In myopes, when correcting with contact lenses, the induced prism tends to be in which direction?

In myopes, when correcting with contact lenses, the induced prism tends to be in which direction?

• A. BO prism
• B. BI prism
• C. No prism
• D. BU prism

Answer: (B)

When contact lenses sit on the eye, any prismatic effect comes mainly from decentration of the lens relative to the pupil. In typical myopes, the lens tends to sit a bit temporally (toward the temple). For a minus-power lens, this temporal decentration shifts the optical center in relation to the pupil in a way that produces a prism with base toward the nose. In other words, the induced prism is base-in. This contrasts with spectacles, where other factors like vertex distance can lead to different prism tendencies.

When contact lenses sit on the eye, any prismatic effect comes mainly from decentration of the lens relative to the pupil. In typical myopes, the lens tends to sit a bit temporally (toward the temple). For a minus-power lens, this temporal decentration shifts the optical center in relation to the pupil in a way that produces a prism with base toward the nose. In other words, the induced prism is base-in. This contrasts with spectacles, where other factors like vertex distance can lead to different prism tendencies.