Ability of the human eye to focus images accurately on the retina is called

Step 1: Analyze the question The question asks for the term describing the eye's ability to focus images (near or far) accurately on the retina.

Step 2: Explain the concept Light from an object passes through the cornea and lens and must land exactly on the retina to form a sharp image. To see objects at different distances, the eye changes the shape of the lens. This is done by the ciliary muscles and suspensory ligaments:

• Near objects: ciliary muscles contract, suspensory ligaments slacken, and the lens becomes thicker (more convex), so the focal length is shorter.
• Distant objects: ciliary muscles relax, suspensory ligaments tighten, and the lens becomes thinner (less convex), so the focal length is longer.

This adjustment of the lens to focus light on the retina is called accommodation.

Step 3: Check each option

• A. Astigmatism: a defect caused by an uneven curvature of the cornea or lens, so images are blurred. It is a defect, not the focusing ability.
• B. Myopia: short-sightedness, a defect in which distant objects look blurred because the image forms in front of the retina.
• C. Adjustment: a general word, not the correct biological term for this process.
• D. Accommodation: the correct term for the eye's ability to focus images on the retina by changing lens shape.

Step 4: Answer The correct option is D. accommodation.

Exam tip: Remember that accommodation means the eye "accommodates" (adapts to) different distances. Defects in vision, such as myopia, hypermetropia, astigmatism, and presbyopia, are the failures of this process, so they are never the answer to a question about the ability to focus.