Farsightedness is corrected by using:

DSSSB 14 August 2024

Applied Physiology

Easy

Appeared in: DSSSB 14 August 2024

Explanation

Farsightedness (hypermetropia) is a common vision problem where distant objects may be seen clearly, but near objects appear blurry.
This occurs because light rays entering the eye focus behind the retina, often due to a shorter-than-normal eyeball or a lens that is too flat.
A convex lens is thicker in the center and thinner at the edges, causing light rays to converge or bend inward.
By placing a convex lens in front of a farsighted eye, it adds the necessary refractive power to bend the light more sharply, shifting the focal point forward onto the retina where it belongs.

Option A: A cylindrical lens does not provide uniform correction in all directions. It is specifically designed to correct for astigmatism.
Option B: A bifocal lens contains two prescriptions, it is not a single type of lens for one specific error. While one segment might be convex, the primary purpose is to address presbyopia.
Option C: A concave lens diverges light rays, which would worsen farsightedness by moving the focal point even further behind the retina.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Refractive Errors and Corrective Lenses as background academic context rather than a clinical decision trigger.
Nurses should be aware that uncorrected farsightedness can cause symptoms like eye strain, headaches, and fatigue, especially after close work. Recognizing these symptoms can prompt a referral for a vision test.
Patient safety is a key concern. For example, an older adult with uncorrected hypermetropia may struggle to read medication labels correctly, leading to dosage errors. Ensuring patients have appropriate corrective eyewear is a part of holistic care.
What if? If a patient has both farsightedness and astigmatism, a simple convex lens is not enough. They would need a special 'toric' lens, which combines the spherical correction of a convex lens with the cylindrical correction for astigmatism.

How to Approach the Question

First, identify the key term in the question: 'Farsightedness'.
Recall the underlying optical problem in farsightedness (also known as hypermetropia): light focuses behind the retina.
Think about the goal of correction: to move the focal point forward onto the retina.
Consider the properties of the lenses offered. A convex lens converges light, increasing focusing power. A concave lens diverges light, decreasing focusing power.
Logically deduce that a converging (convex) lens is needed to add focusing power and correct the deficit in farsightedness.
Rule out the other options by remembering what they correct: concave for nearsightedness, cylindrical for astigmatism, and bifocal for presbyopia.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 3 pp. 143-145, 142-144, 137-139