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Flashcards in Optics Deck (19)
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1

What does an ideal "wave plate" do? What does it NOT do?

Wave plates do NOT reflect or absorb light. The transmittance should be 100%.
Wave plates change the PHASE SHIFT of light

2

What happens to the retinoscopy light reflex as it approaches neutrality?

Becomes BROADER, faster, and brighter.

3

What is Mohindra Retinoscopy?

Retinoscopy done on a child that you cannot dilate. Occlude one eye and ret the other. Use a working distance of -1.25.

4

What is the power of a plane mirror?

PLANE mirrors have NO POWER

5

How tall is a 20/20 Snellen optotype at 20 feet?
How tall is a 1M optotype at 1 M?

Snellen = 8.73 mm
1M = 1.45 mm

6

For every 1mm increase in axial length there is a ____ increase in myopia

1mm increase in axial length = -3.00D of myopia

7

Define entrance pupil

The IMAGE of the aperture stop by the PRECEDING lenses

8

According to ANSI standards, what can patients tolerate in sphere? Cyl axis?

Sphere: Below 6.50 D -> ± 0.13D
Above 6.50 D -> 2% of D
Cyl: Above 1.50 D -> ± 2°

9

What three improvements do aspheric lenses make?

Reduce spherical aberration
Improve cosmesis
Decrease weight

10

Point-focal lenses correct _______
Percival lenses correct ______

Point-focal lenses correct RESIDUAL ASTIGMATISM
Percival lenses correct CURVATURE OF FIELD

11

What are the only two parameters you need to solve image jump problems?

1. Add power
2. Segment height

12

What spectacle parameters will increase spectacle mag?

Increasing base curve
Increasing center thickness
Increasing vertex distance

13

What is the relationship between Dk and water in traditional soft lenses? Silicone Hydrogels?

Traditional - High water content -> High Dk
Silicone Hydrogel - Higher water content -> Low Dk

14

What percent of the population is an emmetrope / low hyperope?

70%

15

What type of astigmatism is associated with the development of myopia?

ATR

16

What property of light does not change when traveling from one medium to another? What properties do change?

Frequency does NOT change
Wavelength and Speed DO change

17

What is the difference between Gross and Net Retinoscopy?

Gross - Through the ret rack
Net - Calculated with working distance

18

Convex mirrors typically have a negative or positive power?

Negative

19

A real object to the left of the first focal point of a plus lens creates what type of image?

real, inverted, magnified