Peter Ericson’s review published on Letterboxd :
"Oculus" may officially belong to the horror genre, pure and simple, but there’s more to it than that. In my opinion, the film is really closer to being a psychological horror drama. It contains several genuinely scary scenes, but they are effective only in the moment and are unlikely to give the viewer nightmares. What "Oculus" does quite well, however, is conjure up an unsettling atmosphere and a palpable sense of dread.
In the movie, co-writer/director/editor Mike Flanagan and co-writer Jeff Howard interweave the past and the present in a rather clever way. The story plays out during two different time periods, following the same central characters (at different ages, obviously). It is certainly an interesting conceit, executed with aplomb, and one that works in favor of the film.
Another major strength of "Oculus" can be found in its use of unreliable narrators. On a number of occasions in the movie, things are not what they seem. The filmmakers mess with the viewer’s head to a certain extent, and the resulting feeling of confusion is thrilling.
The fact that the film doesn’t provide an explanation of the supernatural powers of the Lasser Glass, the ominous-looking mirror at the center of the story, contributes to the effectiveness of the proceedings. Alas, the final scenes lack the punch they ought to have. The ending is unsatisfactory on an emotional level, but it makes perfect sense from an intellectual as well as a financial standpoint.
I also want to call attention to the aural experience one gets when watching "Oculus". The use of eerie sounds and silence is excellent, as is the sound mixing. The Newton Brothers’ appropriately spooky music completes the soundscape.
Karen Gillan’s fine performance as Kaylie Russell convincingly conveys the character’s obsession with proving that her brother did not commit the crime of which he was convicted by attempting to scientifically document the supposed preternatural force that she holds responsible for the terrible events in the siblings’ childhood. Brenton Thwaites, on the other hand, is a little wooden in the role of Tim, Kaylie’s brother, who has come to terms with what he thinks he did and is therefore skeptical toward his sister’s endeavor. Both Annalise Basso and Garrett Ryan, who play the younger versions of Kaylie and Tim (respectively), bring to their parts a naturalness that evokes one’s sympathy for their characters. Katee Sackhoff and Rory Cochrane do solid turns as Marie and Alan (respectively), Kaylie and Tim’s parents.