358 Br J Ophthalmol 1999;83:358–368 ORIGINAL ARTICLES—Laboratory science Early drusen formation in the normal and aging eye and their relation to age related maculopathy: a clinicopathological study S H Sarks, J J Arnold, M C Killingsworth, J P Sarks Abstract development of age related maculopathy Aim—To describe the early formation of (ARM). The prevalence of drusen in the drusen and their relation to normal aging normal aging population has been addressed by changes at the macula and to the develop- several large population based surveys using ment of age related maculopathy (ARM). graded fundus photography, notably the Chesa- 1 2 Method—Histopathological features of peake Bay and Beaver Dam studies in the 353 eyes without histological evidence of United States, the Rotterdam study, 3 and the ARM are described and correlated with Blue Mountains study, Australia.4 All reported the clinical appearance. In addition, 45 of that one or more drusen were found in these eyes were examined by transmission 95.5–98.8% of the population, with small hard electron microscopy. drusen less than 63 µm being the most frequent Results—Drusen were detected histo- type in all age groups. While the prevalence of pathologically in 177 (50%) eyes but were drusen larger than 63 µm and soft drusen seen clinically in only 34% of these. Drusen increases with age, the prevalence of small hard were mainly small hard drusen with an drusen is not related to age or sex. However, occasional soft distinct drusen: no soft drusen of similar appearance may also be found indistinct drusen were seen. Only those in large numbers and lead to visual loss from drusen deposits larger than 25–30 µm in geographic atrophy or choroidal neovasculari- diameter were detectable clinically. Pre- sation (CNV). Since small hard drusen can clinical drusen in eyes with only an occa- thus be present in normal eyes without ARM as sional drusen were seen on electron well as those with ARM, what then is the microscopy as entrapment sites of coated significance of these drusen, and what is their relation to ARM? In this report we present the membrane bound bodies which formed clinical and pathological findings in 353 eyes adjacent to the inner collagenous zone of from 202 patients. All eyes on funduscopy were Bruch’s membrane. In contrast, preclinical normal or were without soft indistinct drusen, drusen deposits in eyes with many drusen the clinical marker of ARM, and on histopatho- were seen as accumulations of amorphous logical examination were without a continuous Department of material which appeared hyalinised by Ophthalmology, layer of basal laminar deposit (BLD), the histo- University of NSW, light microscopy. A distinct feature were logical hallmark of ARM.5–7 Sydney, Australia and rows of dense hyalinised microdrusen (1–2 Prince of Wales µm in diameter), over which larger globu- Medical Research lar hyalinised drusen formed. Materials and methods Institute, Randwick, —Histological and ultrastruc- A bank of 616 eyes (364 patients) had been Sydney Australia Conclusion S H Sarks tural examination can recognise and dis- collected from 1967 to 1994. All the patients J P Sarks tinguish the earliest drusen formed as a had been examined clinically by one of us result of normal aging from those associ- (SHS) at 1–3 yearly intervals, the last examina- Department of ated with ARM. In eyes without diVuse tion being 2 weeks to 60 months before death Ophthalmology, deposits, histologically all drusen were of (mean 13.9 months). Examination included Aberdeen University, best corrected visual acuity and direct fundus- Aberdeen the hard hyalinised variety or their deriva- J J Arnold tives; no soft drusen composed of mem- copy. Fundus photography and, from 1976, branous debris were found. These findings fluorescein angiography was carried out where South Western Area support and explain those of other authors possible using the Zeiss 30° fundus camera. Pathology Service, who do not consider the presence of a few Only eyes considered on clinical examination Sydney, Australia small hard drusen to be a risk factor for to be normal or with age related macular M C Killingsworth the development of ARM. changes were included; excluded were eyes in Correspondence to: (Br J Ophthalmol 1999;83:358–368) which the fundus could not be visualised and Dr S H Sarks, 15 Parnell those with other retinal pathologies including Street, Strathfield, NSW pathological myopia, retinal vascular diseases, 2135, Australia. The presence of a few small hard drusen less moderate to severe diabetic retinopathy (some Accepted for publication than 63 µm diameter is common and is no patients with mild background retinopathy 1 September 1998 longer considered to be a risk factor for the were included), and end stage glaucoma. Early drusen formation in the normal and aging eye and their relation to age related maculopathy 359 Table 1 General features of study eyes stained by the picro-Mallory method with an average of 15 (range 8 to over 40) sections Group 1 Group 2 No BLD Patchy BLD Total examined per eye. Histopathological findings on some of these eyes have been previously Number of eyes (patients) 139 (80) 214 (122) 353 (202) presented.5 8–10 The eyes were divided into six Females (%) 8 (10%) 9 (7%) 17 (9%) Average age (years) 61.7 73.8 69.0 groups depending on the appearance of the Age range (years) 43–83 60–96 43–96 BLD, as this reflects the stage of degeneration Examined EM (number of eyes) 18 27 45 of the retinal pigment epithelium (RPE).5 BLD = basal laminar deposit; EM = electron microscopy. Briefly, eyes with no BLD (group 1) or those with only patchy BLD (group 2) were consid- All eyes in the bank were examined by light ered normal. ARM was diagnosed when the microscopy (LM) and over 100 were addition- BLD formed a continuous (diVuse) layer ally examined by transmission electron micro- beneath the RPE (groups 3 and 4). The end scopy (EM) by standard techniques. Serial stages of age related macular degeneration, sections 8 µm thick were cut horizontally geographic atrophy, and CNV were classed as through the macula to include the foveola, groups 5 and 6 respectively. optic nerve, and cornea, so that the type, size, This paper presents the results of the and number of drusen outside the macula subgroup of 353 eyes of 202 patients defined as could also be recorded. Every tenth section was normal with no BLD (group 1) or normal aged with only patchy BLD (group 2). Forty five of these eyes were examined by EM. Bruch’s membrane was defined as a trilami- nar structure consisting of the inner and outer collagenous zones separated by the elastic layer and excluding the basement membranes of the RPE and the choriocapillaris.11 Light micro- scopic definitions of BLD,12 and hard and soft drusen710 were used, based on the picro- Mallory method and periodic acid SchiV (PAS) staining, in conjunction with the international classification for ARM.13 BLD was defined on LM as the material found between the plasma and basement membrane of the RPE, staining blue on the picro-Mallory method.12 Hard drusen (nodular drusen7) have a globular hyalinised appearance, are strongly PAS posi- tive, and stain red with the picro-Mallory method. Soft drusen (accumulation of the basal linear deposit7) are faintly PAS positive and stain a pale blue with a finely granular or ground glass appearance on the picro-Mallory method. They have sloping edges and, on semithin sections, may appear optically empty. They only occur in the presence of a continuous layer of BLD at the macula. Clinically, the following drusen were defined10 13: small hard drusen were <63 µm in diameter with sharply defined borders and early bright hyperfluorescence on fluorescein angio- graphy; soft distinct drusen were >63 µm with solid nodular appearance and distinct edges; soft indistinct drusen were >63 µm with blurred margins, and only faint late hyperfluorescence on fluorescein angiography. Drusen size was measured on fundus photo- graphy using the Wisconsin grid and circle templates designed for use with Zeiss 30° films. On LM size was estimated using a measuring graticule in the ×25 and ×40 eyepiece objective. The width of one RPE cell (approximately 12–14 µm) was found to be a useful reference. On EM size was calculated from photographs using the known magnification. Results Figure 1 Basal lamina deposit over drusen of mixed composition. (A) Earliest BLD from a There were 139 eyes in group 1 and 214 in group 2 eye consisting of irregular nodules of fibrillar material (arrow) continuous with the RPE basement membrane; there is no membranous debris. (B) In comparison, later BLD group 2 (see Table 1). seen here in an eye from group 4 consists of fibrillar, amorphous, and long spacing collagen material with a palisading or banded appearance. Membranous debris (arrow) is CHANGES IN BRUCH’S MEMBRANE interspersed between the strands of BLD and within the drusen. (A) A 56 year old man with normal fundal appearance, vision 6/6. (B) A 68 year old man with soft indistinct Thickening and hyalinisation of Bruch’s mem- (membranous) drusen and a few small hard drusen, vision 6/6. (A) ×21 600 (B) ×11 400. brane, indicated by a change from blue to red 360 Sarks, Arnold, Killingsworth, et al Table 2 Comparison of material seen in Bruch’s membrane, entrapment sites, and membranous debris Deposit Site Ultrastructural features on EM Bruch’s membrane change predominantly OCZ coated membrane bound bodies intact or ruptured Entrapment sites rest on ICZ as above raise RPE bm coated membrane bound bodies Membranous debris three sites: coiled membranes (1) internal to RPE bm bilayered structure of lipids (2) within RPE bm not coated (3) external to RPE bm only in presence of BLD EM = transmission electron microscopy; OCZ = outer collagenous zone of Bruch’s membrane; ICZ = inner collagenous zone of Bruch’s membrane; RPE bm = basement membrane of the retinal pigment epithelium; BLD = basal laminar deposit.