For me, the key to effective antihistamine use is consistency. I find them most effective when I use them preemptively and regularly.
I take them every day year round and my symptoms are now minimal for hayfever, leaf mould allergy, tree pollen and grass pollen allergy.
Cetirizine hydrochloride is best for me for year round use, I also use loratidine and then for spring summer I use fexofenadine. You can buy fexofenadine OTC, or for stronger dose you need a script. I also use a nasal steroid everyday.
Branded antihistamines are a con. Read the ingredients to find the drug name and buy cheaper unbranded.
You haven't mentioned what or how you have used antihistamines, but if you haven't already try taking one everyday for at least two weeks. Switch to a different one if this doesn't work, them ramp up to fexofenadine and then add a nasal spray.
Another thought is; maybe it's not an allergy?
it could be gases from cleaning chemicals and also new furniture, carpets etc also "off gas" which could be effecting your eyes??
If you are sitting at a computer, could it be too bright? Have you been checked for eye health recently?