Ciliary body issues: http://www.thirdeyehealth.com/ciliary-body.html
In my case, the causes are:
– intense reading and writing, virtually 15 hours a day, with barely any rest.
– limited blinking (staring at the computer) leading to static load on eye muscles.
– limited stretching of eye muscles
When you look at a distant object (more than 10 feet away) the ciliary body relaxes and the lens flattens out. When you read or look at an object within arm's length, the ciliary body contracts and the lens becomes more rounded.
Significant lactic acid and its toxic byproducts that were not cleared from the system. Very similar to RSI.
NOTES: The normal blink rate in human eyes is 16–20 per minute. Studies have shown that the blink rate decreases to as low as 6–8 blinks/minute for persons working on the computer screen. This leads to dry eyes. Also, the near focusing effort required for such long hours puts strain on ciliary muscles of the eye. This induces symptoms of asthenopia and leads to a feeling of tiredness in the eyes after long hours of work. [Source]
USE OF GLASSES MAY BE WORSENING THE SITUATION:
REFERENCE: Must read this: Computer Vision Syndrome: A widely spreading but largely unknown epidemic among computer users