What is a homonymous hemianopia?

Loss of the same half of the visual field in both eyes — e.g., right half lost in both right and left eye. This localizes posterior to the optic chiasm (optic tract, LGN, optic radiations, or visual cortex).

Why does a chiasmal lesion cause bitemporal hemianopia?

The optic chiasm is where nasal fibers (carrying temporal visual field input) cross. A lesion here interrupts crossing fibers from both eyes, leaving only uncrossed temporal fibers intact — resulting in loss of both temporal fields.

How do I distinguish cortical from tract hemianopia?

Optic tract lesions produce incongruous (asymmetric) homonymous defects with a relative afferent pupillary defect (RAPD). Cortical (occipital) lesions produce congruent (symmetric) defects and often spare the macula, with no RAPD.

What is macular sparing and why does it occur?

In occipital cortex strokes, the posterior pole (macular representation) may be preserved due to dual blood supply from both middle and posterior cerebral arteries. This produces homonymous hemianopia with macular sparing.

Is this tool a substitute for formal perimetry?

No. This is an educational reference for lesion localization based on pattern recognition. Clinical decisions require formal automated perimetry, fundoscopy, and imaging.

Visual Field Defect Interpreter

Name: Visual Field Defect Interpreter
Availability: InStock
Author: Nham Vu

Select the pattern of visual field loss and get the probable anatomical lesion location along the visual pathway with a brief explanation.

Step 1 — Which eyes are affected?

Choose the laterality of the visual field loss.

One eye only (monocular)

Loss confined to a single eye

Both eyes — temporal fields lost

Outer (temporal) halves of both visual fields

Both eyes — same side lost (homonymous)

Right or left half lost in both eyes equally

Select a defect pattern on the left to see the localization.

Summary

Select the pattern of visual field loss and get the probable anatomical lesion location along the visual pathway with a brief explanation.

How it works

Select the affected eye(s): one eye (monocular), both eyes with bitemporal loss, or both eyes with homonymous (same-side) loss.
Choose the defect pattern that best matches the visual field loss description.
Review the probable anatomical location and the clinical explanation.
Use the pathway diagram to visualize where along the visual pathway the lesion lies.
Cross-reference with clinical signs to confirm localization.

Use cases

Ophthalmology residents learning visual pathway anatomy.
Clinicians correlating perimetry results with imaging findings.
Medical students studying neuro-ophthalmology for exams.
Neurologists localizing lesions from bedside confrontation testing.
Optometrists reviewing Humphrey field analyzer reports.
Educators creating teaching cases around visual field defects.

Frequently Asked Questions

Last updated: 2026-07-26 · Reviewed by Nham Vu