Sunday, October 4, 2015

Pterygium is more common on the nasal side: Why?

Why do pterygia occur more commonly in nasal side?

Environmental factors, such as a warm climate, dust and UV light, are the main causes of pterygia.

UV light:
Pterygia are more common on the nasal side of the cornea because this area is more exposed to UV light owing to its reflection from the nose. According to this hypothesis, sunlight passes through the cornea laterally, and the cornea refracts it and focuses it on the limbic area (the border between the cornea and the white of the eye, also known as the sclera). Sunlight coming from the opposite direction, however, is partially blocked by the shadow of the nose.

Pterygium usually occur at nasal side because it lacks tears (Tears are secreted from the lateral side) and because tears drain through the nasolacrimal duct (On the medial side) bringing dust to nasal side.

Warm climate:
Lactic acid in perspiration running down the side of the nose and into the eye has also been suggested as a possible cause.

All these are theories. Nothing has been proved.

1 comment:

  1. difference between chalazion and hordeolum? chalazion is lazy, so far from the edge. hordeolum Hurts.


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