Human Performance – Human Vision

Human Performance – Human Vision

Vision – How we see
  • light enters through pupil
  • ciliary muscles shape the lens
  • image (upside-down) projected onto retina for interpretation by the brain
Blind Spot

Occurs when image focused on the retina falls across the optic nerve.

Refractive Errors

Hyperopia (longsightedness)

  • distant objects clear
  • near objects blurry
  • convex lens to correct

Myopia (shortsightedness)

  • distant objects blurry
  • near objects clear
  • concave lens to correct

Astigmatism

  • distortion of the image
  • different parts unequally focused
  • cylindrical lens to correct

When images are not projecting onto the retina correctly, lenses are used to correct vision. Either prescription glasses or contacts are used.

Visual Acuity

As per Austroads conditions

  • 6/12 Better Eye
    • at 6m can see what a normal eye sees at 12m
  • 6/18 in the Other Eye
  • Or Vision Correction

Vision deteriorates with:

  • Fatigue
  • Alcohol
  • Medication / Drugs
  • G-loadings (greyout, blackout)

At night, the predominant located cones of the Retina are not as effective as the rods, predominantly located in the peripheral vision.

Empty Field Myopia

Empty Field Myopia describes the pilot experience of staring blankly into an empty sky and missing a potential collision with another aircraft. The eye naturally focuses 1 to 2 metres in front.

To avoid this empty-field myopia, you should focus on any available distant object, such as a cloud or a landmark, to lengthen your focus. If the sky is empty of clouds or other objects, then focus briefly on a relatively distant part of the airplane like a wing tip as a means of lengthening your focus. Having spotted an airplane in an otherwise empty sky, be aware that it could be closer to you than it appears to be, because you have no other object with which to compare its size.

Scanning technique to look for traffic: •Look across the sky in 10 degree sections as you do move your focal area closer and further away so that your focus can identify any traffic threats

Visual Illusions

Conflict between ‘Natural’ and ‘Synthetic’ creating Spatial Disorientation

Where are the White Dots?

Are the lines sloping?

Lines are straight, however the illusion indicates they are sloping

Judging distances and heights – Which middle dot is larger?

Both the same. This is really important to show students that perspective can be driven by the surrounding environment. And this may not be correct.

Judging distances and heights – Visual queues

The trees are smaller on the second approach, giving the pilot the illusion they need to fly lower.
Overcoming Illusions

Illusions are worse when environmental conditions reduce visibility eg haze or smog:

  • Don’t totally trust your vision and perception
  • Cross check your height, distance and speed by communicating with your crew
  • Choose areas and orientation to fly which allow depth perception.
  • Choose to land across your sight ie left to right or right to left.
Visual Safety

For your eyes:

  • don’t look directly at the sun
  • Hazard when taking off or landing early mornings or late afternoons
  • Hazard anytime the RPA is between you and the sun

Personal Protective Equipment:

  • hat
  • sunglasses
  • sunscreen
  • long-sleeved shirt