The lens used to correct short-sightedness is known as?

Appeared in: NHM MP Staff Nurse - 2015

Explanation

Short-sightedness, or myopia, occurs when the eye's refractive power is too strong, causing light to focus in front of the retina.
A concave lens is a diverging lens, meaning it spreads light rays apart.
Placing a concave lens in front of the eye diverges the light rays before they enter, effectively reducing the overall focusing power.
This moves the focal point backward, allowing it to land precisely on the retina, thus correcting distant vision.

Option A: A convex lens is a converging lens that increases refractive power. It would move the focal point even further in front of the retina, worsening the myopia.
Option C: A cylindrical lens has different focusing power in different meridians and is specifically designed to correct the irregular curvature of the cornea or lens found in astigmatism.
Option D: This option is incorrect because short-sightedness is a very common refractive error that is effectively corrected using prescription lenses.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Correction of Refractive Errors (Myopia) as background academic context rather than a clinical decision trigger.
Understanding refractive errors is crucial for nurses, especially in pediatric and geriatric settings, to identify potential vision problems and refer patients for ophthalmologic evaluation.
Patient education is a key nursing role. A nurse can explain the nature of myopia to a patient or their family, reinforcing the importance of wearing corrective lenses as prescribed to prevent eye strain, headaches, and safety risks (e.g., driving).
What if? If a patient has both myopia and astigmatism (a very common combination), their prescription will involve a compound lens that has both spherical (concave) and cylindrical correction, specified at a particular axis.

How to Approach the Question

First, identify the key term in the question: 'short-sightedness'.
Recall the medical term for short-sightedness, which is 'myopia'.
Remember the underlying optical problem in myopia: light focuses in front of the retina.
To fix this, you need a lens that spreads light out (diverges it) to move the focal point backward.
Evaluate the options: A concave lens is a diverging lens, while a convex lens is a converging lens. A cylindrical lens is for astigmatism.
Therefore, the concave lens is the correct choice to correct myopia.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 3 pp. 143-145, 137-139

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