Glasses: explained and compared

Questions about Glasses

Each answer below is the short version; the question links to the page that carries it in full, with sources.

• Should I choose glasses or contact lenses?

  Neither is better in general. Glasses are simpler and carry almost no risk of eye infection; contact lenses offer a wider field of view and no frame, at the cost of handling, hygiene and a small infection risk.

• What are varifocals, and how are they different from bifocals?

  Both provide more than one focal distance in one lens. Bifocals have a visible line dividing two zones; varifocals blend the zones gradually, so there is no line and the transition is smoother.

• Can a glasses prescription be inaccurate?

  A prescription can differ between tests, partly because refraction depends on your responses during the test and partly because the eye’s focusing changes through the day, especially when tired or dry.

• Is laser eye surgery better than wearing glasses?

  Neither is better in general. Glasses are reversible and low risk; surgery is permanent and convenient for people it suits. Which one is the better choice depends on your eyes, your prescription and how much the dependence bothers you.

• Why do I need reading glasses after 40?

  Reading glasses become necessary because the lens inside the eye can no longer change shape enough to focus on near objects. The change is gradual and usually noticed first in low light or when tired.

• Can you need glasses again after LASIK?

  Some people do, either for a small residual prescription, for reading as presbyopia develops, or because their prescription drifts over the years.

• Can LASIK eliminate glasses completely?

  LASIK can remove the need for glasses for distance vision in many people, but no procedure can promise that you will never need glasses again at any point in your life.

• What does the prescription on my glasses card actually mean?

  The numbers, measured in dioptres, describe how much and in what direction light needs to be bent to focus on your retina. A minus value means short sightedness, a plus value means long sightedness, and a cylinder value describes astigmatism.

• Can cataract surgery reduce dependence on glasses?

  It can, and the extent depends on the lens chosen and on your eyes. Distance vision is commonly much less dependent on glasses afterwards, while reading often still needs help unless a lens designed for a range of distances is used.

• Do I need special glasses for computer work?

  Some people benefit from a lens designed for intermediate distances, particularly if they already need reading correction, because a standard reading prescription is set for closer work than a screen.

• Do blue light glasses work?

  Blue light filtering lenses have not been shown to reliably reduce eye strain or prevent eye damage from screen use. Some people report that they feel more comfortable, and that is a legitimate reason to wear them, but it is not the same as a protective effect.

• What are the signs a child may need glasses?

  The signs worth acting on are squinting, sitting very close to a screen or book, holding things close, tilting the head, complaining of headaches after reading, or one eye turning.