The visual field test can be a good indication of the health of your eyes and indeed the whole of your visual system. It is a useful part of the eye examination â for example, it is used in the diagnosis and monitoring of glaucoma, and it can show up many other problems as well.he visual field test can be a good indication of the health of your eyes and indeed the whole of your visual system. It is a useful part of the eye examination â for example, it is used in the diagnosis and monitoring of glaucoma, and it can show up many other problems as well.