Why Not Just Use Water?
Despite the fact that eye wash looks like a clear, watery solution - there is a whole lot more to it than that. As with most medical marvels of the modern age, it would be naive of people to think that eye wash was simply water in a bottle. If this were the case, the process of washing your eyes would be ineffective, uncomfortable, and actually particularly dangerous.
Just think back to when you opened your eyes in the shower last. You probably didn't cringe with pain when it happened - but then again it probably wasn't the nicest feeling in the world, and hence you would have wiped your face with your hand or a towel to get the remaining trapped water out.
For anyone who has used eye wash before - they will tell you that it is almost impossible to tell that there is even a liquid being tossed around the eye. This is because one of the first considerations that eye wash manufacturers give to the product composition is its pH level. For those who do not know, water is actually not at the same pH level as the mucus membranes of the human body. For this reason, it tends to have a harsh, drying effect on these areas.
This is why the feeling of getting water in your eye is not particularly pleasant. Eye wash, on the other hand, is synthetically pH balanced - meaning that the level of acidity in the solution is at exactly the standard pH of the mucus membranes. This ultimately allows you to put the solution in your eyes, and not feel any discomfort whatsoever.
Safety First
Another consideration you should given when thinking about water and eye wash is the level of safety that each has, when placed in the eye. Water is usually sourced from a tap - and hence this has come through an array of underground pipes, and has most likely picked up a fair amount of bacteria along the way.
Placing this in your eye is particularly dangerous - especially if it is for an extended period of time. Eye wash, on the other hand, is completely free of any living organisms, meaning that it is sterile. Hence, it is completely safe to use in the eye - and there need be no fear that it will lead to a secondary infection.
