You don't need to strike them hard with the finger tips to get a good response. If you strike the eyes most will back off and their hands will raise up to cover the eyes and this will give you access to striking low lines suck as the knees or groin. You can also be more sophisticated and fein a strike to the eyes to draw that response because you purposely want to strike the low line. This is the Attack By Draw principle from Bruce Lees Jeet Kune Do. If you are in clinch or grappling position you can more often than not access the vision area. Even if you were grabbed by someone and it was pitch black and you can't see anything as long as you are attached you should be able to work out where that persons eyes are.
If we attack the eyes in a self defence situation the attacker has to literally stop what they are doing to protect their eyes. It's how the body works. It understands that the vision is under attack and must look to protect this immediately. So this buys us time to counter to overwhelm and escape.
To train is simple, we can strike focus pads but look to strike the top of the pad so you fingers slide over it keeping them safe and also developing accuracy. You can use the BOB dummy in the gym as it has facial features and doesn't mind being hit. You can also go old school and have a partner hold a piece of transparency paper out in front of their face which will get you being able to focus a targeted strike.
If someone has an aversion to striking eyes then drop it down a notch to the throat. Just be aware that you need to drop the power down and rely on speed here. Although every situation is different so you need to judge the level of force that is required. And yes, this will still work even if they wear glasses as they still have a flinch response. Keep in mind the eye strike generally is a fast light touch. A gouge is something else. Best thing to do is get training, work out what works for you. Share the knowledge the with your partner and give everyone the basic skills to stay safe.