The right contact lens is the one your optician fitted and specified for your eyes. The choice you do get is mostly about how often you replace the lenses: daily disposables are worn once and thrown away, while two-weekly and monthly lenses are cleaned and stored every night and replaced on a fixed schedule.
Daily lenses are the easiest to look after because there is no solution or case to manage. Two-weekly and monthly lenses usually cost less per day of wear, but only if you follow the cleaning routine every single time. If you wear lenses only a few days a week, dailies often work out cheaper than they first look, because an opened monthly lens has to be replaced after a month whether you wore it or not.
Whatever you choose, buy the brand, curve, diameter and power on your contact lens specification. Swapping to a different lens because it is cheaper is a change your optician should approve, since lenses of the same power can fit and behave very differently on the eye.
What your contact lens specification tells you
A glasses prescription is not enough to buy contact lenses. After a fitting, the optometrist or contact lens optician gives you a contact lens specification that lists the exact lens: brand and name, base curve, diameter and power, plus extra values for astigmatism or multifocal lenses. In the UK, sellers are required to supply lenses against a valid specification, and the specification carries an expiry date set by the practitioner who fitted you.
Typical values look like this:
| Value | Example | What it means |
|---|---|---|
| PWR or SPH | -2.75 | The lens power; minus for short sight, plus for long sight |
| BC | 8.6 | Base curve in mm, how curved the back of the lens is |
| DIA | 14.2 | Diameter of the lens in mm |
| CYL and AX | -1.25 x 180 | Correction for astigmatism (toric lenses only) |
| ADD | Medium | Reading addition (multifocal lenses only) |
When you reorder, check each value against your specification before you pay. Left and right eyes often differ, so make sure you order the right lens for each eye.
Replacement schedules compared
| Type | How long one lens lasts | Cleaning needed | Suits |
|---|---|---|---|
| Daily disposable | One day of wear | None, a fresh pair each day | Part-time wearers, sport, travel, people who find routines hard |
| Two-weekly | Up to 14 days from opening | Clean and store every night | Regular wearers who want lower cost per day |
| Monthly | Up to 30 days from opening | Clean and store every night | Daily wearers who are careful with care routines |
| Extended wear | Some monthly lenses are licensed for overnight wear | As prescribed | Only when your optician recommends it |
The schedule starts when you open the lens, not on the days you actually wear it. Write the start date on the box.
You can compare daily, two-weekly and monthly brands side by side in the contact lenses range and the wider contact lens section.
Lens types for different eyes
Most people wear soft lenses, and within soft lenses there are a few main types:
- Spherical lenses correct short or long sight. They are the most common type.
- Toric lenses correct astigmatism. They are weighted or shaped so they stay in the right position on the eye, which is why the CYL and AX values must match your specification exactly.
- Multifocal lenses help people over roughly 40 who need help with close work as well as distance. Fitting them often takes a couple of trial pairs.
- Silicone hydrogel lenses let more oxygen through to the cornea than older hydrogel materials. Many current daily and monthly brands use them.
- Rigid gas permeable lenses are smaller, harder lenses used for some prescriptions and eye conditions. They are fitted individually and usually bought through the practice that fits them.
Some monthly lenses, such as Air Optix Night and Day Aqua, are licensed for continuous wear including sleep. Only sleep in lenses if your optician has fitted you for it and told you how many nights are safe, and remove them at once if your eyes become red, painful or blurred.
Solutions and cases for reusable lenses
Two-weekly and monthly lenses need a solution that cleans, rinses and disinfects them. The two common systems are:
- Multipurpose solution, which cleans, rinses and stores in one bottle. Rub and rinse each lens as the instructions say, even if the bottle says no rub, and always use fresh solution in the case.
- Hydrogen peroxide systems, which disinfect thoroughly but must neutralise for the full time stated, usually six hours, before the lens goes back in the eye. Never put peroxide solution straight into your eye.
Replace the lens case at least as often as the instructions say, typically every month when you open a new bottle. Many solution packs, such as multi-bottle packs of lens solution with cases, include fresh cases for this reason.
Water, sleep and other habits that matter
Contact lens problems usually come from habits rather than the lens itself. UK optical bodies give the same advice again and again:
- Never rinse lenses or cases in tap water, and do not shower, swim or use a hot tub in lenses unless you wear goggles. Water can carry Acanthamoeba, an organism that can cause a serious eye infection.
- Wash and dry your hands before touching your lenses.
- Even lenses with a UV blocker do not cover the whole eye, so wear sunglasses in bright sun.
- Do not top up old solution; empty the case, rinse it with fresh solution and leave it to air dry.
- Do not sleep in lenses unless they are licensed for it and your optician agrees.
- Keep a pair of up to date glasses so you can give your eyes a break. The glasses guide explains what to check when you order a pair online.
Quick checklist
- Valid contact lens specification, in date.
- Brand, BC, DIA and power match the specification for each eye.
- Replacement schedule that suits how often you wear lenses.
- Fresh solution and a new case for reusable lenses.
- No tap water, no swimming or showering in lenses.
- Aftercare check booked with your optician, usually once a year.
- Back up glasses for days when lenses are uncomfortable.
Common questions
Can I switch from monthly lenses to dailies myself?
Not without your optician. Daily and monthly lenses of the same power can have a different curve, diameter and material, so the fit changes. Ask your optician to specify the new lens, often with a trial pair first.
Are daily lenses more expensive?
Per lens, yes. Per day of actual wear, it depends on how often you wear them. Daily wearers usually pay less with monthlies plus solution; occasional wearers often pay less with dailies, because unused days of a monthly lens are lost once the pack is opened.
What should I do if my eye is red or painful?
Take the lens out and do not put it back in. If the redness, pain or blurred vision does not settle quickly, contact your optician or an eye doctor the same day, and bring the lens and case with you.
