Letter charts are not only used to measure visual acuity, they are also used as targets for subjective refraction. This is the main reason distance acuity is measured more often than near acuity. At a long distance, accommodation is relaxed, so that the refraction can be more accurate.
Popliteal artery. The popliteal artery branches off from the femoral artery. It is located in the knee and the back of the leg. Its courses near the adductor canal and the adductor hiatus, distinctive open areas inside the thigh. At its far end, it splits into the anterior and posterior tibial arteries. During its course, the popliteal artery branches into other significant blood vessels.
The popliteal fossa also has a floor and a roof. The floor of the popliteal fossa is formed by the posterior surface of the knee joint capsule, and by the posterior surface of the femur. The roof is made of up two layers; popliteal fascia and skin. The popliteal fascia is continuous with the fascia lata of the leg.