In this Macromedia Flash tutorial you will learn how to make a cool computer eye scanning effect, also know as iris security scan system.

1.
Start by importing an eye image into the stage (it may be a good idea to optimize the image in photoshop or another image software first).
File -> import -> import to stage and located your image.

2.
In the layers panel (next to the timeline) lock the layer containing the eye image, click the icon with a lock.
Make a new layer for the next step.

3.
Now with the oval tool, select a green color for the stroke and none fill color.
Drag an oval inside the eye as shown in the image below.

4.
Drag out the edges along the corners of the eye, then draw one more line for the inner eye.
and draw an oval with the same green color as fill. Now your image should look like the one below.

5.
Drag and select all the elements we just drew, right click and choose convert to symbol -> convert to movie clip.

6.
Now we will go to the filters panel and add some glow filter to the effect.
So in the filters panel add a glow filter and a blur filter as shown below.

7.
Now in the layers panel, make a new layer above the glow effect from before, this is going to be a mask layer.
Draw a rectangle with a default color, all the way to the right of the stage as shown below.
Right click the rectangle and convert it to a movie clip.

8.
Now we will add a motion tween to this rectangle.
In the timeline right click at frame 15 and choose create a new key frame, for all three layers.
Move the rectangle all the way to the left of the stage.
Right click between frame 1 and 15 in the timeline and add a motion tween as shown below.

9.
Now in the layers panel right click the top layer and choose mask.

Now test your movie and you should have accomplished my effect.
To make the effect a bit more interesting you can add blending modes to the green glowing movie clip from step 6 as I did.