1. General Information on Visual Impairments

Contents: Definition, forms of visual impairment, types of visual impairment, summary and conclusion.

Demonstrations are available of selected barriers that may arise when using digital materials in the context of various impairments. Please visit the ‘Simulate’ section for this.

Visual impairments describe differences or limitations in visual functions – that is, in the perception, processing and use of light and colour information. These differences can result from congenital, acquired or degenerative changes to the eyes, the nerve pathways or visual processing in the brain.

Whether a visual impairment results in a disability depends largely on environmental factors – that is, on how spaces, digital content, materials or social situations are designed. A visually accessible environment can enable participation, whilst unfavourable lighting conditions, low-contrast displays or a lack of aids and assistive technologies create barriers.

Types of visual impairment

Visual impairments can vary greatly in severity. They range from a mild impairment of vision to total blindness.

Common functional impairments include:

• Reduced visual acuity: blurred or hazy vision; makes it difficult to recognise details and text.
• Restricted field of vision: loss of central or peripheral vision; makes orientation and reading difficult.
• Sensitivity to light (photophobia): overstimulation caused by brightness or glare; can impair concentration and well-being.
• Colour vision deficiency (e.g. red-green colour blindness): differences in colour perception that make it difficult to recognise colour-coded information.

Many people experience several of these functional differences simultaneously, for example in conditions such as macular degeneration, glaucoma, cataracts or diabetic retinopathy. Neurological causes, for example following brain injuries, can also affect visual functions (cortical visual impairment).

Blindness

Blindness refers to a very severe or complete impairment of visual function, in which adequate vision cannot be achieved even with the aid of optical or medical devices.

Many blind people nevertheless retain some residual perception, such as light-dark contrasts or light sources. The impact on activities and participation depends heavily on environmental and support conditions: tactile or auditory orientation systems, screen readers, Braille displays or clearly structured spaces can break down barriers and promote independent participation.

Visual Impairment

Low vision refers to an impairment of visual function that cannot be fully compensated for even with aids such as spectacles, contact lenses or surgery.

Typical symptoms include blurred vision, tunnel vision or loss of the central field of vision. These can affect reading, recognising faces or finding one’s way in unfamiliar surroundings.

Supportive environmental factors include, for example:

• high-contrast and clear displays;
• flexible adjustment of font size, colour and brightness;
• good lighting without glare;
• assistive technologies such as text-to-speech functions or screen magnification.

Colour Vision Deficiency

Colour vision deficiency means that certain shades of colour are difficult to distinguish or cannot be perceived at all.

The most common form is red-green colour blindness, in which colour information appears similar. Complete colour blindness (achromatopsia) is very rare and often accompanied by sensitivity to light and reduced visual acuity. In this context, accessible design means conveying information not solely through colour – but also through shape, text, or symbols. This ensures that the meaning remains accessible even to people with different colour perception.

Temporary and situational Visual Impairments

Visual functions can also be temporarily or situationally impaired – for example, due to bright light, screen glare, tiredness, allergies or damaged visual aids.

These situations highlight that visual accessibility is relevant not only for people with permanent impairments, but for everyone. Universal design – that is, clearly structured, high-contrast and adaptable displays – supports vision in a wide range of everyday situations.

Summary and Conclusion

Visual impairments affect how people can perceive, process and use visual information. The effects vary from person to person – depending on the nature of the impairment, personal coping strategies and the design of the environment.

Barriers arise when visual information is inaccessible or designed exclusively for a single mode of perception. An inclusive environment – featuring high-contrast displays, customisation options, clear structure and assistive technology – promotes participation and self-determination.

This makes it clear: Disability does not arise solely from a limitation in visual function, but from the interaction between the individual and their environment.