34.18 Vision and Visual Perception

Vision

Good vision is one of the most important medical requirements for a pilot.

Vision is essential for safely operating an aircraft and is used for tasks such as:

• maintaining attitude and position;

• identifying other aircraft;

• judging distance and depth;

• reading instruments and charts;

• identifying terrain and obstacles; and

• assessing movement and relative motion.

Pilots must meet specified visual standards to obtain and maintain the appropriate aviation medical certificate.

The Eye

The eye is a complex organ that receives light and converts it into electrical signals which are transmitted to the brain and interpreted as images.

The structures of the eye work together to:

• focus light onto the retina;

• adjust to different lighting conditions;

• detect colour;

• distinguish fine detail;

• perceive movement; and

• assist with depth perception.

Two important types of light-sensitive cells in the retina are rods and cones.

34.18.2 Distinguish between rod and cone cell functions and distribution in the retina.

Rods

Rod cells are primarily responsible for vision in dim light.

They are highly sensitive to light and are concentrated mainly around the periphery of the retina.