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A. C. Johnson, X. Feng, T. W. Olsen; Analysis of Autofluorescence in Human Donor Eyes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5115.
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Autofluorescent compounds accumulate in the retinal pigment epithelium (RPE) and the relationship between autofluorescence (AF) and age-related macular degeneration (AMD) is unclear. Development of a model for qualitative and quantitative analysis will help define the role of AF with AMD. Our objective is to define the Minnesota Grading System (MGS) for autofluorescent compounds in eyebank eyes to correspond with our current clinical grading system (MGS; Olsen & Feng IOVS 45 (12): 4484-4490, 2004) of AMD.
Human donor eyes (n=72, range=45-98yrs, mean=68±12yrs) were evaluated according to the MGS. A pre-standardized, digital image was taken using the confocal Scanning Laser Ophthalmoloscope (cSLO). The AF image superimposed digital color fundus images on the MGS photograph with precise sizing and orientation. Next, the MGS grid template was placed on the MGS-AF image. The circular grid delineates the region about the macula into 1mm (center) and 6mm (total) diameter regions. Pixel density measurements (D) were acquired using Adobe Photoshop (D=0-255 units). Each zone of the grid has a mean AF density that is calculated by D/area= true AF (tAF) by analyzing the gray-scale pixel values for each point in a designated region and mathematically subtracting areas of atrophy (D=0-38 units).
The 1mm center concentric region about the macula, tAF decreased linearly with increasing MGS level. In the 6 mm region, tAF remains constant in MGS1-3 and decreases at MGS4. One-way ANOVA analysis was significant (p=0.002) and MGS level 4 was statistically different from MGS level 1, 2 and 3 based upon Tukey-Kramer post-hoc analysis.
We have defined a methodology for analyzing fundus AF using eyebank eyes that allows quantification in tissue graded according to the MGS. At MGS level 4, tAF decreases the macula, potentially due to RPE dysfunction. This model of AF (MGS-AF) in conjunction with the MGS will serve as a useful tool in future studies of AMD.
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