9.2.1-2 Vision and Hearing

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Questions and Answers

What can be a consequence of extended wear of contact lenses in dry or dusty environments?

Dryness and irritation of the eyes (correct)

Increased clarity of vision

Reduced risk of irritation

Improved comfort during use

Which factor is most likely to hinder the ability to distinguish an object's edges?

Poor contrast with the surroundings (correct)

The object’s reflection

Background noise levels

The object's movement speed

Which visual cue typically helps in gauging the distance of an object?

Size comparison (correct)

Edge sharpness

Shape distortion

Color saturation

What factor does NOT directly affect visual acuity according to the information provided?

Inability to see specific colors Signup and view all the answers

What is the recommended method to protect eyes from dust when wearing contact lenses?

Wearing goggles Signup and view all the answers

What is the primary cause of presbyopia?

Decreased ability of the lens to accommodate Signup and view all the answers

Which visual imperfection is directly associated with exposure to UV light?

Cataracts Signup and view all the answers

How does the transition from bright to dim light affect vision, particularly in older individuals?

It temporarily reduces vision until adjustment occurs Signup and view all the answers

What contributes to the limitations of human performance in tasks?

A combination of physical, mental, and emotional factors Signup and view all the answers

What element can make focusing in low light conditions easier?

Looking slightly to one side of the object Signup and view all the answers

What is the main reason why humans require tools and protective equipment?

To compensate for physical and mental limitations Signup and view all the answers

What is a potential problem caused by airborne particles when spectacles are worn?

They can result in spectacles becoming dirty or scratched Signup and view all the answers

Which of the following best describes visual acuity?

The ability to distinguish sharp details at varying distances Signup and view all the answers

Which physical factor does NOT affect the clarity of sight?

Environmental noise levels Signup and view all the answers

Why is it crucial for aircraft maintenance personnel to understand their physiological and psychological functions?

To enhance their overall performance and safety Signup and view all the answers

What is the most common type of colour vision deficiency experienced by individuals?

Distinguishing between red and green Signup and view all the answers

What impact does ageing have on colour vision?

Causes progressive yellowing of the lens Signup and view all the answers

Which method improves visibility of lights at night?

Gazing slightly to one side of the object Signup and view all the answers

What is the effect of observing an object from an angle compared to front-on?

Inaccurate reading due to parallax error Signup and view all the answers

What is referred to as 'parallax' in the context of observation?

The perceived shift in an object's position when the observer changes perspective Signup and view all the answers

Study Notes

Vision and Hearing Learning Objectives

Explain the importance of vision for aircraft maintenance workers and how vision is affected by various factors, such as certain conditions.
Explain the importance of hearing for aircraft maintenance workers and how hearing is affected by certain conditions.
Describe strategies for protecting hearing in an aircraft maintenance environment.

Human Performance Limitations

Humans have limitations in capability, performing poorly in cold or night conditions, struggling with memory, and stressed situations.
Human performance is influenced by physical and mental characteristics, including vision, hearing, information processing, attention, perception, memory, judgment, and decision-making.
Human performance limitations (physical and mental) must be considered for aircraft maintenance safety.

Factors Affecting Clarity of Sight

Visual acuity is the eye's ability to discern sharp detail at varying distances.
Physical factors such as age and physical imperfections (short/longsightedness) affect visual acuity.
Environment, such as the amount of light, air clarity (dust, mist, rain), and the nature of the object being viewed also affect visual acuity.
Ingesting drugs, alcohol, or cigarettes affects visual clarity.

Physical Factors: Lens Imperfections

Long-sightedness (Hyperopia): The eyeball is shorter than normal; the image focuses behind the retina. A convex lens corrects this.
Short-sightedness (Myopia): The eyeball is longer than normal; the image focuses in front of the retina. A concave lens corrects this.

Ageing and Vision

Presbyopia is a form of long-sightedness, affecting flexibility of the eye lens which, as a person ages, becomes less flexible.
Other factors like cataracts, astigmatism, glaucoma, and migraines can affect vision.

Environmental Factors: Light

Increasing light intensity, to a point, helps vision, but increased illumination can create glare, more impacting older people.
Adapting to different ambient light levels (moving to a dark area from a bright hangar) takes time.
Focusing is sometimes easier when looking slightly off-center.

Environmental Factors: Airborne Particles

Airborne particles (dust, rain, mist) interfere with light, distorting vision.
Spectacles are also susceptible to getting dirty, wet, misted up or scratched.

Contact Lenses in Dry/Dusty Conditions

Contact lenses should not be worn for extended durations (8-12 hours).
Dry or dusty environments can cause irritation or damage to contact lenses.
Goggles should be worn where necessary to prevent dust from entering the eyes.

Viewing Objects (Angle, Size, Contrast, Movement)

Objects viewed from an angle seem different or less clear than viewed directly.
Objects of known size should be used to visually compare to unknown objects.
Lower contrast between object and background can make an object harder to distinguish.
Movement of objects or movement of the viewer can affect the clarity of images.

Colour Vision

Colour-vision deficiency, most commonly distinguishing red and green, is a problem for aircraft maintenance engineers.
Ageing can also affect colour discrimination.
Good colour vision is vital for identifying aircraft markings and components.

Central Vision at Night

Central vision is less effective in low light.
Using peripheral vision (looking slightly to the side of the object) can improve night vision.
Some individuals with perfect day vision may have shortsightedness at night.

Ingestion of Foreign Substances (Vision)

Alcohol and drugs can negatively affect vision.
Smoking reduces oxygen supply to the eyes.

Vision for Aircraft Maintenance

Good vision is essential for maintenance tasks, as vision issues can be gradually noticed.
It's important for individuals to recognize their vision issues, be it temporary or permanent and consider the potential consequences of continuing tasks despite impaired vision.

Ambient and Task Lighting

Proper lighting is essential for safe aircraft maintenance.
Organizations should provide adequate ambient lighting or supplementary lighting for maintenance tasks.

Hearing

The human ear can detect sound in Hz, with most sensitivity around 3000 Hz.
Volume is measured in decibels (dB).

Impact of Noise on Hearing

Noise can be annoying, disrupt communication, lead to accidents (masking warning signals).
Noise can cause fatigue and affect concentration and decision-making.
Noise, especially intermittent and high frequency sounds, can harm hearing temporarily or permanently.

Hearing Impairment

Noise exposure, even short-term, can lead to temporary or permanent hearing loss.
The severity of hearing loss depends heavily on noise intensity.
Hair cells in the inner ear convert sound waves to electrical signals, but loud noise damages these.

Age and Hearing (Presbycusis)

Presbycusis is the gradual decline in hearing that occurs with age.
This decline begins around the age of 30 and typically affects higher-pitched sounds first.

Hearing Protection

Earplugs or earmuffs can reduce noise levels by 20–40 dB.
Hearing protection should be used for noise levels above 115 dB.
Workers should be trained in the appropriate use of hearing protection and should use them as necessary.

Hearing Awareness during Aircraft Maintenance

Hearing damage is possible when conducting aircraft maintenance tasks due to noise exposure.
Workers need awareness of their ears' limited noise protection capabilities and need to properly use hearing protection.

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