Which type of lens requires proper placement of the corridor?

Progressive addition lenses (PALs) are designed with a smooth transition from distance vision at the top of the lens to reading vision at the bottom, incorporating multiple prescription powers without visible line separation. The corridor, which is the area that provides clear vision for intermediate tasks, must be optimally positioned for effective use. Proper placement ensures that the wearer can view objects at various distances comfortably, reducing distortion and enhancing visual comfort.

In contrast, trifocal lenses have distinct sections for distance, intermediate, and near vision, with specific demarcation lines indicating these zones. Blended bifocal lenses use a gradual transition between the two areas but do not require the same level of precise corridor placement as progressive lenses. Iseikonic lenses are tailored for binocular vision correction but don’t involve corridors in the same capacity as PALs. Thus, proper placement of the corridor is critical for the effectiveness and comfort of progressive addition lenses.