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Maharashtra State BoardSSC (Marathi Semi-English) 10th Standard Board Exam [इयत्ता १० वी]
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Defects of Vision and Their Corrections > Hypermetropia

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  • Key Points: Hypermetropia
Maharashtra State Board: Class 10

Hypermetropia and Its Causes

Hypermetropia (Hyperopia), also known as farsightedness, is a common vision defect where a person can see distant objects clearly, but nearby objects appear blurry. This occurs because light rays focus behind the retina instead of directly on it. It is common in newborn babies due to small eyeball size but often corrects itself as the eyeball grows.

Farsightedness

Hypermetropia occurs due to structural abnormalities in the eye that prevent proper light focusing.

Structural Causes:

  • Shortened eyeball → Light focuses behind the retina, causing blurred vision.
  • Flattened cornea or lens → Reduces the converging power of the eye, preventing proper focus.
  • Increased focal length of the eye lens → Leads to improper light convergence.
  • Stiffening of ciliary muscles → Reduces the ability of the eye to adjust its focus.

Maharashtra State Board: Class 10

Types and Symptoms of Hypermetropia

  1. Simple Hypermetropia: It is the most common type. Includes axial hypermetropia (short eyeball) and curvature hypermetropia (flat cornea/lens).
  2. Pathological Hypermetropia: It is caused by congenital (birth-related) or acquired conditions. Includes senile (age-related), positional, aphakic (absence of lens), and consecutive hypermetropia.
  3. Functional Hypermetropia: Occurs due to third cranial nerve palsy or internal ophthalmoplegia, causing paralysis of accommodation.

Hypermetropia is categorised based on severity (lens power required for correction):

Severity Power (Diopters, D)
Low Up to +2 D
Moderate +2.2 to +5 D
High More than +5 D

Symptoms of Hypermetropia:

  • Blurred vision while focusing on close objects.
  • Eye strain and fatigue while reading or working on screens.
  • Headaches, particularly in the forehead region.
  • Difficulty in adjusting focus, causing discomfort in switching from distant to near objects.
  • Double vision in severe cases due to excessive eye strain.
Maharashtra State Board: Class 10

Hypermetropia Correction and Treatment

A. Spectacles and Contact Lenses

  • Convex lenses (positive power lenses) are used to converge incoming light rays before they reach the eye lens.
  • The eye lens then further converges them, forming a sharp image on the retina.
  • Glasses and contact lenses are the most common correction methods.

B. Surgical Treatments for Hypermetropia

  1. Photorefractive Keratectomy (PRK): It removes a small portion of the cornea to improve refraction. May cause temporary corneal haze and astigmatism.
  2. Laser Epithelial Keratomileusis (LASEK): It is similar to PRK but uses alcohol to loosen the corneal surface before reshaping it.
  3. Laser-Assisted In Situ Keratomileusis (LASIK): It reshapes the cornea to correct the refractive error, eliminating the need for glasses or contact lenses.
CBSE: Class 10
Maharashtra State Board: Class 10

Key Points: Hypermetropia

  • Hypermetropia is a condition in which distant objects are seen clearly, but nearby objects appear blurred.
  • The near point shifts beyond 25 cm, making close-up tasks like reading difficult.
  • The image of nearby objects forms behind the retina.
  • Causes include reduced curvature of the lens or cornea and shortening of the eyeball.
  • It is corrected using a convex lens of positive power, which converges light rays to focus the image on the retina.

Related QuestionsVIEW ALL [10]

Write scientific reason.

Farsightedness, this defect can be corrected by using convex lens.

Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25 cm.

List two difference in the characteristic properties of the virtual images formed by the two types of spherical lenses (concave and convex). How are these characteristics of the two lenses use in the correction of the two common defects of vision namely myopia and hypermetropia?

The defect of vision in which the person is able to see a distant object distinctly but cannot see nearby objects clearly is called:

Assertion: The near point of a hypermetropia eye is more than 25 cm away.

Reason: Hypermetropia is corrected using spectacles containing concave lenses.

Differentiate between members of the following pair with reference to what is asked in the bracket.

Myopia and Hyperopia (type of lens used for correction).

Name the defect shown in the diagram.

Solve the following example.
Doctor has prescribed a lens having power +1.5 D. What will be the focal length of the lens? What is the type of the lens and what must be the defect of vision?

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