Full-thickness choroidal thinning as a feature of Fuchs Uveitis Syndrome: quantitative evaluation of the choroid by Enhanced Depth Imaging Optical Coherence Tomography in a cohort of consecutive patients

Purpose: To perform a quantitative analysis of choroidal thickness in patients with Fuchs Uveitis Syndrome (FUS) using enhanced depth imaging optical coherence tomography (EDI-OCT). Methods: All patients underwent comprehensive ophthalmic examination, including best-corrected visual acuity, slit-lamp biomicroscopy, applanation tonometry, axial length measurements with a swept-source biometer (IOLMaster 700, Carl Zeiss Medic AG, Jena, Germany) and macular 30° linear EDI- B-scan SD-OCT section (Spectralis HRAII+OCT, Heidelberg Engineering, Heidelberg, Germany) in both eyes. Analysis of choroidal thickness was performed at three different locations: subfoveally, 750 μm nasally, and 750 μm temporally to the fovea. Patients having received any surgery or intravitreal injections in the last 12 months and with axial length variance ≥ 1 mm between both eyes were excluded. Results: Sixteen eyes of eight consecutive patients with unilateral FUS were included. Segmented analysis of the choroid, separately considering Haller’s layer and Sattler’s–choriocapillaris layers, showed statistically significant lower values (p < 0.05) in affected eyes (FEs) compared to fellow eyes (NFEs). In NFEs, total choroidal thickness mean values ranged from 305.62 ± 92.96 μm to 347.50 ± 91.55 μm; in FEs those values were significantly lower (p < 0.05), ranging from 232.62 ± 89.33 μm to 255.62 ± 89.33 μm. Conclusion: Diffuse and full-thickness choroidal thinning in FEs was observed. Considering the absence of significant axial length differences between FEs and NFEs in our patient series, these data seem to suggest that the full-thickness choroidal thinning in FEs may be due to the inflammatory process. In that way, FUS might be regarded as an inflammatory condition involving the whole uveal tunic, even the posterior part of it, definitively supplanting the early definition of “heterochromic iridociclytis”.