) Fluorescein angiography is of major value for the detection and precise location of the neovascular frond in relation to the centre of the foveal avascular zone. Visible or well-defined neovascularisation fills early with dye, often in a cartwheel pat-