Chapter 12

Question 1

How should patients be instructed to care for their eyeglass lenses?

Answer 1

Clean lenses with mild Dish soap and dry with a 100% cotton cloth.
Unless using a specially designed lens cloth, lenses should be cleaned while wet as rubbing fibers over dry lenses may scratch them.

Question 2

Under what circumstances does a change in vertex distance result in the most noticeable change in effective power of the lens?

Answer 2

Refractive prescriptions greater than or equal to +/- 5.00 D. Vertex distance is the distance from the back of the lens to the front of the cornea, and small changes for high powered glasses can effect vision outcomes

Question 3

Opticians recommend fitting the top of a bifocal segment level with what anatomical landmark?

Answer 3

Lower eyelid margin.
The segment height is the distance between the lowest part of the rim and the top of the multifocal segment

Question 4

What should monocular patients be encouraged to do?

Answer 4

Use safety lenses full time even if they do not have a refractive error.
Monocular patients are more susceptible to losing vision in their other eye

Question 5

A Pt is struggling to use his D-segment trifocals glasses to see at arm’s length over his head, what lens configuration could help?

Answer 5

Double-D segment or occupational lenses.
They have a near-power D segment at the bottom, and an inverted intermediate-power D segment at the top

Question 6

What is an advantage of progressive addition lenses?

Answer 6

Lenses can be personalized for the patient’s frame and style. Newer designs can be customized for lens tilt and position of the lens and in highly curved sports frames

Question 7

What is the process for measuring monocular interpupillary distance?

Answer 7

Measure each pupil to the bridge of the nose separately and then add the results. Monocular measurements account for facial asymmetry while binocular measurements just calculate distance pupil to pupil

Question 8

A Pt’s pupillary distance is measured incorrectly, what might be a complaint of the patient?

Answer 8

Double vision due to prismatic effect. When PD does not correspond to the optical centers it can cause optical distortion or even diplopia