If it is improving, it was most likely bacterial conjunctivitis. Bacteria causes marked grittiness/irritation and a stringy, opaque, grey or yellowish mucopurulent discharge (gowl, goop, sleep, or other regional names) that may cause the lids to stick together (matting), especially after sleeping. Another symptom that could be caused by Bacterial Conjunctivitis is severe crusting of the infected eye and the surrounding skin.
It can be treated with antibiotics but often goes away on its own. If it is improving, I suggest getting saline solution to flush it out twice a day and keep an eye on it. If it begins to get worse or stops improving, make an appointment to see your doctor so you can get antibiotics for it.
The following web site has a picture of conjunctivitis. Please let me know if I can be of further assistance!
http://en.wikipedia.org/wiki/Conjunctivitis
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