• AglaSem
  • Schools
  • Admission
  • Career
  • News
  • Hindi
  • Mock Test
  • Docs
  • ATSE
aglasem
No Result
View All Result
aglasem
  • CBSE
    • Date Sheet
    • Syllabus
    • Sample Papers
    • Question Papers
  • ICSE / ISC
  • State Boards
    • Date Sheet
    • Admit Card
    • Result
    • Sample Paper
    • Question Paper
  • NCERT
    • NCERT Books
    • NCERT Solutions
    • NCERT Exempler
    • Teaching Material
  • Mock Tests
  • Study Material
    • Notes
    • Solved Sample Papers
    • Maps
    • Writing Skill Format
  • Olympiads
    • ATSE
    • KVPY
    • NTSE
    • NMMS
  • School Admission
  • Entrance Exams
    • JEE Main
    • NEET
    • CLAT
  • Students Guide
    • Careers Opportunities
    • Courses & Career
    • Courses after 12th
  • Others
    • RD Sharma Solutions
    • HC Verma Solutions
    • Teaching Material
    • Classes Wise Resources
    • Videos
No Result
View All Result
aglasem
No Result
View All Result

Defects of Vision – Study Material

by Anwesha Bose
January 21, 2023
in 12th Class, Study Material
  • BML Munjal Univ 2023 Application - Apply Now!
  • Plaksha University B-TECH Application - Apply Now!

Sometimes, the eye may gradually lose its power of accommodation. In such conditions, the person cannot see the objects distinctly and comfortably. The vision becomes blurred due to the refractive defects of the eye. There are mainly three common refractive defects of vision. These are (i) myopia or near-sightedness, (ii) Hypermetropia or far – sightedness, and (iii) Presbyopia. These defects can be corrected by the use of suitable spherical lenses. We discuss below these defects and their correction.

(a) Myopia

Defects of Vision

Myopia is also known as near-sightedness. A person with myopia can see nearby objects clearly but cannot see distant objects distinctly. A person with this defect has the far point nearer than infinity. Such a person may see clearly upto a distance of a few metres. In a myopic eye, the image of a distant object is formed in front of the retina [Fig. 11.2 (b)] and not at the retina itself. This defect may arise due to (i) excessive curvature of the eye lens, or (ii) elongation of the eyeball. This defect can be corrected by using a concave lens of suitable power. This is illustrated in Fig. 11.2 (c). A concave lens of suitable power will bring the image back on to the retina and thus the defect is corrected.

(b) Hypermetropia

Defects of VisionHypermetropia is also known as far-sightedness. A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly. The near point, for the person, is farther away from the normal near point (25 cm). Such a person has to keep a reading material much beyond 25 cm from the eye for comfortable reading. This is because the light rays from a closeby object are focussed at a point behind the retina as shown in Fig. 11.3 (b). This defect arises either because (i) the focal length of the eye lens is too long, or (ii) the eyeball has become too small. This defect can be corrected by using a convex lens of appropriate power. This is illustrated in Fig. 11.3 (c). Eye-glasses with converging lenses provide the additional focusing power required for forming the image on the retina.

(c) Presbyopia

The power of accommodation of the eye usually decreases with ageing. For most people, the near point gradually recedes away. They find it difficult to see nearby objects comfortably and distinctly without corrective eye-glasses. This defect is called Presbyopia. It arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens. Sometimes, a person may suffer from both myopia and hypermetropia. Such people often require bifocal lenses. A common type of bi-focal lenses consists of both concave and convex lenses. The upper portion consists of a concave lens. It facilitates distant vision. The lower part is a convex lens. It facilitates near vision.

These days, it is possible to correct the refractive defects with contact lenses or through surgical interventions.

Click Here for All Open Educational Resources

To get fastest exam alerts and government job alerts in India, join our Telegram channel.

Tags: Class 12 Sample PapersClass 12thHaryanaSample Papers
Previous Post

Twinkling of Stars – Study Material

Next Post

Motion – Study Material

Related Posts

Class 12 Result
12th Class

Goa HSSC Result 2023 (out for 1st Term) – Check GBSHSE Class 12 Result

Class 11 and 12 Exam Date
11th Class

Assam HS Routine 2023 – Download AHSEC Class 12 Exam Date PDF 

Class 12 Exam Date
12th Class

Goa HSSC Time Table 2023 (Revised) – Download GBSHSE Class 12 Exam Date PDF 

12th Class

Maharashtra Board HSC Admit Card 2023 – Download MSBSHSE HSC Hall Ticket

Leave a Reply Cancel reply

CBSE Board Quick Links

  • CBSE Date Sheet
  • CBSE Result
  • CBSE Syllabus
  • CBSE Sample Papers
  • CBSE Question Papers
  • CBSE Notes
  • CBSE Practice Papers
  • CBSE Mock Tests

Class Wise Study Material

  • Class 1
  • Class 2
  • Class 3
  • Class 4
  • Class 5
  • Class 6
  • Class 7
  • Class 8
  • Class 9
  • Class 10
  • Class 11
  • Class 12

Registration Open!!

  • BML Munjal Univ 2023 Application - Apply Now!
  • Plaksha University B-TECH Application - Apply Now!

Haryana Board

  • Haryana Board Date Sheet
  • Haryana board Result

Study Material

  • Haryana Board Question Papers
  • Haryana board Syllabus
  • Haryana board Question Paper Design
  • Haryana board Books

Open School

  • Haryana Open School Date Sheet
  • Haryana Open School Admit Card
  • Haryana Open School Result

Scholarship Exams

  • ATSE Scholarship Exam for Class 5 to 12
  • Haryana NTSE for Class 10
  • Haryana NMMS for Class 8

Board Exams 2023

  • Solved Sample Papers
  • Maps
  • Revision Notes
  • CBSE
  • State Board

Study Material

  • Class Notes
  • NCERT Solutions
  • NCERT Books
  • HC Verma Solutions
  • Courses After Class 12th

Exam Zone

  • JEE Main 2023
  • NEET 2023
  • CLAT 2023
  • Fashion & Design
  • Latest
  • Disclaimer
  • Terms of Use
  • Privacy Policy
  • Contact

© 2019 aglasem.com

  • CBSE
    • Date Sheet
    • Syllabus
    • Sample Papers
    • Question Papers
  • ICSE / ISC
  • State Boards
    • Date Sheet
    • Admit Card
    • Result
    • Sample Paper
    • Question Paper
  • NCERT
    • NCERT Books
    • NCERT Solutions
    • NCERT Exempler
    • Teaching Material
  • Mock Tests
  • Study Material
    • Notes
    • Solved Sample Papers
    • Maps
    • Writing Skill Format
  • Olympiads
    • ATSE
    • KVPY
    • NTSE
    • NMMS
  • School Admission
  • Entrance Exams
    • JEE Main
    • NEET
    • CLAT
  • Students Guide
    • Careers Opportunities
    • Courses & Career
    • Courses after 12th
  • Others
    • RD Sharma Solutions
    • HC Verma Solutions
    • Teaching Material
    • Classes Wise Resources
    • Videos

© 2019 aglasem.com

LPU Application Form 2023 Apply Now!!