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Harrisburg Corneal Reflex Test Overview
Aug 28, 2024
Harrisburg Corneal Reflex Test
Overview
Also known as the Harsh Bark Test or Corneal Light Reflex Test.
Objective Test
:
Utilizes a pen torch for rough estimation of the angle of manifest strabismus.
Uses the first Purkinje image to assess alignment of eyes or potential strabismus.
Useful for young, uncooperative patients, or when physicians have poor vision in the deviating eye.
Procedure
Setup
:
Patient sits 50 cm away from the examiner.
Execution
:
Examiner turns on the pen light, directing it towards the midline of the nose between the eyes.
Patient instructed to look at the light.
Examiner observes corneal light reflex from both eyes.
Estimation
:
Degree of strabismus estimated by measuring decentration of the reflex from the pupil center.
1 mm deviation = 15 prism diopters.
Measurements and Interpretation
Conversions
:
1 degree = 2 prism diopters.
1 mm = 7 degrees or 14 prism diopters.
Observations and Interpretations
Centered Reflex
:
Interpretation
: Ortho position or normal alignment.
Decentered Temporally
:
Interpretation
: Esotropia.
Decentered Nasally
:
Interpretation
: Exotropia.
Decentered Downward
:
Interpretation
: Hypertropia.
Decentered Upward
:
Interpretation
: Hypotropia.
Deviation Estimation
Reflex between Pupil Center and Pupillary Margin
:
Estimation
: 7 degrees or 15 prism diopters.
Reflex at Pupillary Margin
:
Estimation
: 15 degrees or 30 prism diopters.
Reflex between Pupillary Margin and Limbus
:
Estimation
: 30 degrees or 60 prism diopters.
Reflex at Limbus
:
Estimation
: 45 degrees or 90 prism diopters.
Reflex at Sclera
:
Estimation
: More than 45 degrees or more than 90 prism diopters.
Limitations
This test provides a rough estimation because it is objective and does not use prism measurements.
Key Points
Corneal reflex is opposite to the deviation of the eyes:
Eyes move in (Esotropia) = Reflex moves out.
Eyes move out (Exotropia) = Reflex moves in.
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