The difference between corneal haze and scarring:

"Haze disappears within 6 months, but scars remain for years.

Haze is the product of disruption and death of keratocytes within a depth of 60 μm. As soon as the keratocytes repopulate that area, the cornea becomes homogeneously clear. However, scarring is a deposit of amorphous collagen of keratocytes that has transformed into myofibroblasts. This amorphous collagen needs years to reconfigure before it becomes clear."

Source: [a href="http://bmctoday.net/crstodayeurope/2011/01/article.asp?f=the-future-of-corneal-collagen-crosslinking"] The Future of Corneal Collagen Crosslinking[/a]