Do the Amsler grid test
Keep your glasses
Close one eye at the time and look at the dot in the center grid below minimum 30 seconds (for more information click on the example video button right )
Repeat the test with your other eye
Thereafter, compare your vision with simulations grid at the right of this page
Amsler grid (click on the grid)
If after this test, you see a black spot or distorted lines in the middle of your visual field, talk to your eye care professional.