Instrumentation and Testing Procedures

Question 1

Keratometry measures the central ___ of the cornea

Answer 1

3 mm

Question 2

You can extend the range of a keratometer up to 61 D by placing a ___ the aperture closest to the patient. This extends up an additional ___.

Answer 2

1. +1.25 D
2. 9.00 D

Question 3

At what power do we need to compensate for vertex distance? For spectacles, when the power is over what and for contact lenses when the power is over what?

Answer 3

1. +/- 7.00
2. +/- 4.00

Question 4

Using the conversion factor, if the keratometry readings are 45.00D, the radius of curvature would be ___.

Answer 4

7.50 mm

Question 5

The slit lamp is also referred to as what?

Answer 5

Biomicroscope

Question 6

Which illumination uses the widest slit, longest aperture? The light source will be positioned at an angle of 40°-50°. It is used to view overall area, to observe the ocular adnexa, cornea, sclera, lids, conjunctiva, lens surface, and also lens fitting characteristics.

Answer 6

Diffused illumination

Question 7

What is probably the most useful and important illumination that you will use on the slit lamp?

Answer 7

Direct illumination

Question 8

Which slit lamp illumination is used to observe the layers of the cornea?

Answer 8

Direct illumination / optical section

Question 9

To create ___, the observer uses a focused parallelepiped placed out-of-clic directed at the limbus.

Answer 9

Sclerotic scatter

Question 10

Which filter is used to assess fluorescein staining?

Answer 10

Cobalt blue filter

Question 11

When an observer is using a slit lamp and is in focus, there should be ___ when the illumination system is moved from side to side. If the slit moves “with” ___ if the slit moves “against” ___

Answer 11

1. No displacement
2. Move out
3. Move in

Question 12

The ___ is used to verify power of the lens, optics evaluation, cylinder power and axis location as well as prism in a contact lens.

Answer 12

Lensometer, vertometer, lensmeter (focimeter)

Question 13

What can be used to measure the overall diameter of a contact lens?

Answer 13

V-channel

Question 14

What is the tolerance for the overall diameter of a GP contact lens?

Answer 14

+/- 0.05 mm

Question 15

If a contact lens power is read with the anterior surface facing the examiner and the posterior surface toward the reticule of the lensometer, the reading is called what?

Answer 15

Back vertex power

Question 16

The center thickness of a gas permeable contact lens is measured with a lens gauge. What is the tolerance?

Answer 16

+/-0.02 mm

Question 17

A toric lens power and axis may be verified with the use of a ___ and be verified by the use of ___.

Answer 17

1. Lensometer
2. Radiuscope

Question 18

You may verify the powers and parameters of a soft contact lens by what method below?

Answer 18

Reading the parameters on the vial or box, on the eye

Question 19

If a patient has a prescription of -4.00D and is fit with contact lenses, what consideration must be made?

Answer 19

The power fit will be less because the effective power would be greater as the contact lens is fit directly on the tear film.

Question 20

What would be the best contact lens power selection for a patient whose refractive vertex distance is 12mm and power is -4.00D?

Answer 20

-3.75D