Test Visual Fields
By: Carmen Willings
Updated May 19, 2019
The area that can be seen by the eye without shifting the gaze is known as the visual field. As part of the Functional Vision Evaluation, it is necessary to assess the student's visual fields. The technique used will vary depending on the students cognitive abilities. It is important to assess the student's visual fields even if the eye report indicates that there are no limitations in visual fields. Many optometrists and ophthalmologists will not formally test visual fields due to the student's age and cooperation. Normal visual fields in each area are 60 degrees from the nasal side, 90 degrees from the temporal side, 50 degrees superior (above), and 70 degrees inferior (below) from center.
Visual Field Assessment
Observation can often be the best way to observe the student's use of visual fields and note any areas of concern. Confrontation Field Testing is a way to informally measure the visual field. In a confrontation test, the student is positioned in front of the assessor. The individual is asked to look at the assessor's nose. A highly visible object is presented in a semicircle way from behind the student's head toward the assessor. The student indicates when they are able to perceive the object.
Field Loss Implications
The central visual field is the "what" system, while the peripheral visual field is the "where" system. The visual field is the entire area of vision that can be used without shifting the eyes or moving the head, encompassing 180 degree arcs. Assess the student's visual fields including the student's preferences or limitations. Observe the students response to materials presented in the central visual field and to the peripheral visual fields. Note where the student responds to materials. Estimate the number of degrees from the nose.
Note other signs of possible field loss including: over-scanning; eccentric viewing; holding object to the side, up, or down to inspect it; stumbling over low-lying objects; functional peripheral vision is often a source of distractibility. A student's scanning of an array of objects or looking for a missing object can demonstrate his functional visual field at near point. For example, a compensatory head turn suggests a peripheral field loss to the side of the head turn, since the student has learned to compensate by moving the usable visual field toward the side where information is missing.
The performance of activities, such as scanning a map or doing a word-search puzzle, can also suggest where scotomas (areas of absent vision) may be located, because if students are asked to keep their heads perfectly still while doing them, they may miss information in some areas of the tasks. Students who walk with their heads turned slightly to one side may be compensating for a difference in visual fields. Eye preference, evidenced in typical tasks, can also be evaluated.
Observe special visual behaviors and repetitive behaviors including eccentric viewing, stereotypical behaviors, and fluctuating visual abilities. Observe whether the student uses corrective lenses and tolerates them. Also indicate if the student has received Orientation and Mobility services. Note how the student currently travels indoors, outdoors, in familiar and in unfamiliar environments.
The absence of a full (180 degrees) peripheral field may cause difficulty in sports and social difficulty due to not seeing those in their visual field or by using an odd posture in order to see. They also may not see downward flight of stairs or a curb. It also may limit the amount of letters/words can see at a time.
Suggestions & Strategies
Depending on the results of the Visual Fields Testing, the following strategies, recommendations, and accommodations may be necessary to meet the students unique visual needs:
This presentation provides a walk-through of the process and steps of conducting a Functional Vision Evaluation and Learning/Reading Media Assessment. Key points include interpreting the eye report, materials to use in the assessment, conducting interviews and observations as well as strategies for direct assessment and writing a professional and thorough report that is informative to all audiences. Next steps are also covered including the importance of a low vision assessment, determining the need for additional assistive technology and implications for service.
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