Blue Light Versus Green Light Autofluorescence

IOVS Papers in Press. Published on November 22, 2011 as Manuscript iovs.11-8346
Blue Light versus Green Light Autofluorescence:
Lesion Size of Areas with Geographic Atrophy
Ute EK Wolf-Schnurrbusch 1,2 , Valéry V Wittwer 1,2 , Ramzi Ghanem 1,3 , Martin
Niederhaeuser 2 , Volker Enzmann 1 , Carsten Framme 1 , Sebastian Wolf 1,2
1 Universitätsklinik für Augenheilkunde, Inselspital, University of Bern, Switzerland
2 Bern Photographic Reading Center, Inselspital, University of Bern, Switzerland
3 Helios Klinikum, Aue, Germany
ClinicalTrials.gov Identifier: NCT00494325
Financial interests: none
Word count: 3029
Corresponding author: Ute Wolf-Schnurrbusch
University Eye Hospital
Inselspital
CH-3010 Bern, Switzerland
Phone: +41 31 632 85 75
Fax: +41 31 632 1810
E-mail: ute.wolf@insel.ch
1
Copyright 2011 by The Association for Research in Vision and Ophthalmology, Inc.

Abstract
Introduction
Blue light fundus autofluorescence (FAF) imaging is currently widely used for
assessing dry age-related macular degeneration (ARMD). However, at this
wavelength the fovea appears as circular zone of marked hypofluorescence due to
the absorption of macular pigment (MP). This dark spot could be misinterpreted as
atrophic area and could lead to difficulties in identifying small central changes. The
aim of the study was to analyze differences in image quality, FAF patterns, and lesion
size of using conventional blue (�1=488 nm) and green light FAF (�2=514 nm).
Material and Methods
Patients older than 50 years with central areas of geographic atrophy (GA) secondary
to ARMD were enrolled. Images were recorded with a modified confocal scanning
laser ophthalmoscopy (cSLO). Image quality and patterns were analyzed. The
quantification of the GA was performed with a customized analysis imaging software.
Results
In total 95 eyes were included. Borders of the central atrophic patches and boundaries of
preserved foveal island were better identified in 514 nm images. In both excitation
wavelengths the signal-to-noise ratio was sufficient for the identification of FAF pattern.
We found significant differences in the size of the GA areas detected in the 488 nm and
514 nm wavelength images (4.29 ± 3.76 mm 2 vs. 3.80 ± 3.68 mm 2 ; p

Using only blue light FAF could lead to an over-interpretation of the size of atrophic
patches and the center involvement because it suggests the presence of atrophy in the
fovea.
Introduction
Age-related macular degeneration (ARMD) is related to aging changes in the retinal
pigment epithelium (RPE), Bruch’s membrane and choroid 2-4 . Aging of the RPE is
characterized by massive accumulation of lipofuscin (LF) which contains several
fluorophors. LF has been shown to contain toxic compounds including the dominant
fluophore apyridinium-bis-retinoid (A2-E) which is derived from two molecules of
vitamin A aldehyd and one molecule of ethanolamine 5 . A2E has been shown to
inhibit lysosomal digestion of proteins and to act as a photosensitizer in blue light
generating free radicals within the RPE cell. Based on conventional fundus
photographs, areas of GA have been defined as a sharply demarcated area of
apparent absence of RPE, larger than 175 μm, with visible choroidal vessels and no
neovascular ARMD 25, 28, 29 . This definition is based on histopathological studies that
have characterized clinically visible areas of GA as areas with RPE and outer
neurosensory layer cell death with occasionally visible choriocapillaris 25, 28 . With the
advent of confocal scanning laser ophthalmoscopy (cSLO), fundus autofluorescence
(FAF) can be visualized in vivo 6-8 .
FAF is a relatively novel imaging method that allows topographic LF mapping in vivo
6-11 . In most studies, blue-light FAF images using an excitation wavelength of 488 nm
were analyzed. It is possible to use the non-invasive FAF imaging to monitor disease-
associated changes in-vivo. This is important for the characterization of the atrophic
late-stage manifestation of dry ARMD. This disease is characterized by the
3

development of atrophic patches in the RPE monolayer. Due to the absence of RPE
lipofuscin, areas of geographic atrophy (GA) exhibit a notable reduced FAF signal.
These atrophic areas can be detected clearly and can be quantified precisely in FAF
images.
Imaging of FAF with a cSLO is usually performed with an excitation wavelength of
488 nm. At this wavelength macular pigment (MP) significantly absorbs. This results
in circular zone of marked hypofluorescence (visible as a darker spot) overlying the
fovea and the surrounding area of about 0.5 mm 9, 12, 13 . This reduction of FAF
intensity in the fovea could lead to difficulties in identifying small central changes and
may influence the identification of foveal involvement in central atrophic changes.
The aim of this prospective cross-sectional study was to analyze differences in image
quality, FAF pattern and lesion size measurements of areas with GA at the central
posterior pole using conventional blue light autofluorescence (�1=488 nm) and green
light autofluorescence (�2=514 nm).
Material and Methods
Patients from the outpatient department, Department of Ophthalmology, Inselspital,
University Bern, Switzerland were screened between 5/2007 and 9/2011 for study
participation. Patients older than 50 years with clear optical media and areas of
unifocal or multifocal GA areas secondary to dry ARMD were enrolled. If both eyes
qualified equally for the study, one eye was randomly chosen. Prior to any study
procedures, informed written consent was obtained from every patient with
explanation of the nature and possible risks of the study. The research followed the
4

tenets of the Declaration of Helsinki and was approved by the Institutional Review
Board.
Exclusion criteria were any confluent papillary atrophy in contact with central atrophy,
signs of wet ARMD, any history of retinal surgery (including laser treatment) or
diabetic retinopathy, vascular occlusion, and hereditary retinal dystrophy. We
performed a comprehensive ocular examination with best-corrected visual acuity
(BCVA) using Early Treatment Diabetic Retinopathy Study (ETDRS) charts, dilated
binocular ophthalmoscopy and color fundus photography (FF 450 plus, Carl Zeiss
Meditec, Jena, Germany). All patients underwent fluorescein angiography using the
Heidelberg Retina Angiograph (HRA2, Heidelberg Engineering, Heidelberg,
Germany) to confirm the diagnosis of dry ARMD and to exclude neovascularizations.
FAF images were recorded according to a standardized operation protocol 12, 13 with
a modified cSLO (HRAmp, Heidelberg Engineering, Heidelberg, Germany). This
instrument has been optimized for FAF imaging at excitation wavelengths of
�1=488 nm and �2=514 nm 1 . The patients were positioned in front of the HRAmp and
instructed to look straight and steady. After aligning and focusing using 20°
reflectance images at 488 nm wavelengths the retina was bleached for at least 30
seconds. Then 20° FAF images were acquired at 488 nm and 514 nm wavelengths.
A total of 9 FAF images were recorded for each wavelength. The images obtained for
each wavelength were averaged using the system software to reduce speckle noise.
This improves the signal-to-noise ratio by a factor of 3. The averaged images were
then normalized and graded as follows:
1. Good quality: All areas of GA are clear visible and all boundaries of all GA
areas are delineable. The signal-to-noise ratio is sufficient for the identification
5

2. Intermediate quality: All areas of GA are visible and all boundaries of all GA
areas are discernible. However the signal-to-noise ratio was too low for
sufficient identification of FAF pattern in the junctional zone but still sufficient
for the pattern grading of the posterior pole.
3. Inferior quality. Neither all borders of GA nor FAF abnormalities are entirely
readable.
In all images with good or intermediate quality the FAF patterns and the total size of
GA were analyzed. We quantified the total GA size using the Region Finder software
Version 1.0.16 (Heidelberg Engineering, Heidelberg, Germany). The software
includes algorithms for semi automated segmentation of atrophic areas and for
automated identification of interfering vascular structures 14 . Starting from a user-
defined seed point placed in a dark area of the image a so called “Region grow
algorithm” identifies the border of this dark area and calculates a mean grey value of
the pixels. The FAF intensity of every picture element (pixel) is given in a certain grey value.
The dramatic decrease of the FAF signal in GA areas compared to non-atrophic retinal areas
is used by the Region Finder software for the segmentation of areas with GA. Following the
definition of the center of a region by the operator (reader), the so-called region growing
algorithm tends to grow towards the borders of the region taking into account all pixels with a
signal intensity below a certain threshold. This threshold is defined by a parameter referred
to as “growth power”. The higher the growth power the larger the enclosed area. The proper
adjustment of this parameter allows for the precise measurement of the area with GA. For
scaling, the individual scaling factor that is registered by the HEYEX during acquisition is
used. Given the digital image resolution of 768 x 768 pixels of a 30° x 30° frame, one pixel
roughly corresponds to 11 microns.
6

Two independent and trained readers (MN, VW) assessed the image quality and
quantified the total GA size in FAF images at excitation wavelengths of �1=488 nm
and �2=514 nm. The readers analyzed the images in separate sessions at least one
day apart. In each session the images were presented in a randomized fashion to
minimize any memory effect. For statistical analysis of lesion size the measurements
between the two independent graders were averaged. Inter FAF mode variability was
analyzed using Bland-Altman plots. The inter-observer agreement for both FAF
modes (e.g. �1=488 nm and �2=514 nm) was analyzed with the Bland-Altman plots
and the Lin’s concordance correlation coefficient. We used GraphPad Prism version
5.00 for Windows (GraphPad Software, San Diego California USA,
www.graphpad.com) for all statistical analyses. P values ≤ 0.05 were accepted as
statistically significant given the exploratory nature of these analyses. Demographic
characteristics for the patients were summarized using descriptive statistics.
Descriptive statistics are expressed in terms of means ± standard deviation (M±SD)
or proportions.
Results
In total 95 eyes with GA areas secondary to dry ARMD involving the central posterior
pole of the eye were included into this unmasked, prospective cross-sectional study.
Baseline demographics of all the 95 patients are described in Table 1.
FAF imaging with the modified cSLO was possible in all 95 eyes using the 488 nm
and the 514 nm excitation wavelength. In all eyes, we found a reduced FAF signal in
the GA site when using both wavelengths.
Assessment of the image quality
7

In both, blue (�1=488 nm) and green (�2=514 nm) excitation light FAF images, the
signal-to-noise ratio was sufficient for the quality assessment. We did not observe
differences in the quality assessment between both excitation wavelengths and the
two independent readers.In general the 488 nm images had a slightly better contrast
outside the macula region. Borders of the GA patches involving the macula or
boundaries of any existing preserved foveal island were better to identify in 514 nm
compared to 488 nm FAF images.
We found in 58/95 (61%) eyes a “good” image quality and in 26/95 (27%) a
“intermediate” image quality. Representative examples for the image quality
assessment are shown below in Figure 1 and 2 (good image quality) and Figure 3
(intermediate image quality). An “inferior” quality was found in 11/95 (12%) eyes.
Reasons for reduced image quality, included slow eye movements during image
acquisition which is not corrected by averaging algorithm of the software (9/11 eyes)
and vitreous floaters (2/11 eyes).
Neither the lens status (phacic vs. pseudophakic, p> 0.05 Chi-square test) nor the
type of the intraocular lens (IOL) (clears vs. blue blocking IOL, p> 0.05 Chi-square
test) had any influence on the FAF image quality. The refraction or the spherical
equivalent also did not influence the image quality. For the analyses of the lesion size
and the FAF patterns we excluded all 11/95 (12%) eyes with an inferior quality.
Assessment of the FAF patterns
With both excitation wavelengths (488 nm and 514nm) the signal-to-noise ratio was
sufficient for the identification of FAF pattern. The distribution of FAF patterns was
similar for 488 nm and 514 nm FAF images. A total of 13/84 (15%) eyes showed the
GA without visible abnormal FAF outside the area of atrophy. The rest of the 71/84
(85%) eyes, presented different forms of abnormal FAF patterns surrounding the
8

area of GA. A FAF pattern with a small continuous band at the margin with variable
peripheral extension was noted in the majority of these eyes (48/71, 68%). A FAF
pattern with a diffusely increased autofluorescence at the entire posterior pole was
seen in 12/71 (17%) eyes (Figure 1 and 3), and a FAF with small focal spots of
increased autofluorescence in the junctional zone was observed in 11/71 (15%) eyes
(Figure 2).
Assessment of the total GA size
In all the FAF image sets, the total size of GA was delineated and quantified.
However, in 15 of the 84 (18%) eyes the total size of the atrophic patches was too
large to visualize all peripheral borders in the FAF images (see Figure 4). Therefore,
the size of the GA was only assessable in image sets from 69 eyes. We found
significant differences in the size of the GA areas detected in the 488 nm and 514 nm
wavelength images (4.29 ± 3.76 mm 2 vs. 3.80 ± 3.68 mm 2 ; p 0.05) between both readers for a given
wavelength. The correlation between both observers was good with a Lin
concordance correlation coefficient of 0.965 for 488 nm images and of 0.930 for
514 nm images. Bland-Altman plots for the inter-reader variability are presented in
Figure 5.
Discussion
The majority of epidemiological and natural history studies that have addressed the
enlargement of GA areas with time have used color fundus photographs 23-25 or fundus-
camera based FAF images. While this technique can be used to detect the presence of
GA, graders at reading centers have reported difficulty reproducibly measuring atrophic
9

areas due to inter-subject variability of fundus pigmentation, media opacities and the
presence of drusen and small satellites of atrophy 26-28 .
The aim of this study was to analyze differences in image quality, FAF patterns and
total GA size measurements using conventional blue light autofluorescence (488 nm)
and green light autofluorescence (514 nm). Imaging of FAF distribution using
conventional blue light autofluorescence is a relatively well established method to
assess the LF distribution in a clinical setting 6-11 . For the image acquisition we used
a modified cSLO optimized for macular pigment measurements 1, 15-17, 20 . This
instrument allows FAF imaging with two excitation wavelengths (�1=488 nm and
�2=514 nm) 15-17 .
Good or intermediate image quality is needed no matter what excitation wavelength
is used. In FAF images with “inferior” quality, neither the FAF patterns nor all borders
of GA are readable. A high-contrast difference between atrophic and non-atrophic
areas is necessary for an exact measurement of the GA size. This high-contrast
difference between the atrophic and non-atrophic area is also needed for a clear
delineation of GA boundaries.
In most eyes with clear optical media (87%), good or intermediate FAF imaging
quality was observed with both excitation wavelengths. Overall, image quality and
distribution of FAF patterns did not differ between of the two wavelengths.
Both wavelengths could be used for a fast and non-invasive detection of disease
associated changes in patients with GA. Areas with GA show decreased FAF signal
due to the lack of RPE which contains LF as a dominant fluophore. The areas
adjacent to the GA show a broad spectrum of autofluorescence pattern. These
patterns were well established using blue light autofluorescence images and seem to
offer a certain predictive value for disease progression 18, 19 .
10

In this study areas of GA showed a marked reduced autofluorescence signal with
both wavelengths. Adjacent to the GA areas we were able to detect the previously
described FAF patterns with both wavelengths. The relative distribution of FAF
patterns in the present study was similar to other patients cohorts previously tested
20 .
Quantification of the atrophic patches using customized analysis imaging software
has previously been described 14 . FAF with both excitation wavelengths (488 nm and
514 nm) allowed the delineation of the borders of the GA. Significant differences
were found when comparing the size of the atrophic patches between both used
excitation wavelengths. We observed significant differences in the size of the GA
areas detected in the 488 nm and 514 nm wavelength images (4.29 ± 3.76 mm 2 vs.
3.80 ± 3.68 mm 2 ; p0.05).
Central pathologies were clearer to distinguish and easier visible if the longer
excitation wavelength (514 nm) was used. Preserved foveal islands were clearer to
distinguish in FAF images with 514 nm excitation wavelength. The dominant cause
for misinterpretation at 488 nm wavelength was the dark spot overlaying the fovea
due to MP absorption. This could lead to a false- or an over-interpretation of the GA
size, and the center involvement because it suggests the presence of atrophy in the
fovea. This could explain the differences in the size measurements between both
wavelengths. The differences in the size measurements between both FAF modes
are not important, if only the progression rate or the enlargement of GA areas are studied in
a longitudinal fashion. But in our opinion it is important to give the correct baseline
characteristic for the center involvement and for a correlation with functional values like
BCVA in epidemiological or natural history studies 23-25 .
11

In current clinical studies, only blue-light FAF is used to determine the size of atrophic
lesions. However, an accurate measurement with green light FAF is important in
future clinical trials for the evaluation of the central GA progression. As a result, the
use of green light FAF images could give us a better opportunity in estimating an
approximate time of visual loss. Depending which wavelength is used a detailed
description is needed for a precise interpretation of focally increased or decreased
FAF signals. Therefore future studies are necessary to evaluate the clinical value of
this new imaging method in order to understand green light autofluorescence better.
Although lipofuscin is the dominant fluorophor in the ocular fundus, there are many
other fluorophors present anterior and posterior to the RPE cell monolayer, including
elastin and collagen 21 . Fluorophors like melanin could contribute to the detected FAF
above 695 nm if near infra red (IR) wavelengths were used 22 . This could complicate
the interpretation of FAF images obtained with wavelengths longer than 600 nm
instead of the conventional blue light.
To conclude, the green light FAF images obtained with 514 nm excitation wavelength
are superior for an accurate determination of small central pathologic changes and of
the central atrophic lesion boundaries.
Acknowledgements
We thank Ms. Anita Zenger for her help in the image acquisition and Bettina
Rotzetter for the reading of the manuscript.
12

Figures
Figure 1:
Example of a FAF image with good quality (right eye, O-Y, f, 78 years old, BCVA 63
letters, correction +1.25 dpt. and +0.5 dpt. / 96°). All areas of GA are clear visible and
all boundaries are delineable. The signal-to-noise ratio is sufficient for the
identification of the FAF patterns in the junctional zone around the GA and for the
detailed grading of the posterior pole.
Left: FAF image with an excitation wavelength of 488 nm (total GA size 1.621 mm 2 ).
Middle: FAF image with an excitation wavelength of 514 nm (total GA size 1.554
mm 2 ).
Right: color fundus photography.
13

Figure 2:
Example for a FAF image with good quality (right eye, WL, f, 92 years old, BCVA 38
letters, correction -1.00 dpt. and +0.50 dpt. / 112°). Central boundaries of the atrophic
areas were more clearly visible if the “dark spot” produced by the MP was absent.
This resulted in a significantly smaller size of the atrophic patches if FAF with an
excitation wavelength was used.
Left: FAF image with an excitation wavelength of 488 nm (total GA size 4.789 mm 2 ).
Middle: FAF image with an excitation wavelength of 514 nm (total GA size 3.917
mm 2 ).
Right: color fundus photography.
14

Figure 3:
Example for a FAF image with intermediate quality (right, AA, f, 90 years old, BCVA
44 letters, correction -1.00 dpt. and +0.75 dpt. / 172°). All areas of GA are visible and
all boundaries of all GA areas are discernible. The signal-to-noise ratio was too low
for sufficient identification of all FAF patterns in the junctional zone.
Left: FAF image with an excitation wavelength of 488 nm (total GA size 2.643 mm 2 ).
Middle: FAF image with a excitation wavelength of 514 nm (total GA size 2.169
mm 2 ).
Right: color fundus photography.
The foveal island is clearer visible especially in the 514 nm FAF image (see middle
figure) because the “dark shadow” produced by the MP is not covering the central
region. If only FAF images with an excitation wavelength of 488 nm (left) is used this
could lead to a false interpretation of the involved central region.
15

Figure 4:
Example of a FAF image with intermediate quality (right eye, PB, f, 78 years old,
BCVA 27 letters, correction -0.5 dpt.).
It was not possible to visualize all peripheral borders in the FAF images because the
atrophic patches were too large. Therefore we excluded this eye because we were
not able to calculate the exact size.
The sizes of the preserved foveal islands are obviously different when comparing the
two used wavelengths. In the 514 nm image an intact connection is precisely visible
between the two preserved RPE islands (see middle figure).
Left: FAF image with an excitation wavelength of 488 nm.
Middle: FAF image with an excitation wavelength of 514 nm.
Right: color fundus photography.
16

Figure 5:
Bland-Altman plot for the differences between the 488 nm and 514 nm FAF modes
17

Figure 6:
Bland-Altman plots for the inter-reader variability for each FAF mode (488 nm, 514
nm)
18

Tables
Table 1:
Demographic data of all patients (n=95)
Mean Age � SD
(range)
78.8�7.4 years
(range 62.9 to 90.9 years)
Gender male: 34 (36%), female: 61 (64%)
Mean letter score � SD
(range); LogMar
Spherical equivalent � SD
(range)
55 ± 20 letters
(0 to - 81 letters); -0.6
+0.5 ± 0.27 dpt.
(+ 5.0 to – 12.0 dpt.)
Lens status phacic: 47 (49%) eyes,
pseudophacic: 48 (51%) eyes
Typ of IOL clear IOL: 29 (60%) eyes
blue-blocking IOL: 19 (40%) eyes
SD: standard deviation, IOL: intra ocular lens, dpt.: diopters
19

References
1. Wüstemeyer H, Jahn C, Nestler A, Barth T, Wolf S. A new instrument for the
quantification of macular pigment density: first results in patients with AMD and
healthy subjects. Graefe's Arch Clin Exp Ophthalmol 2002;240:666-671.
2. Bird AC. Pathogenesis of retinal pigment epithelial detachment in the elderly;
the relevance of Bruch's membrane change. Eye 1991;5:1-12.
3. Green WR, Enger C. Age-related macular degeneration histopathologic studies.
Ophth 1993;100:1519-1535.
4. Pauleikhoff D, Harper A, Marshall J, Bird A. Aging changes in Bruch´s
membrane. A histochemical and morphologic study. Ophth 1990;97:171-178.
5. Reinboth JJ, Gautschi K, Munz K, Eldred GE, Reme CE. Lipofuscin in the
retina: quantitative assay for an unprecedented autofluorescent compound
(pyridinium bis-retinoid, A2-E) of ocular age pigment. Exp Eye Res
1997;65:639-643.
6. Bird AC, Bressler NM, Bressler SB, et al. An international classification and
grading system for age-related maculopathy and age-related macular
degeneration. Surv OPhthalmol 1995;39:367-374.
7. Delori FC, Fleckner MR, Goger DG, Weiter JJ, Dorey CK. Autofluorescence
distribution associated with drusen in age-related macular degeneration. Invest
Ophthalmol Vis Sci 2000;41:496-504.
8. Lois N, Halfyard AS, Bunce C, Bird AC, Fitzke FW. Reproducibility of fundus
autofluorescence measurements obtained using a confocal scanning laser
ophthalmoscope. Br J Ophthalmol 1999;83:276-279.
9. Solbach U, Keilhauer C, Knabben H, Wolf S. Imaging of retinal
autofluorescence in patients with age-related macular degeneration. Retina
1997;17:385-389.
10. Okubo A, Rosa RH, Jr., Bunce CV, et al. The relationships of age changes in
retinal pigment epithelium and Bruch's membrane. Invest Ophthalmol Vis Sci
1999;40:443-449.
11. von Rückmann A, Fitzke F, Bird A. Fundus autofluorescence in age-related
macular disease imaged with a scanning laser ophthalmoscope. Invest
Ophthalmol Vis Sci 1997;38:478-486.
12. Hammond BR, Jr., Wooten BR, Snodderly DM. Density of the human crystalline
lens is related to the macular pigment carotenoids, lutein and zeaxanthin.
Optom Vis Sci 1997;74:499-504.
13. Snodderly DM, Handelman GJ, Adler AJ. Distribution of individual macular
pigment carotenoids in central retina of macaque and squirrel monkeys. Invest
Ophthalmol Vis Sci 1991;32:268-279.
14. Deckert A, Schmitz-Valckenberg S, Jorzik J, Bindewald A, Holz FG, Mansmann
U. Automated analysis of digital fundus autofluorescence images of geographic
atrophy in advanced age-related macular degeneration using confocal scanning
laser ophthalmoscopy (cSLO). BMC Ophthalmol 2005;5:8.
15. Jahn C, Wüstemeyer H, Brinkmann C, et al. Macular pigment densitiy subject to
different stages of age-realted maculopathy. 2004;ARVO Abstract.
20

16. Wüstemeyer H, Moessner A, Jahn C, Wiedemann P, Wolf S. Macular pigment
density in healthy subjects quantified with a modified confocal laser scanning
ophthalmoscope. Graefes Arch Clin Exp Ophthalmol 2003.
17. Wolf-Schnurrbusch UE, Roosli N, Weyermann E, Heldner MR, Hohne K, Wolf
S. Ethnic differences in macular pigment density and distribution. Invest
Ophthalmol Vis Sci 2007;48:3783-3787.
18. Bindewald A, Dolar-Szczasny J, Sieber H, et al. Fundus autofluorescence
patterns in the junctional zone als prognostic determinats for spreas of
geographic atrophy in age-related macular degeneration (AMD). 2004;ARVO
Abstract.
19. Holz FG, Bindewald-Wittich A, Fleckenstein M, Dreyhaupt J, Scholl HP,
Schmitz-Valckenberg S. Progression of geographic atrophy and impact of
fundus autofluorescence patterns in age-related macular degeneration. Am J
Ophthalmol 2007;143:463-472.
20. Wolf-Schnurrbusch UE, Enzmann V, Brinkmann CK, Wolf S. Morphologic
Changes in Patients with Geographic Atrophy Assessed with a Novel Spectral
OCT-SLO Combination. Invest Ophthalmol Vis Sci 2008;49:3095-3099.
21. Schweitzer D, Schenke S, Hammer M, et al. Towards metabolic mapping of the
human retina. Microsc Res Tech 2007;70:410-419.
22. Keilhauer CN, Delori FC. Near-infrared autofluorescence imaging of the fundus:
visualization of ocular melanin. Invest Ophthalmol Vis Sci 2006;47:3556-3564.
23. Sunness JS. The natural history of geographic atrophy, the advanced atrophic form of
agerelatedmacular degeneration. Mol Vis 1999;5:25.
24. Schatz H, McDonald HR. Atrophic macular degeneration. Rate of spread of geographic
atrophy and visual loss. Ophthalmology 1989;96:1541-1551.
25. Change in Area of Geographic Atrophy in the Age-Related Eye Disease Study: AREDS
Report Number 26. Arch Ophthalmol 2009;127:1168-1174.
26. Scholl HP, Dandekar SS, Peto T, Bunce C, Xing W, Jenkins S, Bird AC. What is
lost by digitizing stereoscopic fundus color slides for macular grading in agerelated
maculopathy and degeneration? Ophthalmology 2004;111:125-132.
27. Sunness JS, Bressler NM, Tian Y, Alexander J, Applegate CA. Measuring
geographic atrophy in advanced age-related macular degeneration. Invest
Ophthalmol Vis Sci 1999;40:1761-1769.
28. Pirbhai A, Sheidow T, Hooper P. Prospective evaluation of digital non-stereo color fundus
photography as a screening tool in age-related macular degeneration. Am J
Ophthalmol 2005;139:455-461.
28. Sarks JP, Sarks SH, Killingsworth MC. Evolution of geographic atrophy of the retinal
pigment epithelium. Eye 1988;2 552-577.
29. Sarks SH. Ageing and degeneration in the macular region: a clinico-pathological study.
Br J Ophthalmol 1976;60:324-341.
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