"Cannot see the target", is that cannot see it at all, or is it just blurred? If blurred, that's how it's supposed to be and you concentrate on the sights. Go to a shop selling Ready Reading glasses and see if you can find a lens giving you a better image. Rather than new glasses, this company will reglaze any frames you have, very economically:- https://www.reglaze-glasses-direct.com/ Use them after your annual eye test too.
Walther CP-2 Match, FAS 604 & Tau 7 target pistols, Smith & Wesson 6" & 4" co2 pistol,
Baikal IZH 53 pistol, Gamo CFX Royal,177, Umarex SA-10 CO2 pistol.