How many eye drops per dose are needed?

Research: how many eye drops per dose are needed?

How many eye drops per dose are actually needed? Many people squeeze the bottle twice or even three times just to be sure. Yet for most prescribed eye medication, one properly administered drop per eye is sufficient.

The eye can only hold a limited amount of fluid. A second drop therefore often runs over the eyelid margin, ends up on the cheek or washes part of the first drop back out of the eye.

Scientific research also shows that eye drops from standard bottles are often already larger than the amount the eye can hold without overflowing. Using more drops therefore does not automatically mean the medicine works better. It can in fact cause waste, an empty bottle sooner and possibly greater absorption of the active substance into the body.

In this research, the Oculoo Research Team analyses how many eye drops per dose are needed, why one drop is usually enough and what you can do when you are not sure whether the drop reached the eye.

Summary of the key conclusions

The key conclusions from the consulted studies and medical instructions are:

• For most prescribed eye medication, one drop per eye per administration is sufficient.
• A standard eye drop often contains more fluid than the eye can hold.
• A second drop usually does not increase the effect.
• Excess fluid runs out of the eye or drains through the tear duct.
• Only when you are certain the drop missed the eye completely can you usually instil another drop.
• Your doctor’s prescription, the pharmacy label and the package leaflet always take precedence.

The Rotterdam Eye Hospital advises patients to use one drop per eye. For many prescribed medicines too, including various glaucoma medicines and anti-inflammatory eye drops, the usual dose is one drop per administration.

How much fluid can an eye hold?

The eye surface is relatively small. Between the lower eyelid and the eyeball there is a space in which the eye drop lands. This space is often called the conjunctival sac.

Research estimates that under normal conditions this space can hold about 30 microlitres of fluid before it overflows. The exact capacity varies by person, posture, blink reflex and amount of tear fluid.

A 2023 study compared standard eye drops with smaller drops. The standard bottles produced drops of about 40 microlitres on average. That is already more than the amount the eye can usually hold without overflowing.

This explains why fluid often runs down the cheek after a single eye drop. That does not automatically mean the entire drop was lost. Part of it may already have reached the eye surface.

Is one eye drop really enough?

For most medicinal eye drops one drop is sufficient, provided it lands properly in the eye.

A second drop usually no longer fits fully into the eye. The extra fluid may:

• run over the eyelid margin;
• end up on the skin;
• partly wash away the first drop;
• flow through the tear duct into the nose;
• be absorbed into the bloodstream faster.

That is why hospitals and medicine information sources usually advise letting one drop fall into the lower eyelid pocket.

There are exceptions. For certain moisturising eye drops or artificial tears, the package leaflet may state that one to two drops may be used. For special treatments the ophthalmologist may also prescribe a different schedule. Your personal prescription therefore always takes precedence over general advice.

Why do people still use multiple drops?

Many people cannot clearly feel whether an eye drop has reached the eye. An eye drop is small, falls quickly and can land on the eye, the lashes or the eyelid at the same time.

That is why people sometimes squeeze again as a precaution. Other common reasons are:

• the bottle is squeezed too hard;
• several drops come out at once unintentionally;
• the user blinks before the drop reaches the eye;
• the drop hits the lashes;
• the bottle is not positioned properly above the eye;
• due to reduced vision the user cannot see where the nozzle is;
• it is difficult to apply exactly the right pressure.

A 2025 study observed 187 people with glaucoma while instilling eye drops. Although 84.5% managed to get at least one drop into the eye, only 36.4% met all criteria for a fully correct administration. Only 62% managed to squeeze exactly one drop from the bottle during the observation.

These results show that getting a drop into the eye is not the same as performing the whole procedure correctly.

What happens if you use too many eye drops?

When two or three drops enter the eye at once, the excess usually runs out of the eye. Accidentally using too many drops on a single occasion generally does not cause direct harm, but it is not wise to do so routinely.

The bottle empties faster

Anyone using several drops per administration uses more medication than necessary. As a result, the bottle may be empty before a new one is available.

This is especially relevant for eye medication that must be used daily and long term, such as for glaucoma. An unexpectedly empty bottle can lead to missed treatment moments.

More medicine may drain through the tear duct

Eye drops can flow through the tear duct into the nose and throat. From there, part of the active substance can enter the body.

With some eye medicines this can increase the risk of side effects outside the eye. Dutch medicine information therefore advises, for various eye drops, gently pressing the tear duct closed for about one minute after administration.

The first drop may be washed away

When another drop is administered immediately after the first, excess fluid can run over the eyelid margin. With various types of eye medication, the second drop can also wash away part of the first drop.

It is therefore advised to wait at least five minutes between different types of eye drops.

What should you do if you don’t know whether the drop reached the eye?

It can be difficult to determine whether the eye drop actually reached the eye.

Watch for the following signs:

• you briefly feel moisture or coolness on the eye;
• the eye starts to water slightly more;
• your vision is temporarily blurrier;
• a small amount of fluid runs along the corner of the eye;
• you feel a brief stinging or burning sensation.

These signs are not present with every product or every user. Feeling no sensation therefore does not automatically mean the drop missed the eye.

Are you certain the drop only landed on your cheek or forehead? Then you can usually try again. Moorfields Eye Hospital states that someone who thinks they missed the eye completely may try again straight away. Excess fluid then usually runs out of the eye.

Are you merely unsure, but part of the drop may have reached the eye? Then do not routinely instil several extra drops. For important prescribed medication, ask your pharmacy or ophthalmologist which advice applies to your medicine.

How do you prevent several drops coming out of the bottle?

The amount of force needed varies greatly per eye drop bottle. Some bottles are soft and quickly release several drops. Other packaging is stiff and requires a lot of squeezing force.

These steps can help:

1. Practise beforehand on a clean tissue

Squeeze the bottle gently once and see how much force is needed to form one drop. The Rotterdam Eye Hospital recommends this as an exercise when dosing is difficult.

2. Hold the bottle steady above the eye

Do not make quick movements. First make sure the bottle is positioned properly, then squeeze.

3. Squeeze gradually

Increase the pressure slowly until one drop releases. Stop squeezing as soon as the drop falls.

4. Gently pull the lower eyelid down

This creates a small pocket for the drop to fall into. That is often easier than aiming directly at the centre of the eye.

5. Use a mirror

A mirror can help you check the position of the bottle. This works especially well when your vision is sufficient and you can keep your head steady.

6. Ask for instilling instructions

A pharmacy assistant, nurse or eye care professional can demonstrate the procedure and check where it goes wrong. Apotheek.nl advises patients who find instilling eye drops difficult to ask for guidance or an aid.

Why the packaging affects the number of drops

Not every eye drop bottle produces the same drop size. Drop size is influenced by, among other things:

• the shape of the nozzle;
• the bottle opening;
• the thickness of the fluid;
• the temperature;
• the angle at which the bottle is held;
• the force used when squeezing.

Research shows that standard bottles can release relatively large drops. In a 2023 study, an adapted dispenser reduced the average drop size by about 62%. The researchers saw this as a possible opportunity to limit medicine waste and unnecessary exposure.

A 2025 study on pupil-dilating eye drops also showed that smaller drops could have a comparable effect to standard drops. This does not mean patients should adjust their own dose or packaging, but it does support the conclusion that a larger amount of fluid does not automatically give a better effect.

Should you blink after instilling?

After administration it is best to close the eye gently. Squeezing the eyelids tightly or blinking rapidly can push part of the fluid out of the eye.

Then, if this is advised for your medication, gently press the inner corner of the eye next to the nose closed for about one minute. This keeps the drop on the eye longer and less medication drains away through the tear duct.

A good sequence is:

1. Let one drop fall into the lower eyelid pocket.
2. Close the eye gently.
3. Do not squeeze the eyelids tightly.
4. Gently press the inner corner of the eye closed.
5. Wipe excess fluid from the skin with a clean tissue.
6. Do not touch the nozzle.
7. Close the bottle immediately.

When is one drop not enough?

One drop is not a universal rule for every product and every medical situation.

Always follow a different instruction when:

• the ophthalmologist prescribes several drops;
• the package leaflet mentions one to two drops;
• a treatment must be repeated in quick succession;
• you receive eye drops for an eye examination;
• you use artificial tears as needed;
• the doctor prescribes an intensive schedule for inflammation or a sudden rise in pressure.

Never change the dose of prescribed eye medication on your own. Using more can cause side effects, while using less can make the treatment less effective.

Aids can support accurate dosing

Instilling eye drops requires several actions to go well at the same time. The user must position the head, keep the eye open, aim the bottle above the eye and apply exactly the right force.

With reduced hand function, poor vision, trembling hands or uncertainty, this can be difficult. Research links poorer instilling technique to older age, reduced vision, arthritis and problems with manual dexterity, among other factors.

An eye drop aid can provide support in positioning or operating a suitable eye drop bottle. The aid does not change the prescribed dose. The aim is to get the prescribed drop into the eye in a more controlled way.

Frequently asked questions about how many eye drops per dose

How many eye drops should I use per dose?

For most prescribed eye medication you use one drop per eye per administration. Always follow the label, the package leaflet and your doctor’s prescription.

Is instilling twice better than once?

Usually not. The eye can only hold a limited amount of fluid. A second drop therefore often runs out of the eye or washes away part of the first drop.

Is it a problem if two drops come out by accident?

Using two drops on a single occasion is usually no reason for concern. Wipe away the excess fluid and use the prescribed amount again next time. Contact your pharmacy if you have complaints or doubts.

May I instil another drop if I missed the eye?

When you are certain the drop landed entirely outside the eye, you can usually try again. Unsure whether part of the drop did reach the eye? For prescribed medication, ask your pharmacy for advice.

Why does the eye drop run down my cheek?

A standard eye drop can be larger than the amount the eye can hold. Blinking, squeezing the eyelids tightly or using several drops can also cause overflow.

Should I use one or two drops of artificial tears?

This differs per product. Some artificial tears advise one drop and others one to two drops. Therefore check the packaging or package leaflet.

How much time should there be between different eye drops?

Usually leave at least five minutes between different types of eye drops. This prevents the second drop from washing away the first.

Conclusion

How many eye drops per dose are needed ultimately depends on the prescription and the product used. For most medicinal eye drops, one properly administered drop per eye is sufficient.

A second or third drop usually does not improve the effect. The extra fluid often runs out of the eye, is wasted or drains away through the tear duct.

Correct positioning and controlled squeezing are therefore more important than instilling several times. Do you regularly fail to get the drop properly into the eye, or do several drops keep coming out of the bottle at once? Then ask for instilling instructions or enquire about a suitable eye drop aid.

This research contains general information and does not replace personal advice from a doctor or pharmacist. Always use eye medication according to the label, the package leaflet and the prescribed treatment schedule.