Which condition is described by the phrase 'The inability to focus different meridians simultaneously'?

Which condition is described by the phrase 'The inability to focus different meridians simultaneously'?

• A. Nearsightedness
• B. Astigmatism
• C. Presbyopia
• D. Hyperopia

Answer: (A)

Light from a point should be focused to a single point on the retina. When the eye’s curvature is not the same in all directions, one meridian focuses light at one distance and a perpendicular meridian at a different distance. Because the focal points don’t align, you can’t bring all meridians to focus at once, so the image is blurred or distorted. This describes astigmatism, where uneven corneal or lens curvature causes different meridians to focus at different depths. Nearsightedness and farsightedness involve the overall position of the focal point relative to the retina (in front of or behind it), and presbyopia is about a loss of accommodation with age; none describe the simultaneous misfocusing of multiple meridians.

Light from a point should be focused to a single point on the retina. When the eye’s curvature is not the same in all directions, one meridian focuses light at one distance and a perpendicular meridian at a different distance. Because the focal points don’t align, you can’t bring all meridians to focus at once, so the image is blurred or distorted. This describes astigmatism, where uneven corneal or lens curvature causes different meridians to focus at different depths. Nearsightedness and farsightedness involve the overall position of the focal point relative to the retina (in front of or behind it), and presbyopia is about a loss of accommodation with age; none describe the simultaneous misfocusing of multiple meridians.