Myopia is also known as:

Correct — B, Near-sightedness. Myopia is the defect in which the eye's optical system converges light too strongly for its own length, so parallel rays from a distant object come to a focus in front of the retina and reach the light-sensitive layer already spreading out again. The result is a blurred image of anything far away. Near objects, whose rays arrive diverging rather than parallel, are brought to focus correctly, so a myopic eye sees close work clearly — hence near-sighted, or short-sighted. The two usual causes are an eyeball that is too long from front to back, and a cornea or lens that is too sharply curved; either produces the same mismatch. It shows up in the far point, the most distant point the eye can focus on. A normal eye's far point is at infinity; a myopic eye's has moved in to some finite distance, and the correction is a concave, that is diverging, lens of negative power, which spreads the incoming rays slightly before they reach the eye so that the focus falls back onto the retina. English keeps two names for the condition and both are in circulation, which is exactly what the question is checking.

• (a)Far-sightedness — That is hypermetropia, the opposite defect. There the image of a near object would form behind the retina, near vision blurs, and the correction is a convex lens.
• (c)Cataract — Not a focusing error at all but a clouding of the lens itself, which scatters light and dims vision. It is treated by surgically replacing the lens, and no spectacle can correct it.
• (d)Presbyopia — The age-related loss of accommodation. The lens hardens and the ciliary muscle weakens, so the near point recedes and reading becomes difficult with age. It can occur together with myopia, which is why bifocals exist, but it is a different condition.

The eye focuses by changing the curvature of its lens, a process called accommodation, so that images always land on the retina. When that fails, the failure has a direction. In myopia the focus falls short, in front of the retina, and distance vision suffers; in hypermetropia the focus falls long, behind the retina, and near vision suffers. Each is corrected by shifting the incoming rays the other way — a diverging concave lens for myopia, a converging convex lens for hypermetropia. Presbyopia is a third and separate problem: not a mis-set focus but a loss of the ability to change focus, which arrives with age in almost everyone. Cataract is not an optical error but an opacity of the lens.

The four options are not four random eye conditions; they are two pairs. Myopia and hypermetropia are opposite focusing errors, and the question is whether you can attach the right everyday word to the technical one. Presbyopia and cataract are the age-related pair, and both are there to catch a candidate who reasons that anything to do with poor sight might do. The safest mental hook is the root: myo- relates to closing or narrowing, from the habit of screwing up the eyes to see distant things more sharply, and the ending -opia simply means a condition of sight. If the root does not stick, work from the physics instead — image before the retina means distance blurred means near-sighted. Myopia matters beyond the exam: its prevalence has been rising sharply among school-age children worldwide, and time spent outdoors in daylight is one of the few factors consistently associated with slower progression.

• In myopia the image of a distant object is focused in front of the retina, so distant vision is blurred and near vision is clear.
• The usual causes are an eyeball elongated from front to back, or a cornea or lens curved too sharply.
• It is corrected by a concave, or diverging, lens of negative power.
• The far point of a normal eye is at infinity; in a myopic eye it moves in to a finite distance.
• Hypermetropia, or far-sightedness, is the opposite defect, corrected by a convex lens.
• Presbyopia is the age-related loss of accommodation as the lens hardens and the ciliary muscle weakens; it is corrected by convex or bifocal lenses.
• Cataract is a clouding of the lens, treated by surgery rather than by spectacles.

• Swapping near- and far-sightedness. Myopia is near-sighted: near vision is what still works.
• Assuming every eye complaint is a lens-correctable focusing error; cataract is an opacity and needs surgery.
• Treating presbyopia as a form of hypermetropia. Both are helped by convex lenses, but presbyopia is a loss of accommodation, not a mis-set focus.

As a synonym item like this one, as a defect-to-remedy match, or as an optics question on where the image forms and which lens corrects it.

• practice — not a real PYQ

  A myopic eye is corrected by which one of the following?

  • (a)A convex lens of positive power
  • (b)A concave lens of negative power
  • (c)A cylindrical lens
  • (d)A plane mirror

  Answer(b) A concave lens of negative power — it diverges the incoming rays slightly so that the focus, which was falling in front of the retina, moves back onto it.

• practice — not a real PYQ

  The gradual loss of the eye's power of accommodation with advancing age is called which one of the following?

  • (a)Myopia
  • (b)Hypermetropia
  • (c)Presbyopia
  • (d)Astigmatism

  Answer(c) Presbyopia — the lens hardens and the ciliary muscle weakens, so the near point recedes and close work becomes difficult.