Functional Assessment of Vision

Presented on Friday 5 May 2006

Janis Sugden & Lesley Reid

Seven functions are considered necessary to give an understanding of the spectrum of visual functioning. 

The actual assessments used will depend upon the developmental and chronological age of the child.

Age is an important factor in understanding vision. Very young children are likely to be still developing their visual functions.

1. Visual Acuity (VA)
2. Visual Field
3. Contrast Sensitivity
4. Light Sensitivity
5. Colour Discrimination
6. Oculomotor control
7. Accommodation

Visual Acuity

Visual acuity (VA) is the ability to resolve fine detail. VA is normally measured by reading successfully smaller letters on an eye chart. "Distance VA" chart is positioned at a distance of approx. 6M. "Near VA" chart positioned quite close approx 35 cm.
Actual assessments used will depend upon the developmental and chronological age of the child.

Name of Assessment	Age/ Stage it is appropriate for		Comments
Preferential Looking
Cardiff Cards
Kay Picture Test
BUST
Snellen
Name of Assessment	Age/ stage appropriate for	Comments

Note of any questions or queries.

Using this information. Care must be taken when using this assessment. An example of this could be when a person has very limited peripheral vision and yet have excellent visual acuity.

Visual Fields

This is the area we are able to see.

The quality of vision within the visual field is usually better centrally and poorer on the edges.

Defects can be central or peripheral. Likely to have greatest implications for moving around safely if peripheral, reading etc if central vision loss.

Name of Assessment	Appropriate Age /Stage	Comments

Note of any questions or queries.

Contrast Sensitivity

Individuals are able to detect various levels of contrast. It depends upon the size and detail of what a person is looking at.
Generally, contrast sensitivity is worse for people with poor VA but it can be poor even when VA is good eg; cataract and good when VA is poor eg; albinism.

Name of Assessment	Age/ stage appropriate	Comments
Hiding Heidi
LogMAR

Notes of any questions or queries    

Light Sensitivity

Many children with VI are very sensitive to light levels.

Notes of questions or queries

Colour

Most colour discrepancies occur in people who otherwise have normal vision. They can occur in people who have impaired retina or optic nerve problems.

Name of Assessment	Appropriate Age /Stage	Comments

Note of any questions or queries.

Oculomotor Control

The control of eye movements can be disrupted when a person's vision is impaired. One such condition is nystagmus.

Assessments?

Comments.

Questions and Queries.

Accommodation

The brain automatically sends a message to the eye causing the lens to adjust its focusing power when we look at something close up.

References

• Lueck, Amanda Hall (Ed) Functional Vision: A Practitioner's Guide to Evaluation and Intervention. AFB, 2004
• Goodman, Stephen; Wittenstein, Stuart H (Eds) Collaborative Assessment. AFB, 2003
• Miller, Cyral. On the LOOK OUT for Functional Vision Assessment/Evaluation http://www.tsbvi.edu/assessment/2445-on-the-look-out-for-functional-vision-assessmentevaluation-1 accessed 24/04/2006
• Anthony, Tanni L, Functional vision assessment for children who are young and/or multi-disabled. Colorado Department of Education, 1993
• Verweyen, Petra. 'Measuring vision in children.' Community Eye Health, Vol 17 (50) 2004 pp 27-29
• Hyvarinen, Lea Assessment of Low Vision for Education Purposes and Early Intervention (Presentations)
  http://www.lea-test.fi/en/assessme/visasses.html accessed 24/04/06.

Where next

• Functional vision assessment