Ageing and degeneration in the macular region: a …Ageing and degeneration in the macular region: a...

Brit. J. Ophthal. (1976) 6o, 324

Ageing and degeneration in the macular region:a clinico-pathological study

S. H. SARKSLidcombe Hospital, Sydney, Australia

Certain changes at the macula can be attributed tonormal ageing. Metabolic waste accumulates inthe cells of the retinal pigment epithelium. Con-nective tissue, especially altered collagenous fibres,increases in Bruch's membrane, and vascularchanges inherent in the vessels themselves can beshown in the choroid. Which of these ageingprocesses is implicated in the pathogenesis ofsenile macular degeneration or at what stage theybecome pathological is uncertain. Most cases ofsenile macular degeneration are believed to be dueto sclerosis and obliteration of the choriocapillarisin the central area (Duke-Elder, I966), whileelectron microscopic studies by Hogan (I967,1972) emphasized the role of ageing changes inBruch's membrane and the retinal pigment epi-thelium.

Senile macular degeneration shows a widespectrum of clinical appearances, reflecting thedifferent anatomical levels predominantly affectedat the time. Thus the fundus may present a distur-bance of retinal pigmentation, exposure and abnor-mality of the choroidal vessels, drusen of variousappearances, evidence of exudation, haemorrhageor neovascularization from the choroid, and intra-retinal and preretinal changes. This has resultedin the recognition of many distinct and generallyunrelated entities since the disease was originallydescribed by Haab (I885). The most significantadvance in recent years stems from the originaldemonstration by Verhoeff and Grossman (1937)that senile disciform degeneration results from theorganization of haemorrhage beneath the retinalpigment epithelium. The cause of this haemorrhagewas investigated by subsequent observers, notablyby Maumenee (I965), and by Gass (I967), whoformulated our current knowledge of the predisci-form state when he proposed that neovasculariza-tion from the choroid may occur in response to theaccumulation of abnormal deposits beneath thepigment epithelium and that this may precedehaemorrhage.

Current interest therefore centres on the recogni-

Address for reprints: S. H. Sarks, Lidcombe Hospital, Sydney,Australia

tion of the predisciform state and the use of plhoto-coagulation to prevent the complications of sub-retinal neovascularization. A definitive form oftreatment has thus been evolved, although appli-cable to only a limited number of patients sufferingfrom an advanced degree of degeneration. Further,it has been difficult to rationalize and to evaluatethis treatment because the natural history of thedisease remains poorly understood (Gass, 1973).Not surprisingly, therefore, the majority of ophthal-mologists regard degenerative disease of the retinaand the macula as the most difficult to treat and themost in need of research (Hammond and Spalter,'973).The present investigation reports the results of

clinical and pathological examination of 378 eyes.The aim of this study was to identify the age-related changes in the retinal pigment epithelium,Bruch's membrane, and choriocapillaris whiclcould be regarded as normal and to relate the pro-gression of these changes to the evolution of senilemacular degeneration.

Material and methodsHistological examination was performed on 378 eyesin which the macula had presented a variety of clinicalappearances ranging from normal to the late manifesta-tions of senile macular degeneration. This series did notinclude eyes suffering from degenerative myopia,retinal vascular disease affecting vision, advancedsimple glaucoma, or eyes in which an adequate view ofthe macula had niot been obtained clinically. The 378eyes were collected during the period I966-75 from 2i6patients, I99 men and 17 women, whose ages rangedfrom 43 to 97 years. All patients had been admitted toLidcombe Hospital, generally for long-term care, and afull ocuklr examination was performed at intervals.Fundus photographs were taken whenever possible andselected vtients were submitted to fluorescein angio-graphy. Thne average interval between the last clinicalexaminatioii and the time of death was I6-4 months.When e es became available after death they were

fixed in Lillie's buffered formalin. They were opened inthe horizontal plane and examined macroscopically.The position on the sclera corresponding to the maculawas localized by observing the tip of a fine probe duringtransillumina ;ion, and the spot was marked with con-

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Ageing and degeneration in the macular region 325

centrated Harris's haematoxylin solution. The eyeswere then double embedded (Tait Smith, I976).Serial sections 8 [±m thick were cut horizontally throughthe disc and the macula. Every tenth section wasstained by the picro-Mallory method as modified byLendrum, Fraser, Slidders, and Henderson (i962) andexamined histologically. This stain was selected forroutine use as it distinguishes fibrin (red), collagen(blue), and neural tissue (pink). In areas of interest theintervening sections were examined after staining withthe following: haematoxylin and eosin, luxol fast blue,periodic acid-Schiff, Verhoeff's elastic stain, chloranilicacid, Wilder's silver stain, Mallory's PTAH, and congored.

Results

Histological changes associated with ageing weredetected at the level of the retinal pigment epithe-lium, Bruch's membrane, and choriocapillarisbefore clinical abnormality became apparent.Subsequent changes in these tissues also correlatedclosely with the clinical progress of senile maculardegeneration. In the present investigation theageing and degenerative changes at the maculawere therefore classified according to the histology.The age-related changes in Bruch's membrane

comprised thickening, hyalinigation, patchy baso-philia, and precipitation of calcium crystals withchloranilic acid. These changes were first seenbeneath the macula and adjacent to the disc andremained most advanced in these regions. Anarbitrary assessment of the findings was made insections beneath the fovea. The thickness of arepresentative segment of the membrane wascompared to the vertical diameter of the under-lying choroidal capillary. The thickness was thenexpressed according to whether Bruch's membrane:choriocapillaris was one-quarter or thinner, one-third, or one-half or thicker (Fig. i).

Hyalinization of the membrane was indicatedby increased periodic acid-Schiff positivity and achange from blue to red staining with the picro-

Mallory method. The extent was noted to thenearest half disc diameter and four grades wererecognized. Grade i referred to small patcheswhich appeared in the fifth decade and later becamecontinuous. Grade 2 hyalinization extended intothe intercapillary pillars (Fig. 2) and grade 3hyalinization reached the level of the outer surface ofthe choriocapillaris (Fig. 3). Hyalinization com-pletely surrounding several choroidal capillarieswas occasionally observed (grade 4).Two types of drusen were noted on Bruch's

membrane. Some deposits were hyalinized andglobular in shape, others were dome-shaped andhad a granular structure. These drusen could alsobe distinguished on clinical examination, theformer appearing round and discrete while thelatter showed greater variation in size and shapewith ill-defined outlines.The earliest light microscopic evidence of

disturbance to the pigment epithelium was asso-ciated with the appearance of a finely granulardeposit at the base of the cells. This material waseosinophilic, was unstained with luxol fast blue,was only moderately positive to periodic acid-Schiff, but stained blue with the picro-Mallorymethod. The formation of this basal linear depositbeneath the macula proved the most reliable histo-logical criterion of the stage of the disease andcorrelated most closely with the clinical findings,although this was influenced to some extent by thetime interval between clinical and histologicalexaminations.

HISTOLOGICAL GROUPS

The eyes were divided into six groups accordingto the degree of histological abnormality (Fig. 4).The first four groups reflected the progressivedevelopment of the basal linear deposit and thevisual acuity recorded in these eyes is shown inTable I. Groups V and VI represented the latestages of geographical atrophy and disciform

FIG. 4 Diagram illustrating histological classification of 378 eyes acccrding to developmentof basal linear depositunder retinal pigment epithelium

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326 British Journal of Ophthalmology

FIG. I Example of Group II.Section passing through macularregion of patient aged 86 withnormal fundus and 6/I2 vision.Marked thickening of Bruch'smembrane encroaching onchoroidal capillary, ratiothickness membrane: capillarylumen almost i:I. Localizeddeposit of blue staining finelygranular material related tothickened membrane.Picro-Mallory. x 500

FIG. 2 Example of Group I.Section through normal maculaof left eye of patient whose rightfundus is illustrated in Fig. 5.Bruch's membrane shows grade 2hyalinization and there is noevidence of basal material underretinal pigment epithelium. Thepigmented choroid is of normalthickness and vessels are normal.Picro-Mallory. x 150

FIG. 6 Example of Group II.Section through paramaculararea of left eye of 72-year-oldman with 6/6 vision and normalfundus. Beneath retinal pigmentepithelium localized deposits offinely granular material arerelated to deeply stainingsegments of Bruch's membrane.These segments were basophilicwith haematoxylin and eosinstain. Picro-Mallory. x 500

FIG. 7 Example of Group III.Section through macula of79-year-o!d man whose fundushad appeared normal with 6/9vision. Basal linear deposit nowforms thin continuous layer andBruch's membrane showswidespread grade 3 hyalinizationextending into the intercapillarypillars to the level of outersurface of choriocapillaris.Picro-Mcllory. x 75

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FIG. 3 Example of Group IV, showing thickbasal linear deposit related to grade 3

hyalinization of Bruch's membrane. Section ofeye shown in Fig. I I. Picro-Mallory. x 500

FIG. 8 Example of Group IV. Section throughmacula of 83-year-old man whose fundus hadshown coarse pigmentary disturbance although

vision had remained 6/9. Note thick continuousbasal linear deposit and degeneration of

overlying pigment epithelium with liberation ofpigment-laden cells into subretinal space.

Bruch's membrane shows thickening and pillarsof grade 3 hyalinization. Picro-Mallory. x 150

FIG. I7 Example of Group IV progressing toGroup V. Sections passing through macula of

eye in Fig. i6. Basal linear deposit formscontinuous hyalinized and very thickened layer

under macula. Pigment epithelium shows markedattenuation and seems about to disappear.

Top: periodic acid-Schiff. x 45.Bottom: Picro-Mallory. x I 50

FIG. 22 Example of Group VI. Section passingthrough disciform scar in eye of 8o-year-old

patient. Hyalinized basal linear deposit has beenfolded into the mass by successive waves of

fibrous tissue. Picro-Mallory. x 300

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degeneration in which vision was greatly reducedwhen the fovea was involved. Table II shows theassociated histological and clinical findings, andTable III shows the age distribution of the 2i6patients.

Group I (No basal linear deposit)In this group (I20 eyes) there was no trace of thebasal linear deposit and the retinal pigment epi-thelium appeared normal. The average extent ofgrade 2 hyalinization of Bruch's membrane wasz2o disc diameters, and even eyes from patients inthe 40 to 50 year age group showed some evidenceof grade i hyalinization. Small drusen of the hya-

Table I Visual acuity recorded in Groups I-IV(333 eyes)

Visual Group Group Groutp Grouipacuity I II III IV

6/6 66 (55.0) 29 (26-i) 6 (ioo-) 2 (4 8)6/9 I7 (04a2) 32 (28 9) 23 (38 3) 2 (4-8)6/12 6 (50) i8 (I6-2) I2 (20z0) 8 (19-0)6/I8-6/24 4 (3-3) 9 (8sI) 12 (20-0) I7 (40 5)< 6/24 2 (1'7) I (o-9) I (I 7) I0 (23 8)Unknown 25 (20o8) 22 (i9-8) 6 (Io-o) 3 (7-I)

Total 120 III 6o 42

Percentages are shown in parentheses

FIG. 5 Normal right fundus of man aged 67. Leftfundus was identical. Vision 6/6 in both eyes

linized globular variety were noted in 23 eyes

but had no detectable effect on vision, althoughnone was located at the fovea.The average age of patients in this group was

67-5 years and no pigmentary changes were notedon clinical examination. Figs 2 and 5 illustratethese normal findings. 6/6 vision was recorded in

Table II Clinical and histological findings in 378 eyes, grouped according to appearance of basallinear deposit

No. of eyesBasal linear deposit

Bruch's membrane/choriocapillaris(a) Average limits of

hyalinization in discdiametersGrade 2Grade 3

b) Thickness of membrane*capillary lumen

Incidence of subretinalneovascularization (percentage)

Clinical disturbance ofpigmentation (percentage)

NilFineCoarse

Average age of patients (years)

Group I Group II

120 III

Absent Patchy

Group III Group IV

6o 42

Thin Thickcontinuous continuous

Group V Group VI

24

Persistsafter lossof pigment

2I

Incorporatedinto scar

2-0 2'5 3-0 3 9 5-I 5.7Nil odd pillars i-o 3-0 3-7 3-3

I I I I I I

3-7 3-4 2-9 2.3 2-2 2.4

0

96.43.6

0

75.3

0

4I .6

46.7

8i 9

14.3

4.7I6.7

78-6

84-0

417

Geographicatrophy

85-6

100

Disciformdegeneration

8I 9

*Average

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Ageing and degeneration in the macuilar region 329

Table III Age distribution of patients according to histological classiJication of 378 eyes

Group IAge Group II Group III Grouip IV Group V Group VI Totalgroup Vision 6/6 Vision <6/6

-59 i6 I5 2 0 0 0 0 33

6o-69 29 7 25 4 o 0 0 6570-79 21 I7 43 x4 II 2 7 II580-89 0 I5 38 34 22 20 I4 14390+ 0 0 3 8 9 2 0 22

Total 66 54 III 6o 42 24 21 378

only 66 of the 120 eyes, and in none of the eyes ofpatients aged 8o years and over (Table III). Inmost eyes the lowered visual acuity was ascribed tohazy media or to failure of concentration, but inothers no cause was apparent.

Group II (Patchy basal linear deposit)

In this group (iii eyes) the basal linear depositappeared in patches beneath three to eight retinalpigment cells, which showed slight distortion. T'heaverage extent of grade z hyalinization of Bruci'smembrane was 2'5 disc diameters with occasionalpillars of grade 3 hyalinization. Grade 3 hyaliniza-tion was associated with widening of some pillarsand also with thickening of the membrane, resultingin encroachment on the choriocapillaris. It wasat this stage that degenerative changes in theoverlying pigment epithelium were first observed(Figs i, 6). Drusen were present in the macularregion in 22 eyes and were predominantly of thehyalinized globular variety.The average age of patients in this group was

75-5 years and nearly all eyes showed no clinicaldisturbance of pigmentation (Table II). The mostcommonly recorded visual acuity was 6/9 (Table I),with an about equal incidence of eyes in whichvision was better (26-i per cent) and worse (25-zper cent).

Group III (Thin continuous basal linear deposit)In this group (6o eyes) the linear deposit formed athin continuous layer under the macula. Theaverage extent of grade 3 hyalinization was Ix0disc diameter but the deposit sometimes extendedmore widely, becoming patchy before petering out(Fig. 7). The overlying pigment cells were irregularand the outline of individual cells was less distinctso that they appeared fused together. The rod andcone processes were generally separated from thepigment epithelium at the macula and some ap-peared stunted. Drusen were present in 25 eyes

with an about equal incidence of the hyalinizedand granular varieties.The average age of patients in this group was

819 years. The most common visual acuity wasagain 6/9, but 6/6 vision was recorded in onlyIo per cent of the eyes. More than half the eyesshowed a clinical disturbance of pigmentation,predominantly a fine clumping of pigment (TableII), and this included 23 of the 25 eyes with histo-logical evidence of drusen. The incidence of fundusabnormality is probably underestimated owing tothe interval after the clinical examination.

Group IV (Thick continuous basal linear deposit)This group (42 eyes) showed thickening of thebasal linear deposit, sometimes to about the heightof normal pigment epithelium (Fig. 8). Globules ofhyalinized material and small foci of calcificationwere sometimes demonstrated in the material. Thepigment epithelium appeared as an attenuatedlayer in which cell outlines were lost and nucleiwere few. In some areas proliferative changes wereobserved, large pigment-laden cells being shed intothe subretinal space, and occasional cells containedhyalinized material or developed cystic changes.Localized mounds of pigment granules were alsonoted. The photoreceptors, which were sometimesabsent over the mounds of pigment granules,showed a greater degree of retraction and distor-tion in this group. The basal linear deposit attainedits maximum thickness over grade 3 hyalinizationof Bruch's membrane, the average extent of whichwas 3 o disc diameters. The underlying choroidalcapillaries were wide-spaced and often narrowed,so that the average ratio of membrane thickness tocapillary lumen was almost 1:2. This was due notonly to encroachment by the thickened membranebut also to reduction of the capillary lumen bysurrounding fibrous tissue. Drusen were.present inIS eyes. They were mainly of the granular typeand several were undergoing calcification.

Six of the 42 eyes (14-3 per cent) showed thin

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330 British Yournal of Ophthalmology

FIG. 9 Section throughmacular area of 72-

* year-old man whosefundus had shown coarsepigmentary disturbance,vision 6/i8. Capillary(arrow) passes throughsmall gap in Bruch'smembrane to invadebasal linear deposit.Picro-Mallory. x 300

FIG. 10 Sectionshowing giant cellbeneath thinned segmentof Bruch's membrane ineye from 77-year-oldman. There were severalareas of fibrovascularinvasion but serialsections did not show

< break in Bruch'smembrane at site ofgiant cell.

L Picro-Mallory. x 500

capillary membranes passing through gaps inBruch's membrane and spreading beneath theretinal pigment epithelium in the macular regionfor up to half a disc diameter. Drusen were aconspicuous feature in two of these eyes but werenot immediately related to the breaks in the mem-brane, the capillaries invading the basal lineardeposit (Fig. 9). Giant cells were often prominentnear the gaps in the membrane but were alsofound in relation to thinned segments of the mem-brane where serial sections did not show a breakin the immediate vicinity (Fig. io).The average age of patients in this group was

84 years and the youngest was aged 70. The mostcommonly recorded visual acuity was 6/24 andalmost all eyes showed a clinical disturbance ofpigmentation which was predominantly coarse.Fig. ii shows the tigroid fundus of a go-year-oldman with fine pigmentary changes and 6/9 vision.The basal linear deposit was widespread under themacula (Figs I 2, I3) and was appreciably thickenedover grade 3 hyalinization (Fig. 3). An electronmicroscopic section was taken from the paraffinblock in this area. This technique is unsatisfactoryfor fine detail but shows the thick deposit lying onBruch's membrane (Fig. 14). The hyalinized mem-brane and the intercapillary pillars contain irregular-banded collagen, vesicles, and tube-like structures.The electron micrograph (Fig. I5) represents themacular region of a man aged 71 who showedcoarse pigmentary mottling in both eyes, and

histological examination of the fellow eye showeda thick layer of basal material. The deposit containsbanded material lying between the plasma infoldingsof the retinal pigment epithelium and the base-ment membrane.

Fig. i6 shows the tigroid fundus of an 8o-year-

FIG. xi Tigroidjundus of 90-year-old man. Maculashowed fine pigmentary disturbance. Vision 6/9

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old man. Coarse clumps of pigment were distributedaround a central hypopigmented area. Sectionsthrough this area showed the basal linear depositto be much thickened and hyalinized, while thepigment epithelium remained only as a veryattenuated layer and seemed about to disappear(Fig. I7). This was the most extreme example ofthickening of the deposit found in Group IV, as inthe other eyes it did not exceed the height of thenormal pigment epithelium. Further, this groupincluded three eyes in which the deposit did notshow thickening although the pigment epitheliumwas similarly attenuated and formed occasionalmounds of pigment granules. In these eyes thedeposit was not hyalinized and appeared to havefaded with the pigment epithelium.

Group V (Basal linear deposit with loss of overlyingpigment)In this group (24 eyes) loss of the retinal pigmentepithelium produced areas of geographical atrophyvisible clinically (Fig. i8). On histological examina-

FIG. 12 Section throughmacula of eye shown in Fig.iI. Note thinning of choroidaccentuating prominence oflarger vessels.Picro-Mallory. x go

FIG. 13 Section throughparamacular area of same eyeshowing grade 3 hyalinizationof Bruch's membrane andcontinuous basal lineardeposit. Pigment cells showirn egularity, cystic spaces,and indistinct cell outlines.In a choi oidal artery there isreplacement of muscle byfibrillar fibrous tissue.Picro-Mallory. x 300

tion the hyalinized basal linear deposit could betraced throughout the depigmented area in mosteyes. The deposit also extended for some distancebeneath the adjacent pigment epithelium, whichshowed the same changes as noted in Group IV.At the edge of the depigmented area the histologicalchanges were constant. The pigment epitheliumoften ended in a group of proliferated cells, whilethe photoreceptors showed progressive degenera-tion as they approached the atrophic area in whichthey disappeared. The external limiting membraneended in a curved line and the outer nuclear layeralso disappeared so that the outer plexiform layerrested directly on the basal material (Fig. I9).Occasionally an island of persisting photoreceptorsconverged on a cluster of degenerating pigmentcells. The choroid was often more atrophic inthese eyes and many choroidal capillaries showedpartial obliteration by fibrous tissue in the depig-mented area. The narrowing of the capillaries oftenoccurred abruptly where the pigment epitheliumended (Fig. 20). In relation to these capillariesBruch's membrane appeared disproportionately

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FIG. 14 Electron micrograph of eye in Fig. iI. Section taken from area of basal linear deposit depicted in Fig. 3.This technique is unsuitable for fine detail but shows a thick layer of amorphous material (BLD) lying on Bruch'smembrane (BM). The material in intercapillary pillars extends to level of outer suirface of choriocapillaris (CC) andconsists of irregular-banded collagen, vesicles, and tube-like structures. x 6820

thick but in actual measurements the membranewas often thinner than in Group IV, particularlyin those eyes in which clinical observation hadconfirmed the loss of the pigment epithelium tobe of long standing (Fig. 2I).

Fifteen eyes showed drusen of both types. Allof the granular variety showed calcification andsome also contained avascular fibrous tissue. Neo-vascularization from the choroid was demonstratedin io eyes, including six of the eyes with drusen,

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Ageing and degenteration in the macular region 333

FIG. 15 Electron micrograph from macular region of man aged 71 whose fundus had shown coarse pigmentary changes.Histological examination of the fellow eye revealed thick basal linear deposit. The deposit (BLD) contains bandedmaterial lying between plasma infoldings of retinal pigment epithelium (arrow) and the basement membrane (bm).BM=Bruch's membrane. x 19 250

and in seven eyes the breaks in Bruch's membranewere multiple. The fibrovascular tissue was moreextensive than in Group IV but did not obscurethe underlying choroid on clinical examination,unlike the thicker scars of disciform degeneration.The areas of geographical atrophy were either

present at the time of the first clinical examinationor were observed to develop gradually within anarea of coarse pigmentary mottling. The averageage of patients in this group was 85-6 years andthe most commonly recorded visual acuity whenthe fovea was involved was 3/60.

Group VI (Disciform degeneration)In this group of 21 eyes fibrovascular invasionfrom the choroid resulted in clinically visiblescars of varying size. The basal lincar depositremained identifiable as a hyalinized layer foldedinto the mass, sometimes separating fibrous tissueof different ages (Fig. 22). The deposit also ex-tended for some distance beyond the scar and wasattended by corresponding changes in the pigmentepithelium and Bruch's membrane. Under the scarthe choroid was generally thicker than in Group Vand the arteries showed more pronounced sclerosis.

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FIG. i6 Tigroidfundus of 8o-year-old man. Maculashows coarse clumps of pigment distributed aroundcentral hypopigmented area. Vision 6/24

The average age of the 14 patients in this group

was 8i 9 years. Disciform degeneration was bilateralin seven patients while in four the second eye

showed geographical atrophy which was alsoassociated with new vessels. Although serous

detachments of the retinal pigment epitheliumwere noted clinically during the evolution ofdisciform degeneration, only one eye subsequentlyshowed such detachment on histological examina-

tion (Fig. 23). Fibrin was demonstrated in theserous fluid and vessels appeared to be extendinginto the serous detachment from an adjacentmound of fibrovascular tissue.

Cuticular material was occasionally observedin the scars, lying between rows or clusters ofproliferating retinal pigment cells (Fig. 24). Thismaterial was eosinophilic, intensely positive toperiodic acid-Schiff, and of hyaline appearancebut stained blue with picro-Mallory, unlike thehyalinization of Bruch's membrane or of the basallinear deposit, which both showed a change instaining reactions to red with this method.

SENILE CHANGES IN CHOROID

The frequency with which the fundus presented atigroid appearance rose sharply after the age of75 years. This picture differed from the tigroidfundus seen in younger patients in that the choroidalvessels became visible beneath the macula andtheir margins were clear-cut. The senile halowas often pronounced (Fig. iI).

Although a pigmentary disturbance was com-monly associated, the senile tigroid fundus wasalso observed in eyes in which the macula wasotherwise normal. Histological examination con-firmed that the clinical prominence of the vesselswas due to thinning of the choroid, due particu-larly to loss of the middle layer, so that the largervessels occupied almost the full thickness of thechoroid (Fig. I2). Degenerative changes were alsonoted in some choroidal arteries similar to thoseseen in cerebral vessels, particularly in the choroidplexus. The vessels were shrunken and showed

FIG. i8 Left fundus of 84-year-oldman first seen four years previouslywhen fundus showed only peripapillarychoroidal sclerosis and fine pigmentarydisturbance at the macula. He graduallydeveloped area of depigmentation nasal

j to the fovea, vision falling from 6/9to 6/24 during this period

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FIG. 19 Section betweenmacula (at left) and disc of eyein Fig. i 8. There is loss ofpigment epithelium, rod andcone processes, external limitingmembrane, and outer nuclearlayer. Outer plexiform layerrests directly on hyalinizedbasal linear deposit.Picro-Mallory. x 150

replacement of muscle by fibrillar fibrous tissue(Fig. I3). The remains of occluded vessels withcollapsed fibrous walls were also seen. The majorityof the vessels, however, showed only fibrousreplacement of the media with the retention of

FIG. 2o Right fundus of 83-year-old man sufferingfrom central choroidal atrophy in both eyes. The areasincreased slowly in size over period of six years. Notelarge vein which retains normal blood column. Visionwas counting fingers in both eyes

wide lumina. In normotensive patients hyaliniza-tion was observed only in extreme old age affectingthe small vessels near the disc.

Discussion

In the elderly the macula typically shows loss ofthe foveal reflex, fine granularity of the retinalpigment, increased visibility of the choroidal vessels,and a few discrete drusen. These changes areconsidered to lie within normal limits, but in thepresent investigation 6/6 vision was recorded infewer than half of the eyes showing these appear-ances and in none of such eyes belonging to patientsaged 8o years and over. In most eyes this could beattributed to a failure of co-operation or to hazymedia, but in others no cause was apparent. Thisdecline in visual acuity with age was first noted byDonders (I864), and Weale (I975) calculated thatthe deterioration could be explained if the rate ofcell fall-out found in the cerebellum was appliedto the visual pathways. It follows that the limitsof normal ageing are difficult to define in terms offundal appearances or visual acuity.The natural history of senile macular degenera-

tion is similarly difficult to predict from clinicalobservation. Some cases show a progressive distur-bance of retinal pigmentation, with or withoutprominent drusen, and culminate in geographicalatrophy. During the evolution of the disease,however, the appearance of the choroidal vesselsmay become sufficiently abnormal to lead to therecognition of senile choroidal atrophy as a separate

-4_b-

* _..., _ _

FIG. 2I Section throughmacula of eye in Fig. 20. Thereis loss of retinal pigmentepithelium and photoreceptorsbut basal linear deposit can betraced across depigmented area.The choriocapillaris is absentand dilated thin-walled veinoccupies full thickness ofchoroid.Picro-Mallory. x 75

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336 British Yolurnal of Ophthalmology

FIG. 23 Righit eye of

86-year-old mnan sufferingfront disciform degenerationt.Section shows seroutsdetachment of retinalpigment epitheliumcontaining fibrovasculartissue, and an adljacentmound of cutticular materialand proliferating pigmentcells. Break in Bruch'smembrane was rentote frontthe detachment.Picro-Mallory. 75

e itity. At other times subretinal exudation, hac-morrhage, and neovascularization may occur toalter the clinical picture and influence the prog-

nosis. In the present clinicopathological investiga-tion, therefore, the changes associated with ageingand degeneration of the macula were recordedaccording to the degree of histological abnormalityoccurring at the level of the retinal pigment epithe-lium, Bruch's membrane, and choriocapillaris.

BRUCH S MIEMBRANE

The age-related changes in Bruch's membranecomprised thickening and hvalinization, increasedperiodic acid-Schiff positivity, and basophilicstaining. The use of the term hyalinization requiresexplanation, since it merely denotes that themembrane appears glassy or without structure. Inthe present discussion the term has been retained

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and has been applied when the membranie showeda change in staining properties from blue to redwith the picro-Mallory method, increased periodicacid-Schiff positivity, and green staining withluxol fast blue. Picro-Mlallory was one of severalstaining methods developed by Lendrum andothers (i962) for the demonstration of fibrin, andGarner (I975) has suggested that the thickening ofthe mcmbrane is due to the accumulation of plasmaconstituents secondary to undue permeability ofthe endothelium of the choriocapillaris. Stainingwith Mallory's PTAH, however, does not producethe dark blue appearance characteristic of fibrin,nor does the membrane subsequently develop thestaining properties which Lendrum, Slidders, andFraser (I972) found to accompany the ageing offibrin. The change from blue to red staining of themembrane may be due to a reduction in the sizeof the intermicellar pores so that they accept only

FIG. 24 Sectioni throutgh*. * eye of 75-year-old patient

suffering from disciform_ ,_q _ degeneration. An irregular

imass of hyaline cuticular

ntaterial surrounded on allaspects by abnormal retinalpigment cells lies on inneraspect of fibrous tissue.Picro-Mallory. X 500

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the smaller molecule of the acid fuchsin dye. Thisexplanation is suggested by the electron micro-scopic demonstration of increasing density of themembrane.The electron microscopic changes which develop

in the membrane with age appear to fall into twomain groups. The accumulation of vesicular,granular, and filamentous material begins in theinner collagenous zone at around the age of 20(Hogan, I967). Residual bodies and undigestedouter rod segments have been identified in thismaterial which represents debris derived from theretinal pigment epithelium. On the other hand,after the age of 40 changes develop in the collagenand elastic fibres of the membrane. There is an

increase of normal and intermediate collagenand of fibres resembling long-spacing collagen.Hogan, Alvarado, and Weddell (I97I) also describedlong, coiled osmiophilic fibres which they sug-gested may be altered collagen fibrils on whichan electron-dense substance is deposited. Theelastic fibres also show increasing density andundergo calcification.

RETINAL PIGMENT EPITHELIUM AND BASAL LINEAR

DEPOSIT

The earliest light microscopic evidence of degenera-tion of the retinal pigment epithelium was associatedwith the development of a finely granular depositbeneath the cells, although hyalinization of Bruch'smembrane was already established. This materialwas simply described as a basal linear deposit inorder to distinguish it from drusen. The depositcontrasted with the hyalinized membrane bystaining blue with picro-Mallory, being onlymoderately periodic acid-Schiff positive and re-

maining unstained with luxol fast blue. Gass(i967) described this deposition as an eosinophilicgranular material and noted that it stained bluewith Masson's stain, suggesting a collagenouscomponent to its composition. The electron micro-scopic findings (Figs 14, 15) show this deposit tolie between the basal plasma infoldings and thebasement membrane of the retinal pigment epi-thelium and to consist mainly of spindle-shapeddeposits, often embedded in a granular material.These deposits contained structures with widely-spaced striations with a periodicity of I 20 nm,

which Hogan (1972) considers to resemble short-segment, long-spacing collagen such as is obtainedby the in-vitro precipitation of tropocollagen(Gross, I957). Basement membrane is collagenousin nature and may briefly be defined as tropocol-lagen in carbohydrate-rich mucoprotein (Ashton,1974). Tripathi (I974) suggested that under certainconditions long-spacing collagen may originate

from a direct polymerization of basement mem-brane material.

Long-spacing collagen fibres have also beendescribed in other tissues, notably in Descemet'smembrane (Jakus, 1962), where they appearedto be the result of abortive attempts to formnormal membrane (Hogan, Wood, and Fine,1974), in the cortical zone of the trabecular beams(Garron, Feeney, Hogan, and McEwen, 1958),and in association with the basement membraneof the neuroepithelium of the utricular macula(Friedmann, Cawthome, and Bird, I965). Presentindications are that these deposits which accumu-late in the region of the basement membrane are amanifestation of gradual degeneration of theassociated cells.

INTERPRETATION OF AGEING AND DEGENERATION IN

MACULAR REGION ACCORDING TO BASAL LINEARDEPOSIT

The development of the basal linear depositbeneath the retinal pigment epithelium appeared tobe the most reliable histological criterion of thedegree of degeneration of the overlying cells. Theeyes were therefore classified according to thehistological appearance of this deposit. Groups Iand II broadly represented normal ageing, GroupsIII and IV represented the development and pro-gress of degeneration, and Groups V and VIshowed the subsequent end-results.

Groups I and II

In Group I the deposit could not be demonstratedalthough ageing of Bruch's membrane was alreadyin evidence, starting in the fifth decade as patchesof hyalinization under the macula and adjacent tothe disc. With advancing age hyalinization andthickening spread over a wider area and also ex-tended into the intercapillary pillars. The basallinear deposit first appeared in Group II in relationto thickened or basophilic segments of the mem-brane, or over the occasional widened intercapillarypillar showing hyalinization extending to the levelof the outer surface of the choriocapillaris (grade 3).Nearly all eyes in these two groups retained anormal fundus appearance, often with 6/6 vision,and the histological changes were considered tobe within the limits of normal ageing.

Groups III and IV

In Group III the basal deposit became a thincontinuous layer and grade 3 hyalinization ofBruch's membrane extended for almost one discdiameter under the macula. These changes wereconsidered to have become pathological, since

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338 British Yournal of Ophthalmology

more than half the eyes had developed a clinicaldisturbance of pigmentation and in most vision wasreduced. In Group IV clinical abnormality waswell established, manifest predominantly as coarsepigmentary clumping. This group was charac-terized by thickening of the basal deposit and morepronounced degenerative and proliferative changesin the pigment epithelium. Gradual disappearanceof the cells led to the circumscribed areas ofdepigmentation which characterized Group V. Anumber of eyes appeared to show this transition,since they contained only a thin layer of pigment.In several eyes the deposit appeared to fade as thepigment epithelium disappeared, but in most itremained as a thickened- hyalinized layer.

Neovascularization was first detected in GroupIV, in which six of the 42 eyes (14.3 per cent)showed capillary membranes growing beneath thepigment epithelium in the macular region. Thesecapillaries were found to be invading the basallinear deposit, and Gass (I967) also describedcapillaries coursing through this eosinophilicmaterial in two cases. None of the eyes in GroupIV showed evidence of a serous detachment of thepigment epithelium with which new vessels arecommonly associated (Teeters and Bird, I973a, b).The present series therefore appears to confirmthe suggestion by the same authors that bloodvessels may grow into the subpigment epithelialspace without previous detachment of the pigmentepithelium. The retinal pigment epithelium isnormally firmly anchored to the choroid by finefilaments of the basement membrane which ex-tend from its inner and outer surfaces to join thecell membrane and the inner collagenous zone ofBruch's membrane (Hogan and others, I97),and probably the basal linear deposit disturbs thisattachment. This may allow spontaneous detach-ment of the pigment epithelium to occur and mayalso predispose to the ingress and spread of newvessels. Further, the demonstration of macro-phages and giant cells in relation to thinned butunbroken segments of Bruch's membrane suggeststhat there may be an attempt at organization,since in other tissues these cells may precede theappearance of granulation tissue.

Groups V and VI

In the later stages of macular degeneration thebasal linear deposit becomes hyalinized andassumes the same staining properties as hyalinizedBruch's membrane. The deposit generally remainsafter the pigment epithelium has disappeared andtraces of the deposit could be found in the depig-mented area of all eyes belonging to Group V.Commenting on the aetiology of these areas of

geographical atrophy, Gass (I973) observed that

most cases followed the fading of drusen butnoted that this appearance could also result fromthe collapse of a serous detachment of the pigmentepithelium. The latter mechanism was also pro-posed by Blair (1975), who thought that ischaemicchanges in the underlying choriocapillaris would beless likely to produce such a well-demarcated areaof atrophy. However, geographical atrophy wasclinically observed to develop gradually within anarea of coarse pigmentary mottling in severaleyes in the present series. The histological studiesalso suggest that these depigmented areas evolvethrough the stages outlined, and in this respect tobe determined by the initial changes in Bruch'smembrane, retinal pigment epithelium, anciczhorio-capillaris.

Neovascularization was demonstrated in io ofthe 24 eyes (41.7 per cent) in Group V. Thefibrovascular invasion was more extensive than inGroup IV but had not obscured the underlyingchoroid on clinical examination, unlike the thickerscars of disciform degeneration. The clinicalpicture is therefore determined by the extent of theneovascular response and different manifestationsmay occur in the two eyes. The more limited fibro-vascular invasion associated with geographicalatrophy may be related to the tendency for sucheyes to show a greater degree of atrophy of alllayers of the choroid, although it is mote likelythat the final result is dependent upon exudationand haemorrhage from the initial capillary mem-branes. Gass (I973) believed that geographicalatrophy did not signify a basic difference fromserous or haemorrhagic detachment of the retinalpigment epithelium and noted that disciformdetachment sometimes occurred in the other eye.In the absence of neovascularization it is probablethat geographical atrophy is the natural end-resultand that this picture only becomes modified by anexcessive degree of scarring.

In disciform degeneration the basal linear depositbecomes incorporated into the fibrovascular scarand the original derivation of the material is notreadily apparent. Thus Green and Gass (I97I)referred to the separation of the basal linear depositfrom Bruch's membrane by fibrovascular tissueas a splitting of Bruch's membrane. The segmentsof hyalinized basal material which become enve-loped by scar tissue and which no longer showany trace of the pigment epithelium are distinctfrom the laminated cuticular deposits foundbetween rows of proliferating retinal pigment cells.The latter material is also eosinophilic and stronglyperiodic acid-Schiff positive, but is of more hyalineappearance and stains blue with picro-Mallory.Cuticular material has been described in seniledisciform degeneration (Verhoeff and Grossman,I937; Frayer, 1955; Klien, 195I), fundus dystrophy

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(Ashton and Sorsby, 1951), melanosis of the retina(Parsons, I904), ringschweile of the ora in long-standing retinal detachment (Hogan and Zimmer-man, i 962) and reactive proliferation of the retinalpigment epithelium (Tso and Albert, I972),where the authors referred to it as basementmembrane-like material. In several eyes in thepresent series the basal linear deposit resembledcuticular material, and the two deposits appearrelated.

DRUSEN

The incidence of eyes containing drusen in themacular region rose from I9-2 per cent in Group Ito 52-5 per cent in Group V, due mainly to anincrease in the granular variety. In the first threegroups the drusen did not appear to affect vision,although none was located at the fovea. In GroupIV, however, degeneration of the pigment epi-thelium was sometimes more pronounced over thelarger deposits.Drusen are a common clinical manifestation of

the predisciform stage, but this investigationfailed to find any histological evidence that drusenpredispose to neovascularization. The drusenwere not immediately related to the breaks inBruch's membrane and any drusen in the vicinityof the new vessels appeared to be only the resultof chance. Instead the vessels ramified within thebasal linear deposit, and the drusen may simply bean independent manifestation of degeneration ofthe pigment epithelium. However, this series didnot provide any information upon the relationshipbetween drusen and pigment epithelial detachments.

In Group V drusen within the depigmentedareas were observed clinically to become lessprominent or to develop glistening foci of calcifi-cation. Gass (1973) noted that drusen in such anarea may fade, and disappearance of some drusenwas noted in the present series. Most, however,remained as calcified deposits, often partly replacedby avascular fibrous tissue.

CHOROID

Thinning of the choroid, interpreted as senilechoroidal atrophy, became more common withadvancing age. Clinically this was manifest asthe senile tigroid fundus, the incidence of whichrises sharply after the age of 75 (Sarks, 1974). Thisappearance has been termed depigmentation-in situ(Klien, I958) and benign choroidal sclerosis(Archer, Krill, and Newell, I971), the increasedvisibility of the choroidal vessels being attributedto disturbance of the overlying pigment epithelium.However, although degenerative changes in thepigment epithelium were commonly associated,

the present investigation confirmed that the promi-nent choroidal pattern resulted when the largervessels occupied a greater proportion of the attenu-ated choroid.

Senile choroidal atrophy was noted in all groupsin this series and modified the clinical pictureaccordingly. This was particularly evident inGroup V, in which the exposed vessels sometimesremained pink and at other times showed sheathingby white lines or appeared as solid white cords.The white lines of sheathing were caused by thedisproportionate thickening of the lateral walls ofthe vessels which were flattened in the thinnedchoroid. The macroscopic dissection of severalspecimens showed that the vessels retained suffi-cient transparency for any contained blood columnto become visible, suggesting that vessels whichappeared as solid white cords no longer containedblood. Although degenerative changes were foundin some choroidal arteries identical to those foundin the ageing brain, most vessels showed onlynormal ageing changes with the retention of widelumina.

Comment

Although senile macular degeneration seems inex-tricably bound to the ageing process the lack ofuniversality suggests it is not essential to ageing.However, the mechanisms proposed to explainnormal ageing can also be applied to the degenera-tive changes. Hogan (I972) believes there is agradual run-down in the metabolic activity ofthe retinal pigment epithelium leading to theaccumulation of metabolic waste in Bruch's mem-brane and consequent decrease in its permeability.The basal linear deposit subsequently developsover the more abnormal segments of the membraneand at this stage histological changes can bedemonstrated in the retinal pigment cells. Clinicalevidence of senile macular degeneration, however,does not develop until the changes become con-tinuous under the macula.

Thickening of the basal linear deposit is asso-ciated with progressive degeneration of the pigmentepithelium. If neovascularization does not develop,or if the fibrovascular response is limited, thenatural end-result of this process is geographicatrophy. Since this is an uncommon manifestationand evolves slowly, useful vision may be retainedfor many years. Visual loss is accelerated when newvessels lead to complications, and treatment istherefore directed to their prevention or oblitera-tion. However, since the histological abnormalitiesmay extend over several disc diameters, thedisciform response can be multifocal and particu-larly endangers the fovea where the changes aregenerally most severe.

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Prophylactic photocoagulation may come intoincreasing use but as Bird (I974) points out, thereare as yet no means of identifying those eyes athigh risk from those at low risk. Drusen have beenimplicated in initiating the disciform response andin this study these were noted more frequently atthe stage when neovascularization occurs, but thedrusen were not related to the new vessels andmay represent an independent expression of themetabolic failure of the pigment epithelium. Thepresent investigation merely indicated that theeyes most prone to neovascularization were thosewith a coarse pigmentary disturbance and moderatevisual loss whether drusen were present or not,and that the new vessels may also develop in theabsence of pigment epithelial detachments.

SummaryClinical and pathological examination was per-formed on 378 eyes from 2I6 patients aged 43 to97 years. This series represented eyes in which thefundi were normal or showed various manifesta-tions of senile macular degeneration. The eyeswere divided into six groups according to thehistological appearance of a linear deposit at thebase of the retinal pigment cells. Groups I and IIwere considered to represent normal ageing,Groups III and IV the progressive development ofsenile macular degeneration, and Groups V andVI the end-results.Group I showed no basal linear deposit. Thicken-

ing and hyalinization of Bruch's membrane wasnoted as early as the fifth decade. Group II showedpatchy development of the basal linear deposit inrelation to thickened or basophilic segments ofBruch's membrane, or over intercapillary hyalini-zation extending to the level of the outer surfaceof the choriocapillaris. Almost all eyes in thesetwo groups retained a normal fundus appearancebut visual acuity declined with age even in theabsence of other causes. In Group III the basaldeposit formed a thin continuous layer associatedwith moderate degeneration of the retinal pigmentepithelium. More than half the eyes had developeda clinical disturbance of pigmentation and in most

vision was reduced. Group IV was characterizedby thickening of the deposit and more pronounceddisturbance of the pigment epithelium. Clinicallymost eyes showed coarse pigmentary changes andvision was in the order of 6/24. I4-3 per cent ofeyes in this group showed early neovascularizationfrom the choroid. In Group V the pigment epi-thelium disappeared to produce circumscribedareas of depigmentation. The basal linear depositcould be traced throughout the depigmented areain most eyes. Thin fibrovascular sheets were foundbeneath the pigment epithelium in 41.7 per cent ofeyes. Group VI represented disciform degeneration.The basal linear deposit could often be demon-strated as a disrupted hyalinized layer incorporatedinto the scar. Disciform degeneration was analternative end-result to geographical atrophy. Ineach group the clinical and histological findingsmay be modified by the presence of drusen or byatrophy of the choroid.The basal linear deposit consisted of banded

fibres embedded in granular material lying betweenthe plasma infoldings and the basement membraneof the retinal pigment epithelium. This depositseems to be a manifestation of gradual failure ofthe pigment epithelium and proved to be the mostsuitable criterion by which to study the naturalhistory of senile macular degeneration.

I am indebted to Associate Professor A. Tait Smith,Department of Pathology, Prince Henry Hospital,Sydney, for his advice and for the provision of thepathology facilities. I also wish to thank Mr L. Vorbach,Mrs E. King, and Mrs D. Lord for their technicalassistance, the Department of Medical Illustration,Prince of Wales Hospital, Sydney, for the photomicro-graphs, Associate Professor E. Finckh, Institute ofClinical Pathology, Lidcombe Hospital, Sydney, forthe facilities of the EM Department, and Dr K. Taylorand Mr R. Boadle for the electron micrographs.This work was supported in part by the Unit of

Clinical Investigation, Lidcombe Hospital, Sydney, theLaura Bushell Trust, and Grants from the NationalHealth and Medical Research Council and the Ophthal-mic Research Institute of Australia. Permission topublish figures i8, 19, 20, and 2I was given by theAustralian Journal of Ophthalmology.

ReferencesARCHER, D., KRILL, A. E., and NEWELL, F. W. (1971) Amner. J. Ophthal., 71, 226ASHTON, N. (I974) Brit. J. Ophthal., 58, 344

, and SORSBY, A. (I95I) Ibid., 35, 751BIRD, A. C. (I974) Ibid., 58, 367BLAIR, C. J. (I975) Arch. Ophthal. (Chic.), 93, 19DONDERS, F. C. (I864) New Sydenham Soc., LondonDUKE-ELDER, S. (I966) 'System of Ophthalmology', vol. 9, p. 6io. Kimpton, LondonFRAYER, W. C. (I955) Arch. Ophthal. (Chic.), 53, 82FRIEDMANN, I., CAWTHORNE, T., and BIRD, E. S. (I965) Nature (Lond.), 207, 171GARNER, A. (975) Trans. ophthal. Soc. U.K., 95, 54

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GARRON, L. K., FEENEY, M. L., HOGAN, M. J., and MCEWEN, W. K. (I958) Amer. J. Ophthal., 46, 27GASS, J. D. M. (I967) Ibid., 63, 573

(I973) Arch. Ophthal. (Chic.), 9o, zo6GREEN, W. R., and GASS, J. D. M. (I97I) Ibid., 86, 487GROSS, J. (I957) 'Connective Tissue', p. 45. Blackwell, OxfordHAAB, O. (I885) Zbl. prakt. Augenheilk., 9, 383HAMMOND, E. C., and SPALTER, H. F. (I973) Amer. J. Ophthal., 76, 389HOGAN, M. J. (I967) Trans. ophthal. Soc. U.K., 87, II3

(1972) Trans. Amer. Acad. Ophthal. Otolaryng., 76, 64ALVARADO, j., and WEDDELL, J. E. (1971) 'Histology of the Human Eye; An Atlas and Textbook', p. 344.

Saunders, Philadelphia, WOOD, I., and FINE, M. (I974) Amer. J. Ophthal., 78, 363, and ZIMMERMAN, L. E. (I962) 'Ophthalmic Pathology', 2nd ed., p. 437. Saunders, Philadelphia

JAKUS, M. (I962) Invest. Ophthal., I, 202KLIEN, B. A. (95i) Amer. 7. Ophthal., 34, 1279

- (1958) Arch. Ophthal. (Chic.), 6o, I75LENDRUM, A. C., FRASER, D. S., SLIDDERS, w., and HENDERSON, R. (I962) . clin. Path., 15, 40I

, SLIDDERS, w., and FRASER, D. S. (1972) Ibid., 25, 373MAUMENEE, A. E. (I965) Trans. Amer. Acad. Ophthal. Otolaryng., 69, 69iPARSONS, J. H. (1904) ioth Int. Cong. Ophthal., Lucerne, BI5ZSARKS, S. H. (1974) Aust. J. Ophthal., 2, 57TAIT SMITH, A. (1976) J. Stain Tech., in pressTEETERS, V. W., and BIRD, A. C. (I973a) Amer. Y. Ophthal., 75, 53- and (1973b) Ibid., 76, iTRIPATHI, R. C. (I974) Trans. ophthal. Soc. U.K., 94, 663TS3, M. 0. M., and ALBERT, D. M. (I972) Arch. Ophthal. (Chic.), 88, 27VERHOEFF, F. H., and GROSSMAN, H. P. (1937) Ibid., i8, 56iWEALE, R. A. (1975) Trans. ophthal. Soc. U.K., 95, 36

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