Editors

MattiSeppänen

Blindness and Visual Impairment

Essentials

The information provided in this article is based on policies and practices applied in Finland. Country-specific differences may exist. Find out also about the local policies and practices.
A visual acuity of 0.3 has been recommended as a general cut-off point for international reporting purposes. As a single measure, it is not sufficiently accurate for assessing the level of visual impairment.
People can be considered blind, if
- their best corrected visual acuity in the better eye is less than 0.05 or
- the diameter of their visual field is less than 20 degrees.
In practice, contrast sensitivity, for example, is highly significant for vision, and visual acuity alone does not describe the quality of vision or visual impairment.
A general practitioner (GP) can perform basic examination of vision in a person with visual impairment. The GP should be aware of the possibilities of visual rehabilitation and the aids used for this purpose.
In a vision rehabilitation unit, investigations performed by an ophthalmologist and an optometrist are used to plan individual rehabilitation, monitoring and suitable aids for people with visual impairment (see Table T1).
Visual rehabilitation of children with visual impairment must be started early enough to obtain optimum results.

Prevalence

Globally, there are over 2.2 billion people with vision impairment http://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment.
- There are estimated to be 50 000 people of 30 years or older with visual impairment in Finland (population 5.5 million). Of these less than 10 000 are of working age.
The most common causes of visual impairment:
- Age-related macular degeneration (41%)
- Hereditary retinal degeneration (10%)
- Visual pathway defects (9%)
- Glaucoma (7%)
- Diabetic retinopathy (5%)
- Congenital developmental disorders (5%)

Examination of vision

In people with visual impairment, extensive examination of vision is essential for effective rehabilitation, for achieving the best possible functional vision, and for the choice of suitable aids.
Examination of vision by a GP
- Uncorrected visual acuity with each eye separately at distances of 4 m and 40 cm
- Best visual acuity with the patient's glasses at 4 m with each eye separately and both eyes together
- Best visual acuity with the patient's glasses for close-up work at a distance of 40 cm
- Best visual acuity with aids available for reading (such as magnifying glass, loupe)
For methods of examining vision, see separate article Assessment of Vision.
Examinations by an ophthalmologist or optometrist
- define optimum vision with corrective glasses
- assess any benefit from additional correction for close work (ADD)
- aim at prescribing special near glasses providing optimum reading vision
- define the strength of magnifying binocular glasses, as necessary.
Further investigations in a vision rehabilitation unit
- Visual field tests and optical coherence tomography (OCT) of the ocular fundus, as necessary
- Measurement of reading speed helps to assess the usability of various aids.
In rehabilitation, it is assessed how the visual impairment affects the patient's ability to
- communicate
- move in various environments
- cope with daily activities
- cope with close-range tasks requiring precision (e.g. reading, hobby crafts and handicrafts).

Vision rehabilitation

Vision rehabilitation is for patients with
- best corrected vision below 0.3 and permanently impaired vision or
- significant visual field defects.
The patients need referral to the vision rehabilitation unit. Find out about local services and their practices.
For children with visual impairment, multiprofessional rehabilitation is provided.
- As 60% of children with visual impairment have multiple disabilities, it is essential to consider their other disabilities in vision rehabilitation, too.
- Sufficiently early start of rehabilitation of children with visual impairment creates the best possible prerequisites for growing, learning and creating social relationships.
Vision rehabilitation in practice
- In vision rehabilitation, rehabilitation advisors find the most suitable adjustment training courses. Individual rehabilitation periods are planned depending on what is available. Rehabilitation advisors advise how to seek rehabilitation, and help with obtaining the required statements.
- On courses, people with visual impairment get valuable peer support and guidance for coping with their everyday life.
- For vision aids, see Table T1.
- For special features of vision rehabilitation at various ages, see below here.

Vision aids

Magnifying glasses	Efficacy and purposes of use vary. Hand-held magnifying glasses can often be used for reading, neck-wear magnifying glasses are easy to take along and help with shopping.
Magnifying glasses	In a vision rehabilitation unit, patients can be offered various kinds of magnifying glasses to try.
Strong glasses for near vision	Near vision becomes worse with age. In people with presbyopia, the maximum near correction in near vision glasses is often +2.50, more rarely +3.00.
Strong glasses for near vision	In the vision rehabilitation unit, an ophthalmologist or optometrist can, using a trial lens frame, fit a stronger than usual near vision correction on top of the person's own best correction for distant vision, such as +5.00, decreasing the reading distance to very close to the eye. This way, people with visual impairment may in some cases achieve reading vision even if it is impossible for them to read with normal glasses.
Binoculars	Theatre binoculars or a telescope-like aid used in front of one eye (monocular) can be tested for people with low vision.
	Binoculars/monoculars help to read bus and train timetables and to see street signs.
	Adapters are available for monoculars to enable them to be used as very strongly magnifying aids for reading.
Sunglasses and absorption glasses	If glare is a problem in a patient with a disease causing visual impairment, prescription sunglasses may help, and so may separately fitted absorption glasses. Examples of such diseases are advanced glaucoma, retinitis pigmentosa and diseases causing corneal degeneration.
	For fitting absorption glasses, there are trial sets available that patients can use in bright sunlight or in artificial light at home to see what type of absorption glasses work best for them.
	In people with retinitis pigmentosa, orange or reddish brown absorption glasses often improve contrast sensitivity.
	Contrast sensitivity charts can be used to assess how various absorption glasses improve contrast sensitivity.
Lamps, loupe lamps	On a home visit, a rehabilitation advisor can plan additional lighting to facilitate coping at home.
Lamps, loupe lamps	Loupe lamps can help to achieve reading vision.
Table type and portable electronic magnifiers	The magnifiers consist of a camera and a monitor; most of them can be used to take a picture of a text and magnify it to the size of the patient's choice. Some devices also include a speech function, i.e. the device will read the text aloud.
Table type and portable electronic magnifiers	Portable electronic magnifiers help with shopping and reading prices.
IT aids	Computer utility programs can be chosen according to individual needs; some operating systems have utility programs included. Magnifier and speech programs Display arms Braille displays, printers and scanners Magnifying mouse
Cell phones and tablets	Smartphones and tablets often include a high-quality camera and an accurate display and, in most cases, a screen reader. Depending on the operating system, smartphones have either user-friendly or operating assistance features.
Talking book products	Talking book products are available through various services. Find out about locally available web sites and other services. These may also be available at or through the local library.
White cane	Mobility aid for people with severe visual impairment
	The cane will help to detect stairs, kerbs and other obstacles.
	The white cane shows others that the user has low vision.
Guide dog	The need for and suitability of a guide dog can be assessed at a vision rehabilitation unit.
	Helps to cope independently.
	To submit a guide dog application, the following are required: ability to take care of the dog ability to trust the dog in guiding tasks sufficient interactive skills and physical performance capacity to work with the dog.
	If a patient is granted a guide dog, fulfilment of the requirements will be reassessed later, as necessary.
	It must be possible to ensure that the dog gets sufficient rest and leisure time when it is not performing its guiding tasks.

Source: Seppänen M. Kääriäinen T. Nä�nkuntoutuksen apuvälineet. (aids for vision rehabilitation) In: Silmätautien käsikirja. (manual of ophthalmology) Kustannus Oy Duodecim 2019.

Vocational rehabilitation

The GP should be aware that even patients who do not have visual impairment are entitled to vocational rehabilitation.
To assess the need for vocational rehabilitation due to partial or full vision loss, patients should be referred to a vision rehabilitation unit.

Vision rehabilitation in various age groups

Infants
- If an infant is estimated to have a permanent visual impairment, early rehabilitation should be started without delay.
- The need for rehabilitation of infants can be estimated based on signs of visual communication between infant and parent. Signs of normal communication include, for example,
  - eye contact at the age of 6 weeks
  - smile response no later than at 12 weeks.
- If the infant is found to have developmental delay, and if visual communication develops slowly, an examination by an ophthalmologist and referral for assessment for vision rehabilitation should be made immediately.
School-aged children
- Practising learning techniques
- Use of aids
- Practising movement
Working-age people
- Seeking retraining, as necessary
- Examining the need for aids
- Practising the use of aids
- Learning movement skills
Elderly people
- Find out about locally relevant guidance.

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