why test only *once*? statistically, over 85% of all heritable traits which will affect a dog, will be symptomatic by 24-MO. so IMO, testing at 12-MO, 14-MO, or 20-MO would be pretty doggone silly - research has shown that if U wait to breed until both sire & dam are 24-MO before breeding, that adds an average 2-years to their pups' lifespans - surely among the simplest & least-expensive ways of extending a lifespan! :yesnod: as dogs age beyond 2-YO, especially past 5-YO & markedly past 8-YO, all eye-diseases become more likely - everything from cataracts & PRA to dry-eye or detached retinae, including glaucoma [high pressure in the eye]. if a breeding-candidate tested with normal intra-ocular pressure at 18-MO & U bred her/him then, & the dog later developed glaucoma at 2 or 5 or 7, that trait would already have passed to the pups. IME, most breeders whose breed has a tendency to glaucoma test their breeding stock annually, & once the dog retires from active breeding, at least bi-annually [every 2-years - just in case].