Refraction and Best Corrected Visual Acuity (BCVA) using Early Treatment of Diabetic Retinopathy Study Methodology (ETDRS)

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Visual acuity is the most important tool used to assess your visual function. Refraction with ETDRS BCVA is used to determine your precise visual acuity at study visits. To do this, you will sit in a specific chair wearing trial frames over your eyes (these frames look like glasses). You will look through the frames and focus on an eye chart exactly 20 feet in the distance. We will insert different lenses of different strengths into the frames to assess your best possible visual acuity. We will ask you if the chart appears more or less clear when different lenses are in place. The test is performed one eye at a time.