There is an awesome quote in the brilliant book Le Petit Prince by Antoine de Saint-Exupéry that is commonly translated to english as "what is essential is invisible to the eye" or simple "the essential is invisible to the eyes". I'm trying to translate it to latin for a birthday card and the best that I could was "quod est per se invisibilis oculum". It is right? Does anyone suggest a better translation?

There is an awesome quote in the brilliant book "Le Petit Prince" by Antoine de Saint-Exupéry that is commonly translated to English as "what is essential is invisible to the eye" or simple "the essential is invisible to the eyes". I'm trying to translate it to Latin for a birthday card and the best that I could was "quod est per se invisibilis oculum". It is right? Does anyone suggest a better translation?