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At this age they can often suffer with sticky eyes. They sleep a lot more so they don't clean and the eyes are shut for long periods so the secretions can dry and stick them shut. Try bathing them with a cotton ball soaked in saline (cooled boiled water with salt in it) If it opens and looks OK then you can wait.
Often when they are starting to decline they eyes will be constantly gummy and stuck and the stress of opening them can be too much for them. If they look red or something else seems amiss then you should see the vet again.