That is undoubtedly a bacterial problem that is most likely due to humid/moist weather. Monitor it...but these are usually minor issues.

Yes there has been wet weather for a week. The week before the wet weather came the leaves looked perfect.

Here in NY some pear varieties are easy to grow and others are very difficult at some sites. Between scab, fabracea and pear psyla, I usually don't get a precise bead on the issue but can keep pears healthy with a 2% early oil spray and several aps of a good pear fungicide like Flint or Mancozeb and sometimes a follow up insecticide that can handle psyla (not counting a couple insecticide sprays to protect fruit).

What is the variety that is suffering? If the tree defoliates by about mid-summer you will need to either do a lot more spraying or grow tougher varieties. If it is just a few leaves that look like that then forget my advice and let the tree be.

The pear trees received an oil spray but no fungicide. The damaged leaves are from a Bartlet pear tree. A Moonglow next to it looks ok. A Keiffer tree I have has a small amount of damage.

Never seen that before. Only issue i've ever had with pears is blister mites...that looks totally different. Sounds good what others have said.

Update.
The condition shown on the previous picture worsened and spread to the Moonglow pear but not as bad. I sprayed with Monterey Fungi-Fighter (Propiconazole) and Bayer Disease Control (Bacillus subtilis) several times during the season and the condition slowed. This spring I did a dormant oil spray and copper spray before the pears leafed out. Once leaves started to form in April I sprayed with Bacullus subtilis and again a week later. Now in May the leaves are fully formed and they are all perfect. I'll be watching them closely.