Renee Zellweger may have undergone a series of facial cosmetic procedures, a renowned Berverly Hills plastic surgeon explained about the sudden change on the award-winning actress' face.

Renee Zellweger  was a hot topic among netizens because the sudden change of her appearance when she attended Elle 21st Annual Women In Hollywood Celebration in Beverly Hills, Calif.,

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ET interviewed Beverly Hills plastic surgeon Dr. Stuart Linder to find out about what really happened to the Academy Award-winning actress' face.

"Ms. Renee Zellweger has obviously had a lot of different changes occur to her face," Dr. Linder divulged with ET.

He was sure that the actress had her eyes touched because "they look very different."

The doctor also mentioned about her jawline, which "dramatically changed her face with the procedures that she's had."

However, the doctor was not really sure what specific procedure did she undergo, although she hypothesized that she might have had botox.

"Looking at the three different parts of her face -- upper third, lower third and middle third -- it appears that she may have had Botox," he said, given that "no wrinkles in her forehead" are noticeable.

But taking a closer look at the photos alone, one could speculate that the 45-year-old actress had opted for more invasive procedures.

"Looking at her eyes, they have dramatically changed from her before pictures from just a couple years ago," Dr. Linder observed.

"The upper eyelids may have undergone [a procedure] where you remove the skin, and I think it's pretty reasonable that she has had this because the positions of her eyebrows have gone down in her current pictures, and the eyelid crease is more prominent. And if you look at her outer eyebrows, called the lateral brow, they've come down as well. And that's also a telltale sign of having skin removed from the upper lids."

Dr. Linder also speculated that Zellweger might have even gone through facelift and a necklift.

"Renee's transformation is very, very significant," Dr. Linder said, concluding that it was not just one operation, but "several different procedures [have been] done."

TagsRenee Zellweger, Elle 21st Annual Women In Hollywood Celebration, Dr. Stuart Linder