FINAL ROUND LEADERBOARD:
-15 R Karlsson (Swe) -12 A Quiros (Spa) -11 L Westwood (Eng), B Rumford (Aus) -8 O Wilson (Eng), P Casey (Eng), B Dredge (Wal)
Selected others: -7 T Bjorn (Den) -6 Pe Lawrie (Ire) -5 N Dougherty (Eng), G McDowell (NIre) -3 S Garcia (Spa)
Karlsson missed four months of last season with an eye problem
Sweden's Robert Karlsson fired a final-round bogey-free 65 to claim a three-shot victory in the Qatar Masters.
The European Ryder Cup star held off defending champion Alvaro Quiros (67) of Spain to finish 15 under in Doha.
Australian Brett Rumford (69) and England's Lee Westwood (70) ended 11 under as overnight leaders Paul Casey and Bradley Dredge slipped back.
England's Casey carded 74 to end eight under, the same mark as Welshman Dredge as Karlsson overhauled a two-shot lead.
The 40-year-old, who in 2008 became the first Swedish player to be named European number one, missed four months of last season after suffering from blurred vision caused by fluid behind the retina in his left eye.
"It was a tough time coming back," said Karlsson, who won the last of his nine other professional victories at the Dunhill Links Championship in 2008.
"I had a couple of good finishes at the end of last year with Henrik (Stenson) at the World Cup and with a second in Japan, but it is fantastic to be back now.
"I am really happy to be back playing well, it is the first time I have played really well for a long time and the way I finished off today was very satisfying."
European number one Westwood saw his chance of victory vanish when he three-putted the par-four 16th for bogey, but he held firm to claim a 12th top-10 finish in his last 15 events.
Westwood was forced to use a new driver after cracking the face of his previous club during Saturday's third round.
He put himself in contention with four birdies in five holes after the turn, moving him within one shot of Karlsson with four holes remaining.
But after his mistake at the 16th Karlsson pulled clear with back-to-back birdies over his closing two holes.
"It's hard to imagine anything else going wrong this week so 11 under is an unbelievable score," said Westwood.
"Long, straight driving is one of my strengths and if you take someone's strengths away from them it is going to very difficult to compete."
World number nine Casey, who is back to fitness after a long-term rib injury, dropped three shots on his front nine to go out in 39 and added two further bogeys mixed with three birdies on the way home.
Dredge, who won the last of his two European Tour titles in 2006, handed in a card the exact reverse of Casey's - 35 out and 39 back.
England's Oliver Wilson (71) finished with a hat-trick of birdies to share fifth at eight under, while Thomas Bjorn carded 69 for eighth place at seven under.
Scotland's Marc Warren had a disappointing 74 to finish 11 shots adrift of Karlsson, with compatriot Richie Ramsay four shots further back after a 70.