Contact Lenses

Authored by , Reviewed by Dr Colin Tidy | Last edited | Meets Patient’s editorial guidelines

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Contact lenses are optical devices that sit over of the clear front surface of your eye (the cornea). They are most commonly worn as an alternative to spectacles to correct problems with your vision. They need to be looked after carefully.

For most people, contact lenses are a convenient way of avoiding the need for spectacles. They don't mist up in the heat, you don't waste time trying to remember where you put them, they don't catch on your eyelashes when you blink, or make your eyes look bigger or smaller, and they don't get in the way during sport.

Contact lenses are not suitable for everyone. You need to learn to put them in and take them out, which some people find difficult. They need handling and changing in a careful and hygienic manner. Poor care of contact lenses can lead to serious eye problems, particularly corneal infection (keratitis). Whilst these problems are uncommon, they can damage your vision.

Most contact lenses are used to correct problems with the focusing of your vision, such as short-sightedness (myopia) and long-sightedness (hypermetropia), astigmatism and age-related long-sightedness (presbyopia). In this they are an alternative to spectacles, usually chosen for cosmetic reasons.

Some conditions affecting the front of the eye (cornea) are treated using a contact lens. These include keratoconus (where the cornea is cone-shaped rather than curved), irregularities in the surface of the cornea, and anisometropia (when your two eyes have unequal ability to focus).

In the UK around 3.5 million people use contact lenses. People over 65 years of age are much less likely to choose contact lenses over spectacles but there is no upper age limit for wearing contact lenses.

Soft contact lenses

These lenses sit over the coloured part of the eye (the iris) and are soft and flexible. They contain a lot of water, and are oxygen-permeable, allowing your cornea to 'breathe' through the lens. They are the most comfortable type of lens to wear but may not always give the very best vision. They come as daily disposable lenses or as lenses which you wear daily but keep for different periods of time, most commonly a month but often longer.

Hard (rigid) lenses

These were the first contact lenses in general use but are now mainly used to treat disorders of the cornea (like keratoconus). They are not gas-permeable so they tend to 'starve' the cornea of oxygen over a few hours. They give a very good, reliable result for your vision. Because they are hard they are a little easier to fit and remove and they last a long time.

Gas-permeable rigid lenses

These combine the best properties of hard and soft lenses. They let oxygen through to the cornea but are a bit easier to handle than soft lenses. They give a good result for your vision and some can be worn overnight. Some are made specifically for people with short sight (myopia) to wear overnight, in an effort to reshape the cornea so that they are not needed during the day. Gas-permeable lenses are smaller than the iris of your eye.

Scleral lenses

These are large, rigid lenses that rest on the white of the eye (the sclera) and don't touch the cornea. They are mainly used for medical conditions affecting the cornea.

Treatment lenses

Soft bandage lenses and collagen shields are not for normal wear but are types of treatment lens used for some conditions affecting the cornea.

Coloured lenses

These are often worn cosmetically, to correct unevenness in colour between the two eyes, and in conditions like albinism and coloboma where the iris is pale or incomplete. It is also possible to have refractive soft contact lenses tinted with colour.

Contact lenses are usually fitted by an optometrist, often working from a high street optician's premises. Some specialist contact lenses need to be fitted by eye specialists.

Cosmetic, non-prescription contact lenses can be purchased online.

It usually takes a few days for your eyes to get used to wearing soft contact lenses, and a week or two to get used to the harder, gas-permeable lenses. After this time your lids stop 'noticing' the edge of the lenses as you blink.

This depends on the lenses and, particularly, on how much oxygen they allow through to your cornea. Daily disposable lenses are designed to be worn just for the day, then discarded - they should not be worn for sleep. Extended-wear contact lenses can be worn continuously (day and night) for specific periods. Some silicone hydrogel lenses allow so much oxygen through that they can be worn continuously for 30 days.

Taking care of your eyes means taking care of your contact lenses too. Care of contact lenses is aimed at preventing them from becoming contaminated with chemicals or debris, or with bugs (pathogens) that can damage your eyes. In particular a bug called acanthamoeba can cause serious eye infection.

Care of your eyes involves washing your hands, thoroughly and with soap (avoiding moisturising soaps, which are not good for lenses), every time you handle your lenses or touch your eyes. You need to wash the whole of your hands, including the fingers and fingertips (which are the parts that will handle the lens and touch the eye).

Tap water, saliva and swimming pool water should not touch the lens; you should only swim or splash in a tub if you are wearing watertight goggles. Contact lenses should be taken out and discarded if they come into contact with water.

Daily disposable lenses

These are thrown away at the end of the day: you can't use lens cleaning solutions to try to prolong their life and you don't need to disinfect them.

Reusable lenses

Reusable lenses must be cleaned, rinsed and disinfected after wear, and are stored in special solution to keep them hydrated. In some cases you may also need to use protein removers to clean deposits (produced by your eyes) off your lenses. They must not be rinsed with tap water, which can contain acanthamoeba, the very bug (pathogen) you are most trying to avoid.

  • You must use fresh solution every time, as once the solution has been handled germs (bacteria) will get into it and can grow.
  • Cleaning removes protein deposits, cosmetics and other debris. You should rub the lens in the palm of your hand with a few drops of solution, then rinse the lens well with lens solution. Place the lens in the (cleaned) lens case and fill with fresh solution (don't top up old solution). Disinfecting kills bugs (pathogens) on the lens.
  • Depending on how much protein your eyes deposit on your contacts, you may need to use a product for protein removal. Cleaning removes some protein but it can build up on extended-wear lenses and can make them uncomfortable. Products include weekly enzymatic cleaners and daily protein removal liquids.
  • Lenses need to be kept hydrated when not in use, also using a lens solution. All-in-one solutions can be used to clean and store the lenses.
  • If your eyes are dry you can use contact lens eye drops to lubricate them and re-wet your lenses.
  • If you develop an allergy to the contact lens solution, switch products to those which are preservative-free.
  • You should clean, rinse and air-dry your contact lens case immediately after removing your lenses, rubbing the inside of the case, rinsing it with fresh multipurpose solution or sterile saline (not water), then air-drying it upside down.
  • Lens cases can easily become contaminated with bugs (pathogens), so you should replace your lens case every month.

Lens care products

  • Saline solution is for rinsing and storing your lenses. You also may need it for use with cleaning tablets or cleaning/disinfecting devices. Never use saline solution for cleaning and disinfection.
  • Daily cleaner is just for cleaning lenses.
  • Multipurpose solution is for cleaning, rinsing, disinfecting and storing lenses.
  • Hydrogen peroxide solution is for cleaning, disinfecting, rinsing and storing your contact lenses. It is useful if you are sensitive to the preservatives in multipurpose solutions. You need to use neutralisers as part of a hydrogen peroxide system. Never rinse your contacts with hydrogen peroxide solution and apply them directly to your eyes without completing the neutralising step, as hydrogen peroxide is alkaline and can cause a painful chemical injury to the eye.
  • Cleaning/disinfecting devices clean and disinfect your contact lenses using ultrasonic waves or subsonic agitation and ultraviolet light.
  • Protein cleaners and enzyme cleaners are for removing protein build-up on your lenses. You are more likely to need these if you are using extended-wear lenses.
  • Eye drops for contact lens users can help lubricate your eye and the lenses. It is essential to use brands intended for contact lens wearers.

80% of people who use contact lenses are unaware that failing to keep contact lenses clean and to take them out at the right time carries a small but very real risk of serious eye infection. A short internet search will show you people blogging about how they wished they had known about this before it happened to them.

The main disadvantage is the need for careful lens care. We know that many people don't take this seriously and don't always wash their hands or clean their repeated-use lenses. This is like gambling with your eyesight - most of the time you won't have a problem, but if you do have a problem it may be very difficult to solve and it could damage your vision.

You can experience problems with the lens, with your cornea (the clear part of the eye at the front) or with your conjunctiva (the clear part of the eye over the white, and on the underside of your eyelids). The most serious problem is microbial keratitis.

Problems with the lens

Poor lens fit
Tight lenses feel comfortable at first, getting worse over a few hours. The cornea swells and little scrapes (erosions) develop. Your lens will not move on blinking and seems fixed. Loose lenses result in the lens moving on the eye and you may notice your vision varying when you blink.

Poor lens care

  • Not cleaning the lenses properly may lead to the build-up of protein deposits on them. This can cause irritation and impair your vision.
  • Bugs (pathogens) can live on the lens and fungi can grow into it, making keratitis more likely.
  • Chemicals such as hairspray, smoke and sun cream can get on to the lens and blur it.

Lens damage

  • Soft lenses are most easily damaged. If the lens is chipped or cracked it may get a sharp edge which can irritate the cornea, and the lens is more prone to pick up bugs.
  • Warping of the lens may occur if it is squeezed too much during cleaning of kept in a hot place. Wearing a lens which has distorted can change the shape of your cornea, which then may not fit your normal lenses and can take months to return to normal.
  • If wearing lenses tends to stop you blinking, as it does for some people, the lens and your eye may become dry.

Problems with the conjunctiva

Allergic conjunctivitis
Allergic conjunctivitis is usually due to preservatives in some lens care solutions. You get redness, burning and itching which are worst when you put the lenses in and reduces over time. The condition may not develop until many months after you start using the lenses.

Giant papillary conjunctivitis
This an allergy to the lens itself, making the eye irritated and red. If you develop this you may have to leave the lens out for a while and then try a different shaped lens.

Toxic conjunctivitis
In this condition, the chemicals in the cleaning solution, or substances you get on your hands, become absorbed into the lens and then you react to them. This is mainly a problem with soft lenses.

Problems with the cornea

The cornea is the clear window on the front of your eye. It plays a major role in focusing your vision but it also needs to stay clear in order for you to see. It is extremely sensitive and when inflamed or infected, can be extremely painful.

Corneal inflammation
Corneal inflammation (superficial punctate keratitis) is the most common problem due to lens wear and may occur as a result of you developing dry eyes, often through not blinking. Smoke, dusty conditions, medication and some types of air conditioning may make it worse. The surface of the eye becomes irritated and your eye may feel sore and look red.

Corneal injury
Scratches and scrapes to the cornea can result from a damaged lens, from your fingers or fingernails when inserting or removing the lens, or from fine grit trapped under the lens when you put it in. When you have a corneal injury, your eye will be sore, red, gritty and watery.

Contact lens-induced red eye
This is a deeper inflammation than superficial punctate keratitis and is known as infiltrative keratitis. You will have an inflamed, sore, very red eye which, although not actually infected, can appear to be. It is usually related to wearing extended use contact lenses for long periods. You may need to revert back to shorter duration of wear, after a break to rest the eyes.

Corneal infection
Infection of the cornea (microbial keratitis, or MK) makes your eye red and painful, with a feeling as if there is something in it. The pain can be severe, particularly in acanthamoeba keratitis. MK can be caused by a number of different bacteria, viruses, protozoa and fungi.

MK is the most severe complication of contact lens use, as it can damage your vision. It affects about 2-4 per 10,000 wearers per year. It is more common in soft lens users who leave their lenses in for longer than recommended (in this group it affects 20 per 10,000 per year). It is most commonly caused by infection with bacteria, but a rarer and more damaging form is caused by single-celled creature (a protozoan) called acanthamoeba.

  • Bacterial keratitis:
    • Most bacteria don't easily penetrate the surface of the cornea and get right into it, but they are more likely to do so if you wear your contact lenses for too long, or don't keep them clean enough. Some bacteria get into the eye more easily than others.
  • Acanthamoeba keratitis:
    • Acanthamoeba can cause a damaging, long-lasting and extremely painful infection of your cornea. Acanthamoeba is found in air, water (fresh, salty, tap, swimming pool and hot tub), dust, soil or sewage. It survives freezing, boiling and chlorination. It causes grittiness, reduced vision and pain (which can be severe, even when the eye looks fairly normal). Ulcers can form on the cornea. It needs urgent specialist treatment.
    • Acanthamoeba keratitis is rare, affecting around 20 contact lens wearers out of every million each year. By far the most of these live in hard water areas. Most recover without harm, slowly; however, about 2 out of 10 need surgery such as corneal grafts (replacements) and some will permanently lose some vision.
  • Viral keratitis:
    • Viruses can also cause keratitis, which may cause an ulcer on the surface of the eye. Whilst this is not particularly caused by contact lens wear, if you develop a viral eye infection and are a contact lens wearer you will need to take your lenses out until the infection has settled.
    • Cold sore viruses (herpes simplex) and the shingles virus (chickenpox) are the most common causes:
      • If you get shingles (herpes zoster) affecting your eye you should take your lenses out until the condition is resolved.
      • If you have a cold sore and wear lenses you should think about leaving the lenses out until the sore has resolved. If leaving them in you should only touch your eyes after thorough hand washing, to avoid transferring the virus to your eye.

Serious eye infections are rare complications of contact lens use. Excellent lens hygiene, including hand washing, cleaning nails, care in inserting and removing the lenses, and using lenses only for as long as intended all help prevent serious infection.

Gas-permeable lenses carry the lowest risk of microbial keratitis. Daily disposable soft lenses are not quite as low-risk, but infections tend to be less severe than in reusable contact lenses, probably because the more harmful germs (bacteria) that get on lenses actually breed in the contact lens case (and you don't need one with daily disposables).

Many people (6 in every 100 contact lens wearers) will experience problems with their lenses at some point. Most of these are not serious, although you do need to have your eyes checked. The most common symptoms are redness, soreness and irritation.

Some conditions make contact lens problems more likely, including:

  • Dry eyes.
  • Eyelid inflammation (blepharitis).
  • Atopic or allergic conjunctivitis.
  • Prolonged lens wear including overnight wear.
  • Smoking.
  • Immunosuppression.
  • Trauma or surgery.
  • Increasing age.
  • Systemic diseases such as rheumatoid arthritis and ankylosing spondylitis.

Ask yourself:

  • Does my eye look good?
  • Does the eye feel good?
  • Is the vision out of that eye normal?

If the answer to any of these questions is no then you should take out your contact lens.

If you develop a red or painful eye, or your vision worsens, you should immediately stop wearing the contact lens and seek advice from your optician or doctor.

Can I use eye ointment or drops when wearing contact lenses?

  • You can't use ointment with contact lenses; they will smear and blur.
  • You should not wear lenses when you are treating a red eye (in case it is keratitis).
  • It's better not to use drops with soft lenses but if you need to then use preservative-free drops, as preservatives accumulate in soft lenses and can cause irritation.
  • Rigid lenses can be worn with some drops.

Will my medication affect my contact lenses?

Some medicines can affect your eyes and make wearing your lenses more difficult by increasing protein deposits on the lens, making eyes drier or more swollen, discolouring the lens or making the eye inflamed. These include many common antidepressants, antibiotics, anxiety medications, blood pressure medicines and the contraceptive pill.

When you are given a new prescription check the list of side-effects on the information leaflet and see if contact lenses are mentioned. If in doubt, ask your optician or doctor.

Can I swim whilst wearing contact lenses?

You should not swim wearing your contact lenses unless you can be absolutely certain that you have watertight goggles. Even then it may be hard to prevent water getting on to your lenses when you get out of the pool and dry off. Water, including tap water and pool water, may contain acanthamoeba which can cause the rare but extremely serious acanthamoeba keratitis. If you are a swimmer and decide you really need to risk it and wear lenses under your goggles, daily disposables are the best type, as the chance that you will need to throw them away after your swim is fairly high.

At what age can you start using contact lenses?

Small children can occasionally need contact lenses for medical reasons but they would not normally manage the lenses themselves.

Children can use contact lenses once they are ready and mature enough to manage the lens hygiene and learn to put the lenses in and take them out. Optometrists often suggest that at around 8 years of age many children who want to do so can try contact lenses.

Can I play sport whilst wearing contact lenses?

Contact lenses are probably the best way of correcting your vision during sport, since they will not become dislodged and you do not risk breakage.

Can contact lenses permanently improve my vision?

Some soft contact lenses are worn at night to reshape the cornea, so that short sight is improved even without lenses during the day.

Can I have coloured prescription lenses?

You can usually order coloured soft lenses. Gas permeable lenses are not coloured, as they are smaller than the iris (coloured part of your eye) so this would look odd.

How do I decide which kind of lenses to choose?

You should discuss this with your optometrist, as the choice may partly depend on the health and vision of your eyes. Most people tend to start with soft lenses, as daily disposables.

I am going travelling in a remote environment. Should I take my lenses?

You need to judge whether you will be able to manage your lens hygiene. If you are travelling in a remote environment for a long period, hygienic care of reusable lenses may be impossible. You could take daily disposable lenses with you but you need to be meticulous with your hand washing before handling the lenses and your eyes. Take spectacles as a back-up, in case your eyes become sore or red.

I need bifocals or multifocals. Can contact lenses help me?

Contact lenses are available as bifocals or multifocals. The near prescription is usually at the bottom of the lens, as with bifocal and varifocal spectacles. Various techniques are used to keep the lens the right way up, including shaping it and weighting it.

It is possible to have a 'monovision' fit, when one contact lens has a distance correction and the other has a near correction. Most people's eyes learn to manage this so that you have both sorts of vision, although initially some double vision or 'ghosting' can occur..

A hybrid bifocal fit involves one contact lens with a distance zone in the centre and the other with a near zone in the centre; both lenses have an intermediate zone in the surrounding area. People whose vision has altered a lot as they have aged can find this very helpful.

Can contact lenses get lost around the back of my eye?

Contact lenses cannot get around the back of your eye, as there is no access for them to get there. If a lens slips away from the front of your eye as you try to put it in or take it out, and you can't find it, it is likely to be under your eyelid, on your finger or to have fallen on the floor.

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