Ординатура / Офтальмология / Английские материалы / Scanning Laser Imaging of the Retina Basic Concepts and Clinical Applications_Theelen_2011

Fundus autofluorescence in retinaldystrophies 141

were characterized by a generally decreased FAF. This gradual loss of FAF in later disease stages indicates that this subretinal material of increased FAF gradually disappears when RPE cell death progresses and atrophy and/or scars develop.

FUNDUS AUTOFLUORESCENCE IN CENTRAL AREOLAR CHOROIDAL DYSTROPHY

Most cases of autosomal dominant CACD appear to be associated with mutations in the peripherin/RDS gene, but genetic heterogeneity has been described.45-47 In our study, patients with autosomal dominant CACD showed increased FAF in the macular area early in the course of the disease, suggesting lipofuscin accumulation in the macular RPE. In late stage II CACD, zones of decreased FAF may become more prominent, suggesting gradual loss of RPE cells. Thus, our FAF findings indicate a progressive lipofuscin accumulation and consecutive RPE

damage during the first two stages. With time, lesions may extend beyond the retinal vascular arcades and optic nerve head.45,48 FAF in stage III CACD shows sharply demarcated areas of

severely decreased to absent FAF. These atrophic areas develop within the areas of granular FAF changes. Therefore, the initial diffusely affected RPE may finally result in regions of total loss of RPE, which enlarge and finally involve the foveal RPE in end-stage CACD. In this stage, a well-defined, round to oval area of absent FAF is seen, bordered by a small area of increased FAF. Interestingly, FAF abnormalities may precede ophthalmoscopically visible changes in CACD.45 This makes FAF imaging especially suitable for non-invasive screening of families with CACD.

FUNDUS AUTOFLUORESCENCE IN PATTERN DYSTROPHIES

The phenotypically and genetically heterogeneous group of pattern dystrophies is characterized by a variety of deposits of yellow, orange or gray pigment, predominantly in the macular area.49-52 The classification of Gass discriminates between five main categories of pattern dystrophies: adult-onset foveomacular vitelliform dystrophy (AFVD), butterfly-shaped pigment dystrophy, reticular dystrophy of the pigment epithelium, multifocal pattern dystrophy simulating fundus flavimaculatus (MPD), and fundus pulverulentus.35

In the group of AFVD patients in the present study, all lesions were smaller than one disc diameter in size and generally showed increased FAF. These results correspond with previous FAF findings in AFVD patients and with the histopathologic finding of increased lipofuscin in AFVD lesions.53-55 One patient showed small multifocal lesions of increased FAF, while another patient had lesions with a scrambled-egg and pseudohypopyon aspect, features that are also seen in BVMD.

In patients with MPD, which is often caused by peripherin/RDS mutations, the posterior pole may be scattered with irregular flecks mimicking STGD1 on FAF, as well as on ophthalmoscopy and optical coherence tomography.23 Like in STGD1, the flecks in MPD may extend beyond the macular area. In later stages, these flecks may show confluence to a ring-shaped area of abnormal FAF, surrounding the macula and optic disc. Central macular lesions show a broad range of FAF changes, often with predominantly increased FAF, especially in earlier stages. In time, macular lesions may also show markedly decreased FAF due to profound chorioretinal atrophy. Therefore, it may be difficult to discriminate between STGD1 and MPD on the basis of the FAF aspect. Distinguishing features between MPD and STGD1 are the autosomal dominant pattern of inheritance, the relatively late age at onset, the comparatively good

142Chapter 5.3

and stable visual acuity and the absence of a “dark choroid” on fluorescein angiography.23 Molecular genetic analysis may aid in the differential diagnosis between these different entities.

In butterfly-shaped pigment dystrophy, patients display macular lesions with a spoke-like

pigment pattern surrounded by a zone of depigmentation, thus somewhat resembling the shape of a butterfly.56 The phenotype of butterfly-shaped pigment dystrophy is genetically heterogeneous.57,58 In a case caused by a peripherin/RDS missense mutation (Cys213Tyr),

increased amounts of lipofuscin have been found in the RPE on histopathologic examination.22 This corresponds with the finding in our study of increased FAF of the pigmented part of the lesion in the patient with butterfly-shaped pigment dystrophy.

Pattern dystrophy phenotypes may also be associated with syndromes, such as myotonic dystrophy, pigment dispersion syndrome, and mitochondrial syndromes like maternally inherited

diabetes and deafness (MIDD) and mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome.59-63 MIDD and MELAS are associated with mutations in the mitochondrial DNA, the 3243A>G point mutation being the most frequently identified mutation.64 As much as 86% of patients with maternally inherited diabetes and deafness (MIDD) may show some form of pattern dystrophy. In our study, RPE changes in MIDD patients were easily defined on FAF as speckled areas of increased and decreased FAF in the

macula and surrounding the optic disc. The intriguing feature of foveal sparing can be observed on FAF in a MIDD patient with advanced pattern dystrophy,65 which is illustrated in Fig. 5.18G.

CONCLUSIONS

FAF imaging is a useful tool for the identification and follow-up of lesions associated with lipofuscin accumulation or RPE cell loss. As such, FAF imaging may yield important additional information in a diagnostic setting in relatively frequent retinal dystrophies such as STGD1, BVMD and in retinal dystrophies associated with peripherin/RDS mutations. FAF may visualize more lesions compared to ophthalmoscopy. Moreover, FAF imaging provides

qualitative information, as it reflects the lipofuscin content in lesions, and FAF changes appear to relate to functional abnormalities in at least some retinal dystrophies.1,29,66 However,

non-lipofuscin accumulating parts of a lesion may be missed with FAF. Therefore, FAF alone may not be useful for lesion size measurement. Retinal dystrophies may present with a considerable clinical variability. Late stages with RPE cell loss may look similar in various retinal dystrophies and in other retinal disorders such as age-related macular degeneration. In this respect, FAF may be of limited use in the differential diagnosis between different forms of retinal dystrophy. Molecular genetic testing may be very helpful in these cases. Compared to fluorescein angiography, FAF imaging, as a non-invasive imaging modality, is a straightforward and relatively patient-friendly means to get an overview of the accumulation of fluorophores like lipofuscin and atrophic changes within the RPE-photoreceptor complex.2,6 Therefore, FAF imaging may constitute a convenient tool for cross-sectional and family studies, as well as in the follow-up of various retinal dystrophies. In addition, FAF imaging may also play a role as a parameter for the evaluation of therapeutic effects in future clinical treatment trials.

Fundus autofluorescence in retinaldystrophies 143

REFERENCES

1.Robson AG, Saihan Z, Jenkins SA, Fitzke FW, Bird AC, Webster AR, Holder GE. Functional characterisation and serial imaging of abnormal fundus autofluorescence in patients with retinitis pigmentosa and normal visual acuity. Br J Ophthalmol 2006;90:472-479.

2.von Rückmann A, Fitzke FW, Bird AC. In vivo fundus autofluorescence in macular dystrophies. Arch Ophthalmol 1997;115:609-615.

3.von Rückmann A, Fitzke FW, Bird AC. Distribution of pigment epithelium autofluorescence in retinal disease state recorded in vivo and its change over time. Graefe’s Arch Clin Exp Ophthalmol 1999;237:1- 9.

4.Wabbels B, Preising MN, Kretschmann U, Demmler A, Lorenz B. Genotype-phenotype correlation and longitudinal course in ten families with Best vitelliform macular dystrophy. Graefe’s Arch Clin Exp Ophthalmol 2006;244:1453-1466.

5.Wabbels B, Demmler A, Paunescu K, Wegscheider E, Preising MN, Lorenz B. Fundus autofluorescence in children and teenagers with hereditary retinal diseases. Graefe’s Arch Clin Exp Ophthalmol 2006;244:36-45.

6.Delori FC, Dorey CK, Staurenghi G, Arend O, Goger DG, Weiter JJ. In vivo fluorescence of the ocular fundus exhibits retinal pigment epithelium lipofuscin characteristics. Invest Ophthalmol Vis Sci 1995;36:718-729.

7.Bui TV, Han Y, Radu RA, Travis GH, Mata NL. Characterization of native retinal fluorophores involved in biosynthesis of A2E and lipofuscin-associated retinopathies. J Biol Chem 2006;281:18112-18119.

8.Eldred GE, Katz ML. Fluorophores of the human retinal pigment epithelium: separation and spectral characterization. Exp Eye Res 1988;47:71-86.

9.Sparrow JR, Boulton M. RPE lipofuscin and its role in retinal pathobiology. Exp Eye Res 2005;80:595606.

10.Lakkaraju A, Finnemann SC, Rodriguez-Boulan E. The lipofuscin fluorophore A2E perturbs cholesterol metabolism in retinal pigment epithelial cells. Proc Natl Acad Sci U S A 2007;104:11026-11031.

11.Sparrow JR, Nakanishi K, Parish CA. The lipofuscin fluorophore A2E mediates blue light-induced damage to retinal pigmented epithelial cells. Invest Ophthalmol Vis Sci 2000;41:1981-1989.

12.Sparrow JR, Cai B. Blue light-induced apoptosis of A2E-containing RPE: involvement of caspase-3 and protection by Bcl-2. Invest Ophthalmol Vis Sci 2001;42:1356-1362.

13.Sparrow JR, Fishkin N, Zhou J, Cai B, Jang YP, Krane S, Itagaki Y, Nakanishi K. A2E, a byproduct of the visual cycle. Vision Res 2003;43:2983-2990.

14.Sparrow JR, Cai B, Fishkin N, Jang YP, Krane S, Vollmer HR, Zhou J, Nakanishi K. A2E, a fluorophore of RPE lipofuscin: can it cause RPE degeneration? Adv Exp Med Biol 2003;533:205-211.

15.Sparrow JR, Vollmer-Snarr HR, Zhou J, Jang YP, Jockusch S, Itagaki Y, Nakanishi K. A2E-epoxides damage DNA in retinal pigment epithelial cells. Vitamin E and other antioxidants inhibit A2E-epoxide formation. J Biol Chem 2003;278:18207-18213.

16.Sparrow JR, Cai B, Jang YP, Zhou J, Nakanishi K. A2E, a fluorophore of RPE lipofuscin, can destabilize membrane. Adv Exp Med Biol 2006;572:63-68.

17.Weiter JJ, Delori FC, Wing GL, Fitch KA. Retinal pigment epithelial lipofuscin and melanin and choroidal melanin in human eyes. Invest Ophthalmol Vis Sci 1986;27:145-152.

144Chapter 5.3

18.Zhou J, Jang YP, Kim SR, Sparrow JR. Complement activation by photooxidation products of A2E, a lipofuscin constituent of the retinal pigment epithelium. Proc Natl Acad Sci U S A 2006;103:1618216187.

19.Delori FC, Goger DG, Dorey CK. Age-related accumulation and spatial distribution of lipofuscin in RPE of normal subjects. Invest Ophthalmol Vis Sci 2001;42:1855-1866.

20.Bakall B, Radu RA, Stanton JB, Burke JM, McKay BS, Wadelius C, Mullins RF, Stone EM, Travis GH, Marmorstein AD. Enhanced accumulation of A2E in individuals homozygous or heterozygous for mutations in BEST1 (VMD2). Exp Eye Res 2007;85:34-43.

21.Mata NL, Weng J, Travis GH. Biosynthesis of a major lipofuscin fluorophore in mice and humans with ABCR-mediated retinal and macular degeneration. Proc Natl Acad Sci U S A 2000;97:7154-7159.

22.Zhang K, Garibaldi DC, Li Y, Green WR, Zack DJ. Butterfly-shaped pattern dystrophy: a genetic, clinical, and histopathological report. Arch Ophthalmol 2002;120:485-490.

23.Boon CJF, van Schooneveld MJ, den Hollander AI, van Lith-Verhoeven JJC, Zonneveld-Vrieling MN, Theelen T, Cremers FPM, Hoyng CB, Klevering BJ. Mutations in the peripherin/RDS gene are an important cause of multifocal pattern dystrophy simulating STGD1/fundus flavimaculatus. Br J Ophthalmol 2007;91:1504-1511.

24.Zhuk SA, Edwards AO. Peripherin/RDS and VMD2 mutations in macular dystrophies with adult-onset vitelliform lesion. Mol Vis 2006;12:811-815.

25.Allikmets R. A photoreceptor cell-specific ATP-binding transporter gene (ABCR) is mutated in recessive Stargardt macular dystrophy. Nat Genet 1997;17:122.

26.Cideciyan AV, Aleman TS, Swider M, Schwartz SB, Steinberg JD, Brucker AJ, Maguire AM, Bennett J, Stone EM, Jacobson SG. Mutations in ABCA4 result in accumulation of lipofuscin before slowing of the retinoid cycle: a reappraisal of the human disease sequence. Hum Mol Genet 2004;13:525-534.

27.Delori FC, Staurenghi G, Arend O, Dorey CK, Goger DG, Weiter JJ. In vivo measurement of lipofuscin in Stargardt's disease-Fundus flavimaculatus. Invest Ophthalmol Vis Sci 1995;36:2327-2331.

28.Weng J, Mata NL, Azarian SM, Tzekov RT, Birch DG, Travis GH. Insights into the function of rim protein in photoreceptors and etiology of Stargardt's disease from the phenotype in abcr knockout mice. Cell 1999;98:13-23.

29.Lois N, Halfyard AS, Bird AC, Holder GE, Fitzke FW. Fundus autofluorescence in Stargardt macular dystrophy-fundus flavimaculatus. Am J Ophthalmol 2004;138:55-63.

30.Cideciyan AV, Swider M, Aleman TS, Sumaroka A, Schwartz SB, Roman MI, Milam AH, Bennett J, Stone EM, Jacobson SG. ABCA4-associated retinal degenerations spare structure and function of the human parapapillary retina. Invest Ophthalmol Vis Sci 2005;46:4739-4746.

31.Gerth C, Andrassi-Darida M, Bock M, Preising MN, Weber BH, Lorenz B. Phenotypes of 16 Stargardt macular dystrophy/fundus flavimaculatus patients with known ABCA4 mutations and evaluation of geno- type-phenotype correlation. Graefe’s Arch Clin Exp Ophthalmol 2002;240:628-638.

32.Cideciyan AV, Swider M, Aleman TS, Roman MI, Sumaroka A, Schwartz SB, Stone EM, Jacobson SG. Reduced-illuminance autofluorescence imaging in ABCA4-associated retinal degenerations. J Opt Soc Am A Opt Image Sci Vis 2007;24:1457-1467.

33.Paskowitz DM, Lavail MM, Duncan JL. Light and inherited retinal degeneration. Br J Ophthalmol 2006;90:1060-1066.

Fundus autofluorescence in retinaldystrophies 145

34.Petrukhin K, Koisti MJ, Bakall B, Li W, Xie G, Marknell T, Sandgren O, Forsman K, Holmgren G, Andreasson S, Vujic M, Bergen AA, Garty-Dugan V, Figueroa D, Austin CP, Metzker ML, Caskey CT, Wadelius C. Identification of the gene responsible for Best macular dystrophy. Nat Genet 1998;19:241247.

35.Gass JD. Heredodystrophic disorders affecting the pigment epithelium and retina. In: Stereoscopic atlas of macular diseases: diagnosis and treatment. 4th Ed. Vol. 1. St. Louis: C.V. Mosby, 1997:304-311.

36.Boon CJF, Klevering BJ, den Hollander AI, Zonneveld MN, Theelen T, Cremers FPM, Hoyng CB. Clinical and genetic heterogeneity in multifocal vitelliform dystrophy. Arch Ophthalmol 2007;125:1100-1106.

37.Mullins RF, Oh KT, Heffron E, Hageman GS, Stone EM. Late development of vitelliform lesions and flecks in a patient with Best disease: clinicopathologic correlation. Arch Ophthalmol 2005;123:15881594.

38.Frangieh GT, Green WR, Fine SL. A histopathologic study of Best's macular dystrophy. Arch Ophthalmol 1982;100:1115-1121.

39.Mullins RF, Kuehn MH, Faidley EA, Syed NA, Stone EM. Differential macular and peripheral expression of bestrophin in human eyes and its implication for Best disease. Invest Ophthalmol Vis Sci 2007;48:3372-3380.

40.O'Gorman S, Flaherty WA, Fishman GA, Berson EL. Histopathologic findings in Best's vitelliform macular dystrophy. Arch Ophthalmol 1988;106:1261-1268.

41.Weingeist TA, Kobrin JL, Watzke RC. Histopathology of Best's macular dystrophy. Arch Ophthalmol 1982;100:1108-1114.

42.Renner AB, Tillack H, Kraus H, Kramer F, Mohr N, Weber BH, Foerster MH, Kellner U. Late onset is common in Best macular dystrophy associated with VMD2 gene mutations. Ophthalmology 2005;112:586-592.

43.Spaide RF, Noble K, Morgan A, Freund KB. Vitelliform macular dystrophy. Ophthalmology 2006;113:1392-1400.

44.Jarc-Vidmar M, Kraut A, Hawlina M. Fundus autofluorescence imaging in Best's vitelliform dystrophy. Klin Monatsbl Augenheilkd 2003;220:861-867.

45.Downes SM, Fitzke FW, Holder GE, Payne AM, Bessant DA, Bhattacharya SS, Bird AC. Clinical features of codon 172 RDS macular dystrophy: similar phenotype in 12 families. Arch Ophthalmol 1999;117:1373-1383.

46.Hoyng CB, Heutink P, Testers L, Pinckers A, Deutman AF, Oostra BA. Autosomal dominant central areolar choroidal dystrophy caused by a mutation in codon 142 in the peripherin/RDS gene. Am J Ophthalmol 1996;121:623-629.

47.Hughes AE, Lotery AJ, Silvestri G. Fine localisation of the gene for central areolar choroidal dystrophy on chromosome 17p. J Med Genet 1998;35:770-772.

48.Keilhauer CN, Meigen T, Weber BH. Clinical findings in a multigeneration family with autosomal dominant central areolar choroidal dystrophy associated with an Arg195Leu mutation in the peripherin/RDS gene. Arch Ophthalmol 2006;124:1020-1027.

49.Francis PJ, Schultz DW, Gregory AM, Schain MB, Barra R, Majewski J, Ott J, Acott T, Weleber RG, Klein ML. Genetic and phenotypic heterogeneity in pattern dystrophy. Br J Ophthalmol 2005;89:11151119.

50.Marmor MF, Byers B. Pattern dystrophy of the pigment epithelium. Am J Ophthalmol 1977;84:32-44.

146Chapter 5.3

51.Pinckers A. Patterned dystrophies of the retinal pigment epithelium. A review. Ophthalmic Paediatr Genet 1988;9:77-114.

52.Weigell-Weber M, Kryenbuhl C, Buchi ER, Spiegel R. Genetic heterogeneity in autosomal dominant pattern dystrophy of the retina. Mol Vis 1996;2:6.

53.Dubovy SR, Hairston RJ, Schatz H, Schachat AP, Bressler NM, Finkelstein D, Green WR. Adult-onset foveomacular pigment epithelial dystrophy: clinicopathologic correlation of three cases. Retina 2000;20:638-649.

54.Patrinely JR, Lewis RA, Font RL. Foveomacular vitelliform dystrophy, adult type. A clinicopathologic study including electron microscopic observations. Ophthalmology 1985;92:1712-1718.

55.Renner AB, Tillack H, Kraus H, Kohl S, Wissinger B, Mohr N, Weber BH, Kellner U, Foerster MH. Morphology and functional characteristics in adult vitelliform macular dystrophy. Retina 2004;24:929939.

56.Deutman AF, van Blommestein JD, Henkes HE, Waardenburg PJ, Solleveld-van Driest E. Butterflyshaped pigment dystrophy of the fovea. Arch Ophthalmol 1970;83:558-569.

57.den Hollander AI, van Lith-Verhoeven JJC, Kersten FF, Heister JG, de Kovel CG, Deutman AF, Hoyng CB, Cremers FPM. Identification of novel locus for autosomal dominant butterfly shaped macular dystrophy on 5q21.2-q33.2. J Med Genet 2004;41:699-702.

58.van Lith-Verhoeven JJC, Cremers FPM, van den Helm B, Hoyng CB, Deutman AF. Genetic heterogeneity of butterfly-shaped pigment dystrophy of the fovea. Mol Vis 2003;9:138-143.

59.Chew EY, Deutman AF. Pigment dispersion syndrome and pigmented pattern dystrophy of retinal pigment epithelium. Br J Ophthalmol 1983;67:538-541.

60.Chew EY, Deutman AF, Cruysberg JRM. Macular changes in myotonic dystrophy. In: Ryan S, editor. Retinal disease. Florida: Grune and Stratton, 2007:141-148.

61.Hayasaka S, Kiyosawa M, Katsumata S, Honda M, Takase S, Mizuno K. Ciliary and retinal changes in myotonic dystrophy. Arch Ophthalmol 1984;102:88-93.

62.Isashiki Y, Nakagawa M, Ohba N, Kamimura K, Sakoda Y, Higuchi I, Izumo S, Osame M. Retinal manifestations in mitochondrial diseases associated with mitochondrial DNA mutation. Acta Ophthalmol Scand 1998;76:6-13.

63.Massin P, Virally-Monod M, Vialettes B, Paques M, Gin H, Porokhov B, Caillat-Zucman S, Froguel P, Paquis-Fluckinger V, Gaudric A, Guillausseau PJ. Prevalence of macular pattern dystrophy in maternally inherited diabetes and deafness. GEDIAM Group. Ophthalmology 1999;106:1821-1827.

64.Malecki MT. Genetics of type 2 diabetes mellitus. Diabetes Res Clin Pract 2005;68 Suppl1:S10-S21.

65.Bellmann C, Neveu MM, Scholl HP, Hogg CR, Rath PP, Jenkins S, Bird AC, Holder GE. Localized retinal electrophysiological and fundus autofluorescence imaging abnormalities in maternal inherited diabetes and deafness. Invest Ophthalmol Vis Sci 2004;45:2355-2360.

66.Robson AG, El-Amir A, Bailey C, Egan CA, Fitzke FW, Webster AR, Bird AC, Holder GE. Pattern ERG correlates of abnormal fundus autofluorescence in patients with retinitis pigmentosa and normal visual acuity. Invest Ophthalmol Vis Sci 2003;44:3544-3550.

CHAPTER 5.4

Fundus autofluorescence in patients with inherited retinal diseases

Patterns of fluorescence at two different wavelengths

Thomas Theelen, Camiel J.F. Boon, B. Jeroen Klevering, and Carel B. Hoyng

From the

Department of Ophthalmology, Radboud University Nijmegen Medical Centre

Adapted and translated from: Theelen T, Boon CJ, Klevering BJ, Hoyng CB.

Fundus autofluorescence in patients with inherited retinal diseases: patterns of fluorescence at two different wavelengths. (in German)

Ophthalmologe 2008;105:1013-22

with kind permission from Springer Science & Business Media

148 Chapter 5.4

Fundus autofluorescence at two different wavelengths 149

SUMMARY

BACKGROUND: Fundus autofluorescence (FAF) may be excited and measured at different wavelengths. In the present study we compared short-wavelength and near-infrared FAF patterns of retinal dystrophies.

METHODS: We analyzed both eyes of 108 patients with diverse retinal dystrophies. Besides color fundus photographs, FAF images were obtained with the Heidelberg Retina Angiograph (HRA 2). We used excitation wavelengths of 488 nm (blue; filter at 500 nm) and 787 nm (near-infrared; filter at 810 nm). For improvement of signal-to-noise ratio a total of 9 images were averaged, and the mean images were compared to each other.

RESULTS: Useful FAF images of both excitation wavelengths were achieved in all patients. We observed characteristic FAF patterns, which differed between excitation wavelengths dependent on the disease. During time, FAF pattern changes and progression could be observed.

CONCLUSION: FAF of both wavelengths were helpful for phenotype description in retinal dystrophies. Apparently near infrared and short wavelength FAF may show different pathologic changes in the same eye. However, any conclusions may be limited by the yet incomplete knowledge about the prognostic value of FAF in the diseases studied here.

INTRODUCTION

After the first reports on fundus autofluorescence (FAF) in the short-wavelength1 and the near-infrared2 range there has been a growing scientific and clinical interest in FAF of patients with inherited and acquired retinal diseases.3-7 This is hardly surprising, as FAF is an inherently non-invasive, patient-friendly technique, which provides a topographical overview of the functional state of the retinal pigment epithelium (RPE).1 Due to the strong autofluorescence signals, FAF imaging is particularly suited for diseases with excessive

accumulation of lipofuscin where pathological fundus changes will appear most clearly on FAF.8;9

In recent years, FAF imaging with excitation by short-wavelength light has been established for patients with inherited retinal and macular diseases.10-13 The benefit of the technique is based on the strong autofluorescence of the frequently accumulated lipofuscin in those cases. Lipofuscin fluoresces brightly in the orange-yellow spectrum if irradiated with blue light. Usually, a confocal laser scanning ophthalmoscope (Heidelberg Retina Angiograph, HRA) is applied, resulting in an 8-bit gray value image giving a topographical overview of FAF, which allows a straightforward analysis for clinical applications.

In addition to blue light, light from the near-infrared spectrum seems to be appropriate for

exciting RPE fluorophores. Obviously not lipofuscin but melanin seems to play an important role in the near-infrared spectrum.14;15 However, this still needs to be established by ex-vivo

examinations.

Different compilations and distributions of the causal fluorophores result in significantly different appearances of FAF, which appears already in the healthy eye, independent of whether the examination was done with either blue light (FAF488) or light of the near infrared range (FAF787) (Fig. 5.19). Table 5.2 suggests factors that may affect FAF images at different