PURPOSE. To determine whether longitudinal changes in mesopic visual function on microperimetry occurred independent of its associations with microstructural parameters on spectral-domain optical coherence tomography (SD-OCT) in the early stages of AMD. METHODS. Forty-one AMD eyes underwent microperimetry testing and SD-OCT scans over a 12-month period at 6-month intervals. Microstructural parameters analyzed include the retinal pigment epithelium-drusen complex (RPEDC) layer thickness, number

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... f hyperreflective foci (HF) and their inner retinal migration (represented by a weighted axial distribution score; AxD), and the number of atrophic areas. RESULTS. Microperimetric sensitivity was 0.29 dB (95% confidence interval [CI] ¼ À0.38 to À0.20 dB, P < 0.001) and 0.13 dB (95% CI ¼ À0.22 to À0.03 dB, P ¼ 0.008) lower in each sector for every 10-lm higher RPEDC layer thickness and 1-HF present, but was not associated with the AxD score or the number of atrophic areas present (P 0.464). However, each 10lm greater RPEDC layer thickness and 1-HF present was not independently associated with a further decline in sensitivity (À0.08 dB/year, 95% CI ¼ À0.24 to 0.07 dB/year, P ¼ 0.288 and 0.09 dB/year, 95% CI ¼ À0.06 to 0.24 dB/year, P ¼ 0.242, respectively) over time when accounting for the association between RPEDC layer thickness and number of HF with microperimetric sensitivity. CONCLUSIONS. Longitudinal changes in mesopic visual function measured on microperimetry paralleled changes in the microstructural changes over a 12-month time frame, without any changes occurring independent of the associations between structure and function alone.