This answer is not a substitute for medical advice and medical advice questions are off-topic here. If you have concerns about your eyesight you must speak to your optometrist (or ophthalmologist if you are under their treatment).
Question 1 - Can nearsightedness be just a result of eyes getting accustomed to working at very close distances most of the time?
In people with short-sightedness, the eye has usually grown slightly too long.
This means that when you look at distant objects, the light isn't focused directly on to your retina, but a short distance in front of it.
Image source: WebMD - What Is Myopia
The NHS website has a good set of pages about myopia (short-sightedness) where it is found that
Spending a lot of time focusing your eyes on nearby objects, such as reading, writing and possibly using hand-held devices (phones and tablets) and computers can increase your risk of developing short-sightedness.
However, myopia cannot be halted permanently.
Short-sightedness usually stops getting worse at around the age of 20.
There's currently no single treatment available that appears to stop this progression.
But it may be slowed by treatments involving eye drops of a medication called atropine, or special contact lenses.
Research has shown that atropine eye drops can slow the progression of short-sightedness, but it can cause side effects at high strengths (such as difficulty reading and sensitivity to bright light). (Source: NHS - Myopia Treatment)
Questions 2 and 3 regarding anti-corrective glasses to make those short distances seem longer
As highlighted by the Mayo Clinic, it is a myth that wearing eyeglasses that have the wrong prescription will damage the eyes, but it may make your vision worse and cause other problems such as headaches.
Eyeglasses change the light rays that the eye receives. They do not change any part of the eye itself. Wearing glasses that are too strong or otherwise wrong for the eyes cannot harm an adult's, although it might result in a temporary headache. At worse, the glasses will fail to correct vision and make the wearer uncomfortable because of blurriness, but no damage to any part of the eye will result.
The use of so called anti-corrective lenses is a topic of discussion in many blogs but I would heed caution on taking advice from blogs.
There have been scientific studies on "undercorrection" of myopia in children (Chung, et al. 2002) which found that it enhances rather than inhibits myopia progression.
How to slow down, and maybe halt progression of myopia
If you use computer screens over a long period each day, especially if you do so as part of your job, wearing the correct prescribed eyewear would be the best thing to do.
Employers must provide and pay for eyesight tests and any resulting prescription where requested by the employer in law under the Health and Safety (Display Screen Equipment) Regulations 1992 here in the UK, and in the European Union under Council Directive 90/270/EEC of 29 May 1990. Employers must also ensure that employees take regular and adequate breaks from looking at their screens.
This applies whether you work at home, hotdesk at different locations or workstations, or work at a fixed workstation.
The Heath and Safety Executive website points out that
The law says employers must arrange an eye test for display screen equipment (DSE) users if they ask for one, and provide glasses if an employee needs them only for DSE use.
DSE work does not cause permanent damage to eyes. But long spells of DSE work can lead to:
- tired eyes
- temporary short-sightedness
DSE work is visually demanding, so it can make someone aware of eyesight problems they have not noticed before (including changes in eyesight that happen with age).
Employees can help their eyes by:
- checking the screen is well positioned and properly adjusted
- making sure lighting conditions are suitable
- taking regular breaks from screen work
More can be read on this via the main page at http://www.hse.gov.uk/msd/dse
Chung, K., Mohidin, N., & O’Leary, D. J. (2002). Undercorrection of myopia enhances rather than inhibits myopia progression. Vision research, 42(22), 2555-2559. doi: 10.1016/S0042-6989(02)00258-4 PubMed: 12445849