When i use a computer in a dark room sometimes my vision is blurry. why could that be?

2 possibilities: Two possibilities: we often stare at computer screens, without blinking enough. This can cause the surface of the cornea to dry out, blurring vision. A second possible cause is due to pupil dilation the dark, reducing the focusing ability of the eye.

Drying tear film: Computer use (staring at the computer often results in decrease in blinking) is well known to dry out the tear film which leads to blurry vision. Purposeful blinking, closing the eye to take a break, looking away, or using artificial tears should be able to replenish your tear film and restore clarity of vision.

Pupillary dilation: If you are fixated on the computer screen, which is bright, your pupils are likely constricted more. This allows your to read the screen. Additionally, your lens changes shape for near focus, called accommodation. The distant objects, when your eye is in this state, will appear blurrier.