Glasses & contact lenses: Questions and Answers
Independent Clinic verification in progress Medical review pending Updated
Glasses and contact lenses remain the benchmark every procedure is measured against. This section covers lens safety, wearing schedules, the complications that matter, and what to do about lenses before an examination or surgery.
Quick answer
Glasses and contact lenses remain the benchmark every procedure is measured against. This section covers lens safety, wearing schedules, the complications that matter, and what to do about lenses before an examination or surgery.
General educational information. It does not replace an examination, and it cannot tell you what is happening in your own eyes.
- Answers
- 24
- Topics
- 4
- Subject
- Glasses & contacts
Contact lenses change the shape of your cornea while you wear them, and for a short time afterwards. That is a practical detail with a real consequence: a surgical measurement taken too soon after lens wear can be wrong, which is why the stopping period is asked about so carefully.
The rest of this section is about the ordinary questions, like how long is too long to wear a lens in a day.
Glasses & contact lenses questions and answers
Glasses & contacts
Glasses and contact lenses remain the benchmark every procedure is measured against. This section covers lens safety, wearing schedules, the complications that matter, and what to do about lenses before an examination or surgery.
Glasses 4
Prescriptions, lens types and reading correction.
Should I choose glasses or contact lenses? Answer
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.
Many people use both, which is often the best answer for comfort and for giving the eye a rest from lenses.
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
What are varifocals, and how are they different from bifocals? Answer
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.
Varifocals take some adaptation, particularly for peripheral vision, and the amount varies between lens designs. That is worth knowing if the first pair feels wrong rather than assuming you will adjust.
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Can a glasses prescription be inaccurate? Answer
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.
If new glasses feel wrong after a couple of weeks, the answer is usually a recheck rather than persistence. That is a normal part of getting it right, not a complaint.
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Do I need special glasses for computer work? Answer
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.
This is determined by measuring the distance you actually work at rather than by buying a category of lens. Someone whose screen sits far away may need nothing at all.
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Contact lenses 8
Schedules, hygiene and comfortable wear.
Are contact lenses safe? Answer
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.
That is why the advice is unusually specific compared with most things here: no sleeping in lenses unless they are designed and prescribed for it, no tap water, and replace them when they are due to be replaced.
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
How long can I wear contact lenses in a day? Answer
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.
Wearing a lens past comfortable tolerance leaves the eye red and dry, and it is the pattern that most often leads to people concluding that they cannot wear lenses at all when a different lens or a shorter schedule would have worked.
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
How should I clean my contact lenses? Answer
With the solution the lens is designed for, by rubbing and rinsing it and storing it in fresh solution in a clean case. Never with tap water, never with saliva, and never by topping up the solution already in the case.
Reusable lenses are a medical device that lives against the surface of the eye. The steps are short and the reason for each is the same: whatever is on the lens goes onto the cornea, and the cornea has less defence against micro-organisms than skin does.
What this depends on
- Whether the lenses are reusable or daily disposable
- Whether your solution is compatible with the lens material
- How often you replace the case
Sources American Academy of Ophthalmology , National Eye Institute, National Institutes of Health (US)
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
What are daily disposable lenses? Answer
Lenses worn once and thrown away at the end of the day. They remove the cleaning routine from the equation, which is why they are often recommended for occasional wear, for people who travel, and for anyone whose hygiene routine is likely to be the weak point of reusable lenses.
What this depends on
- How often you wear lenses
- Whether you need astigmatism or reading correction in the lens
- How much the higher cost per day matters to you
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Should I choose soft or rigid contact lenses? Answer
Soft lenses are made of a flexible, water-containing material that conforms to the eye and is comfortable quickly. Rigid gas-permeable lenses are smaller, firmer and sit on the tear film, and they can give very clear vision and last longer, at the cost of a longer adaptation period.
Rigid lenses are still used for irregular corneas, where a soft lens cannot provide a smooth optical surface. That is the sense in which rigid lenses remain current rather than old-fashioned.
What this depends on
- Your corneal shape, including any irregularity
- How much of the day you wear them
- How much handling comfort matters to you
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
What is ortho-k? Answer
Orthokeratology uses rigid lenses worn overnight to flatten the centre of the cornea temporarily, so that vision is clear during the day without lenses or glasses. The effect reverses if you stop, and control of short sightedness progression in children is one reason it is used.
What this depends on
- How much short sightedness you have
- Whether you can commit to wearing lenses every night
- Whether your child can manage the routine reliably
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Can I wear contact lenses during pregnancy? Answer
Often yes, and comfort frequently changes: hormonal shifts alter the tear film and can make lenses that were comfortable feel dry or unstable. A fitting review is usually the answer rather than abandoning lenses entirely.
What this depends on
- How your eyes feel now compared with before
- Whether your prescription has shifted
- How far into the pregnancy you are
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Why do my contact lenses feel uncomfortable by evening? Answer
Usually because the eye is drier by then. Blinking rate falls during screen work, air conditioning dries the surface, and a lens that fits well on a moist eye can feel gritty on a dry one. A drier eye at night is the pattern, not the lens deteriorating during the day.
The practical fixes are the ones that change the surface: lubricant drops suitable for lens wear, shorter wearing days, and a review of the lens material and fit. If discomfort is new and one-sided, that is worth an examination rather than an adjustment.
What this depends on
- How many hours you wear them
- Whether you work in air conditioning or on screens
- Whether the lens is near the end of its replacement cycle
Sources American Academy of Ophthalmology , Peer-reviewed literature (via PubMed Central)
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Contact lens safety 8
The complications worth knowing about, and how to avoid them.
Can contact lenses damage your eyes? Answer
This answer explains what the symptom commonly indicates. If it has come on suddenly, or is accompanied by pain or loss of vision, seek urgent care rather than waiting for an appointment.
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.
The single highest-risk behaviour is sleeping in lenses that are not prescribed for overnight wear. The second is using water, including tap water, on lenses or cases.
Which symptoms need urgent care
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Can I sleep in contact lenses? Answer
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.
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
What are the signs of a contact lens related infection? Answer
This answer explains what the symptom commonly indicates. If it has come on suddenly, or is accompanied by pain or loss of vision, seek urgent care rather than waiting for an appointment.
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.
The practical first step is to remove the lens and keep it, in case it is useful to whoever examines you. Do not put another lens back in that eye.
Which symptoms need urgent care
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Can I shower or swim in contact lenses? Answer
This answer explains what the symptom commonly indicates. If it has come on suddenly, or is accompanied by pain or loss of vision, seek urgent care rather than waiting for an appointment.
Best avoided. Water carries organisms that can adhere to a lens and reach the cornea, and this is one of the recognised routes to the serious infections that contact lens wearers are warned about. If water gets in your eye with a lens in it, remove the lens and discard it if it is disposable.
The risk is small per exposure and the consequence is uncommon, which is exactly why the advice is easy to dismiss and worth keeping. Swimming in goggles with lenses in is the compromise most clinicians accept.
What this depends on
- Whether the water is chlorinated, salt or fresh
- Whether the lens is disposable
- Whether you have any break in the surface of the eye
Which symptoms need urgent care
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Do contact lenses expire? Answer
Yes, both the lenses and the solution. Lenses past their expiry date have a degraded material, solution past its date and past four weeks after opening no longer disinfects reliably, and neither problem is visible from looking at them.
What this depends on
- The expiry date on the packaging
- When the bottle of solution was opened
- How the lenses have been stored
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Can contact lenses cause astigmatism? Answer
They do not cause corneal astigmatism, and a lens that fits badly can temporarily distort the cornea so that measurements taken while you are wearing it are inaccurate. That temporary change is the reason for the stopping period before an assessment.
What this depends on
- How the lens fits
- How long you have been wearing lenses of this type
- Whether the change persists after leaving them out
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
What should I do if a contact lens is stuck in my eye? Answer
This answer explains what the symptom commonly indicates. If it has come on suddenly, or is accompanied by pain or loss of vision, seek urgent care rather than waiting for an appointment.
Do not keep picking at it. Put lubricant drops in, wait a few minutes, and try again with clean hands, looking in the same direction as you move the lid. If it will not move, treat it as a clinical problem and be seen the same day rather than persisting.
A lens that will not come out is often folded or displaced under the upper lid, and the eye will usually settle with drops and time. What must not be delayed is the case where the eye is painful, red or the vision is reduced: those need examination rather than another attempt.
What this depends on
- Whether the eye is painful or just uncomfortable
- Whether vision is affected
- Whether the lens was damaged before it went in
Which symptoms need urgent care
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Are coloured or decorative contact lenses safe? Answer
They are as safe as clear lenses of the same quality, properly fitted. The problems come from lenses bought without a fitting: an unsuitable fit, a material not intended for prolonged wear, and no way to check the health of the eye that is wearing them.
What this depends on
- Whether the lens was fitted for your eye
- Whether it is a regulated medical device in the country it was bought
- How long you wear it at a time
Sources American Academy of Ophthalmology
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Lenses before assessment or surgery 4
Stopping periods, and why they exist.
Can I have laser eye surgery if I wear contact lenses? Answer
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.
The period depends on the lens type and on how long you have worn them, and rigid lenses need longer than soft ones. Tell the clinic what you wear when you book.
Sources The Royal College of Ophthalmologists (UK)
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
What happens if I wear contact lenses to my eye examination? Answer
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.
For a routine sight test the effect is small. For a surgical assessment it matters, because the corneal shape is one of the measurements the surgical plan is built from.
Sources The Royal College of Ophthalmologists (UK)
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
Can I switch from contact lenses to SMILE? Answer
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.
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
When can I put a contact lens in again after laser surgery? Answer
Not until the clinic that treated you says so and the surface has healed, which is measured in weeks rather than days. Putting a lens on a healing surface is a route to infection and, after a flap procedure, to disturbing the flap.
What this depends on
- Which procedure you had
- How the surface looks at the follow-up visit
- Whether the lens is being used for a prescription or for appearance
Sources StatPearls, NCBI Bookshelf
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
No answer matches that yet. Try a simpler phrase, or ask the question directly. Questions that come up often get written up and added here.
Looking for something specific? Ask a question
These answers describe what is generally true. They are not a diagnosis and they cannot say whether a treatment is suitable for you, because suitability depends on measurements taken during an examination. Only a qualified ophthalmologist who has examined you can decide.
Sources & further reading
We prefer primary sources. Where a claim comes from a manufacturer, a single study or a regulator, it is labelled as such below.
- EyeSmart: eye health information for the public
Patient-facing material from the largest ophthalmology professional body, covering conditions, tests and treatments outside refractive surgery.
Used for Cross-checking patient-facing explanations of non-refractive eye conditions; Describing what tests such as dilation and OCT involve.
Link checked 23 September 2026
- The Royal College of Ophthalmologists
The UK professional body for ophthalmologists, which publishes standards and commissioning guidance for refractive surgery services.
Used for What good preoperative assessment and consent look like.
Link checked 22 September 2026
- Eye Health Information
Condition-by-condition eye health information from a US government research institute, written for patients rather than for clinicians.
Used for Plain-language explanations of eye conditions and their symptoms; Healthy vision and screening guidance.
Link checked 23 September 2026
- Refractive surgery and dry eye: an update
An update on how different refractive procedures affect the ocular surface, with attention to preoperative screening for dry eye.
Used for Why tear film assessment belongs in preoperative screening.
Link checked 22 September 2026
- Laser In Situ Keratomileusis (LASIK)
The equivalent clinical reference chapter for LASIK, used so that comparisons describe both procedures symmetrically.
Used for How LASIK creates and manages a corneal flap; LASIK complication categories.
Link checked 22 September 2026