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NBEO Part 1 > Optics > Flashcards

Optics Flashcards

1
Q

What type of image does a negative lens produce when a real object is presented?

A

A virtual, upright, and smaller image

This holds true regardless of whether the object is placed in front of or behind the first focal point.

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2
Q

What is the function of field-expanding lenses, such as Fresnel lenses?

A

To enhance the field of view in applications like rear windows of vans or RVs

Fresnel lenses are designed to reduce the amount of material required while maintaining optical performance.

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3
Q

What type of image is produced when a real object is placed between the first focal point and a plus lens?

A

A virtual, upright, enlarged image

This principle is the basis for single lens magnifiers.

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4
Q

What type of image does a plus lens produce when a real object is placed to the left of the first focal point?

A

A real, inverted image

This principle is foundational for imaging systems such as the eye, camera, and projector.

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5
Q

Fill in the blank: A real object presented to a _______ lens will always produce a virtual, upright, and smaller image.

A

negative

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6
Q

Fill in the blank: The basis for single lens magnifiers is when a real object is placed between the first focal point and a _______ lens.

A

plus

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7
Q

True or False: A plus lens will always produce an upright image regardless of the object’s position.

A

False

A plus lens can produce both real and virtual images depending on the object’s position relative to the focal point.

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8
Q

What is the wavelength range of UV-A light?

A

315-380 nm

UV-A is the longest of the three types of UV light.

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9
Q

How does UV-A radiation compare to other types of UV light in terms of damage?

A

Considered the least damaging

UV-A penetrates deeper into the skin.

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10
Q

Which type of UV light is more abundant at the Earth’s surface?

A

UV-A radiation

UV-A is much more abundant than UV-B and UV-C.

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11
Q

What is the wavelength range of UV-B light?

A

280-315 nm

Overexposure to UV-B can lead to sunburn.

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12
Q

What health issues are associated with UV-B exposure?

A

Sunburn, skin cancer, cataract formation

UV-B has a higher correlation with these issues than UV-A.

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13
Q

What is the wavelength range of UV-C light?

A

100-280 nm

UV-C has a shorter wavelength and is high-energy.

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14
Q

What condition can prolonged exposure to UV-C lead to?

A

Solar keratitis

The majority of UV-C light is absorbed by the ozone layer.

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15
Q

Which part of the eye absorbs the majority of UV-C light?

A

The cornea

The cornea protects the eye from UV-C exposure.

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16
Q

What absorbs the majority of UV-A and UV-B light in the eye?

A

The crystalline lens

This protects the retina from potential UV damage.

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17
Q

What can occur over time to the lens of the eye as a result of UV exposure?

A

Formation of a cataract

The lens may become impaired over time.

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18
Q

How much light is needed in order to trigger a single molecule of rhodopsin?

A

1 quanta of light (smallest amount of light possible)

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19
Q

As the power of a condensing lens increases what happens to the FOV, magnification and working distance?

A

Increase in power = increase FOV, decrease in mag and decrease in working distance

Ex: 90 D vs 78 D lens

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20
Q

Which astigmatic dial is fixed?

A

Clock dial
* Target is not mobile

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21
Q

What is the most common complication of RGPs?

A

3-9 staining (peripheral corneal desiccation)

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22
Q

What is the most common complication associated with rigid gas permeable contact lens wear?

A

Peripheral corneal desiccation, also known as 3-9 staining

23
Q

What symptoms do patients typically report with peripheral corneal desiccation?

A

Mild symptoms of interpalpebral redness and slight irritation

24
Q

What does a slit lamp examination reveal in cases of peripheral corneal desiccation?

A

Superficial punctate staining that can vary from small to larger coalescing areas of SPK, with deep fluorescein staining

25
Q

What is dellen formation associated with in contact lens wear?

A

Deep fluorescein staining

26
Q

What causes the signs of peripheral corneal desiccation?

A

Excessive edge lift of the contact lenses leading to tear film disruption

27
Q

How can the signs and symptoms of peripheral corneal desiccation be minimized?

A

Adjustments to the fit of the contact lenses to decrease edge lift and increase lid apposition

28
Q

What adjustments can be made to achieve better fit and minimize symptoms?

A

Steepening the base curve and/or steepening the peripheral curves of the contact lens

29
Q

What additional modifications can help minimize peripheral corneal desiccation?

A

Thinning the contact lens edge and lenticulating higher minus lenses

30
Q

Is changing the material of the lens beneficial in reducing corneal signs related to 3-9 staining?

A

No, studies have shown it has no benefit

31
Q

True or False: 3-9 staining is purely fit related.

A

True

32
Q

How to calculate JND?

A

Divide denominator by 100

Ex: 20/400
400/100 =4

With trial frame show +2.00 and -2.00 lenses

33
Q

What is the ANSI standard tolerance for cylinder axis of prescriptions with a cylinder power of 1.75 diopters or greater?

A

2 degrees in any direction

This tolerance applies to prevent significant visual distortion.

34
Q

What was the ordered cylinder axis in the prescription?

A

042

The cylinder axis indicates the orientation of the lens correction.

35
Q

What was the verified cylinder axis in the prescription?

A

045

This discrepancy exceeds the ANSI tolerance for cylinder axis.

36
Q

Does the cylinder axis difference of 3 degrees meet ANSI standards?

A

No

The difference exceeds the permissible tolerance of 2 degrees.

37
Q

What is the meridian of the highest absolute power in the prescription?

A

axis 135

This axis indicates where the lens power is strongest.

38
Q

What is the power at the meridian of highest absolute power?

A

-15.50 D

This value represents the maximum lens correction needed.

39
Q

What was the sphere power sent from the lab?

A

-15.25 D

This is the measured power compared against the prescribed power.

40
Q

What is the difference between the prescribed power and the lab’s power?

A

0.25

This difference is crucial for determining compliance with ANSI standards.

41
Q

What is the ANSI tolerance for sphere powers above 6.50 D?

A

+/- 2% of the power

This tolerance helps ensure adequate visual correction.

42
Q

Does the difference of 0.25 meet the ANSI standards for sphere powers?

A

Yes

0.31 is allowed (2% of 15.50 D), and 0.25 is within this limit.

43
Q

What is the ANSI standard for error tolerance in cylinder power for cylinder powers of 2.25 to 4.50 D?

A

+/- 0.15 D

This tolerance ensures that the cylinder power is accurate for effective vision correction.

44
Q

Did the above prescription meet ANSI standards for cylinder power?

A

Yes

There was no difference between what was ordered and what was measured.

45
Q

What is the equivalent logMAR acuity of 20/60?

A

0.48

explanation: take reciprocal of decimal acuity
20/60 =0.333

Now take the log of the reciprocal
Log(1/0.333)=0.478

46
Q
A

Make sure you know how to calculate!!

47
Q

What is the process called when lenses are inserted into frames without using heat?

A

Cold snapping

This method is used for certain frame materials that do not require heat.

48
Q

What is a major variant in the lens insertion process for plastic frames?

A

Whether or not heat is used

The amount of heat can also vary depending on the material.

49
Q

What material requires high amounts of heat to insert lenses?

A

Optyl

Optyl can bend under its own weight when heated properly.

50
Q

At what temperature can Optyl material be safely heated?

A

100-130 degrees Celsius

Heating beyond this range may damage the material.

51
Q

Which materials utilize only minimal amounts of heat if lenses cannot be cold snapped?

A
  • Cellulose acetate
  • Cellulose proprionate
  • Carbon fiber

These materials may allow for some heat but not extensive heating.

52
Q

What should not be done to polycarbonate and polyamide materials during lens insertion?

A

They should not be heated at all

Heating these materials can lead to warpage.

53
Q

What is required for edged lenses when using polycarbonate and polyamide materials?

A

They must be fabricated exactly to size

This is crucial to avoid issues during lens insertion.

54
Q

True or False: All plastic frame materials require heat for lens insertion.

A

False

Some materials can use cold snapping, while others require heat.

NBEO Part 1 (15 decks)

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