Heteronymous bilateral field defects

This code describes a visual field defect affecting both eyes, where the loss of vision occurs on opposite sides of the vertical midline in each eye. This typically indicates a lesion affecting the optic chiasm or optic tracts, leading to a specific pattern of visual impairment.

Use this code when documentation specifies a heteronymous bilateral field defect, such as bitemporal hemianopsia (loss of outer half of the visual field in both eyes) or binasal hemianopsia (loss of inner half of the visual field in both eyes). This diagnosis is often supported by visual field testing (perimetry) results.

• Differentiate from homonymous hemianopsia (H53.46-), where the visual field loss is on the same side in both eyes.
• Ensure the documentation clearly specifies "heteronymous" or describes the specific pattern (e.g., bitemporal, binasal) to support this code.
• Consider sequencing this code after the underlying cause of the field defect, if known and documented (e.g., pituitary tumor, stroke).