How to choose eye drops

Eye drops to help lubricate the surface of the eyes have been around for many years and over that time their function, form and uses have evolved. Initially they were usually only available on prescription from your doctor and some older types still are. Newer products tend to be licensed in a different way so can usually be bought over the counter. 

1st generation:
These add volume or bulk to the tear film and typically contain ingredients like hypromellose, cellulose or glycerine and are often preserved.

2nd generation:
These have staying power so do not need to be used as often.  They contain ingredients like sodium hyaluronate (also referred to hyaluronic acid) or HP guar and will usually be preservative-free or utilise a ‘soft‘ preservative.

3rd generation:
These are more about protection and usually have a combination of a second-generation lubricant along with some clever or novel ingredient to perform another function in the eye. Again they are usually preservative-free or utilise a ‘soft‘ preservative.

Gels/Ointments:
In order to achieve longer lasting results, gels are ideal for overnight use.

Eye drops need to be kept sterile and this can be achieved either using preservatives (traditional and 'soft') or novel bottles that do not let microbes into the products. 

Preserved: 
Using a preservative is a cheap and effective way to keep an eye drop sterile. For short term use this is a very valid and commonly used method e.g. antibiotic eye drops. In dry eyes where the products are likely to be used for months or even years, long term use of preservatives can be counterproductive. Over time you can become sensitive to the preservative so while the drops are supposed to be soothing to the eyes they are actually making the irritation worse.

Preservative-free on the eye: 
New preservatives are often called ‘soft’ preservatives and this is because they have a clever method of action. In the bottle they act like a traditional preservative keeping the eye drops sterile but in contact with the eye the preservative is broken down into a mix of water, oxygen and electrolytes. This means while preserved in the bottle, the eye drops are considered preservative-free on the eye.

Preservative-free: 
Drops considered to be truly preservative-free either come in vials designed for single use and thrown, meaning no preservative is necessary or in a clever multi-dose bottle. These bottles have a system of filter in the neck which prevent microbes entering the bottle allowing the solution inside to remain sterile. While these products can initially seem more expensive, because they often last 2 or 3 months once opened they can work out much more cost effective over time.

In an ideal world all eye drops should either only use a ‘soft’ preservative or be completely preservative-free.

There are a number of other features that vary from one product to another.

Osmolarity: 
There is evidence that the tonicity or osmolarity of eye drops can also be important. Ideally it needs to match that of the eyes, particularly that of an eye suffering dryness. In this case it is thought that hypotonic eye drops are preferred.

Buffering agents: 
Usually citrate or phosphate based these are used to control the pH of eyes drops so they are suitable for use in the eye. Phosphate buffers have been linked to increased damage of weakened corneas, particularly in severe dry eyes, so may be something to avoid.

Viscosity: 
Thicker eye drops can be more beneficial, but this is not always the case and sometimes you can have too much of a good thing. Thicker eye drops either contain: a different form of a lubricant e.g. a higher % or high molecule; or additional ingredients to bulk out the drop.

Suitable for use wearing contact lenses: 
If you wear contact lenses you need to ensure a drop is suitable for use while wearing them. Most drops will be fine to use before or after wearing your contact lenses, but only some can be used while wearing lenses. Remember, if you don’t wear lenses it doesn’t mean you have to avoid a product that is suitable for contact lens wearers.

You can use eye drops as often as necessary through the day, for example every hour, although every few hours is usually sufficient with newer products. It is better to use the drops to prevent discomfort rather then when it occurs. So don't wait until your eye is sore before putting more drops in. Remember if you do use drops regularly,  choose a preservative-free version. 

Finally, if an eye drop doesn't seem to be helping do not give up. Ensure you are following the advice you have been given, using them often enough and if necessary choose another with a different lubricant, preservative or other ingredient. It can take a bit of  trial and error to find the drop that is right for you.

We hope you find this guide useful and the filters we have included on our website will help you narrow down your choice of eye drops based on some or all of these criteria.

If you want to know what else you can do to help your dry eyes, read our eye health information page 'About Dry Eyes'.