Midline tilting between seeing and nonseeing areas in hemianopia

Area of Science:

• Ophthalmology
• Neurology
• Visual Science

Background:

• Hemianopia, a visual field defect, is typically characterized by a vertical dividing line between seeing and non-seeing areas.
• Causes of hemianopia include vascular accidents, trauma, tumors, and neurosurgery for convulsive disorders.

Observation:

• A tilted, non-vertical line separating seeing from non-seeing visual fields was identified in 24 out of 200 patients with various hemianopias.
• This tilting phenomenon was confirmed and distinguished from testing artifacts using binocular fixation and red-green color testing.

Findings:

• The study identified a tilted visual field boundary in patients with homonymous hemianopia, homonymous quadrant hemianopia, homonymous scotomata, and bitemporal hemianopia.
• A difference in the overlapping visual fields of the two eyes was noted specifically in areas with this tilted boundary.
• The tilting can occur superiorly or inferiorly, affecting different types of hemianopia.

Implications:

• The findings suggest a potential explanation for this visual field incongruity lies in variations in the anatomical determination of crossing and non-crossing optic nerve fibers at the retinal level.
• This observation may refine our understanding of visual field defects and their underlying neuro-anatomical basis.