Optics: Subjective Snd Objective Refraction

Question 1

What are devices that control the focus of the retinal image for the purpose of measuring the power of the eye?

Answer 1

Optometers

Question 2

A simple optometer consists of a _________ target and a fixed ___________ lens.

Answer 2

Movable target

Fixed positive power lens

Question 3

What is an advantage of a simple optometer?

Answer 3

Allows both positive and negative vergence

Question 4

What is a disadvantage of a simple optometer?

Answer 4

Image size will vary as target moves

Question 5

How did the Badal optometer overcome the challenges of the simple optometer?

Answer 5

Movable Auxiliary Lens

Question 6

In the Badal Optometer, an Auxiliary lens is placed in between the _________ and the ________ lens.

Answer 6

Target and the badal lens

Question 7

Badal Optometer: Auxiliary lens is a ________ lens.

Answer 7

Minus

Question 8

Badal Optometer: Badal lens is a __________ lens.

Answer 8

Plus

Question 9

What remains independent of the target distance with a Badal Optometer?

Answer 9

Target vergence and angular size

Question 10

With Badal Optometer, power is ________ related to the actual target distance.

Answer 10

Linearly

Question 11

With Badal Optometer, the angular size of the target remains __________.

Answer 11

Unchanged

Question 12

With Badal Optometer, the irradiance of the source at the eyes is ___________ for any distance of the Target.

Answer 12

Constant

Question 13

With Badal Optometer, the apparent position of the eye will be at the ___________ for all position of the target.

Answer 13

Optical infinity

Question 14

What is a badal optical system?

Answer 14

A system in which an object can be moved toward or away from the eye without changing the retinal image’s angular subtense

Question 15

With a badal optical system, the size of the image is __________ regardless of its optical distance.

Answer 15

Constant

Question 16

Consider a Badal Optometer with a +5D Badal Lens and a -6D auxiliary lens. What are the ocular Vergence and angular magnification at the eye for d= 0 m?

Answer 16

Q= -0.83D, M = 0.833x

Question 17

Consider a Badal Optometer with a +5D Badal Lens and a -6D auxiliary lens. What are the ocular Vergence and angular magnification at the eye for d= 0.2m?

Answer 17

Q= 4.17D, M = 0.833x

Question 18

What is the Badal Optometer Ocular vergence formula?

Answer 18

Ocular Vergence, Q = [-F - F2(1- d*F a)/ Fa]

Question 19

What is the Badal Optometer Magnification formula?

Answer 19

Magnification, M = (-F/ Fa)

Question 20

What optometer uses a laser light reflected from a surface or transmitted through a diffuser?

Answer 20

Laser speckle Optometer

Question 21

The apparent velocity of the speckles in the pattern is determined by the distance between the _________ and the ______________.

Answer 21

Plane of stationarity and the plane of focus

Question 22

In a myopic eye, the speckle pattern appears to move in what direction?

Answer 22

Same direction as the moving screen

Question 23

In a Hyperopic eye, the speckle pattern appears to move in what direction?

Answer 23

Opposite direction of motion is observed

Question 24

If the point source is adjusted Axially until it is conjugate with the retinal plane, how will the speckle appear?

Answer 24

That it is not moving and appears to boil

Question 25

What is the resting place of accommodation?

Answer 25

The distance at which the eyes focus when there is nothing to focus on

Question 26

What is the eyes default accommodation distance?

Answer 26

Resting place of accommodation

Question 27

When using a chromatic optometer, an emmetrope sees a ________ disc.

Answer 27

Purple disc ## Footnote Because the red and blue images are approximately equal in size

Question 28

When using a chromatic optometer, a myope sees a ________ disc.

Answer 28

Red central spot surrounded by a blue annulus

Question 29

When using a chromatic optometer, a hyperope sees a ________ disc.

Answer 29

Blue central spot surrounded by a red annulus

Question 30

What gives the refractive correction when using a chromatic optometer?

Answer 30

Strongest positive or weakest negative lens that reduces fringes to a single purple disc

Question 31

What does the Duochrome test use in the determination of the near end of the refraction?

Answer 31

Chromatic aberration

Question 32

In the Duochrome test, refraction is adjusted until what occurs?

Answer 32

The letters on the two colored backgrounds appear equally clear

Question 33

Nagel optometer uses a _______ lens whose posterior focal point is coincident with ______________.

Answer 33

Plus lens ## Footnote The nodal point of the eye

Question 34

What does stigmatoscopy optometer measure?

Answer 34

Accommodative response to the VA stimulus