Hypermetropia: Definition, Causes, and Correction Explained

The topic of Hypermetropia is important in physics and biology, especially in understanding how our eyes work and the ways to correct common vision problems. This concept is widely discussed in optics chapters and also forms a crucial part of medical entrance exam syllabi.

Understanding Hypermetropia

Hypermetropia, also known as farsightedness, is a defect of vision where a person can see distant objects clearly but finds it difficult to see nearby objects. This defect is mainly caused when light rays from an object form an image behind the retina instead of precisely on it. Hypermetropia is commonly covered along with hyperopia (its synonym), myopia (short-sightedness), and refractive defects in eye studies.

Causes and Explanation of Hypermetropia

There are several reasons for hypermetropia in the human eye:

• The eyeball is too short from front to back.
• The cornea is flatter than normal, so it refracts (bends) light less.
• The lens cannot become curved enough or loses its power to focus.

Because of these structural issues, the light rays from a nearby object do not converge on the retina but focus at a point behind the retina. As a result, close-up objects appear blurry while distant objects remain in focus.

Correction of Hypermetropia: Working Principle

The most common method to correct hypermetropia is by using a convex lens (also called a converging or plus lens). The convex lens helps by converging the incoming light rays before they enter the eye, allowing the image to form directly on the retina. The corrective power needed can be measured in dioptres (D).

Ray Diagram for Hypermetropic Eye

The ray diagram for hypermetropia shows parallel rays from a nearby object focusing behind the retina. With a convex lens in front of the eye, the rays are bent inwards and brought into sharp focus on the retina, allowing the person to see clearly.

You can explore diagrams and additional explanations about lenses here: Concave and Convex Lens Differences.

Here’s a useful table to understand hypermetropia better and compare it with myopia:

Comparison: Hypermetropia vs Myopia

Worked Example / Practical Experiment

Let’s solve a basic example to understand the correction of hypermetropia:

1. A person’s near point is 50 cm from the eye (normal is 25 cm).
2. Required power of lens:
Power (P) = 1/f
Using lens formula: 1/v - 1/u = 1/f
(Here, v = -25 cm, u = -50 cm)
Calculate f, then Power.
Conclusion: The lens with this power will help form the image on the retina for close objects.

Practice Questions

• Define hypermetropia with an example.
• Which type of lens is used for correcting hypermetropia?
• Draw the ray diagram for a hypermetropic eye before and after correction.
• How is hypermetropia different from myopia?
• Explain the formula to calculate the power of contact lens for hypermetropia correction.

Common Mistakes to Avoid

• Confusing hypermetropia (farsightedness) with myopia (nearsightedness).
• Using a concave lens for correction instead of a convex lens.
• Misrepresenting the ray diagram or placing the image on the wrong side of the retina.
• Forgetting that both children and adults can have hypermetropia, but causes may differ.

Real-World Applications

Hypermetropia is not just a textbook concept. It affects many people in real life and forms the basis for designing eyeglasses and contact lenses. This condition is also relevant in the design of optical instruments and in visual sciences. Learning about hypermetropia with Vedantu helps students link theory with practical, everyday solutions in optics and eye health.

In this article, we explored hypermetropia—its definition, causes, ray diagrams, correction, and real-world uses. For more on related topics, check The Human Eye Structure and Functions, Lens Maker’s Formula, and Eye Defects and Correction Overview. Keep learning with Vedantu to master optics and physics concepts.