Ophthalmic Optics Flashcards

A patient's prescription reads +2.50 -1.25 x 090. What type of lens is indicated?

Answer: Compound hyperopic astigmatic lens

A plus sphere combined with a minus cylinder indicates a compound hyperopic astigmatic correction.

Which term describes the bending of light as it passes from one medium to another of different density?

Answer: Refraction

Refraction is the change in direction of light as it crosses the boundary between two media with different indices of refraction.

What is the vertex distance, and why does it matter in ophthalmic prescriptions?

Answer: The distance from the back of the lens to the cornea; affects effective power

Vertex distance is the distance from the back surface of a lens to the corneal apex, and it affects the effective power delivered to the eye, especially in high prescriptions.

A lens with a shorter focal length has which property?

Answer: Higher power

Lens power in diopters equals 1 divided by the focal length in meters, so a shorter focal length means greater power.

Which type of prism is incorporated into spectacle lenses to treat binocular vision disorders?

Answer: Base-in or base-out prism

Base-in or base-out prism is prescribed to help patients with convergence or divergence problems align their eyes properly.

What does the term 'index of refraction' measure in ophthalmic lens materials?

Answer: How much the material bends light relative to air

The index of refraction is the ratio of the speed of light in air to its speed in the lens material, indicating how much the material bends light.

When a patient's optical center is decentered from their pupil center, what optical effect occurs?

Answer: Unwanted prismatic effect

According to Prentice's rule, decentering a lens produces an unwanted prismatic effect proportional to the lens power and the amount of decentration.