I would imagine having eye drops three times a day would stress him out. Do not forget guinea pigs hide any signs of distress or discomfort.
I would think it'd depend on the personality of the pig whether or not it were stressed out.
I have had to administer eye drops quite a few times to pigs over the years, some more than 3 x a day. It's not something they particularly enjoy but neither would I & none have ever been stressed to the point they've started chewing their nails.
Not all guinea pigs hide signs of distress/discomfort, some will happily wheek their heads off at being touched where they don't wish to be touched.