Diffusion tensor imaging reveals normal geniculocalcarine-tract integrity in acquired blindness

Area of Science:

• Neuroscience
• Ophthalmology
• Medical Imaging

Background:

• Acquired blindness (AB) affects the visual pathway, including the optic nerve and geniculocalcarine tract (GCT).
• Understanding structural changes in AB is crucial for diagnosing and managing visual impairment.

Purpose of the Study:

• To investigate the structural integrity of the optic nerve and GCT in individuals with acquired blindness.
• To compare imaging findings between acquired blindness and normally sighted individuals.

Main Methods:

• Used magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) on 20 individuals with AB and 20 normally sighted (NS) controls.
• Analyzed transverse diameters and diffusion indices (mean diffusivity, fractional anisotropy) of the optic nerve and GCT.

Main Results:

• Optic nerves in NS individuals had significantly larger transverse diameters than in AB participants.
• AB participants showed increased mean and transverse diffusivity, and decreased fractional anisotropy in the optic nerve, indicating axonal degeneration.
• No significant differences in diffusion indices were observed in the GCT between AB and NS groups, suggesting preserved white matter integrity.

Conclusions:

• Acquired blindness is associated with axonal degeneration in the optic nerve.
• The geniculocalcarine tract maintains white matter integrity in acquired blindness, independent of visual afferent input after development.