Are you squinting and straining just because you constantly have to lean forward to reach your keyboards and see your screen? You can solve the problem by attaching a separate monitor and keyboard (if you use a laptop).
Avoid crossing your legs which can make it difficult for you to keep your spine straight and shoulders squared. You will also put risk overstretching the muscles around your pelvis, causing you to develop varicose veins by interrupting blood flow.
Don't get the habit of pinning the phone between your ear and your shoulder while you multi task. It will also be tough for the neck! Instead, use a headset or speakerphone for any calls that lasts for more than 5 minutes.