Defects of Vision - UNSOLVED PRACTICE SET

Q7. Define myopia. State
(a) the symptom,
(b) the position of the image in a myopic eye, and
(c) two possible causes of myopia.

Q8. Define hypermetropia. How does the image of a nearby object form in a hypermetropic eye? What is the typical near point of a hypermetropic person?

Q9. What is presbyopia? How is it different from hypermetropia, even though both affect near vision? Which age group is most affected?

Q10. Distinguish between myopia and hypermetropia in terms of:
(a) the type of objects not clearly visible,
(b) where the image forms, and
(c) the cause (eyeball shape or lens curvature).

Q11. What is astigmatism? How does it differ from myopia and hypermetropia? What type of lens is used to correct it?

Q12. A grandfather in a Tamil Nadu family holds the newspaper at arm's length to read it. What defect does he likely have? Explain what is happening optically in his eyes.

Q13. Explain myopia (short-sightedness) in full detail. Your answer must cover:
(a) what the person can and cannot see clearly,
(b) the near point and far point of a myopic person,
(c) why the image forms in front of the retina — explain using the concept of excessive refraction,
(d) the two structural causes of myopia (elongated eyeball and overly curved cornea/lens), and
(e) a ray diagram description showing the image formation in a myopic eye and the corrected image after using the appropriate lens.

Q14. Explain hypermetropia (long-sightedness) in detail. Your answer must cover:
(a) what the person can and cannot see clearly, 

(b) how the image forms behind the retina for nearby objects,
(c) the two structural causes (short eyeball or weak cornea/lens curvature),
(d) the far point and near point of a hypermetropic person, and
(e) a description of the ray diagram showing image formation in a hypermetropic eye and after correction. How is this different from presbyopia?

Q15. Describe presbyopia and compare all three defects of vision — myopia, hypermetropia, and presbyopia — in a structured way. Your answer must:
(a) explain what presbyopia is and why it occurs with age,
(b) present a comparison table or structured comparison under: who is affected, symptom, cause, image position, and correction,
(c) explain why some elderly people need bifocal lenses,
(d) give one specific example of each defect from Indian daily life, and
(e) explain why presbyopia cannot be fully corrected by spectacles.

Q16. A myopic student cannot see objects beyond 80 cm.
(a) What is his far point?
(b) He wants to see a distant object (at infinity). The correcting lens must form a virtual image of the distant object at his far point (v = −80 cm, u = −∞). Find the required focal length f.
(c) Calculate the power of the lens.
(d) What type of lens is used?

Q17. A hypermetropic woman has a near point of 60 cm. She wants to read a book at 25 cm.
(a) The correcting lens must form a virtual image of the book (object at u = −25 cm) at her near point (v = −60 cm). Using the lens formula, find the focal length.
(b) Calculate the power.
(c) What type of lens is used?
(d) If a different woman has near point 100 cm, recalculate the required power.

Q18. A man aged 60 has myopia: far point = 2 m. He also has presbyopia: near point = 50 cm. He needs bifocal lenses.
(a) Calculate the power of the upper half of his bifocals (for distance vision — correct far point to infinity): u = −∞, v = −2 m.
(b) Calculate the power of the lower half of his bifocals (for reading at 25 cm with near point at 50 cm): u = −25 cm, v = −50 cm. 

(c) Explain why he needs two different lenses in one frame.