Roca cape lighthouse in Portugal, West most point of Europe ( Cabo da Roca) Vertical. Roca cape lighthouse in Portugal, West most point of Europe ( Cabo da Roca) Vertical. The obelisk with a large white cross at Cabo da Roca. It is a cape which forms the westernmost extent of mainland Portugal and continental Europe.
[Read more about children's eye exams .]. 20/20 vision (or really, 20/20 visual acuity) is considered normal vision, meaning you can read at 20 feet a letter that most human beings should be able to read at 20 feet.
Eye Strain and Reading in Dim Light. When you walk into a room where light is low, your eye adjusts in several ways. First, the rod and cone cells on the retina begin to produce more light-sensitive chemicals. These chemicals detect light, convert it to an electrical signal and transmit that signal to the brain.o do this, the iris, as well as the muscles that control the shape of your lens, must contract to keep the focused image on the retina. If you read in low light, your visual muscles get mixed signals: Relax to collect the most light, but at the same time, contract to maintain the focused image.