Which type of lens is used to correct Myopia?

Appeared in: Central Institute of Psychiatry - 9 July 2022

Explanation

Myopia, or nearsightedness, occurs when the eye focuses images of distant objects in front of the retina, rather than on the retina itself.
This is typically because the eyeball is too long or the lens system has too much refractive power.
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 overall focal point backward, allowing it to land correctly on the retina and produce a clear image.

Option B: A convex lens converges light rays. Using it for myopia would move the focal point even further in front of the retina, worsening the blur.
Option C: A bifocal lens contains two prescriptions and is not the primary single lens type for correcting simple myopia.
Option D: A cylindrical lens corrects for uneven focus in different planes, which is not the primary issue in simple myopia.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Correction of refractive errors, specifically myopia as background academic context rather than a clinical decision trigger.
Nurses play a role in vision screening programs, identifying children who may have uncorrected refractive errors by observing behaviors like squinting, sitting too close to screens, or complaining of headaches.
Patient education is key. Nurses can instruct patients on the proper use and care of glasses or contact lenses to ensure optimal vision and prevent complications.
Recognizing the symptoms of different refractive errors helps in referring patients to an ophthalmologist for timely diagnosis and correction, preventing potential complications like amblyopia (lazy eye) in children.

How to Approach the Question

First, identify the key term in the question: 'Myopia'.
Recall the definition of myopia. It is also known as 'nearsightedness', meaning a person can see near objects clearly, but distant objects are blurry.
Understand the underlying optical problem: in myopia, the eye's focal point for distant objects is in front of the retina.
Determine the goal of the corrective lens: to move the focal point backward onto the retina.
Consider the properties of the available lenses. A lens that spreads out or 'diverges' light is needed to achieve this.
Match this function to the correct lens type. A concave lens is a diverging lens, while a convex lens is a converging lens. Therefore, a concave lens is the correct choice.

Concept Tested & Keywords

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

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 pp. 1719-1721, 1720-1722

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