NOCE NOCE Contact Lens Fitting and Care 2

Question 1

Which instrument is used to verify the base curve and power of a rigid gas-permeable (RGP) contact lens?

Accepted Answer

Radiuscope

Answer

A radiuscope (also called an ophthalmometer or lens clock for RGPs) is used to measure the radius of curvature of the back surface of rigid contact lenses.

Question 2

When fitting a soft contact lens, which observation indicates an excessively STEEP (tight) fit?

Accepted Answer

Reduced or absent lens movement with a push-up test

Answer

A steep or tight soft lens fit shows reduced movement on blink and poor mobility on the push-up test because the lens is gripping the cornea too tightly.

Question 3

Vertex distance compensation in contact lens prescribing is generally required when the spectacle prescription exceeds what power?

Accepted Answer

±4.00 D

Answer

Vertex distance correction is clinically significant for prescriptions of ±4.00 D or greater, as the difference in back vertex distance between spectacles and contact lenses changes the effective power.

Question 4

What does lag (or lens lag) describe in contact lens fitting assessment?

Accepted Answer

The movement of the lens in the opposite direction after an eye movement

Answer

Lens lag refers to the movement of a contact lens in the opposite direction to that of eye movement, used to assess lens fit by observing how the lens responds when the eye moves laterally.

Question 5

The push-up test during soft contact lens fitting is used to assess what parameter?

Accepted Answer

Lens movement and fit tightness (lens mobility)

Answer

The push-up test assesses lens mobility by using a finger to push the lower lid against the lens edge; a properly fitting lens should move smoothly and return to its original position.

NOCE - National Opticianry Competency Examination Practice Test

NOCE - National Opticianry Competency Examination Practice Test

NOCE NOCE Contact Lens Fitting and Care 2