Pseudomyopia is a temporary shift towards near-sightness and occurs when the ciliary muscle inside of your eye temporarily locks up due to extended periods of closeup focus, resulting in blurred distance vision. This is usually the condition people get before they go to the optometrist, and then go onto to develop lens-induced myopia. If the ciliary muscle spasm is not relieved, then that muscle spasm's degree can worsen over time. Now, it will take longer to fully relax that muscle. Proper eye strain management and active focus habits will help to tackle this.
The 20-20-20 rule is useful to avoid a lock up of the ciliary muscle.