White part around pupil turning blue/gray?

Corneal arcus: Likely this blue gray appearance is located in the peripheral cornea and represents cholesterol deposition that accumulates with aging. If present before 40 years of age, there may be underlying abnormalities in your lipid profile. Your doctor would have told you this if a problem, particularly relative to your history of stroke. Otherwise this condition, called arcus sinelis, is normal.

Scleral ectasia: This could be arcus senilus as mentioned by dr. Fishburn, but a blue/gray color on the white part of the eye may be a scleral ectasia. This is a thinning of the sclera (white part of the eye), allowing the layer below it (the choroid) to show through. This is a normal aging change in some people. Also, a surface pigmentation (conjunctival nevus), could also give such a look. See an eye care pro.