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Sci Tech
Jaundice eyed
Why do the eyes of a jaundiced person look greenish yellow?
SYAM SUNDAR
Neti, Puducherry
The bile which is secreted in the liver, is stored in the gall bladder. It gets concentrated to a level. It contains two important pigments like haemoglobin in the red blood cells. They are called biliverdin and bilirubin.
These pigments are greenish yellow, as they contain cyanin in their molecule. The biliverdin and bilirubin are the end products of haemoglobin breakdown called haematin and globin.
These two pigments are separated from the blood stream by the liver cells and stored in the gall bladder. They are then let down the intestinal tract. The colour of the faecal matter is due to this greenish yellow pigment.
These pigments are not usually let into the blood stream in large quantity, and the normal bilirubin content of the blood is maximally 0.9 mg per decilitre. Any level beyond this, in the blood, causes symptoms of jaundice.
This bilirubin in the blood exists in a fixed ratio as conjugated bilirubin and unconjucated free bilirubin which is soluble in water.
Whenever there is an obstruction — to clear this bile from the gallbladder, or when there is a failure of extraction of these bile pigments from the blood — level of these pigments increase in the blood.
These pigments have an affinity to settle themselves in the connective tissues, and loose areolar tissues in the body. Such tissues are available in the sclera of eye, (the white portion of the eye ball), underneath the skin, tip of nose, as well ears, and underneath the tongue.
The pigments settle down there, colouring such white tissues, giving a final colour of greenish yellow which is the colour of the pigment.
More so, in the eye, since the sclera is visible externally, these pigments have a spectral dispersion, to emit greenish hue in UV light, when seen in sunlight.
It is interesting to know that, once these pigments settle down, it takes a long time for them to get cleared.
Hence, the colour of the jaundiced person’s eye sclera is yellowish green, and this remains for a fortnight, to get cleared, in spite of the reduction of level of the bile pigments in the blood.
DR. NAGARAJAN VENKATARAMAN
Profesor Emeritus in Neuro Sciences
Tamil Nadu Dr MGR Medical University
Madurai, Tamil Nadu
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