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 Table of Contents  
ORIGINAL ARTICLE
Year : 2013  |  Volume : 1  |  Issue : 3  |  Page : 31-36

Comparison between fundus autofluorescence images and color fundus photos in patients with late dry age-related macular degeneration


1 Lecturer of Ophthalmology, Faculty of Medicine, Alexandria University, Egypt
2 General Ophthalmologist, Egyptian Ministry of Health Hospital, Egypt

Date of Web Publication1-Nov-2014

Correspondence Address:
Ahmed Mahmoud Abdel Hadi
24 Fawzy Moaz Street, Safwa 5, Entrance 2, Alexandria
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2347-5617.143445

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  Abstract 

Purpose: The purpose was to compare between color fundus photography (CFP) images and fundus autofluorescence (FAF) images of cases with geographical atrophy (GA) about size. To evaluate the relation between different phenotypes of FAF changes and best corrected visual acuity (BCVA) in cases with late dry age-related macular degeneration (AMD) (GA). Materials and Methods: This study was conducted on 18 eyes of 18 patients aged 55 years. Patients unwilling to participate in the study, suffering from hereditary fundus diseases, had previous laser photocoagulation treatment for any cause, were excluded. BCVA using Snellen chart was measured. Retinal imaging including CFP with 50° field camera: Topcon TRC-50 IX - and FAF using spectralis Heidelberg retinal angiograph (HRA) + optical coherence tomography (HRA, Heidelberg Engineering, Germany) were done. All images were optimized and then manually measured using image analysis software (Adobe Photoshop version CS6; Inc., San Jose, California, USA). Images of fundus autofluorescence in cases of late dry AMD were classified to phenotypes at the junctional zone according to the classification of abnormal FAF patterns. Results: According to sex distribution, 33.3% (6 eyes) were males and 66.7% (12 eyes) were females . The mean age of the study participants was 72.89 ± 9.09 years. About surface area of GA, the mean surface area of GA by FAF was 71094.56 ± 21490.53 pixels and by color fundus camera were 46236.56 ± 13153.46 pixels. About FAF phenotypes in late dry AMD cases, Twelve eyes (66.7%) had diffuse pattern, 11.1% (2 eyes) had a none pattern (no specific pattern), and 22.2% (4 eyes) had focal pattern. Color fundus camera underestimated the surface area of GA in cases of late dry AMD. BCVA was best in cases with no specific pattern of autofluorescence at the junctional zone of the GA, followed by cases with focal pattern of hyperautofluorescence while cases with diffuse increases of autofluorescence at the junctional zone showed the worst VA. Conclusions: CFP underestimated the size of the GA, as compared with FAF measured sizes. BCVA was best in cases with no specific pattern of autofluorescence at the junctional zone of the GA, followed by cases with focal pattern of hyperautofluorescence while cases with diffuse increases of autofluorescence at the junctional zone showed the worst VA.

Keywords: Fundus autofluorescence, geographic atrophy, late dry age-related macular degeneration


How to cite this article:
Hadi AM, Andrawos KG. Comparison between fundus autofluorescence images and color fundus photos in patients with late dry age-related macular degeneration . Egypt Retina J 2013;1:31-6

How to cite this URL:
Hadi AM, Andrawos KG. Comparison between fundus autofluorescence images and color fundus photos in patients with late dry age-related macular degeneration . Egypt Retina J [serial online] 2013 [cited 2022 May 24];1:31-6. Available from: https://www.egyptretinaj.com/text.asp?2013/1/3/31/143445


  Introduction Top


Age-related macular degeneration (AMD) is the leading cause of irreversible visual impairment and blindness in the elderly population. [1] The development of AMD is a slow progressive process that occurs with aging and mainly affects people over age 60. [2]

Fundus autofluorescence (FAF) imaging of the human living eye is a relatively new imaging method that provides a topographic map of the distribution of lipofuscin (LF) in the retinal pigment epithelium (RPE). The detection of FAF is limited by its low intensity (approximately two orders of magnitude lower than the peak background fluorescence of an ordinary fluorescein angiography) and the autofluorescence characteristics of the anatomic structures of the eye, including those of the optical media, especially of the lens. [3]

Different Imaging methods of FAF include Fundus spectrophotometry. This was developed by Delori et al. who designed it to determine the spectrum of excitation and fluorescence emission from small areas of the retina (2° diameter). [4]

A new Confocal scanning laser ophthalmoscope (cSLO) was recently developed by Bellmann et al. using a low-energy laser source to scan the retina. [5] Currently, there are three different cSLO systems for FAF imaging: The Heidelberg retinal angiograph (HRA) (based on the HRA classic, HRA 2 and the Spectralis HRA) (Heidelberg Engineering, Dossenheim, Germany); the Rodenstock cSLO (RcSLO; Rodenstock, Weco, Düsseldorf, Germany); and the Zeiss prototype SM 30 4024 (ZcSLO; Zeiss, Obercochen, Germany). [6]

Fundus cameras are widely used in clinical routine for imaging the retina as fundus photographs, reflectance photographs and fluorescein angiography. Spaide has obtained images of the spatial distribution of FAF intensities over larger retinal areas up to 50Ί with his new modified fundus camera. [7]

Fundus autofluorescence imaging shows a consistent pattern of autofluorescence distribution in normal eyes. Such common findings have been reported in children as young as 4 years old. [8]

The macular FAF signal is reduced at the fovea because it is limited by the presence of lutein and zeaxanthin in the neurosensory retina. The signal is higher in the parafoveal area and tends to increase as we move away from it, peaking at the most peripheral retinal areas. It has been suggested that this FAF pattern is caused by the melanin deposition and density of LF granules at the different areas of the retina. [9] The optic nerve head typically appears dark mainly due to the absence of RPE. The retinal vessels are associated with a markedly reduced FAF signal because of the blocked fluorescence. The changes in signal intensity are qualitatively described as decreased, normal, or increased as compared to the background signal of the same eye. [10]

Geographic atrophy-part of advanced AMD scope is thought to be the natural end stage of the atrophic AMD process when choroidal neovascularization (CNV) does not appear. Geographical atrophy (GA) occurs in areas where the RPE is dead, and the outer neurosensory retina and choriocapillaris disappear. [11] Due to the loss of RPE and LF, the atrophic area appears dark in FAF imaging. High contrast between the atrophic and the nonatrophic retina defines the area of GA more precisely than color fundus photography (CFP), permitting a clearer and more specific study of GA, as well as its natural development and evolution. [12]

The GA patches usually become larger and coalesce as AMD progresses. An excessive accumulation of LF and therefore an increased FAF in the junction are highly suggestive of the appearance or progression of preexisting GA. Preliminary observations suggest that different phenotypes may appear associated with junction FAF changes. [13] Recently, a new classification for junction FAF patterns has been proposed in GA patients [Table 1] and [Figure 1] . [14]
Table 1: Fundus autofluorescence phenotypes in late age-related macular degeneration

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Figure 1: Fundus autofluorescence phenotypes in late age-related macular degeneration

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In the current study, we compared between CFP images and FAF images of cases with GA from dry AMD. We tried to evaluate the relation between different phenotypes of FAF changes, and best corrected visual acuity (BCVA) in cases with late dry AMD (GA).


  Materials and Methods Top


This study was conducted on 18 eyes of 18 patients aged 55 years or more who attended the ophthalmology department outpatient clinic of the Alexandria Main University Hospital during the period from April 2012 to December 2012.

Patients with previous posterior segment surgery, suffering from hereditary fundus diseases, had previous laser photocoagulation treatment for any cause, were subjected to previous ocular trauma, diagnosed with wet type of AMD diagnosed clinically or by optical coherence tomography (OCT) patients with myopia >6 diopters (spherical equivalent were excluded), eyes with poor CFP or FAF as identified by the observers were also excluded.

All patients in this study were subjected to standard ophthalmological examination with emphasis on the following BCVA using Snellen chart, Anterior segment examination using slit-lamp biomicroscopy, fundus examination using contact and noncontact lens after full pupillary dilation using tropicamide 1% eye drops.

Retinal imaging including CFP with 50° field camera - Topcon TRC-50 IX - and FAF using Spectralis HRA + OCT (HRA, Heidelberg Engineering, Germany) were done.

All images were optimized using image analysis software (Adobe Photoshop version CS6; Adobe systems Inc, San Jose, California, USA). Images were imported then the optimization started by stretching the histogram using the entire range of available pixel values (0-255), superimposition of the images on each other was done so that the arcades overlapped. The area of atrophic changes seen in CFP and the area of FAF atrophic changes seen in FAF images were measured manually by mouse driven arrow on Adobe Photoshop by two different analysts in a masked manner. When drusen in the FAF images were identified to have the same FAF grade of black depigmentation and were contiguous with the main GA area they were calculated as part of the GA in FAF [Figure 2] and [Figure 3].
Figure 2: Photoshop screen showing how to define and measure atrophic areas in color photography

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Figure 3: Photoshop screen showing how to define and measure atrophic areas in fundus autofluorescence

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Images of fundus autofluorescence in cases of late dry AMD were assessed for FAF phenotypes at the junctional zone according to the classification of abnormal FAF patterns in the junctional zone of geographic atrophy in patients with AMD study. [14]


  Results Top


This study was conducted on 18 eyes of 18 patients aged 55 years. According to sex distribution 33.3% (6 eyes) were males, and 66.7% (12 eyes) were females . The mean age of the study participants was 72.89 ± 9.09 years . About surface area of GA, the mean surface area of GA by FAF was 71094.56 ± 21490.53 pixels and by color fundus camera were 46236.56 ± 13153.46 pixels [Figure 4].
Figure 4: Comparison between surface area of geographical atrophy by colour fundus camera and surface area of geographical atrophy by fundus autofluorescence in late dry age related macular degeneration

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According to the classification FAF phenotypes in late dry AMD cases, 12 eyes (66.7%) had diffuse pattern, 11.1%

(2 eyes) had a none pattern (no specific pattern), and 22.2% (4 eyes) had focal pattern [Figure 5] and [Figure 6].
Figure 5: Diffuse pattern (a) color fundus camera (b) fundus autofluorescence)

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Figure 6: Focal pattern (a) color fundus camera (b) fundus autofluorescence)

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These measurements show statistical difference in surface area of GA by FAF and by color fundus camera where colour fundus camera underestimated the surface area of GA in cases of late dry AMD.

Relation between FAF phenotypes and BCVA in late dry AMD (GA) is described in [Table 2] .
Table 2: Relation between FAF phenotypes and BCVA in late dry age related macular degeneration


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In view of the limited data available, in particular when subdividing into groups, it is hard to know if a nearly normal distribution is present for BCVA. As the medians of the data in [Table 2] suggests the BCVA was best in cases with no specific pattern of autofluorescence at the junctional zone of the GA, followed by cases with focal pattern of hyperautofluorescence, while cases with diffuse increases of autofluorescence at the junctional zone showed the worst VA [Figure 7].
Figure 7: Relation between fundus autofluorescence phenotypes and best corrected visual acuity in late dry age-related macular degeneration

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  Discussion Top


Fundus autofluorescence imaging is a noninvasive imaging method that allows for topographic mapping of LF distribution in the RPE cell monolayer in-vivo. Due to the absence of RPE LF, atrophic areas in eyes with GA have a severely reduced signal. The high contrast of these hypoautofluorescent areas, compared with nonatrophic retina, allows for easy and accurate determination of lesion boundaries, particularly when compared with conventional fundus photography. Using customized image analysis software, atrophic patches can be quantified, and the spread of the total size of atrophy can be determined over time. [11]

Th e present study was compared with the study performed in 164 eyes of 107 patients whose digital FAF images were recorded using a cSLO (cSLO; excitation 488 nm, detection above 500 nm) as part of a prospective multicenter natural history study (FAM study). The FAM study showed that image quality was sufficient for classification of FAF patterns in 149 eyes (90.9%) with lens opacities being the most common reason for insufficient image quality. Abnormal FAF outside GA in 149 eyes was classified into four patterns: Focal (12.1%), banded (12.8%), patchy (2.0%), and diffuse (57.0%), whereby 12.1,% had normal background FAF in the junctional zone. In 4%, there was no predominant pattern. [14]

As regard the distribution of the cases in the present study according to surface area of GA, their measurements showed statistical difference in the surface area by FAF and by color fundus camera, where color fundus camera underestimated the surface area of GA in cases of late dry AMD. This is in agreement with Bindewald et al., who reported that areas with abnormal increased or decreased FAF signals may or may not correspond to funduscopically visible alterations. [3]

On the other hand, in the study published by Khanifar et al. carried out on 72 eyes of 72 patients, eyes with GA secondary to AMD had color fundus photos and FAF imaging on the same day. Three graders calculated GA area using digital imaging software. They reported that both color fundus photos and FAF imaging are reliable for measuring GA area. Interobserver agreement was slightly higher for FAF images. The high agreement between modalities suggests that either would be appropriate for measuring GA area, using both may be the best approach for following GA progression. [15]

In the current study, the available data was not enough to consolidate an opinion regarding the BCVA relation to the different patterns of FAF, nevertheless the medians showed better BCVA for cases with no specific pattern, followed by eyes with focal pattern of FAF, with the least BCVA recorded for the eyes with a diffuse pattern of FAF at the junctional zone. We could not find a study comparing directly the FAF phenotype with the BCVA but n analysis conducted within the framework of the FAM study showed that in eyes with geographic atrophy, focal increase FAF could be identified, similarly a focal plaque-like patterns in eyes with CNV, was found. With these findings in mind, the patchy pattern (focal plaque like) can be a risk pattern in the transition to exudative AMD and consequently a worse final visual acuity. [16]

Holz et al. found that annual progression rate of the disease in eyes with a banded or diffuse pattern around the atrophic area was significantly higher relative to those with other FAF patterns and the trickling pattern in the diffuse category was the most progressive type. This study showed that phenotypic features of FAF abnormalities had a much stronger impact on GA progression than any other risk factors. They identified a new, abnormal FAF pattern that has extremely rapid atrophy progression and introduced the term "diffuse trickling" for this pattern, which is associated with a significantly faster atrophy progression compared to all other patterns. Holz proposes that this is most likely attributed to the fact that the groups with no abnormal and focal FAF patterns tend to have smaller baseline atrophies compared with the banded and diffuse FAF pattern groups. Identification of high-risk characteristics will also be helpful in future clinical trials that research novel identifications to slow down the progression of atrophy. [13]

From the previous work, we can conclude that: CFP under estimated the size of the geographic atrophy, as compared with FAF measured sizes. BCVA was best in cases with no specific pattern of autofluorescence at the junctional zone of the GA, followed by cases with focal pattern of hyperautofluorescence while cases with diffuse increases of autofluorescence at the junctional zone showed the worst VA.

 
  References Top

1.
Friedman DS, O'Colmain BJ, Muñoz B, Tomany SC, McCarty C, de Jong PT, et al. Prevalence of age-related macular degeneration in the United States. Arch Ophthalmol 2004;122:564-72.  Back to cited text no. 1
    
2.
Gehrs KM, Anderson DH, Johnson LV, Hageman GS. Age-related macular degeneration: Emerging pathogenetic and therapeutic concepts. Ann Med 2006;38:450-71.  Back to cited text no. 2
    
3.
Bindewald A, Bird AC, Dandekar SS, Dolar-Szczasny J, Dreyhaupt J, Fitzke FW, et al. Classification of fundus autofluorescence patterns in early age-related macular disease. Invest Ophthalmol Vis Sci 2005;46:3309-14.  Back to cited text no. 3
    
4.
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;36:718-29.  Back to cited text no. 4
    
5.
Bellmann C, Holz FG, Schapp O, Völcker HE, Otto TP. Topography of fundus autofluorescence with a new confocal scanning laser ophthalmoscope. Ophthalmologe 1997;94:385-91.  Back to cited text no. 5
    
6.
Bellmann C, Rubin GS, Kabanarou SA, Bird AC, Fitzke FW. Fundus autofluorescence imaging compared with different confocal scanning laser ophthalmoscopes. Br J Ophthalmol 2003;87:1381-6.  Back to cited text no. 6
    
7.
Spaide RF, Schmitz-Valckenberg S, Bird AC. Autofluorescence imaging with the fundus camera. In: Holz FG, editor. Atlas of Autofluorescence Imaging. Germany, Berlin: Springer; 2007. p. 49-54.  Back to cited text no. 7
    
8.
Wabbels B, Demmler A, Paunescu K, Wegscheider E, Preising MN, Lorenz B. Fundus autofluorescence in children and teenagers with hereditary retinal diseases. Graefes Arch Clin Exp Ophthalmol 2006;244:36-45.  Back to cited text no. 8
    
9.
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;83:276-9.  Back to cited text no. 9
    
10.
Lois N, Halfyard AS, Bird AC, Fitzke FW. Quantitative evaluation of fundus autofluorescence imaged "in vivo" in eyes with retinal disease. Br J Ophthalmol 2000;84:741-5.  Back to cited text no. 10
    
11.
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.  Back to cited text no. 11
    
12.
Dreyhaupt J, Mansmann U, Pritsch M, Dolar-Szczasny J, Bindewald A, Holz FG. Modelling the natural history of geographic atrophy in patients with age-related macular degeneration. Ophthalmic Epidemiol 2005;12:353-62.  Back to cited text no. 12
    
13.
Holz FG, Bindewald-Wittich A, Fleckenstein M, Dreyhaupt J, Scholl HP, Schmitz-Valckenberg S, et al. Progression of geographic atrophy and impact of fundus autofluorescence patterns in age-related macular degeneration. Am J Ophthalmol 2007;143:463-72.  Back to cited text no. 13
    
14.
Bindewald A, Schmitz-Valckenberg S, Jorzik JJ, Dolar-Szczasny J, Sieber H, Keilhauer C, et al. Classification of abnormal fundus autofluorescence patterns in the junctional zone of geographic atrophy in patients with age related macular degeneration. Br J Ophthalmol 2005;89:874-8.  Back to cited text no. 14
    
15.
Khanifar AA, Lederer DE, Ghodasra JH, Stinnett SS, Lee JJ, Cousins SW, et al. Comparison of color fundus photographs and fundus autofluorescence images in measuring geographic atrophy area. Retina 2012;32:1884-91.  Back to cited text no. 15
    
16.
Einbock W, Moessner A, Schnurrbusch UE, Holz FG, Wolf S, FAM Study Group. Changes in fundus autofluorescence in patients with age-related maculopathy. Correlation to visual function: A prospective study. Graefes Arch Clin Exp Ophthalmol 2005;243:300-5.  Back to cited text no. 16
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
    Tables

  [Table 1], [Table 2]



 

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