Contact Lenses: NCLE Chapter 1

The first successful contact lenses, which were originally molded to conform to the shape of the cornea, were known as ________ lenses.

a. corneal

b. haptic

c. inter palpebral

d. gas permeable

b. haptic

The first successful contact lenses, which were originally molded to conform to the shape of the cornea, were known as haptic lenses.

Corneal contact lenses ______________________.

a. are a typical design of a soft lenses.

b. bridge the limbus and lie partially on the conjunctiva tissue overlying the sclera.

c. are used only as a last resort when other contact lens designs would fail.

d. are the most common design for rigid and gas permeable lenses.

d. are the most common design for rigid and gas permeable lenses.

Corneal contact lenses are the most common design for rigid and gas permeable lenses.

The majority of soft lenses fit today are ________________.

a. corneal lenses

b. semi - scleral

c. haptic lenses

d. hydrophobic `````````````````````````

b. semi scleral

The majority of soft lenses fit today are semi scleral.

A liquid coming in contact with a hydrophilic lens material with a relatively small wetting angle would be likely to _________________.

a. form beads on the surface

b. quickly evaporate

c. spread evenly over its surface

d. none of the above

c. spread evenly over its surface

A liquid coming in contact with a hydrophilic lens material with a relatively small wetting angle would be likely to spread evenly over its surface.

A contact lens with a diameter larger than that of the cornea is called a _______ lens.

a. corneal

b. generalized

c. hydrophobic

d. haptic

d. haptic

A contact lens with a diameter larger than that of the cornea is a called a haptic lens.

All of the following are symptoms of a loose fitting lens except:

a. lid sensation

b. constant awareness

c. burning

d. feeling the lens move

c. burning

Lid sensation, constant awareness and feeling the lens move are the only symptoms of a loose fitting lens except burning.

Of those curves listed, which indicates the flattest base curve?

a. 7.50 mm

b. 37.50 diopters

c. 8.60 mm

d. 49.00 diopters

b. 37.50 diopters

The flatest base curve would be 37.50 D out of a 7.50 mm, 37.50 D, 8.60 mm 49.00 D.

A contact lens was ordered with a base curve of 7.85 mm but was received back from the laboratory with a base curve measuring 7.800 mm. The base curve of the actual lens is _____________.

a. .25 D flatter than the lens ordered.

b. .25 D steeper than the lens ordered.

c. .50 D steeper than the lens ordered.

d. .50 D flatter than the lens ordered.

b. .25 D steeper than the lens ordered

A contact lens was ordered with a base curve of 7.85 mm but was received with a 7.80 mm reading the base curve of the actual lens is .25 D steeper.

It is noticed that a rigid contact lens containing a base curve of 7.42 mm is fitting quite loose. A tighter fit may be achieved by changing the base curve to __________________.

a. 7.46

b. 7.85

c. 8.04

d. none of the above

d. none of the above

A base curve of 7.42 mm lens is fitting quite loose. A tigther fit may be achieved by changing the base curve to anything less than 7.42 mm, 7.46 mm, 7.85 mm, 8.04 would all be looser fits.

A contact lens has a base curve of 7.50 mm. Its posterior peripheral curve would most likely be:

a. 7.45 mm

b. 42.50 D

c. 7.35 mm

d. 30.00 D

b. 42.50 D

A contact lens has a base curve of 7.50 mm, its posterior peripheral curve would most likely be 42.50 D.

The secondary curve of a rigid contact lens is generally:

a. steeper than the CPC

b. 1 to 2 diopters flatter than the CPC

c. 2 to 4 diopters flatter than the CPC

d. none of the above

c. 2 to 4 diopters flatter than the CPC

The secondary curve of a rigid contact lens is generally 2 to 4 diopters flatter than the CPC

The term "Haptic Lens" is used in reference to:

a. a prism-ballast lens

b. a truncated lens

c. a scleral lens

d. a spin-cast lens

c. a scleral lens

Scleral lenses are another term for "Haptic Lens"

The Central Posterior Curve (CPC) of a contact lens measures 7.5 mm radius of curvature. Its power in diopters is:

a. 41.00 D

b. 43.00 D

c. 45.00 D

d. 47.00 D

c. 45.00 D

The CPC of a 7.5mm radius lens would have a power of 45.00 D.

The fitting characteristics of a rigid gas permeable contact lens may be altered by ____________.

a. changing the radius of curvature of the CPC

b. increasing the diameter

c. Widening the Peripheral Posterior Curve (PPC)

d. all of the above

d. all of the above

The fitting characteristics of a rigid gas permeable contact lens may be altered by changing the radius of curvature of the central posterior curve, increasing the diameter, or widening the the peripheral posterior curve.

A soft contact lens demonstrates excessive movement. This may be remedied by _____________.

a. a larger diameter lens

b. a smaller diameter lens

c. a flatter lens

d. disinfecting the lens

a. a larger diameter lens

A soft contact lens demonstrates excessive movement. This may be remedied by a larger diameter lens.

The term "sagittal value" refers to ____________.

a. a poorly fitted lens

b. scleral show

c. the vaulting effect of a contact lens

d. nothing of significance

c. the vaulting effect of a contact lens

The term "sagittal value" refers to the vaulting effect of a contact lens.

When determining the best lens material to use, which of the following should be considered?

1. the patient's working conditions

2. pre-corneal tear film evaluation

3. full-time vs. part-time wear

a. 1 only

b. 1 and 3 only

c. 2 and 3 only

d. 1, 2, and 3

d 1, 2 and 3

When determining the best lens material to use the following should be considered: The patient's working conditions, pre-corneal tear film evaluation, full-time vs. part-time wear.

The gas permeability of a CAB lens is largely dependent upon _______________.

a. the diameter of the central posterior curve

b. the width of the posterior peripheral curve

c. the lens thickness

d. the overall diameter

c. the lens thickness

The gas permeability of a CAB lens is largely dependent upon the lens thickness.

A rigid gas permeable lens with a base curve of 7.50 mm is found to be fitting slightly tight. To improve the fit we might consider changing the base curve to which of the following?

a. 7.40

b. 7.45

c. 7.55

d. 7.65

c. 7.55

If A 7.50 mm base curve RGP lens is fitting slightly tight, to improve the fit we might consider changing the base curve to 7.55

If the Central Peripheral Curve of a rigid contact lens is held constant while the diameter is increased, it would result in ______________.

a. a tighter fit

b. a looser fit

c. less vaulting

d. increased gas permeability

a. a tighter fit

If the Central Peripheral Curve of a rigid contact lens is held constant while the diameter is increased, it would result in a tighter fit.

HEMA is abbreviation commonly used to describe ______________.

a. rigid lenses

b. gas permeable lenses

c. soft lenses

d. corneal abrasion

c. soft lenses

HEMA is abbreviation commonly used to describe soft lenses.

Which of the following is true about PMMA lenses?

a. spherical lenses can generally correct for up to 13.00 diopters of corneal astigmatism

b. they are difficult to fabricate

c. they are extremely soft

d. they have almost no gas permeability

d. they have almost no gas permeability

Which of the following is true about PMMA lenses they have almost no gas permeability.

Which of the following is true about soft contact lenses?

a. Spectacle blur is common

b. There is more flare and photophobia than with "conventional" rigid lenses

c. Rapid adaptation to soft lenses is a problem

d. Spherical lenses are less effective in covering large amounts of corneal astigmatism

d. Spherical Lenses are less effective in covering large amounts of corneal astigmatism

The following statement "Spherical Lenses are less effective in covering large amounts of corneal astigmatism.

The distance between a flat surface and the back surface of the central portion of a lens is the ______________.

a. chord diameter

b. sagittal depth

c. principal meridian

d. back surface power

b. sagittal depth

The distance between a flat surface and the back surface of the central portion of a lens is the sagittal depth.

A loose fitting contact lens can be made to fit together by ___________.

a. shortening the radius of curvature of the CPC

b. lengthening the radius of curvature of the CPC

c. decreasing the diameter

d. truncating the lens

a. shortening the radius of curvature of the CPC

A loose fitting contact lens can be made to fit together by shortening the radius of curvature of the Central Peripheral Curve.

The first all plastic corneal contact lens was developed by Kevin Tuohy in:

a) 1888

b) 1936

c) 1947

d) 1971

c. 1947

The first all plastic corneal contact lens was developed by kevin tuohy in 1947.

An example of a hydrophic lens material is:

a. silicone-acrylate

b. CAB

c. PMMA

d. HEMA

d. HEMA

An example of a hydrophoic lens material is HEMA

Bicurve rigid contact lenses are usually:

a. small and steep

b. fit within the interpalpebral fissure limits

c. made with narrow peripheral curves

d. all of the above

d. All of the above

Bicurve rigid contact lenses are usually small and steep, fit within the interpalpebral fissure limits and made with narrow peripheral curves.

When the radius of curvature is held constant while the diameter is increased, the vault of the lens will be:

a. unchanged

b. increased

c. decreased

d. truncated

b. increased

When the radius of curvature is held constant while the diameter is inreased, the vault of the lens will be increased.

If a patient is having difficulty handling their new soft, disposable contact lenses, what can a fitter do to make practice and learning easier?

a. Keep the patient in office until he or she can handle the lenses

b. give the patient a supply of finger costs

c. Change to a lower water contact lens for the initial training

d. Change to PMMA lenses on a permanent basis.

c. Change to a lower water content lens for initial training.

If a patient is having difficult handling their new soft, disposable contact lenses, a fitter can to make practice and learning easier change to a lower water content lens for initial training.

Silicone hydrogel lenses have been approved by the FDA for up to 30 days of wear. This is considered:

a.extended wear

b. disposable

c. daily wear

d. continuous wear

d. continuous wear

Silicone hydrogel lenses are considered by the FDA for up to 30 days of wear is considered continuous wear.

What types of allergic reactions are associated with the use of silicone hydrogel lenses?

a. red and itchy eyes

b. discomfort

c. dryness

d. all of the above

d. all of the above

Red and itchy eyes, discomfort, and dryness are allergic reactions associated with the use of silicone hydrogel lenses.

What will help to relieve a temporary dry feeling when wearing contact lenses?

a. frequent blinking

b. remove the lenses and soak them

c. use of physican-approved eyedrops

d. any of the above can be effective

d. any of the above can be effective

frequent blinking, remove the lenses and soak them, use of physician-approved eyedrops will help to relieve a temporary dry feeling when wearing contact lenses

Tear exchange in a gas permeable lens is critical to an eye receiving adequate oxygen. Which procedure will increase tear exchange in a GP lens?

a. Decrease the optic zone

b. Increase the chord diameter

c. Steepen the peripheral curves

d. Polish the lens

a. Decrease the optic zone

Decrease the optic zone will increase tear exchange in a GP lens.

Peripheral curves:

a. flatten a lens

b. steepen a lens

c. increase edge lift

d. trap tears behind the lens

a. flatten a lens

Peripheral curves flatten a lens