Final answer:
The Amsler Grid is a diagnostic tool used to detect astigmatism, characterized by uneven focus in the eye. It involves observing a patterned grid and noting any distortions or irregularities. Astigmatism can be corrected with cylindrical lenses, which differ from spherical lenses used for other refractive errors.
Step-by-step explanation:
The Amsler Grid is a tool designed to detect astigmatism, which is an unevenness or asymmetry in the focus of the eye. When looking at the grid, if lines along some axes appear darker or clearer than others, it indicates the presence of astigmatism. Astigmatism is often due to irregularities
in the shape of the cornea, the lens, or the retina. Spectacles with a cylindrical correction can at least partially correct for astigmatism, distinguishing them from the spherical corrections used for short- or farsightedness.
To use the Amsler Grid, one should check each eye separately, focusing on the center cross, and without spectacles if they are normally worn. If certain lines appear distorted or are missing, it can be a sign of astigmatism or other issues related to the retina.
The test is a simple, non-invasive way to demonstrate the sensitivity of foveal vision and detect any visual disturbances or irregularities.