I have to tell you that I am not an expert but I can give some guidance based on my (successful) attempt.
I have an Epson although not the one you are using.
Do make sure that the 810 is in the Avasys list, to download that specific model of rpm's.
You must take out the following files from the system :-
/usr/lib/sane/libsane-epkowa.so and /usr/lib/sane/libsane-epkowa.la (to avoid 'losing' these files, I add the suffix .bak to keep them available if the new files do not work!)
Also UNinstall sane-backends-iscan. You can then run the rpm installs - for both Avasys files. The install is with # rpm -i <iscan package xxxx>.rpm (presumably you know this - just added for completeness!)
Hopefully, your 810 will then work ok.