They're called scanlines.
To add them:
- File > New
- 8 x 8 pixels, background contents = transparent, leave the rest default
- Zoom in like 3000%
- Right-click the brush tool and go to the pencil tool
- Set your size to 1 px
- Click on the canvas and create a diagonal line, like so,
Obviously only the one in the middle
- Press Ctrl + A
- Go to Edit at the top > Define pattern
- Save it as 'Scanlines'
- Make a new document for your text or open the one you already have
- Double-click the text > pattern overlay > click the drop-down menu where it says 'Pattern:' and go to the scan lines



thanks for that pic 

