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Anatomy and Function of the Optic Tract
- The optic tract carries retinal information relating to the whole visual field.
- The left optic tract corresponds to the right visual field, while the right optic tract corresponds to the left visual field.
- Temporal retinal fibers from the left eye and nasal retinal fibers from the right eye form the left optic tract.
- Temporal retinal fibers from the right eye and nasal retinal fibers from the left eye form the right optic tract.
- The optic tract contains fibers from the ipsilateral temporal hemiretina and contralateral nasal hemiretina.
- The optic tract is responsible for relaying visual information to the lateral geniculate nucleus (LGN).
Autonomic Functions of the Optic Tract
- The optic tract is responsible for transducing bilateral autonomic reflexes, including the pupillary light reflex and pupillary dark reflex.
- The pupillary light reflex controls pupil diameter in response to increases in illumination.
- Higher light intensity causes pupil constriction.
- Increased light stimulation of one eye will cause pupillary constriction of both eyes.
- The neural circuitry of the pupillary light reflex includes the optic tract joining the optic nerve to the brachium of the superior colliculus.
- The pupillary dark reflex controls pupil diameter in response to decreases in illumination.
- Lower light intensity causes pupil dilation.
- Decreased light stimulation of one eye will cause pupillary dilation of both eyes.
- The neural circuitry of the pupillary dark reflex includes the optic tract joining the optic nerve to the hypothalamus.
Damage and Pathologies of the Optic Tract
- Lesions in the optic tract correspond to homonymous hemianopsia (visual field loss on one side).
- A lesion in the left optic tract causes right-sided homonymous hemianopsia.
- A lesion in the right optic tract causes left-sided homonymous hemianopsia.
- Possible causes of optic tract damage include stroke, congenital defects, tumors, infection, and surgery.
- Peripheral prism expanders and vision restitution therapy may be used for patients with visual field loss due to permanent optic tract damage.
Split-Brain Phenomenon and Optic Tract
- In split-brain patients who have undergone a corpus callosotomy, information from one optic tract does not get transmitted to both hemispheres.
- Split-brain patients may be unable to name what they see in the left visual field due to the speech-control center being in the left hemisphere.
Clinical Significance of Pupillary Reflexes
- Pupillary reflexes, particularly the pupillary light reflex, are diagnostic tools used in clinical and emergency medical practice.
- Lack of equal consensual pupillary constriction to a light stimulus can indicate optic nerve damage, brainstem death, or optic tract damage.
- Marcus Gunn pupil is an example of pupillary reflex abnormality.
In neuroanatomy, the optic tract (from Latin tractus opticus) is a part of the visual system in the brain. It is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and superior colliculus.
| Optic tract | |
|---|---|
 The left optic nerve and the optic tracts. | |
| Details | |
| Part of | Visual system |
| Identifiers | |
| Latin | tractus opticus |
| MeSH | D065866 |
| NeuroNames | 460 |
| NeuroLex ID | birnlex_1684 |
| TA98 | A14.1.08.404 |
| TA2 | 5669 |
| FMA | 62046 |
| Anatomical terms of neuroanatomy | |
It is composed of two individual tracts, the left optic tract and the right optic tract, each of which conveys visual information exclusive to its respective contralateral half of the visual field. Each of these tracts is derived from a combination of temporal and nasal retinal fibers from each eye that corresponds to one half of the visual field. In more specific terms, the optic tract contains fibers from the ipsilateral temporal hemiretina and contralateral nasal hemiretina.
