In laminated materials, repeated cyclic stresses or impact can cause layers to separate. As your front screen is made up of three layers, time, weather and impact can cause your glass to weaken. De-lamination and "milkiness" can also impact negatively upon the quality of windscreens.
Delamination occurs when one or both of the layers of the glass separate from the polyvinylbutyrate interlayer. This can cause different optical effects. Milkiness occurs when the polyvinylbutyral layer separates from the layers of glass and starts to return to its original prelaminated state. The windscreen can start to become opaque and cause difficulty for the driver.
If your screen looks delaminated like the one in the photo, you really should consider changing it in order to maintain the optimal strength in the event of a collision. Feel free to ring or email email@example.com for friendly advice.-Stephen Maher.