Tangent screen perimetry tests the visual field within 30 degrees of central fixation using a flat black surface marked with radial lines and circles. The patient sits 1 meter from the screen and fixes on a central point while a target is moved within their field of view to map out blind spots and detect scotomas. Test results are recorded by marking locations where the target is seen or not seen and connecting points to identify types of visual field defects. Tangent screening provides an inexpensive way to test the visual field within a short distance of central fixation.

1. Tangent screen (Bjerrum screen)

ananta poudel
B.optom. 1st batch
NAMS, bir hospital

2. Tangent screen (bjerrum screen)
 Tangent screen is a type of kinetic perimetry used to test a field
of radius 30 degree
 Testing distance is 1 meter,
 It consist of flat black surace
made up of black felt material
& stitched with redial lines at
15° interval and circles at 5
Degree interval

3.  Tangent screen is not actually a form of perimetry-rather,
it is a form of campimetry. In campimetry, the visual field
is tested on a flat

4. procedures
 Patient should seat at 1m from a 1m tangent screen and
is asked to fixate the central fixation spot
 patient should be wearing their Rx .
 non tested eye must be occluded .
 Target should be brought from non seeing to seeing part of
the field.

5. Cont.
 Map out patient blind spot.
 Test stimulus is used 3 to 10 mm
 Patient is instructed to fixate intently on a central fixation
point

6. Cont..
 To detect scotomas with in central field test object is moved in
radial direction at interval of 5°/ sec, from all direction.
 Smaller the target more sensitive is the test.
 Thus isopters can be made to now the extension of field and
type of scotoma as well.
 LCD with heavy duty chin
rest, modern type

7. Recording .
 Mark the location of each point on the tangent screen by
putting small pin on screen and connect those points on
the diagram/chart, to find type of visual field defect.
 Advantages :
 Inexpensive instrumentation, simple test procedures
 Ability to control all aspects of the examination from
test distance, to screen illumination, to mode of stimulus.
 Test distance magnifies visual-field defects

8.  Disadvantages :
Difficult to achieve consistent test conditions and testing
process.
 static techniques are not possible.
Thank you…

9.  Ref.
Boris clinical refraction
Internet.
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