Glasses vs contact lenses: compared, side by side

Questions about Glasses vs contact lenses

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.

• Are contact lenses safe?

  Contact lenses are safe for most people when they are fitted properly, worn as instructed and cleaned correctly. The risks come almost entirely from overnight wear, water contact and poor hygiene.

• How long can I wear contact lenses in a day?

  How long you can wear lenses depends on the lens type, your tear film and how your eye tolerates them. Comfortable wear is the guide, and a lens that needs removing because it is irritating should come out.

• 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 contact lenses cause dry eyes?

  Contact lenses can cause or worsen dryness, because a lens sits on the tear film and can reduce oxygen reaching the surface while increasing evaporation. Symptoms often improve when lenses are reduced or stopped.

• When is a red eye urgent?

  A red eye needs urgent assessment when it is accompanied by significant pain, reduced vision, light sensitivity, a feeling that something is stuck in the eye, or contact lens wear.

• Can contact lenses cause eye infections?

  Yes. Contact lens wear is a recognised risk factor for corneal infection, and the risk rises sharply with overnight wear, with tap water contact and with poor lens case hygiene.

• How long should I stop wearing contact lenses before an eye examination?

  Soft lenses are usually stopped for a few days before an assessment and rigid lenses for considerably longer, because contact lens wear changes the shape of the cornea and can make the measurements wrong.

• 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.

• 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.

• Can contact lenses damage your eyes?

  Contact lenses can cause damage, most seriously by causing a corneal infection, which is why hygiene and wearing schedules matter so much. Long-term lens wear can also reduce the eye’s tolerance for lenses in some people.

• Can I sleep in contact lenses?

  You should not sleep in lenses unless they were prescribed specifically for overnight wear, because keeping a lens on a closed eye reduces oxygen and tear exchange and raises the risk of infection substantially.