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Types of Vision Loss

Optometrist talking to patient in his office, Centre For Eye Health Sydney NSW

There are broad spectrums of eye conditions which can lead to vision impairment, many resulting in blindness and permanent vision loss. This page describes some of the common types of vision loss and outlines the definition of vision impairment.

Definition of vision loss

Vision impairment is defined as the limitation of actions and functions of the visual system, which places the individual in a position which inhibits their ability to function in the standard manner to that of other human beings.

The U.S. National Eye Institute defines low vision as “a visual impairment not correctable by standard glasses, contact lenses, medication or surgery that interferes with the ability to perform activities of daily living.”

 Types of vision loss

According to the the World Health Organization:

  • Visual acuity is the measure of how well the eyes can see objects from a set distance.
  • For example, 6/60 describes the ability to see objects only at a distance of six metres, while a normal eye can see the same object at 60 metres.
  • Normal visual acuity is 6/6 (20/20 in the imperial measure of feet).
  • The World Health Organization defines blindness as a visual acuity of less than 3/60 (or equivalent).

 Common Eye Conditions

Infographic Of Common Eye Conditions

Age-related Macular Degeneration (AMD) is a degenerative condition affecting central vision. Reading and crossing roads safely may be difficult. Early detection can slow down progression of the disease and improve treatment outcomes.

Cataract is a clouding of the lens, resulting in blurry vision and faded colours. This leads to glare-sensitivity and increases the risk of trips and falls. Cataracts are usually safely treated by surgery. A cataract is a cloudiness that forms in the lens of the eye – the part that allows a focused image to be transmitted onto the retina. This cloudiness creates blurring, affecting both near and distance vision. Cataracts generally result from the ageing process, though they can also develop from other causes such as congenital disability (from birth) or trauma to the eye. Cataracts due to ageing usually develop slowly and affect both eyes at different rates.

Glaucoma is an eye disease that damages the fine nerves connecting the eye to the brain. Glaucoma can result in tunnel vision and even total blindness. Early detection is vital.

Diabetic Retinopathy is caused by diabetes and result in increasingly blurred, patchy and fluctuating vision. Regular eye checks are crucial to reducing acuity.

Neurological Vision Impairment (NVI) can result from an acquired brain injury. Glasses may not improve vision. Homonymous Hemanopia is a common type of NVI.

These conditions can involve loss of central vision or side vision or indeed the whole field of vision. Sometimes people can see both in front and to the sides but their vision is blurry. Other people may see well in daylight but experience great difficulty indoors or at night.

It is important to understand that different people are affected in different ways by their changing vision. Vision impairment can have an impact on a person’s functioning in their home, workplace, school, and so on.

No matter what the vision impairment, there are a range of services and mobility aids that can provide assistance for someone that has problems getting around safely and independently.

Guide Dogs provide advice and training in orientation and mobility, enabling people with vision impairment to move around safely and confidently. As well as guide dogs, their broad range of mobility services includes training with mobility aids such as canes, low vision aids or electronic devices.

For more information on these conditions click here: