Do minus lenses become stronger or weaker as they approach the cornea?

Study for the NBEO Physiological Optics Test. Prepare with flashcards and multiple-choice questions, each question has hints and explanations. Ace your exam!

Multiple Choice

Do minus lenses become stronger or weaker as they approach the cornea?

Explanation:
Vertex distance changes the effective power of a lens. For minus lenses, moving the lens closer to the eye makes the corrective power stronger (more negative). When the lens sits right on the eye (zero vertex distance, like with contact lenses), you get the full minus power. As you move the lens away from the eye, the effective minus power becomes weaker. So minus lenses become stronger as they approach the cornea.

Vertex distance changes the effective power of a lens. For minus lenses, moving the lens closer to the eye makes the corrective power stronger (more negative). When the lens sits right on the eye (zero vertex distance, like with contact lenses), you get the full minus power. As you move the lens away from the eye, the effective minus power becomes weaker. So minus lenses become stronger as they approach the cornea.

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