It's hard to see how engineers are needed in society. I've needed the services of a doctor, lawyer nurse but I can't say I've ever employed an engineer. There are so many specialities to engineering and I'm just wondering which is the best bet. I already have a biological science degree but honestly it's about as useful as toilet paper.
Optical engineering is nonsense. If you want to do that get a degree in physics or optometry. An optical engineering degree would be toilet paper too.
Computer/Electrical Engineering. Specifically embedded systems and electronics are hot right now.
If you want to work for engineering companies, chemical and petrochemical plants, petroleum refineries, and pharmaceutical plants, consider chemical engineering.
If you want to be involved in building roads and bridges, design and construction of structures and buildings, then take civil and structural engineering.
The most common is mechanical engineering. But with a biological science degree, the best bet is chemical engineering.
My advice (having recruited over 50 engineers) is to get a generalist engineering degree (from a good university if possible). Medical engineering does have excellent job prospects but the specific Medical Engineering degrees available aren't as useful and the general degrees. So either a mechanical, electrical of software engineering degree would serve you best.
If salary matters then currently softies get paid the most and mechanical engineers get paid the least but this is simply supply and demand and with every diving into software engineering there will soon be a shortage of mechanical engineers so the salary balance will shift.