Sorsby's Fundus Dystrophy W. KEITH HAMILTON, MD,t CECIL C. EWING, MD,t ELIZABETH J. IVES, MD,t JEAN D. CARRUTHERS, MD2

Abstract: Ever since Sorsby described his pseudoinflammatory dystrophy in five families, its characteristics have been unclear. The findings in ten affected members of a seven-generation pedigree are discussed and the literature is reviewed. Patients with this dominantly inherited fundus dystrophy lose central vision between the second and fourth decade of life. Three variations in the fundus appearances were distinguished: in the first and most common, white to yellow fundus spots (which are not drusen) accompany a disciform macular degeneration; in the second, the fundus spots are absent; in the third, the yellow deposits are associated with atrophic macular degeneration. Atrophy of the retina, pigment epithelium, and choroid then slowly progresses toward the pe­riphery. Treatment does not halt the progress of the disease. Although variations in this dystrophy may be examples of genetic heterogeneity, Sorsby's fundus dystrophy is a distinct clinical disorder. Ophthalmology 96: 1755-1762, 1989

In 1949, Sorsbyl described five families with a fundus dystrophy characterized by dominant inheritance with complete penetrance, loss of central vision from macular degeneration, and progressive peripheral atrophy of the retina and choroid with clumping of the pigment epithe­lium. Fraser and Wallace,2 Hoskin et at,3 and Capon et a14 extended Sorsby's observations in the descendants of these families. Burn,5 Rosen and Leighton,6 Balyeat and Kingsley,? and Dreyer and Hidayat8 described other fam­ilies who may have had Sorsby's dystrophy. Carr et a19

described a family whose disease may have been confused with Sorsby's dystrophy. Because there are few reports of affected families, controversy exists as to whether this is a distinct dystrophy. 10,1 I We describe a family with Sors­by's fundus dystrophy, and after reviewing published re­ports, we discuss the nature of the dystrophy.

Originally received: April 26. 1989. Revision accepted: July 18, 1989.

1 Department of Ophthalmology, University Hospital, University of Sas-katchewan, Saskatoon.

2 Department of Ophthalmology, University of British Columbia. Vancouver.

Presented at the Canadian Ophthalmological Society Annual Meeting, Calgary, Alberta, June 1989.

Supported in part by The Genetic Eye Disorder Research Fund, University of Saskatchewan, and the Brebner family.

Reprint requests to W. Keith Hamilton, MD. Department of Ophthalmology. McGill University, Royal Victoria Hospital, 687 Pine Ave West, Rm H7.53, Montreal, Quebec, Canada.

MATERIALS AND METHODS

We examined 10 of 21 affected members of a seven­generation pedigree (Fig 1). We also examined eight other members who were at ages when they could be expected to be affected and eight children of affected members who were too young to be affected. The examinations per­formed on affected patients are listed in Table 1.

The Farnsworth-Munsell 100-hue (FM 100-hue) test and the Farnsworth 015 (015) test were performed sepa­rately in each eye within a color matching cabinet whose light levels and color temperature conformed to the British standard for assessment of color. 12 The American Optical Company (AOHRR) plates and the Lanthony new color test (NCT) (Luneau, Paris) were administered using stan­dard illuminant C provided by a Macbeth easel lamp. Dark adaptations to determine the absolute threshold us­ing a black-and-white striped, 100% contrast test field of 11 0 at 30 cm were performed using the Goldmann-Week­ers Dark Adaptometerl3 (Haag-Streit AG Ophthalmolog­ical Instruments, Berne, Switzerland) with standardized normal values. 14 Photopic and scotopic electroretinograms were performed with stimulus rates of 0.2 and 1.0 Hz, respectively, with standardized intensity in a Ganzfeld bowl. Acquisition parameters had sensitivities of ±500 and ±250 J.L V, respectively, with filters at 1 Hz (low) and 3000 Hz (high) using gold-foil electrodes.

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00 Normal or unknown I] () Affected by history

Fig I. Pedigree of a seven­generation family found to have Sorsby's fundus dystro­phy. *One female sibling known reported not affected, there may have been other siblings.

•• Affected by ophthalmological exam :i( No known affected descendants ? No offspring o Total normal sibs or offspring ...... Examined by authors ~ Proband

RESULTS

An overview of findings in affected patients is presented in Table 2. Eight older unaffected patients and eight chil­dren of affected patients had normal results on all tests. Although we examined one patient only once, our reviews of the other nine extend for 2 to 27 years, before and after symptoms developed.

The transmission of this family's disorder is autosomal dominant with complete penetrance. We do not know the chromosome and location of the gene, but we have collected DNA from family members so that this can be determined. We have traced this family'S origins to Boyle, county Roscommon, Eire, but we have not found any link with Sorsby's families.

Some patients (6/10) complained of reduced night vi­sion, especially when driving, for 2 to 9 years before they developed metamorphopsia or any impairment of visual acuity. One patient (pedigree VI 12 ) complained of poor color vision 20 years before acuity loss.

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FUNDUS APPEARANCES AT PRESENT A nON

Four patients presented 2 to 17 years before the disci­form maculopathy developed. Three patients presented with macular subretinal neovascularization in one eye only and three with disciform macular scarring in both eyes. Macular disciform scarring eventually developed in all eyes. Five of six patients had faint granularity of the pigment epithelium and small pale yellow spots at the posterior pole 1 to 10 years before losing central vision (Figs 2, 3). The spots later became more obvious and were not related to the site of future neovascular membranes (Fig 4).

VISUAL ACUITY

The ten patients we examined lost visual acuity to a level of 20/200 or less between 26 and 43 years of age (average, 34 years). In 8 of the 12 family members affected but not examined, the age when central acuity was lost in both eyes was determined by history to range from 32 to 45 years (average, 38 years). The presence of the yellow

HAMILTON et al • SORSBY'S FUNDUS DYSTROPHY

spots did not influence visual acuity. Macular scarring reduced visual acuity to less than 20/200 in all affected patients but one (pedigree V s). Although affected for 34 years, he maintained a visual acuity of 20/40 in one eye despite disciform scarring and peripheral degeneration that were similar to his other eye with which he could only count fingers. Other elderly family members had vi­sual acuities ranging from finger counting to hand move­ments in the temporal fields 26 to 40 years after losing central vision. At least three elderly patients known to us by history had only hand movements or light perception vision and were unable to navigate independently.

FLUORESCEIN ANGIOGRAPHY

Unlike drusen, none of the pale yellow spots hyperflu­oresced on fluorescein angiography and some were hy­pofluorescent (Fig 5). Before visual loss, angiograms gen­erally showed a mottled granular appearance, which was probably due to either variable blockage of fluorescence by the yellow fundus spots or to abnormal perfusion of the choriocapillaris. Two patients (pedigrees VIs, VI to), before subretinal neovascularization developed, had patchy delayed filling of the choriocapillaris at the pos­terior pole and a mosaic of choroidal hypofluorescence extending temporally from the macula (Fig 6). Despite normal visual acuity at the time, these two patients com-

Table 1. Examinations

Examination

Visual acuity Farnsworth-Munsell 100-hue Lanthony new color test Farnsworth 015 Electroretinogram Electro-oculogram Dark adaptation Fields

Friedmann Goldmann Octopus 2000 G-1

Fluorescein angiography

Results

10/10 6/10 4/10 2/10 4/10 2/10 5/10

6/10 6/10 2/10 8/10

plained of impaired night vision, had central field depres­sion on static perimetry, and had abnormal color vision on the FM 100-hue test.

VISUAL FIELD STUDIES

Static perimetry (Octopus and Friedmann) was more sensitive than kinetic (Goldmann) in demonstrating im­paired function. We found relative central and paracentral depression despite a visual acuity of 20/25 or better in eight of nine eyes (pedigrees V2 , VI4 , VIs, VI6 , VItO) tested

Table 2. Patient Findings

Age at Visual Acuity Loss* (age at time

Pedigree of study) Fundus Disciform Peripheral No. (yrs) Nyctalopia Spots Maculopathy Progression ERG EOG Colort DA::j: Treatment

V2 43 (64) +§ + + + +A AOHRR None V3 40 (78) + + + + None V4 37 (77) + 7 + + +Unable +>3.0 None V5 40 (74) + 7 + + + + +FM 100 A None

+D15 A VI4 30 (44) + + + + (N)II +NCTT +.5 None

+.8 VI5 36 (42) + + + + (N) +FM 100 T +.6/7+*' Laser

+ NCTT +.6/7+ VI6 27 (38) + + +FM 100 T +1.0 None

+NCT T +1.3 VI10 26 (35) + + + +FM 100 T (N) Laser

+NCT T 7+ VI12 35 (39) + + + (N) (N) +FM 100 D Laser

+D15 D VI18 32 (36) + + + +FM 100 T/TO Laser steroid

ERG = electroretinogram; EOG = electro-oculogram. * Age of visual acuity loss is the age when maculopathy caused central acuity loss in first affected eye. t Color vision tests-FM 100 = Farnsworth-Munsell 100-hue; NCT = Lanthony new color test; D15 = Farnsworth D15; AOHRR

= American Optical Company plates (Hardy, Rand, and Rittler); T = tritanomaly; D = deuteranomaly; A = achromatic. ::j: DA = dark adaptation. Numbers listed refer to log units above three standard deviations from mean. § + = patient has attribute in question, or positive abnormal result on test. II (N) = within normal limits. ** 7+ = borderline.

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Fig 2. Top leji, pedigree VIs. In right eye, pale spots (ar­row) are shown 4 years before acuity loss. Fig 3. Top right, pedigree VI I8 . In left eye,

asymmetric superior distribution of most spots is shown (arrows). Visual acuity is 20/20. A neovascular net has been treated with laser. (Photograph courtesy of Dr. L. Yannuzzi, New York.) Fig 4. Second row leji, pedigree VIs . Same eye is shown as in Figure 2, 3 months before neovascular net extends beyond small subretinal hemorrhage (arrow). Visual acuity is 20/20. Compared with Figure 2, there are more spots. Fig 5. Second row right, pedigree VIs. Fluorescein angiogram taken on the same day as Figure 2. Mottled hypo fluorescence is shown. (Arrow indicates same spot as arrow in Fig 2.) Fig 6. Third row leji, pedigree VIs . Hypofluorescence of choriocapillaris extending temporally from macula is shown (same day as Fig 4). Fig 7. BOllom right, pedigree V. (proband). Composite of the left eye to years after visual loss. Fig 8. Bottom leji, pedigree V 4. Composite of the same eye as in Figure 7 26 years after visual acuity loss shows peripheral extension of the dystrophy.

6 months to 2 years before the maculopathy destroyed central visual acuity. After this, slowly enlarging absolute central scotomas were the rule, although one patient (pedigree V5 ) had a tiny central island amidst the scotoma.

identify the transition from photopic to scotopic adap­tation in seven eyes (4 patients) with macular disciform scarring. In one elderly patient who saw hand movements only, adaptation at 30 minutes was more than 3 log units above normal. In four younger patients, the longer the time elapsed since their visual loss, the worse their ad­aptation: one eye was normal 2 years after losing vision, three eyes were borderline abnormal 6 months to 3 years after visual loss (one of these patients examined on the Friedman Analyzer [Keeler, London] 10 years earlier had

DARK ADAPT AnON

Six of ten affected patients complained of poor night vision 6 months to 10 years before visual loss. Using the Goldmann-Weekers Dark Adaptometer, we could not

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HAMILTON et al • SORSBY'S FUNDUS DYSTROPHY

Fig 9. Pedigree VIs. Typical tritanomolous Farnsworth­MunselllOO-hue plot 3 years :;; --t--;-t-i--:--+--i---;.-i--+-7-'~ before visual acuity loss. Vi­sual acuity is 20/15.

thresholds 0.6 log units above the normal range), and four eyes were 0.5, 0.8, 1.0, and 1.3 log units above normal 10 to 13 years after visual loss.

COLOR VISION

Three patients showed abnormal results on the FM 100-hue test 6 months to 3 years before developing sub­retinal neovascularization. One patient (V 2) was unable to discriminate any of the plates on the AOHRR test de­spite a visual acuity of 20/30 in each eye 2 years before the maculopathy destroyed his central vision. All patients with macular scarring, including two with a visual acuity of 20/25 or better whose extrafoveal subretinal neovas­cular nets had been treated, had abnormal results on FM 100-hue, Lanthony NCT, or 015 tests. The axis on the FM 100-hue was generally in the tritanomalous range (Fig 9), with a slight axis shift later to a deutan or an achromatic axis as vision worsened. Four patients examined with the NCT (macular disease of 6 months to 13 years), two of whom could not perform the FM 100-hue, showed a neu­tral zone in the tritan purple and blue areas. One patient with laser-treated macular disease but a visual acuity of

495 490

20/20 showed a deuteranomalous defect on the 015 and the FM 100-hue tests (pedigree VI12 ).

ELECfROPHYSIOLOGY

Electroretinography (ERG) results on one patient 4 years before visual loss and on two patients within 2 years after visual loss were normal. One of the latter patients had a normal simultaneous electro-oculogram (EOG). Electroretinography amplitudes were diminished and EOG results were abnormal (light rise, 1.5 in both eyes) in one patient 34 years after he lost his central vision.

EVOLUTION OF THE DISEASE

Within 6 months to 6 years (average, 2 years), macular disciform degeneration developed in the fellow eye. Around the disciform scar, pale yellow spots, choriocap­illaris atrophy, and juxtaposed atrophy and hyperplasia of the pigment epithelium progressed to the equator and beyond (Figs 7, 8).

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Table 3. Summary of Published Articles

No. in Pedigree/ Age at Pale Progressive Affected Onset Fundus Disciform Peripheral

Reference (seen)* (yrs) Nyctalopia Spots Maculopathy Atrophy ERG/EOG Colort DA

Sorsbyl

(Randall) 16/15 ±40 + + (Carver) 45/25 ±40 + + (Ewbank) 17/10 ±40 + + + (Kempster) 18/11 ±40 + + +

Fraser and Wallace2 84/11 (2) ±40 + + ?MILD D (Randall)

Hoskin et al3 41/13 (7) 37-45 + + + (N) (N) (Ewbank)

Capon et al4 >60/29 (10) 38-50 + + + + (N) ERG +T + (Kempster) +EOG

Burns 40/11 (7) 45-55 + + + Rosen and Leighton6 13/5 (3) ±40 + + + Balyeat and Kingsley? 16/7 (5) 26-35 + + + ? +ERG ? +

+EOG Dreyer and Hidayat8 33/13 (2) 37-60 ? + +ERG

+EOG Carr et al9 11/8 (4) 29-35 + (N) +A Current study >60/21 (10) 26-40 + + + + (N) EARLY +T +

+ LATE

ERG = electroretinogram; EOG = electro-oculogram; N = within normal limits; DA = dark adaptation . • No. in pedigree/no. affected by history (no. examined). t T = tritanomaly; D = deuteranomaly; A = achromatic.

TREATMENT

Seven eyes in four patients with parafoveal subretinal neovascularization were treated with krypton or argon laser photocoagulation (Fig 3); however, within 2 years, the neovascularization had spread under the fovea despite treatment of recurrences. Three eyes in two patients could not be treated because the neovascularization was sub­foveal.

DISCUSSION

In 1949, Sorsby described five families (the Cranston sisters, the Randalls, the Carvers, the Ewbanks, and the Kempsters) in whom a maculopathy developed at ap­proximately 40 years of age that was usually associated with edema, hemorrhage, and exudation and that pro­gressed to atrophy of the central retina with hypertrophy of the pigment epithelium and choroidal sclerosis. The process gradually involved the whole fundus and was dominantly inherited. Ashton and SorsbylS later reported the histologic findings in the Cranston sisters; however, dominant inheritance was not proven and they are prob­ably not examples of Sorsby's dystrophy. An overview of the literature is presented in Table 3.

The Randall family showed the basic features noted above. Fraser and Wallace2 described two descendants of the Randalls identified by Kalmus and Seedburghl6 and

1760

found mild deuteranomaly in unaffected family members that was probably inherited independently. Neither study of the Randalls reported yellow fundus spots or poor night vision.

The Carver family showed atrophy at the posterior pole that progressed peripherally but no subretinal neovascu­larization was shown. One patient at 47 years of age was only affected in one eye and two others were only slightly affected. Sorsby described whitish spots in a few patients but did not report poor night vision. Bird (personal com­munication) extended the study of this family and con­firmed the atrophic nature of the dystrophy and the pres­ence of pale fundus spots.

The Ewbank family showed the basic features of the dystrophy, but none of the patients Sorsby examined was old enough to exhibit "the terminal stage of total retinal and choroidal atrophy."l He described mottling of the pigment epithelium and scattered pale spots. One patient complained of night blindness. Hoskin et al3 reported 13 new members. Five were unable to navigate independently late in life, and in two, fluorescein angiography showed that the fine yellow spots hypo fluoresced early and hy­perfluoresced later. One affected patient had drusen and angioid streaks that we feel were coincidental. Two as yet unaffected family members had yellow spots in the fundus. In all Hoskin's patients, results of the EOG, ERG, and D15 tests were normal. Hoskin et al conjectured that ab­normal perfusion of the choriocapillaris might explain the mottled hypofluorescence on angiography but that

HAMILTON et al • SORSBY'S FUNDUS DYSTROPHY

these changes might be secondary to "the accumulation of debris [which] appears to be the initial clinical abnor­mality.,,3

The Kempster family also showed the same basic fea­tures. One patient complained of night blindness and four had unspecified color vision defects. Whitish spots were seen in two patients. Capon et al,4 who extended the study of the family, noted deposits of sub retinal yellow material throughout the fundi, evidence of peripheral retinal dys­function on electrophysiologic studies, and a tritan color defect in two of three eyes with normal vision. Two lost central vision from atrophic disease. Mottled choroidal hypofluorescence on angiography corresponded to the sites of yellow subretinal material, but large choroidal vessels remained visible, suggesting uneven choriocapil­laris perfusion as opposed to obscuration of the choroidal fluorescence by accumulating subretinal material. Diffi­culty with night vision up to 25 years before onset of visual loss was reported in eight of ten patients.

BurnS described seven patients with a dystrophy re­sembling that of the Ewbank's and Kempster's. None complained of night blindness. Rosen and Leighton6 re­ported on a family with disciform maculopathy, pale fun­dus spots, and progressive peripheral atrophy, but it is not clear how closely his findings resembled those seen in Sorsby's and our families.

Balyeat and Kingsley? reported a family in which poor night vision began in childhood in four affected patients. Amplitudes on ERG testing were diminished, EOG ratios were abnormal or borderline, and dark adaptations were abnormal. Color vision tests showed one patient to be normal, one deuteranomolous, and one tritanomolous. The pale yellow spots at the posterior pole reportedly cor­responded to mottled hyperfluorescence on fluorescein angiography, which is more typical of drusen and different from our findings.

Dreyer and Hidayat8 described a "pseudo-inflammatory macular dystrophy" showing a dominant atrophic mac­ular degeneration with variable penetrance in two patients, one of whom had near normal acuity despite degenerative changes extending beyond the vascular arcades. Drusen were reported in two patients who were not examined by the authors themselves. An intact but thickened Bruch's membrane and marked atrophy of the photoreceptors, the choriocapillaris, and the pigment epithelium were seen at the macula and the midperiphery on histologic ex­amination of one patient. Results of ERG were abnormal in all three eyes, and EOG results were abnormal in two of three eyes. This family may be similar to the Carvers, but further study of family members is needed.

Carr et al9 described a family with a "hereditary hem­orrhagic macular dystrophy" but no reported yellow fun­dus spots. Because peripheral progression also was not described, we doubt that this family had Sorsby's fundus dystrophy.

Our family resembles the Ewbanks and, especially, the Kempster families of Sorsby. Before losing vision, one half of our patients complained of trouble with night vi­sion and all but one had yellow fundus spots with mottled

hypofluorescence on angiography. Laser photocoagulation only delayed the onset of visual loss. Clumping and atro­phy of the pigment epithelium with choriocapillaris ab­normalities continue to extend peripherally in our pa­tients. Before losing vision, some patients had abnormal central static perimetry and a tritanomolous color defect. Dark adaptation deteriorated with disease duration. Our few ERG and EOG results suggest relatively normal func­tion of the retina and pigment epithelium until extensive peripheral degeneration has occurred.

The pathophysiology of this dystrophy is unclear. We can distinguish the pale spots from drusen by angiography. Histologic examination of an elderly member of the Kempster family (personal communication, Bird) showed an accumulation of material between the retinal pigment epithelium and Bruch's membrane with underlying atro­phy of the choriocapillaris. Do the yellow spots indicate a pigment epithelial defect causing accumulation of the material that produces choroidal atrophy? Does the early hypofluorescence of the choriocapillaris extending tem­porally from the macula on angiography suggest a primary defect in the choriocapillaris or does it reflect the blockage of choroidal fluorescence by the accumulating yellow ma­terial?

CONCLUSION

This condition has been called "Sorsby's pseudoin­flammatory macular dystrophy"l?; however, "pseudoin­flammatory" is not a helpful adjective and "macular" ig­nores the peripheral progression of the disease. Sorsby's fundus dystrophy is a better name.

There are three major variations of this dominant dys­trophy. The largest group shows macular subretinal neo­vascularization, yellow or white fundus spots, and mottled hypofluorescence on angiography; it includes our family, the Ewbanks, the Kempsters, and perhaps those of Burns. In some, sensitivity on static perimetry and color vision is affected before acuity is lost. Poor night vision is a com­mon complaint, and dark adaptation is abnormal in many affected patients. The Randalls have scarring but no yellow spots. The Carvers have yellow fundus spots but only pro­gressive atrophy without disciform scarring. Neither of these two latter groups has trouble with night vision. These clinical variations are probably the result of genetic het­erogeneity, but the possibility of pleiotropy cannot be ex­cluded.

Part of the tragedy for our patients is that they usually do not know if they are affected until they already have had children. Linkage studies may eventually allow us to say whether more than one gene locus is involved in the transmission of the dystrophy and to provide our patients with better genetic counselling, including prenatal diag­nosis. Until such genetic studies are concluded, apparently unaffected offspring of affected individuals should be ex­amined to see if yellow fundus spots develop and followed with static perimetry, and color vision and dark adaptation tests.

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3. Hoskin A, Sehmi K, Bird AC. Sorsby's pseudoinfiammatory macular dystrophy. Br J Ophthalmol 1981; 65:859-65.

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9 . Carr RE, Noble KG, Nasaduke I. Hereditary hemorrhagic macular dys­trophy. Am J Ophthalmol1978; 85:318-28.

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15. Ashton N, Sorsby A. Fundus dystrophy with unusual features : a his­tological study. Br J Ophthalmol 1951; 35:751-64.

16. Kalmus H, Seedburgh D. Probable common origin of a hereditary fundus dystrophy (Sorsby's familial pseudoinflammatory macular dystrophy) in an English and Australian family. J Med Genet 1976; 13:271-6.

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