Mechanisms compensating for visual field restriction in adolescents with damage to the retro-geniculate visual system.

BACKGROUND

To describe visual field (VF) outcome in three adolescents with damage to the optic radiation and to focus on mechanisms that may compensate the practical functional limitations of VF defects.

DESIGN

Descriptive, prospective multi-case study in a hospital setting.

PARTICIPANTS

Three teenagers with cerebral visual dysfunction because of damage to the retro-geniculate visual pathways.

METHODS

Best-corrected visual acuity and eye alignment were assessed. Visual field function was tested with Goldmann perimetry, and with Rarebit, Humphrey Visual Field Analyzer and Esterman computerized techniques. Fixation was registered with video oculography during Rarebit examination. Magnetic resonance imaging of the brain illustrated brain damage and its relation to the posterior visual system.

RESULTS

One of the three subjects had bilateral asymmetric white matter damage of immaturity, early-onset exotropia, and a relative homonymous VF defect, but normal binocular VF. The second subject also had bilateral asymmetric white matter damage of immaturity and showed an inferior right quadrantanopia, confirmed by the binocular field. Registration of fixation revealed automatic scanning during perimetry. The third subject had an almost total left homonymous hemianopia after resection of a brain tumour in the right temporal lobe. The hemianopia could be compensated for by fast voluntary scanning.

CONCLUSION

Congenital and later-acquired homonymous VF defects may, at least in young subjects, be compensated for by scanning. Exotropia may compensate VF defects and, therefore, the VF should be tested before strabismus surgery.