Which lens is used in myopia?

KGMU 2023

Medical Surgical Nursing

Easy

Appeared in: KGMU 2023

Explanation

Myopia, or nearsightedness, is a refractive error where the eye's shape causes light rays to focus at a point in front of the retina, rather than directly on its surface.
This results in clear vision for near objects but blurry vision for distant objects.
A concave lens is a diverging lens, which means it spreads out light rays before they reach the eye's lens.
This divergence moves the focal point backward, ensuring the image of a distant object is focused precisely on the retina, thus correcting the blurry vision.

Option B: A convex lens is a converging lens that increases the refractive power. It would worsen myopia by bringing the focal point even further in front of the retina.
Option C: A cylindrical lens corrects for refractive errors that are different in different meridians (planes) of the eye, which is not the primary issue in simple myopia.
Option D: While a biconcave lens is a type of concave lens and does correct myopia, 'Concave' is the broader and more fundamental classification. In multiple-choice questions, the most general correct category is often the intended answer.

Visual 1: Diagram - Show the path of light in three scenarios: (1) an emmetropic (normal) eye where light focuses on the retina, (2) a myopic eye where light focuses in front of the retina, and (3) a myopic eye corrected with a concave lens, showing the light being diverged to focus on the retina. This visual helps clarify the underlying physics of the condition and its correction.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Correction of Myopia using Lenses as background academic context rather than a clinical decision trigger.
Nurses play a key role in vision screening programs in schools and communities, helping to identify children and adults with potential refractive errors like myopia.
Patient education is crucial. Nurses can explain to patients and families the importance of wearing prescribed corrective lenses consistently to prevent eyestrain, headaches, and potential worsening of vision.
A nurse should be able to recognize symptoms of uncorrected myopia, such as squinting, sitting too close to the television, holding books close to the face, or difficulty seeing the blackboard in school.

How to Approach the Question

First, identify the key term in the question: 'myopia'.
Recall the definition of myopia. Myopia is also known as nearsightedness, a condition where distant objects are blurry.
Remember the underlying optical problem in myopia: the focal point of the eye is in front of the retina.
Consider the function of different lenses. A diverging lens is needed to spread the light and move the focal point backward.
Identify which of the options is a diverging lens. A concave lens diverges light.
Evaluate the other options. A convex lens converges light (for farsightedness), and a cylindrical lens corrects for astigmatism. A biconcave lens is a type of concave lens, making 'Concave' the best general answer.

Concept Tested & Keywords

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