Hello and thanks for your question.
It sounds as though you've had an exhaustive workup for this without much to show for it. I think that the possible key to this problem is the temporal association of the red eye and working for long hours on the computer. When we do such activities for a long time, our eyes spend less time closed because we blink less. When this happens they are prone to drying out. This dry eye condition can certainly cause and very predictably does cause a sore, red eye. It is also often that one eye is more affected than the other in dry eye, which may be the case with you.
Dry eyes can be due to many different factors. Different medicines such as psychiatric medicines, antihistamines, cold medicines and others can contribute to dry eyes. Allergies in the eyes can also contribute (make dry eyes worse). Some people have an innate deficiency in making their own tears (these people may also have other dry mucus membranes, such as their mouth, nasal passages, or genitalia). Many people have an inflammation in the eyelids called blepharitis which causes the tear film that is supposed to coat the front of the eye to not function as well, and then the eyes dry out. People with blepharitis have morning tearing, burning, and often eyelash mattering. Their symptoms get better as the day progresses, but then they get intermittent blurring when they use their eyes heavily in activities such as reading, watching TV, computer use or driving.
Because blepharitis is so under-diagnosed and the treatment for it is relatively benign, you might consider starting this treatment, while concurrently continuing artificial tears. In order to treat blepharitis, everyday in the morning you should do two things: 1. hot compresses and 2. eyelid scrubs. You should do hot compresses for 5-10 minutes over each eye at the same time. It should be as hot as you can tolerate without burning your skin, massaging the eyelids while they are on there. Then, use either commercially available preparations or a dilute baby shampoo solution to scrub your eyelashes on all 4 eyelids. The commercially available preparations are called Ocusoft or Sterilid which are both over-the-counter eyelash scrubbing treatments. These cost more money but are quicker to use. Otherwise, the cheaper alternative is the dilute baby shampoo (4-5 drops Johnson's shampoo in 1/4 cup warm water), you will take the wipe (or dip a qtip in the dilute baby shampoo solution) and use that to scrub right on the eyelashes of each eyelid for 15 seconds. That will take 60 seconds when done to all 4 eyelids. The scrubbing is done right on the eyelid margin, where the eyelashes come out. After that, just splash some water on the eyes and you're done.
It does take about 3-4 weeks of doing this consistently every day before it really kicks in, so don't stop it thinking it's not working. Also the eyes are still significantly dry during this 3-4 weeks so use the artificial tears you bought 4x/day in both eyes (one drop per application). After 4 weeks you should be able to start tapering off of the tears to as you need them.
Just doing the artificial tears, hot compresses and eyelid scrubs alone would likely start to help you after three or 4 weeks--but remember it could take this long of doing it everyday before you see a significant effect, so don't stop it thinking it's not working.
If you are a person that doesn't make their own tears very well, then you may also benefit from a prescription drop called Restasis, which actually modulates a person's immune system to help them make more of their own tears. This drop actually requires constant usage on a daily basis for up to 10-12 weeks before its effect kicks in (takes awhile to change the immune response in the body).
Does that help address your concerns?
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My opinion is solely informative and does not constitute a formal medical opinion or recommendation. For a formal medical opinion and/or recommendation you must be examined by your doctor.