What is the instruction given to a patient when using the Amsler Grid?

Covering one eye is the appropriate instruction given to a patient when using the Amsler Grid. This method allows for better assessment of central vision in each eye individually, which is crucial for detecting any potential distortions or scotomas (blind spots) in the patient's visual field.

When a patient covers one eye, they can focus on the grid, which consists of horizontal and vertical lines, while monitoring for any visual changes or abnormalities. This isolated observation helps clinicians evaluate the function of the macula, the part of the retina responsible for central vision, and can be pivotal in diagnosing conditions like age-related macular degeneration.

The other choices do not effectively facilitate the intended outcome of the Amsler Grid test. Closing both eyes would eliminate the ability to assess visual function entirely. Looking to the right would also not focus on the grid, thereby failing to provide relevant information about the patient's central vision. Focusing on a bright light does not pertain to the use of the Amsler Grid and could distract from the task at hand. Consequently, instructing the patient to cover one eye is essential for obtaining accurate and reliable results during this visual assessment.