A: Farsightedness is diagnosed during a comprehensive eye exam, particularly while testing refraction. A series of lenses are placed in front of the eyes, using a   phoropter. The optometrist uses a retinoscope, a handheld lighted instrument, to measure how the light focuses in your eye through each lens. The lens power is then refined based on your input regarding the clearest lens. This testing will allow the optometrist to determine your degree of refractive error. Thorough testing is important as farsightedness can be overlooked during a sight test or autorefraction.