Contact lenses: explained and compared

Questions about Contact lenses

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

• 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.

• 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 have laser eye surgery if I wear contact lenses?

  Yes, and wearing lenses does not disqualify you. You do have to stop wearing them for a period before the assessment and before surgery, because lenses change the shape of your cornea.

• 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 I switch from contact lenses to SMILE?

  Many people considering SMILE are long-term lens wearers, and lens wear on its own does not rule it out. The assessment still has to show a cornea suitable for the procedure.

• What happens if I wear contact lenses to my eye examination?

  The consequence is usually that the measurements are less reliable and may need repeating, which can mean a second appointment rather than a wrong result.

• 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.

• 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.

• 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.

• 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.

• What are the signs of a contact lens related infection?

  The signs to act on are eye pain, light sensitivity, a red eye that is getting worse, discharge, or any reduction in vision in a contact lens wearer. Those need prompt assessment rather than waiting.