Agree with Will on the age/life of acrylic. Ours cracked from the outside edge and were obviously cracked right through. We replaced the first one and by the time we had got round to actually making the replacement - others started to fail similarly. I'm not sure the damage was UV but cyclic expansion and contraction over the 2 decades, its sunny in AustraliaThe daamge does look like crazing that is typical of perspex or acrylic from UV and time. As said it is probably ok for many years strength wise but you may have the urge to replace. I have replaced the windows in my little boat and one window yet again and another replacement needed. ie they last about 20 years only. ol'will