What is the difference between alignment and decentration in soft lens wear?

What is the difference between alignment and decentration in soft lens wear?

• A. Alignment means the lens tilts when blink occurs.
• B. Alignment is proper centering; decentration is off-center placement, which can affect vision and edge comfort.
• C. Alignment refers to the tint of the lens.
• D. Alignment is only for rigid gas permeable lenses.

Answer: (B)

Alignment and decentration describe where a soft contact lens sits on the eye. Alignment means the lens is centered over the cornea so the optical zone lines up with the pupil, giving sharp vision and comfortable wear because the lens moves evenly with the eye. Decentration means the lens is off-center, so part of the edge sits closer to the eyelid or sclera. This off-center position can blur or distort vision and cause glare or halos, and it often leads to edge-related discomfort as the lens interacts with the eyelids and tear film. In many designs, especially multifocal or toric lenses, maintaining proper alignment is crucial for the intended optics, so decentration directly affects both vision quality and comfort.