The necessity to consider visual dysfunctions after acquired brain injury

Abstract

Visual information is processed in wide and extensive networks in the brain, and forms part of executive functions, emotions and memories. An acquired brain injury (ABI) often brings about a disruption of these networks and around half of the patients develop visual dysfunctions. Due to these injuries, patients may have a diminished ability to handle an environment full of impressions, to react quickly to danger, or they develop impaired reading- social- or working abilities. Despite these common effects, visual dysfunctions have not been central in neurorehabilitation. The purpose of this thesis was to examine the occurrence of visual dysfunctions after ABI as well as evaluate vision therapy and discuss its effect on neurorehabilitation. All patients included in the studies suffered from medium to severe ABI. In study I the frequency and type of visual deficits were examined. In study II visual dysfunction and their association with fatigue, anxiety or depression were examined. In study III, two different types of subjective and one objective assessment of visual dysfunctions were undertaken in order to evaluate if these assessments correlated or supplemented each other. In study IV the effect of vision therapy (VT) of vergence dysfunctions was examined.

Results: In study I, the answers of 170 patients to a questionnaire, Visual Interview (VI), revealed that half of the patients experienced visual changes, mostly reading disorder (53 %), followed by blurred vision and glare (both symptoms 35%). A fourth of the patients had visual field disorders and a fifth suffered from double vision. Two-tenths of the patients, who did not experience any vision change, answered “yes” 4–9 times to specific questions concerning visual dysfunctions. In study II, with 123 patients included, an association between increased visual dysfunctions and medium to severe fatigue was found. However, there was no such correlation found between increased visual dysfunctions and anxiety or depression. In study III 73 patients answered two questionnaires, VI, and Convergence Insufficiency Symptom Survey (CISS) and underwent a visual examination. All three assessments showed high scores of visual dysfunctions. VI and the visual examination correlated to some extent although VI also covered activity. Two-thirds of the patients who did not report visual changes turned out to have visual dysfunctions when measured objectively. In study IV 48 patients with ABI received visual rehabilitation and, compared to a control group with 41 patients, there was a statistically significant improvement in vergence abilities. The control group also showed some improvement, but except for fusion at distance the changes was not statistically significant.

Conclusion: More than half of the patients experienced visual changes after ABI, regardless of the type of examination, and some of the patients are not aware of their problems. This strongly indicates a need for visual screening as a part of a neurorehabilitation assessment. VT improved the vision function trained, but more research is needed to examine the effect on activity and participation level.