"Last year at Lytham we were given something of a fright because the way the exemptions fell at one point we had 161 competitors, but because of scratching and injuries we got back down to our usual field of 156," Peter Dawson, chief executive of the R&A, said.
"That has caused us to look at our exemptions and cut them back this year because we wanted to maintain the number of qualifying places through international qualifying and local qualifying that we had committed to."
The French Open and the Greenbrier Classic will lose their exemption rights, while only the winner of the Scottish Open and John Deere Classic will be eligible.
The number of qualifiers from the European International qualifying event at Sunningdale has also dropped from 10 to nine competitors.
The complexity of the exemption system means that some players may be eligible in more than one playing category, meaning that not all the 156 players scheduled to pull on their golf clothing at Muirfield could be determined by the time the Open comes around in July.
Dawson said that any gaps in the field will be filled by the highest non-exempt players from the Official World Golf Rankings.
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