i just use below command, and it works for me. ( windows 10 pro 64-bit, Anaconda 4.6.8, Spyder 3.3.2)
(base) C:\Windows\system32> conda install opencv
output like this:
=============================================
Collecting package metadata: done
Solving environment: done
Package Plan
environment location: C:\ProgramData\Anaconda3
added / updated specs:
    - opencv
The following packages will be downloaded:
package                    |            build
---------------------------|-----------------
libopencv-3.4.1            |       h875b8b8_3        37.0 MB
opencv-3.4.1               |   py37h6fd60c2_3           9 KB
py-opencv-3.4.1            |   py37h1b0d24d_3         1.5 MB
------------------------------------------------------------
                                       Total:        38.5 MB
The following NEW packages will be INSTALLED:
libopencv          pkgs/main/win-64::libopencv-3.4.1-h875b8b8_3
opencv             pkgs/main/win-64::opencv-3.4.1-py37h6fd60c2_3
py-opencv          pkgs/main/win-64::py-opencv-3.4.1-py37h1b0d24d_3
Proceed ([y]/n)? y
Downloading and Extracting Packages
py-opencv-3.4.1      | 1.5 MB    | ################################### | 100%
opencv-3.4.1         | 9 KB      | ################################### | 100%
libopencv-3.4.1      | 37.0 MB   | ################################### | 100%
Preparing transaction: done
Verifying transaction: done
Executing transaction: done
============================================================================
finally, i tested it in IPython console and Spyder editor and run, both of them works fine.