Sunglasses are not suitable for using a computer.Some sunglasses have non-prescription lenses, they won't help you see clearly. It sounds like you are nearsighted. The best way is to go to the optician and get prescription glasses. If you spend a lot of time on computer, you'd better buy a pair of computer glasses which can help you relieve from eye strain and prevent your vision getting worse.
As we know, the sunglasses are used to protect our eyes from the uv rays or other bad lights when we are outside. If you keep on using the computer, you'd better choose computer glasses not sunglasses while on a computer. You could do some eye healthy exercises to make your eyes feel comfortable. You could use some eye drops to release the tiredness of the eyes.