Final answer:
The total area you can see as you look straight ahead is called the field of vision. It includes central and peripheral vision, whereas the Snellen chart tests visual acuity, not the field of vision.
Step-by-step explanation:
The total area you can see as you look straight ahead is called your field of vision. This term encompasses everything you can see without moving your head or eyes, which includes both your central and peripheral vision. The Snellen chart is often used in optometry to test visual acuity, which is your ability to see fine details. Visual acuity tests do not measure the field of vision. To test the boundaries of your peripheral vision, an examiner may perform a simple test by asking you to identify when fingers held to the side of your vision are no longer visible. There are also comprehensive tests to examine the visual fields thoroughly. An ophthalmoscope may be used to inspect the optic disk, where the optic nerve emerges from the eye, aiding in the assessment of overall eye health and function.