Chapter 5

Question 1

What is the correct transposition of +1.00 +3.00 x 90 to its negative cylinder form?

Answer 1

+4.00 -3.00 x 90.
You add the cylinder to the sphere, flip the sign of the cylinder, and then add or subtract 90 from the axis

Question 2

What eye has the focal point of light rays meet before the retina?

Answer 2

Myopic.
In most cases, it is caused by the eye being to long and needs to be corrected by divergent lenses

Question 3

What type of lens and property are necessary for increasing the distance of the focal point?

Answer 3

Concave and divergent.
Concave, or negative lenses, cause the light rays to diverge

Question 4

What is the change in lens power between upper and lower of a bifocal called?

Answer 4

Add power.
This provides target vision for patients with presbyopia

Question 5

What is the best technique for determining the total refractive power requirement for the eye?

Answer 5

Perform retinoscopy after administering cycloplegic eye drops, which block accommodation.
Objective refractometry uses a handheld retinoscope to approximate that refractive error of a patient

Question 6

What does a toric Cornea consist of?

Answer 6

Astigmatism.
In a toric cornea the curvature is not uniform, the curvatures are greater in one Meridian than the other like a football. The result is is different levels of myopia or hyperopia in different optical planes

Question 7

What does a lens contain if the lensometer mires can’t be centered?

Answer 7

Prism.
Depending on the refractive power and orientation of a prism, it can shift the stuff the optical center of the lens

Question 8

Distance of -2.00 with +3.00 add, what is the power of the reading portion?

Answer 8

+1.00D.
Distance + Add = Near

Question 9

What type of substance permits the passage of light without significant disruption?

Answer 9

Transparent.
Opaque completely blocks out light and translucent significantly interferes with the passage of light, so behavior of light through transparent objects is most relevant for refractive errors

Question 10

What type of lens Best corrects hyperopia with astigmatism?

Answer 10

Spherocylindrical.
Toric lenses are cut from an object shaped like a football and have different curvatures varying between a meridian of maximum curvature to a meridian 90 degrees away of minimum curvature

Question 11

What is the first step to performing manual lensometry or keratometry?

Answer 11

Focus the eyepiece.
The steps are 1) focus the eyepiece 2) position the eyeglass piece to be measured in the frame-support table 3) measure the sphere power and cylinder power and axis 4) marking the optical center (optional)

Question 12

What is the power in diopters of a convex lens with a focal length of 0.5m?

Answer 12

2.00D
D = 1/f. D = 1/0.5 = 2.00