Bitemporal Hemianopia
This visual field pattern—right eye nasal field defect combined with left eye temporal field defect—is described as bitemporal hemianopia, indicating pathology at the optic chiasm. 1
Understanding the Terminology
The combination you describe represents loss of both temporal visual fields (the outer halves of vision in each eye). This occurs because:
- The right eye nasal field defect means loss of vision on the nasal (inner) side of the right eye's visual field
- The left eye temporal field defect means loss of vision on the temporal (outer) side of the left eye's visual field
- Together, these create bitemporal hemianopia—a heteronymous bilateral field defect affecting opposite halves of the visual fields 2
Clinical Classification
This pattern falls under heteronymous bilateral field defects, which are defined as blind spots in opposite halves of the visual fields of both eyes (binasal or bitemporal patterns) 2. The bitemporal pattern specifically indicates compression or pathology at the optic chiasm where the crossing nasal retinal fibers are affected 1.
Anatomical Localization
Bitemporal hemianopia localizes the lesion to the optic chiasm. The crossing nasal retinal fibers (which carry temporal visual field information) are selectively damaged at the chiasmatic decussation 1. This is distinct from homonymous field defects, which affect the same side of both visual fields and indicate retrochiasmal pathology 2.
Common Etiologies to Consider
The most frequent causes include 1:
- Pituitary macroadenomas extending into the suprasellar cistern
- Meningiomas of the sellar/suprasellar region
- Craniopharyngiomas (especially papillary type in adults)
- Large aneurysms from internal carotid or Circle of Willis vessels
- Hypophysitis or Rathke cleft cysts
- Optic pathway gliomas
- Granulomatous disease or lymphoma infiltrating the chiasm
Important Caveat: Junctional Scotoma
Be aware that unilateral temporal field defects can occur with lesions at the junction of the optic nerve and chiasm (junctional scotoma of Traquair), found in approximately 10% of pituitary adenoma cases 3. This can be confused with early bitemporal hemianopia but represents ipsilateral optic nerve pathology with contralateral superior temporal field involvement.
Documentation Approach
When documenting, specify:
- "Bitemporal hemianopia" as the primary descriptor
- Note whether it's complete or incomplete
- Document any asymmetry between eyes
- Specify if there's associated junctional involvement
This precise terminology immediately communicates chiasmal pathology to consulting physicians and guides appropriate neuroimaging with MRI of the sella and suprasellar region 1.