Purpose:
To determine if foveal swelling in patients with foveal sparing secondary to geographic atrophy exists and to determine the contribution of different foveal layers to this phenomenon as seen with Spectral Domain Optical Coherence Tomography (SD OCT).
Methods:
Two retinal specialists (FT and JM) independently classified the SD OCT images, to obtain patients with presumed foveal swelling. High resolution SD OCT horizontal and oblique B-scans, centered at the umbo were acquired. Of an initial sample of 108 patients with GA, 13 eyes of 10 patients complied with the inclusion criteria, in order to study those eyes in which apparent swelling would not be questionable. A matched control group was used to compare the outcome measures.
Results:
The thickness at the foveal center was similar between patients with apparent foveal swelling (cases) and controls without AMD (226 µm vs 227 µm, p = 0.56), but the apparent ONL was thicker in cases than in controls (125 µm vs 114 µm, p = 0.02). However, when HFL was excluded from the measurements, the results no longer differed (74 µm vs 73 µm, p = 0.82). The retina in the parafoveal area (within atrophy) was thinner in these patients with foveal sparing than in controls (244 µm vs 340 µm, p<0.0001), whereas the peripheral (healthy) retina at 3500 µm was similar between groups (244 µm vs 245 µm, p = 0.92). The thickness from the ELM to the outer border of RPE/BM (sub-ONL) was thinner in cases than controls (83 µm vs 106 µm, p=0.0004).
Conclusions:
Neither foveal nor ONL swelling were found in our study. HFL thickening was observed in foveal sparing secondary to GA and might be related either to photoreceptors axons or Müller cells swelling. Thinning of the retina below the ELM was also observed. The clinical implications of these findings should be addressed by longitudinal studies and may require specific therapeutic approaches.
Keywords: age-related macular degeneration • imaging/image analysis: clinical