Which lens is used to correct Short Sightedness?

Appeared in: Uttarakhand CHO - 2021

Explanation

Short-sightedness, or myopia, is a refractive error where the eye's focusing power is too strong, causing light from distant objects to focus in front of the retina.
A concave lens is a diverging lens, which means it spreads out light rays.
By placing a concave lens in front of a myopic eye, the light rays are diverged before they enter. This effectively reduces the overall refractive power and moves the focal point backward onto the retina, correcting the vision.

Option B: A convex lens is a converging lens that increases refractive power. It would make myopia worse by causing light to focus even further in front of the retina.
Option C: A cylindrical lens has different focusing power in different meridians and does not provide the uniform correction needed for simple myopia.
Option D: An opaque lens blocks light from passing through, so it cannot be used to correct vision. It would cause blindness in the area it covers.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Refractive errors of the eye and their correction as background academic context rather than a clinical decision trigger.
Nurses play a key role in community and school health programs by conducting vision screenings with tools like the Snellen chart to identify children and adults with potential refractive errors like myopia.
Patient education is a critical nursing function. This includes teaching patients about the nature of their refractive error, the importance of wearing corrective lenses as prescribed, and proper care for glasses or contact lenses.
What if? If a patient with myopia mistakenly wears glasses with convex lenses (for farsightedness), their distant vision will become significantly more blurred. The convex lens would converge light even more strongly, moving the focal point further in front of the retina.

How to Approach the Question

First, identify the condition mentioned in the question: "Short Sightedness," which is medically termed myopia.
Recall the basic optical principle of myopia: the eye's focusing power is too strong, or the eyeball is too long, causing the focal point for distant objects to fall in front of the retina.
Determine the type of lens needed for correction. To move the focal point backward, a lens that spreads out or diverges light is required.
Review the options to find the diverging lens. A concave lens is a diverging lens.
Eliminate the other options based on their functions: a convex lens converges light (for long-sightedness), a cylindrical lens corrects irregular curvature (astigmatism), and an opaque lens blocks light.

Concept Tested & Keywords

Q2c35sqLzGbCsZ6yGzcfl9

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

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

Practise the full Uttarakhand CHO - 2021

Attempt every question from this paper in a timed mock, then review the full solution for each one.