Fundus Autofluorescence and Enhanced Depth Imaging Spectral-Domain Optical Coherence Tomography in Hunter Syndrome-New Insights

Introduction: Hunter syndrome or mucopolysaccharidosis type II is a rare progressive multi-systemic disorder, caused by an abnormal storage of glycosaminoglycans (GAGs) in almost every cell type, including most ocular tissues [1,2]. Patients have a short life expectancy and ocular manifestations can be present early in the course of disease [1,2]. Purpose: To report the fundus autofluorescence and tomographic ocular findings in Hunter syndrome. Methods: A 18-year-old male patient with Hunter syndrome with progressive nyctalopia was submitted to color fundus photography, blue fundus autofluorescence (FAF), fluorescein angiography (FA) and spectral domain optical coherence tomography with enhanced-depth imaging (EDI-SD OCT). Results and discussion: Fundus examination and wide-field fluorescein angiogram revealed normal optic discs and bilateral pigmentary atrophic changes at the mid periphery with macular sparing. SD OCT revealed a retinal thinning due to external retinal atrophy affecting the photoreceptor layer beyond the parafoveal area. Although a prominent central external limiting membrane (ELM) was present, both the ellipsoid zone band and ELM could not be tracked beyond the central 2-mm and 2. 5 mm diameter ring, respectively. EDI-SD OCT revealed a highly irregular choroid, especially in its outer boundary, probably due to GAG scleral deposition. Blue FAF presented a symmetric hyperautofluorescent parafoveal ring that corresponded to the area where the ELM was present in the absence of the ellipsoid band. A mottled hyper/hypofluorescent pattern was present at the mid-peripheral retina. Scarce hyperautofluorescent dots were found in the left optic disc resulting from disc drusen which could result from axoplasmic flow disturbances due to GAGs scleral deposition. Conclusions: To our knowledge this is the first report of fundus auto-fluorescence imaging in Hunter syndrome. We also report, for the first time, optic disc drusen in this disease. New imaging techniques can provide new insights for the understanding of this disease, and could potentially provide valuable biomarkers for treatment guidance.