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Translaminar Autonomous System Model for the Modulation of Intraocular and Intracranial Pressure in Human Donor Posterior Segments
Published on: April 24, 2020
Nonuniform pressure generation in the optic chiasm may explain bitemporal hemianopsia
Gregory S Kosmorsky1, William J Dupps, Richard L Drake
1Division of Ophthalmology, Cleveland Clinic Foundation, Cole Eye Institute, Cleveland, Ohio 44195, USA.
Ophthalmology
|December 18, 2007
Summary
Simulating a tumor pressing on the optic chiasm revealed higher pressure in the central aspect than the temporal aspect. This pressure difference may explain why patients develop bitemporal hemianopsia.
Area of Science:
- Neuroscience
- Ophthalmology
- Biomedical Engineering
Background:
- The optic chiasm is crucial for vision, transmitting signals from the retina to the brain.
- Compression of the optic chiasm can lead to visual field defects, such as bitemporal hemianopsia.
- Understanding pressure dynamics within the optic chiasm is vital for diagnosing and treating conditions causing compression.
Purpose of the Study:
- To quantitatively measure simultaneous pressure changes in the temporal and central aspects of the optic chiasm.
- To investigate the effects of simulated tumor compression from below on optic chiasm pressure distribution.
Main Methods:
- An experimental study using 5 unfixed cadaveric specimens.
- Exposure of the optic chiasm via craniotomy.
- Insertion of pressure transducers into the temporal and central aspects of the optic chiasm.
- Simulated tumor compression using an inflating Foley catheter in the sellar region.
Main Results:
- Higher pressures were consistently recorded in the central aspect of the optic chiasm compared to the temporal aspect.
- Mean central pressures ranged from 4 to 19.75 mmHg, while temporal pressures were significantly lower (0-6 mmHg).
- Cadavers aged 70+ exhibited frail optic chiasms unable to sustain pressure increases.
Conclusions:
- Radial expansion from below, mimicking a pituitary tumor, creates greater pressure in the central optic chiasm.
- The optic chiasm's geometry may predispose crossing nasal fibers to stress from inferior compression.
- Nonuniform pressure distribution likely contributes to the clinical manifestation of bitemporal hemianopsia.
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