The Bjerrum tangent screen is a device used in ophthalmology to assess the visual field, particularly the central and paracentral areas. It’s a flat surface with a tangent curve marked on it, used to map out the field of vision.

How it’s used:

1. Patient fixation: The patient fixates on a central point.
2. Stimulus presentation: A stimulus (e.g., a small object or light) is moved along the tangent screen.
3. Visual field mapping: The patient indicates when they see the stimulus, allowing the examiner to map out the visual field.

Purpose:

The Bjerrum tangent screen is used to:

1. Detect visual field defects: Identify defects in the central and paracentral visual field.
2. Monitor glaucoma: Track changes in the visual field associated with glaucoma.
3. Assess optic nerve function: Evaluate the function of the optic nerve.

The Bjerrum tangent screen is a useful tool for assessing and monitoring visual field defects, particularly in glaucoma patients.