the focal length of a lens measured in metres: a power of +5 dpt therefore has a reciprocal length of 1/5 metres or 20 centimetres. What is long-sightedness? In the case of long-sightedness, the eyeball is [...] Objects in our near vision appear blurred. This process usually becomes apparent between the ages of 40 and 65. You will then need a pair of glasses to be able to read at a normal distance of approximately [...] There is no standard answer to this question, as it differs for each vision task: a visual acuity of 0.1 is sufficient for a person to be able to orientate themselves outdoors. However, a visual acuity of