Session 12

Question 1

Characteristics of UVA? 2

Answer 1

315nm - 380nm,
Least harmful of the three

Question 2

Characteristics of UVB? 2

Answer 2

290nm - 315nm
Shorter wavelengths and higher energy than UVA.

Question 3

What can UVA cause? 1

Answer 3

Causes-
skin to tan

Question 4

What can UVB cause? 4

Answer 4

Causes -
sunburn
photokeratitis
cataracts
retinal lesions

Question 5

Characteristics of UVC? 2

Answer 5

200nm - 290nm
Higher in energy compared to UVA and UVB but is effectively filtered out by Earth’s ozone layer.

Question 6

What is a normal transmission for sun lenses?

Answer 6

Between 15% and 30%

Question 7

What happens if the lens transmits more than 30%?

Answer 7

May not help enough in full sunlight

Question 8

What happens if the lens transmits less than 15%?

Answer 8

May cause problems with reflected glare from the back surface.

Question 9

Any colour tint affects your visual acuity T/F
Can you wear sunglasses/Tint for Night Driving?

Answer 9

True
No- advise AR instead + Dry eye drops if AR still ‘does not’ work.

Question 10

What are the 4 categories of Sunglass Tints?

Answer 10

Cosmetic - more oriented for fashion or indoor lighting (headache tint etc) Grade1
General Purpose - Most common - Grade 1+2
Very dark special purpose - Intense light situations- Less than 15%ltf
Strongly coloured special purpose - filters certain spectral colors more heavily than others.

Question 11

What is an ideal tint? 5

Answer 11

-Reduces intensity of sunlight
- Eliminates parts of the optical spectrum that are hazardous + not required for vision.
-Provides enough protection so px dark adaption + night vision are preserved at night
-Maintains normal colour vision - so can distinguish traffic lights.
- Resist impact + scratching - minimum care.

Question 12

What does a color-defective individual lack?

Answer 12

Lack in one of the three different types of retinal cones.

Question 13

Does an AR coating added to a tint change the LTF of the tint?

Answer 13

Yes, it will transmit more light so it will be lighter

Question 14

Where is the tint darkest in a High Minus rx (sph)?

Answer 14

Darkest in the edges, lightest in the middle.

Question 15

Where is the tint darkest in a High Plus rx (sph)?

Answer 15

Darkest in the middle, lightest in the edges

Question 16

Where is the tint darkest in a plano/high minus rx (sphcyl) rx?

Answer 16

Lighter along the lowered powered meridian, darkest along the strongest powered meridian

Question 17

How does changing the tint help colour-defective?

Answer 17

The filter used selectively absorbs certain colors but not others. This changes the intensity of those colors, meaning the px can use light intensity cues to tell the colors apart.

Question 18

What are negative effects of using color defective tints? 2

Answer 18

Colors which were once distinguishable may now be confused when viewed through the filter.
Difference between the two eyes can cause moving objects to appear wrongly located as to how far away they are.

Question 19

What is a photochromatic lens?

Answer 19

A lens which changes color when exposed to UV

Question 20

Name 4 considerations with Photochromatic lenses?

Answer 20

-Plastic photochromatic wear out. Glass photochromatic do not lighten in their clear state.
-The time is takes to change colour depends on how long overall they have been worn outside.
-The more the lens is worn outside the quicker it wears out.
-Do not replace just one lens as they age differently.

Question 21

Which wavelengths are invisble to the human eye?

Answer 21

Ultraviolet (UV)
Infrared (IR)

Question 22

Between which nm does UV. Visible light and Infrared sit on the spectrum.

Answer 22

UV - 200nm-380nm
VL - 380nm-750nm
IR - 750 onwards

Question 23

What does ROY G BIV stand for?

Answer 23

Red
Orange
Yellow
Green
Blue
Indigo
Violet

Question 24

What is the longest and shortest visible wavelength?

Answer 24

Red - longest
Violet - shortest