BSL – Dark Adaptation, your eyes needs!

oooo

The dark adaptation timeline

• Now that we’ve covered some of the basics, let’s look at how this process plays out.
  o
  o

English Version>>

oooo
oooo
oooo
oooo

• After turning off any lights (including smartphones and tablets), your black pupils will quickly widen or enlarge.
  o
• This is called dilated.
  o
• They may dilate to a diameter of 7mm if you’re relatively young, but if you’re middle-aged or older they may only be 5mm.

BSL Version

oooo
oooo

oooo

• The Optic nerve (rods and cones) both become more sensitive during the first few minutes.
  o
• Portion of the retina that can be seen through both undilated & dilated pupils.
  o
• However, after 3-10 minutes, the cones reach their maximum sensitivity.
  o
• This is known as the rod-cone break because it’s the point where rods become more sensitive than cones.
  o
• The rods will continue to become more sensitive over the next few hours as they regenerate a receptor protein called rhodopsin.

BSL Version

oooo
oooo

• It’s difficult to see much improvement beyond this point, and many astronomers consider the 30-minute mark to be the point at which they are well-adapted to the dark.
  o
• Rhodopsin is what allows the rods in our eyes to absorb photons and perceive light, making it essential to our vision in dim light.
  O
• At this point, the rhodopsin has mostly been replenished, so you should be seen the ground.
  O
  O

BSL Version

oooo

oooo
oooo
oooo
oooo

• After a few hours, your dark adaptation may even go beyond the 90% mark.
  O
• This can be hard to do, as it requires a very dark site with essentially no artificial light.
  O
  O

BSL Version

oooo
oooo
oooo

• It is an interesting trait that red dim lights do not trigger the neutralisation of the rhodopsin, so astronomers and safety officials use red dim lights for night lighting to allow night vision to continue.
  o
• To help you see in the dark and won’t spoil your night vision.
  o
• LED Head torches have a red-light setting down, which is less disruptive to night vision and gentler on the eyes ~ ideal for both astronomy and BSL communication.
  o

BSL Version

oooo

• Light exposure affects cones and the inner retina through photon absorption by rhodopsin.
  O
• Exposure to high levels of white light caused severe retinal degeneration your visibility.
  O
  O

BSL Version

oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo

• It is a great lighting source for particular tasks such as astronomy map reading, logging, writing or planning notes.
  o

oooo
oooo
oooo
oooo

oooo

BSL Version