Khiyar al-ru’yah addresses an item bought without adequate viewing, or a material change since its earlier viewing.
Khiyar al-ayb concerns a qualifying defect, even if the buyer saw the item beforehand.
1. Opening a sealed package to view the specified item for the first time: inspection.
2. Finding a pre-existing hidden fault in a previously viewed watch: defect.
The next chapter is Bab Khiyar al-Ayb.