Screenshots of of lan and opt interfaces would be great. But for mean time do you want that pfsense act's like a router between, so it don't nat between two local interfaces?
if so, you'd have to change nat type to manual (Firewall: NAT: Outbound)
go to NAT section
select manual and click save
add new NAT rule
DO not NAT = Check this
Interface= LAN
Protocol = Any
Source = Network, put OPT subnet here
Source port = leave it empty
Destination =Network, put LAN subnet here
Destination port = leave it empty
Leave others empty
Description: opt-2-lan or something descripive
And after that create another rule which is almost the same, change Interface OPT and source and destination switch places
Finalizing touches, move this new rules at the top of the list and save/apply changes. now it should work. (I hope I didn't mess up with interfaces badly)