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Simone Tzaridis, Kristina Heß, Tjebo Heeren, Clarissa Mai, Philipp Herrmann, Peter Charbel Issa, Frank G Holz; Dark adaptation in macular telangiectasia type 2. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1334.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate dark adaptation in patients with macular telangiectasia type 2 (MacTel) and its association with macular pigment optical density.
After a local photobleach (size of 4x4°, 83% bleach), dark adaptation (DA) was measured using a test stimulus (2 degree diameter) projected at 5 degree eccentricity horizontally from the foveal center, either within the temporal or nasal parafovea. Cone plateau, rod intercept time (RIT) and rod recovery rate (S2) were calculated from the resulting DA -curves. For structure-function analyses, findings were compared with local macular pigment optical density (MPOD)-levels, size of ellipsoid zone (EZ) loss (in en face OCT) and disease stages (according to Gass and Blodi).
74 eyes of 37 patients were compared with 36 eyes of 18 healthy controls. Dark adaptation was significantly impaired in patients with MacTel. While differences were most pronounced for parameters indicating rod-mediated recovery (mean RIT of 20.1 ± SD 8.8 min in patients and 6.3 ± SD 0.8 min in controls, p<0.0001, and mean S2 of 0.15 ±SD 0.02 log units/min in patients and 0.49 ± SD 0.04 log units/min in controls, p<0.001), cone-mediated recovery was also decreased, yet to a lesser extent (mean cone plateau of 2.23 ± SD 0.12 log units in patients and 2.71 ± SD 0.05 log units in controls; p<0.01).A comparison of DA curves and parameters of the nasal and the temporal parafovea in patients revealed a significantly elevated mean cone plateau (2.53 ±SD 0.08 log units nasal vs 2.13 ±SD 0.06 log units temporal, p<0.001) as well as a significantly increased mean RIT (14.3 ±SD 2.2 min nasal vs 21.9 ±SD 8.1 min temporal, p<0.01) in the temporal parafovea, while S2 was similar in both groups.Structure-function analyses revealed the strongest association of RIT and S2 with MPOD levels. The cone plateau showed distinct correlations to both the size of EZ-loss and MPOD levels, and a weaker correlation to the disease stage.
The results indicate a distinct impairment of dark adaptation in patients with MacTel. The strong association of rod-mediated recovery and MPOD may shed further light on the relevance and multiple functions of macular pigment and may thus contribute to the understanding of pathophysiological mechanisms of MacTel and other retinal diseases.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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