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Julie Jacob, Valérie Krivosic, Michel Paques, Ramin Tadayoni, Alain Gaudric; Cone density loss on adaptive optics in early macular telangiectasia type 2. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):90.
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© ARVO (1962-2015); The Authors (2016-present)
To study whether cone photoreceptors are early impaired in the progression of Macular telangiectasia type 2 (MacTel 2) disease. MacTel2 is a macular neurodegenerative disease characterized by progressive loss of Müller cells, intraretinal capillary proliferation and ultimately loss of central photoreceptors. Early dysfunction or loss of cone photoreceptors in the course of MacTel2 is debated. We studied cone density, using flood illumination adaptive optics (AO) in early-stage MacTel2.
Design: Eight patients with early signs of MacTel2 and 8 healthy volunteers underwent multimodal retinal imaging including infrared reflectance scanning laser ophthalmoscopy, OCT, fluorescein angiography and flood-illumination AO (rtx 1, Imagine Eyes, France). Cone mosaic was studied in 5 sampling windows ranging from 2° to 7° from the foveal center.<br /> Main Outcome Measure: Structural appearance of cones; cone density, spacing and hexagonal arrangement.
Cone density values in the 10 MacTel2 eyes were inferior to normal at all eccentricities from 2° to 7° (p<0.0001). Mean cone spacing values were larger than normal at all eccentricities (p<0.0001) and mean percentage of hexagonally organized cone photoreceptors was lower at all eccentricities from 2° to 7° (p<0.0001). This difference was more pronounced on the temporal side of the fovea (p<0.0001) but also significant in nasal and was not limited to the area of capillary anomalies. AO images in MacTel2 patients showed an irregular patchy disturbance of the cone mosaic corresponding to some fragmentation of the Cone Outer Segment Tips (COST) line (or Interdigitation zone) on OCT. The Inner/outer segment (IS/OS) line (or ellipsoid zone) remained intact.
Adaptive optics showed that in early MacTel2 the cone mosaic is altered in the macular area. The cone density was inferior to normal even outside the telangiectasia, although the IS/OS line remained intact on OCT. However OCT showed fragmentation of the COST line, which correlated with decreased cone density. These findings do not indicate that the loss of cone density is causative of the disease but that it might be secondary to Müller's cell and rod loss in this area. However cone density assessment could become a useful parameter to follow the progression of the disease.
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