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S. Schmitz-Valckenberg, M. Fleckenstein, H.-M. Helb, P. Charbal Issa, H. Scholl, F. G. Holz; In vivo Imaging of Structural Changes in Foveal Sparing in Advanced Atrophic AMD With Simultaneous cSLO and SD-OCT. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5390.
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The fovea in patients with geographic atrophy (GA) secondary to AMD may be spared until late in the course of the disease. Previously, we have characterized variations in fundus autofluorescence (FAF) associated with GA. In this study, we investigated morphological alterations of the fovea at various anatomical layers in presence of foveal sparing using high resolution in-vivo imaging.
Simultaneous spectral domain optical coherence tomography (SD-OCT, 870 nm, 40.000 A-scans/sec) and confocal scanning laser ophthalmoscopy (cSLO; FAF, redfree, and nearinfrared imaging mode) were performed in 11 GA patients (mean age 79 years, range 68-100) with foveal sparing using a combined instrument (Spectralis HRA+OCT, Heidelberg Engineering, Heidelberg, Germany). All patients had central fixation and visual acuity of 20/40 or better. Anatomical layers were evaluated, and retinal thickness in the central fovea and at the outer macula were measured and compared to age-matched controls.
Instead of the symmetric annulus of decreased intensities in normal subjects, FAF imaging showed an irregular reduced signal at the residual foveal island in all patients. SD-OCT scans revealed an overall increased retinal thickness with disappearance of the foveal pit. An increased, irregular and broad band of reflectivity at the retinal pigment epithelium and outer neurosensory retina was observed. Inner retinal layers appeared to be distorted with tipping over towards perifoveal atrophy where marked retinal thinning and absence of characteristic morphology of outer retinal layers were seen. The mean retinal thickness in the central fovea was 229 µm compared to 189 µm in normals (p = 0.003, Wilcoxon Signed Rank Test). No statistical difference of the thickness in the retinal areas peripheral to the GA was noted (251 versus 262 µm; p = 0.6).
Combined cSLO and OCT high-resolution imaging allowed for visualization of previously unknown and distinct structural foveal alterations despite well-preserved central visual function. Thickening in absence of leakage and cystoid spaces may reflect a preapoptotic stage of foveal neuronal cellular elements indicating incipient atrophy. Longitudinal observations correlating function and morphology will be helpful to better understand the dynamic process of developing foveal atrophy in patients with GA, as well as monitoring future interventions aiming at slowing GA enlargement.
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