Stress
According to studies, opticians' job satisfaction is high and stress levels are about average (source). Simple and to the point, right? Surveys and opticians alike find this job to be, for lack of a more scientific term, "pretty chill."
Opticians usually have the choice to work full- or part-time. Ironically, the part-timers may be the more stressed ones, because even a full-time optician salary would take some stretching to fully provide for a family. Also, part-timers or hourly employees receive fewer (if any) benefits. Money troubles are no joke―in fact, they may be the number one stressor for most Americans these days.
Dealing with customers can also be difficult, especially when something as important as their vision is at stake. People get emotional when making difficult decisions, and it's your job to make them choose between their money and their use of sight. Believe it or not, with the price of some glasses, it can be a hard choice. If a customer doesn't want to accept their options, it puts you between a rock and a hard place.
But mostly the work is made up of juggling a few duties, and passing on relatively simple information to various parties within the office. You communicate with customers, co-workers, doctors, and ophthalmic lab techs on a daily basis, which is probably, overall, a stress reducer.
It's good to have a variety of people around you and a variety of duties (that you know you can handle). It keeps things interesting while enforcing an easy-to-follow routine.