All about atropine

• Atropine 1% concentration can be used in eye exams to dilate the pupil of the eye and stop the eye focusing for measuring prescriptions in some children. This temporary effect causes sensitivity to light and difficulty focusing up close for reading.
• Atropine eye drops can slow myopia progression in children, called myopia control. There is a ‘dose dependent’ effect, which means that higher concentrations have stronger effects on slowing eye growth but also have more side effects.
• Concentrations of 0.01% to 0.05% are more commonly used for long-term myopia control and typically have only small effects on light sensitivity and close up vision. 
• Atropine eye drops have a high safety profile when used normally.

Atropine is a drug that is derived from the Atropa Belladonna plant. In Italian, belladonna means “beautiful woman”, and this name refers to the common practice of women in the 1300's and 1400's rubbing the leaves of the plant on their eyes to enlarge their pupils, believing this would make them more alluring.

First developed in the 1800’s, atropine has been used in medicine for treating a variety of conditions including heart disease, respiratory conditions, bowel disorders, and some eye conditions.¹

A disadvantage of atropine is that it has low therapeutic selectivity, meaning that it affects many different parts of the body. This is the opposite to the aim of modern medicine, which is to achieve high therapeutic selectivity, to target treatments at specific areas of the body.

Despite the low therapeutic selectivity of atropine it is still used for treating some conditions, but the side effects possible across many areas of the body always need to be considered. In particular it can lead to toxicity and potentially fatal effects if used inappropriately, such as being ingested by mouth when it is meant to be used as eye drops.²

When synthesized as an eye drop, atropine provides the same effect as when the Belladonna plant leaves were rubbed on the eye by Renaissance Italian women, in that it causes the pupil to enlarge.

Enlarged pupils help optometrists see the back of the eye with a wider field-of-view. It’s like scanning the back wall of a room through a window instead of through a keyhole. Atropine widens the pupil (keyhole) and makes it easier to see all of the structures at the back of the eye.

Using a drug in this way is called ‘diagnostic’ in that the drug is used to ‘view’ rather than ‘treat’. A disadvantage of atropine as a diagnostic drug for enlarging the pupil is that its effects last far longer than required to view the back of the eye. This has led to development of newer diagnostic drugs that provide a far shorter lived effect. Consequently atropine is now only rarely used to enlarge the pupil.

Atropine eye drops may be used in the following ways:

1. Atropine eye drops are commonly used during an eye examination to temporarily dilate (enlarge) the pupil and stop the eye’s focusing mechanism, to allow for accurate testing of a child’s prescription for spectacles. It is an especially important test for children with amblyopia (lazy eye) or strabismus (turned eye). This is called a cycloplegic refraction, and the drops are usually applied around 30-60 minutes before the eye examination.³ 
2. Atropine eye drops are prescribed as an at-home treatment for amblyopia in children, also known as lazy eye, from age 3 up to age 12. This is used as an alternative to patching the stronger eye.^4,5
3. Atropine eye drops are used to treat eye pain in severe infection or inflammation. These conditions can occur in children or adults ⁶
4. Atropine eye drops can be prescribed for children with progressive myopia, to slow myopia progression^7-9 which is also known as myopia control.

Atropine has been shown to be highly effective in controlling progression of myopia. The first studies using atropine eye drops to slow myopia progression in children used 1% atropine, but these had significant side effects – enlarged pupils made a child sensitive to light, and blurred their close-up vision.⁹

Studies in the last 10 years have instead investigated lower concentrations, which have minimal side effects. The concentration of atropine eye drops which have been researched for myopia control vary from 0.01% right up to 1%.^7-9 The best balance of minimal side effects with maximum effect to slow myopia progression seems to be found with 0.025% to 0.05% concentrations, based on currrent research.⁷

In myopia control, atropine drops are used once per day, at night time. It is not certain how atropine slows myopia progression in children. Scientists are still exploring the mechanism, which is likely how the atropine eye drops influence how chemical signals are conducted in the retina, the light sensitive layer at the back of the eye.¹⁰

Managing myopia progression and expectations for treatment varies across age groups. To read more detail on atropine for myopia control see our following articles according to age group:

• Babies and toddlers read Atropine eye drops for myopia control in babies and toddlers
• Children read Atropine eye drops for myopia control in children
• Teenagers read Atropine eye drops for myopia control in teenagers
• Young adults read Atropine eye drops for myopia control in young adults

Atropine's effect on enlarging the pupil of the eye has already been covered above. It also impacts the focussing lens inside the eye, reducing the ability of the eye to adjust to focus on close up objects, causing blurred vision for reading and close work. This effect is most pronounced for atropine concentrations of 0.1% up to 1%.^8,9

These effects are useful when atropine 1% is used for eye examinations, lazy eye treatment in children or to treat eye inflammation. In myopia control, though, these side effects are unwanted and can impact vision.

Fortunately, recent research has found that effective myopia control benefits of atropine can be achieved with 0.025% to 0.05% atropine concentration. At these low concentrations, atropine has been found to have minimal effect on pupil size and eye focusing, thereby greatly minimizing these unwanted side effects.⁷

Most myopia control research studies have reported some increase in pupil size from atropine treatment, however the effect is typically small and not enough to cause a problem. Atropine 0.025% and 0.05% has been shown to only increase pupil size by around 1mm, whereas 0.1% and stronger can increase the pupil by 3mm or more.^6,7

Any enlargement of the pupil causes more light to enter into the eye, and can thereby lead to increased sensitivity to light. Protection of children’s eyes from ultraviolet (UV) exposure is especially important, because their pupils are wider and focussing lens is clearer, meaning more light and UV reaches the back of the eye than in adults.¹¹

If a child on atropine treatment for myopia control appears to be sensitive to light or glare, such as squinting excessively when outdoors, sunglasses or photochromatic spectacle lenses (which darken in brighter light) can be prescribed.⁷

The other main side effect to watch for is problems with focussing up close for reading and screen work. These effects are typically minimal in concentrations of atropine up to 0.05%, but every child is different.

If you find your child pulling reading text further away from their eyes than normal, or rubbing their eyes when trying to read, then it is wise to alert your optometrist or eye doctor for further advice. Spectacles which incorporate an additional reading power towards the bottom of the lenses (called progressive addition or bifocal lenses) can be prescribed to support reading vision.^7-9

Atropine eye drops should have minimal effect on the rest of the body when applied to the eye and have been shown to be safe for children in 2-4 year myopia control studies.^7-9 After putting an eye drop on the eye, keeping eye closed and pressing the inside corner of the eye for a minute or longer can help to trap the drop on the eye for absorption, and stop extra loss of the drop draining into the nose where it can be absorbed into the rest of the body. This is called the DOT or 'don't open eyes' technique, and is useful for any type of medicated eye drop.

If atropine eye drops are accidentally taken by mouth, it can affect the whole body system. Atropine can cause an increased heart rate, inhibition of sweat and saliva glands, increased body temperature and delirium.¹³ These systemic effects can be very dangerous,² so parental oversight of eye drop use and storage is very important.

Although atropine eye drops should typically have minimal absorption elswhere in the body and be very safe to use,^7-9 there are some children and teenagers for whom it may not be suitable, due to other health conditions or medications being taken.

Children or teenagers with congenital heart conditions may not be suitable for atropine treatment, owing to its potential influence on heart rate.^14,15

Atropine eye drops could have increased side effects in children or teenagers taking medications which have a similar mode of action. These include some medications for asthma, anti-depressant or anti-anxiety or anti-histamine medications.¹⁶ These medications can interact with atropine and lead to additional side effects of either medication. Caution should be applied in atropine treatment for kids taking these medications.

Atropine eye drops used for myopia control are typically in very low concentrations, making it almost impossible for there to be any side effects on the body if applied by the eye. The eye can only hold a very small volume of eye drops before they will overflow and then not be absorbed.¹⁷

Numerous scientific studies of atropine have shown them to be safe and well tolerated in children and teenagers.¹⁸ Talk to your optometrist or eye doctor about any questions you may have, and make sure to adhere to the treatment plan that they have prescribed for your child.