Eye (1987) 1,311-317 Management of the Ageing Macula E. L. CHUANG Miami, Florida Summary Age-related Macular Degeneration (AMD) is responsible for the majority of registered blindness in the elderly. Laser photocoagulation can be offered as a treatment of proven value to only a proportion of patients with neovascular AMD. Clinically, our expectations must be tempered by the high incidence of recurrent subretinal vessels, the anatomic limitations of treatable lesions and the large number of ageing eyes for which there is no place for laser. In addition to improve­ ments in education, referral habits and the application of laser therapy which may have an impact upon visual loss due to AMD, there are promising directions to be explored in alternative modes of treatment and prevention. It is well recognised that the leading cause of laser treatment, completed and in progress, blindness in the elderly is AMD. 1,2 This and and also cover limitations and failures of alternative designations such as senile macu­ therapy. Those manifestations of macular lar degeneration (SMD) are used by many ageing for which no treatment is currently authors to refer to all forms of macular ageing, appropriate will also be considered. Finally, whereas only those changes associated with mention will be made of less conventional loss of function are included under the desig­ therapeutic approaches under study and on nation AMD by others. The former definition the ultimate management, that is, possible is used here for drusen, retinal pigment epi­ prevention. thelial detachment, geographic atrophy and subretinal (choroidal) neovascularisation, State of The Art-Laser Treatment manifestations of ageing which do not occur It is appropriate to begin discussion of laser sequentially but rather exist in an interrelated treatment by reviewing briefly the effects of manner. photocoagulation in the target and neighbour­ Only a small proportion of patients with ing tissues. 4 These are based upon the con­ age-related changes suffer significant visual version of light energy to heat, the effects of loss. 2 Though it is one of the least common which are determined by irradiance, absorp­ manifestations of the ageing macula, subreti­ tion and tissue pathlength. Factors such as nal neovascularisation (SRNV) or disciform power, duration and spot size comprise irra­ degeneration is responsible for the vast diance, while heat absorption depends upon majority of these blind eyes. 3 the wavelength employed relative to pigments A significant proportion of these eyes pass present in the tissues and is affected by heat through a stage in which laser therapy can conduction as well as by light absorption and improve the visual prognosis. This review will scatter due to the lens. In the target tissues, concentrate upon neovascular complications the main heat-absorbing substances are of AMD, outlining the relevant studies of melanin, xanthophyll and haemoglobin, each Correspondence to: E. L. Chuang, Bascom Palmer Eye Institute, PO Box 016880, Miami, Florida 33101. From Retinal Diagnostic Department, Moorfields Eye Hospital, London, 312 E. L. CHUANG of which has a characteristic location lengths which must also be taken into account (pathlength) and relative absorption of dif­ in considering the effects of laser. ferent wavelengths. The clinically available lasers include Argon Blue-green and Green Present Clinical Management of AMD only, Krypton Red and Yellow, and most Photocoagulation is the only effective recently, the tuneable Dye Laser with which a modality presently available for the treatment wavelength may be chosen to best suit the of any of the sight-threatening complications of AMD, and is correctly applied only to neo­ individual setting.5 vascular lesions. Our currently accepted Melanin has a broad spectrum of absorp­ approach is based upon the results of three tion, such that its relative concentration in the recent randomised clinical trials which have retinal pigment epithelium (RPE) and shown significantly improved outcome with choroid is the primary determinant of energy Argon Blue-Green laser treatment for extra­ absorption. Spread of heat to neovascular foveal membranes in elderly populations.7 -9 complexes adjacent to the RPE and originat­ These studies varied in specific criteria used ing from the choroid is the principal means by for patient selection, treatment or follow-up, which closure of SRNV occurs. Melanin con­ but many features were common to all three. centration varies considerably with race and Eligible membranes causing symptoms were age: as the concentration of melanin treated with heavy and confluent burns decreases with age, higher power levels are extending beyond the angiographic limits of needed in order to create the desired photo­ the lesion. Visual results were better in eyes coagulative effects. Melanin absorbs longer treated compared to those observed in all wavelengths less than shorter ones. Therefore three studies. In the Macular Photocoagula­ with Red, more energy penetrates the RPE to tion Study (MPS), visual loss of six or more reach the choroid, a partial explanation for lines of acuity was present in 60 per cent of the deeper burns characteristic of Krypton untreated eyes vs 25 per cent of treated eyes Red versus Argon Blue-Green. 18 months after treatment.7 Stable or Haemoglobin absorbs Blue, Green and improved vision was twice as likely in treated Yellow well, but longer wavelengths poorly. eyes at six months. Similarly, in the British Therefore, retinal vascular and secondary and French studies, all analyses favoured inner retinal damage can be minimised by the treatment over observation.8,9 use of Red, as has been demonstrated histo­ Unfortunately, obtaining and maintaining logically.6 Furthermore, if there is a thin layer the benefits of treatment goes far beyond the of blood associated with a neovascular mem­ technical application of laser. Persistent or brane, relatively better penetration is recurrent SRNV following laser is an all too afforded by Red wavelengths, delivering frequent event. All three randomised studies more energy to the deeper target tissues. as well as other retrospective analyses which Xanthophyll absorbs Blue most, Green have included Krypton Red-treated eyes have minimally and Yellow or Red least. Like identified open vessels in close to 60 per cent melanin, its concentration is partially deter­ of eyes after intended obliterative photo­ mined by race. Furthermore, as melanin con­ coagulation.10--13 The vast majority of these centration decreases with age, the use of arise from the site of the original neo­ increasing power levels in order to create an vascularisation and its treatment, with only 8 adequate burn potentially leads to more sig­ per cent of 'recurrent' membranes in treated nificant absorption by xanthophyll. The pres­ MPS eyes located independently from treat­ ence of xanthophyll in the central macula, ment scars. Virtually all the recurrences arise primarily in the outer plexiform layer means from the foveal treatment edge, underlining that damage to the neurosensory retina can be the well-recognised tendency of neovascular minimised in this location by the use of longer membranes to grow toward the foveola and wavelengths. With ageing, the lens contains perhaps modified laser absorption in this increasing amounts of xanthophyll, leading to location as well as reluctance to apply Blue­ greater absorption and scatter of short wave- Green laser close to xanthophyll pigment. MANAGEMENT OF THE AGEING MACULA 313 The majority appear relatively early: with nised that the biologic behaviour of NVMs almost five year follow-up in the MPS, over 70 includes an initial period of greatest activity per cent of recorded recurrences were identi­ and growth. 18 Experience has identified an fied within the first year. 10 It is of significance interval of weeks from the onset of symptoms that analysis to date has not identified specific beyond which laser therapy results in a poorer features other than distance from the foveal visual outcome. 19 After treatment, patients avascular zone, which might be useful predic­ should be clearly and repeatedly informed of tors of eyes at higher risk for recurrence in the means and need to monitor central vision Argon treated eyes. The long-term visual out­ and of the importance of seeking immediate come is worsened because of the high number attention should symptoms arise. They and of recurrences, but still remains better than no referring eye care specialists must also have treatment at all since laser can be reapplied in ready access to appropriate evaluation. These eyes with recurrent SRNV which continue to measures should enhance our ability to meet treatment criteria. 14 approach the highest possible success rate The nature of recurrences reflects not only afforded by photocoagulation. features of the biologic nature of SRNV but In the best of circumstances, there will also less than optimal aspects of our presently always be individuals in whom the location of accepted treatment approach. If we can better an active NVM will begin or become sub­ understand and manage this common sequel foveal, so that there can be no hope for to laser treatment in neovascular AMD, the normal central vision. In such instances, laser visual prognosis in macular ageing will may still improve final visual function. It has undoubtedly improve. Though the use of been proposed that the size of the ultimate Argon Blue-Green is the only modality pres­ scotoma can be limited by