What is Entoptic Phenomenon:
This test is used to check the retinal blood circulation, its health and the function of the macula.
Types:
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Haidinger’s Brush Test
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Blue Field Entoptic Phenomenon
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Purkinjee Entoptic Test
1. Haidinger’s Brush Test:
- This test is especially useful in patients with suspected early macular disease.
- A polarized source of light is used in this test.
Method:
🔹Patient is seated about 30 cm away from the polarized light source.
🔹Ask the patient to look directly at the polarized light.
🔹Explain the patient that he will see a faint pattern of propeller or hourglass shape when he focus into the polarized light.
🔹This phenomenon occurs because the macula selectively absorbs polarized light.
Interpretation: 📜
↪ The patient will see the Haidinger’s brush pattern clearly if he has healthy macula.
↪ If patient sees the distorted pattern this will indicate the macular dysfunction.
2.Blue Field Entoptic Phenomenon:
🔸This test is helpful to assess the blood circulation in the retina.
🔸This test is not directly focused on the macula.
Method:
🔹A blue source of light (blue screen or card) is used inthis test with wavelength of430nm.
🔹Ask the patient to look at that blue field.
🔹Ask the patient if he observe any bright, tiny and moving white spots against the blue background.
🔹These tiny spots are the white blood cells circulating in the retinal capillaries.
🔹The movement of the tiny spots should be in aa wavy, random pattern, following the capillary paths.
Interpretation:
↪Patient with normal retinal blood flowwill see the movement.
↪If patient face difficulty inseeing these spots or seeing them inconsistently will indicate the abnormal retinal circulation, but further tests are required toconfirm retinal vascular problems.
3.Purkinjee Entoptic Test:
🔸It’s useful to check central scotomas or abnormalities in blood vessel structure.
🔸This test is usually not performed in routine practice but it is still a usefultest.
Method:
🔹Patient is seated in dim-lit area.
🔹A bright shource of light usually pen torch is used in this test
🔹Rub the light against closed eyelids with the patient looking in opposite direct.
🔹A good observer will able to see the shadows of posterior pole vessels or may be he can see the avascular foveal zone.
Interpretation:
↪A healthy retina will produce “tree-branch” pattern due tothe shadow of the retinal vasculature.
↪If the pattern looks distorted ornot very clear, it may indicate the retinal or macular pathology.
Final Thought:
These tests are very useful for the screening of macular function however these test should be carried out with other functional tests for the diagnosis purpose.
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