Which is used for correcting hypermetropia?

Appeared in: HPSSC Staff Nurse - 2021

Explanation

Hypermetropia (farsightedness) is a condition where light from distant objects focuses behind the retina.
A convex lens is a converging lens, meaning it bends light rays inward, increasing the eye's focusing power.
By adding refractive power, the convex lens moves the focal point forward from behind the retina to directly onto the retina, correcting the vision.
The provided image visually demonstrates this principle, showing the convex lens bringing the focal point onto the retina.

Option A: A concave lens is a diverging lens that spreads light rays apart. It is used to decrease the eye's focusing power.
Option C: A bifocal lens is defined by having two different optical powers, not by the type of correction it provides for a single refractive error. It is a solution for a combination of vision problems.
Option D: This option is incorrect because a specific and effective corrective lens for hypermetropia exists.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Correction of refractive errors of the eye, specifically hypermetropia as background academic context rather than a clinical decision trigger.
Understanding the principles of refractive errors is crucial for nurses, especially in pediatric, school health, and geriatric settings, to identify potential vision problems in patients and educate them about corrective measures.
Patient education is key. A nurse can explain to a patient or their family why a specific type of lens (e.g., convex for farsightedness) is prescribed and how it works to improve their vision.
What if? If a patient with hypermetropia is mistakenly given concave lenses, their vision will become even blurrier because the diverging lens will push the focal point even further behind the retina, exacerbating the refractive error.

How to Approach the Question

First, identify the key term in the question: 'hypermetropia'.
Recall the definition of hypermetropia (farsightedness) and the underlying optical problem: light focuses behind the retina.
Consider the goal of correction: to move the focal point forward onto the retina. This requires a lens that converges or adds focusing power.
Analyze the function of the lens types in the options. A concave lens diverges light, while a convex lens converges light.
Based on the analysis, conclude that a convex (converging) lens is needed to correct hypermetropia.
Confirm this by cross-referencing with the provided image, which clearly shows a convex lens correcting the condition.

Concept Tested & Keywords

Concept Tested: Correction of refractive errors of the eye, specifically hypermetropia.
Stem keywords: hypermetropia, correcting
Lead-in keywords: Which is used for

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E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1719-1721

E6 Physiology Guyton 4SAE Part 3 p. 142-144

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