DARK ADAPTATION, NIGHT VISION PROTECTION, AND CENTRAL NIGHT BLIND SPOT

Question 1

What is dark adaptation?

Answer 1

Dark adaptation is the process by which the eyes increase their sensitivity to low levels of illumination.

Question 2

Why is the starting level of dark adaptation important?

Answer 2

The lower the starting level the less time is required. Each person adapts in varying degrees and at different rates. Exposure to intense sunlight for 2-5 hours decreases visual sensitivity for up to 5 hours.

Question 3

What happens to the rods during dark adaptation?

Answer 3

Biochemical reaction causes a buildup of rhodopsin (visual purple) and when fully dark adapted the rods become 10,000 times more sensitive than at the start. Total light sensitivity can increase 100,000 times through a dilated pupil.

Question 4

How long does dark adaptation usually take?

Answer 4

30-45 minutes - depending on the individual.

Question 5

How long does it take to re-adapt after exposure to high intensity lighting?

Answer 5

Several to 45 minutes depending on the duration and brightness.

Question 6

What are the ways that you can protect your night vision?

ROSCEL

Answer 6

Red lens goggles and red lighting

Oxygen supply

Sunglasses

Cockpit lighting

Exterior lighting

Light flash compensation

Question 7

What benefit do red lens goggles and red lighting have on night vision?

Answer 7

If worn prior to flight, they can start you into your dark adaptation process. They can also preserve up to 90% of your dark adaptation.

Question 8

What benefit does pre-breathing oxygen / having oxygen available have yon your night vision?

Answer 8

You start to lose night vision at 4,000 feet PA because of lack of oxygen to the RODS. Lack of oxygen to the rods significantly reduces their sensitivity, increasing the time required for dark adaptation and decreasing their ability to see at night. RHODOPSIN IS OXYGEN DEPENDENT.

Question 9

What benefit does wearing sunglasses have on your night vision?

Answer 9

Sunglasses (ND-15 and higher) minimizes the negative effects of sunlight on rhodopsin production, which also maximizes rate of dark adaptation and improves night vision sensitivity and acuity.

Question 10

What can you do to cockpit lighting to help preserve your night vision?

Answer 10

Adjust to the lowest readable level that allows instruments, charts, and maps to be interpreted without prolonged staring or exposure.

Question 11

What can you do to the exterior lights to help preserve your night vision?

Answer 11

Dim or turn them off if possible / if the mission allows.

Question 12

What are some ways we can use light flash compensation?

Answer 12

• Close one eye
• Use short bursts for automatic weapons firing
• Alter course away from the light source

Question 13

Describe the night blind spot.

Answer 13

Occurs when the fovea becomes inactive under darkness or low level illumination - central vision becomes less effective and the night blind spot develops. The night blind spot covers 5-10 degrees of central vision. This is due to the fact that there are no rods on the fovea centralis (the center of vision).

Question 14

Because of the night blind spot - what will happen as object distance increases from the observer?

Answer 14

Larger and larger objects can/will be missed completely without a good scan.

Question 15

How do we compensate for the night blind spot?

Answer 15

Use off center viewing and proper scanning techniques.

Question 16

Describe the day blind spot.

Answer 16

The day (physiological) blind spot is present all the time (including at night). This blind spot results from the position of the optic disk on the retina. The optic disk has no light-sensitive receptors. The physiological blind spot covers an area of approximately 5.5-7.5 degrees and is located about 15 degrees from the fovea.

Question 17

What compensates for the Day blind spot?

Answer 17

Binocular vision - each eye compensates for the blind spot in the optic disk of the opposite eye.