If you spend too much time in front of computers, it surely impact your eyes. Long term staring at the monitor would reduce the frequency of blinking and cause eye strain. As to the mouse laser, there are two different kinds of mice, optic mice and laser mice. Optic mice usually give out red light or sometimes blue light, which is led light. It is better not to staring at the light. Normal application of the optic mice would not cause damages to the eyes, because we can't see any light in the normal application. As to laser mice, the light is invisible for human eyes. You should not to look at it too. Laser mice are more sensitive to the movement and they are more accurate. Anyway, mice are not to be looked at, they are to be moved. Don't try to look at the light or no light to avoid possible damages. Don't let children play it too.
It depends on what types of mouse you use. Usually, most of mouse is simply a red light. It won't cause too much damages to your eyes though looking at bright light can make eyes tired quickly. In fact, i think there is seldom people that will always look at the mouse light. Most of people only focus on the computer screen. So, it make no senses to discuss about those question here. Maybe you can shield your eyes with computer glasses if you often work on computers.
The optical mouse's lasers power is so small that will be little impact to your eyes normally. But please do not stare at the bottom of the mouse. If you want to avoid the light, please change a thick shell's mouse. The mouse lasers will be less than the computer screen. The brand of mouse is important that the wicked mouse would impact your eyes. The mega brand's mouse will make you feel relax. But you can take some exercise after the long time working with the computer, the fresh air and green plants will bring the good eyesight for you.
The mouse emits a laser beam and then the reflected image is received by the CMOS sensor and sent to the DSP (Digital Signal Processor) .. this cycle happens multiple times in a second .The DSP detects patterns and changes in the images and tracks the movement of the mouse and then sends the coordinates to the computer, a typical laser mouse is 2X or 3X more sensitive than optical mice
laser mice can be used on any surface as laser reflects off anything
However, optical mice can't be used on shiny surfaces like glass. So the mouse lasers are bad for eyes. You may put some green plants beside the computer, or have a rest and have a look at the far sight.