Generality
The term cycloplegia is used to indicate the block of contraction of the ciliary muscle of the eye, usually induced by cycloplegic drugs .
Because of this blockage, the accommodative function of the eye is missing, allowing vision at different distances.
As mentioned, cycloplegia is generally induced by drugs that are administered in the eye (eye drops), usually as part of specialist visits for diagnostic purposes. However, in some cases, cycloplegia could be the result of injuries to the third pair of cranial nerves.
Nevertheless, in this article only cycloplegia induced by cycloplegic drugs will be considered; in particular, attention will be focused on the latter and their main characteristics.
What are
What are Cicloplegia and Cicloplegic Drugs?
Cycloplegia can be defined as the paralysis of the ciliary muscle of the eye. More precisely, this paralysis is generally induced by the use of the so - called cycloplegic drugs, ie drugs made with active principles capable of blocking the contraction activity of the muscle in question.
Short Insight: Ciliary Muscle and Focus
The ciliary muscle, whose contraction is blocked by cycloplegic drugs, plays a very important role in focusing and in the ability to see objects at different distances .
In fact, through the contraction and relaxation of the muscles present in the ciliary body, the crystalline lens undergoes a change of shape that allows focusing.
In detail, when the ciliary muscle contracts, the crystalline takes on an almost spherical shape allowing the focusing of near objects .
Cycloplegic drugs are drugs with anticholinergic action, which means that they are able to block the effects of acetylcholine . More in detail, cycloplegic drugs exert this activity by blocking muscarinic receptors, therefore, they are defined as muscarinic receptor antagonists.
Active principles
Active Ingredients contained in Cicloplegic Drugs
Among the active ingredients contained in the cycloplegic drugs currently used in therapy, we find:
- Atropine (Atropine Lux®);
- Homatropin (Omatropina Lux®);
- Tropicamide (Visumidriatic®);
- Cyclopentolate (Ciclolux®).
Did you know that ...
These drugs - in addition to exercising a cycloplegic activity - are capable of inhibiting the action of the sphincter muscle of the iris, so they are also able to induce a mydriatic effect .
Indications
What are Cicloplegic Drugs used for?
Cycloplegic drugs are used to block the contraction of the ciliary muscle of the eye, generally for performing diagnostic examinations during eye examinations . More in detail, the cycloplegia induced by them is particularly useful for the execution of the refraction examination (examination carried out to identify the presence of possible refraction errors).
The mydriatic action exerted by the same drugs, on the other hand, turns out to be useful for measuring the refractive error or in any case for the examination of the transparent means and the bottom of the eye.
Please note
Although cycloplegic drugs have a mydriatic effect, the latter is not always maximal. For this reason, if it is necessary to induce mydriasis in addition to the cycloplegia, it is possible to administer cycloplegic drugs in combination with "proper" mydriatic drugs . An example of this type of drug is given by phenylephrine.
Other Therapeutic Indications
Cycloplegic drugs - in addition to being used in diagnostic tests - can also be used in other circumstances, so they may have slightly different therapeutic indications.
For example, atropine is used - in association with other drugs - even in the case of inflammation of the uvea (uveitis) to favor the relaxation of the ciliary muscle which, in the presence of inflammatory states of the anterior segment, is generally contracted.
Automatine, on the other hand, is also used as an adjunct in strabismus therapy for the re-education of amblyopic eyes.
As for tropicamide, it has indications similar to atropine, so much so that it can replace it in all cases.
Finally, cyclopentolate is useful in all cases where it is necessary to induce mydriasis and cycloplegia in a short time. In fact, it exerts its activity more rapidly than other cycloplegic drugs.
Please note
For more detailed information on all the therapeutic indications of each of the aforementioned active ingredients, we recommend reading the illustrative leaflet of the cycloplegic drug that must be used.
Action mechanism
How do Cicloplegic drugs work?
Cycloplegic drugs perform their action by interacting with muscarinic acetylcholine receptors.
More specifically, they are muscarinic receptor antagonists . This means that they are able to bind to the latter by preventing their binding to acetylcholine. In this way, the ciliary muscle contraction is blocked and the pupil constrictor muscle (or sphincter of the iris, if you prefer) with consequent onset of cycloplegia and mydriasis.
After instilling the cycloplegic drugs, the patient's eyes are adapted for distant vision only; therefore, it is not able to focus, therefore to see in a clear and clear manner, objects less than 5 meters away.
Mode of use
How are Cicloplegic drugs used?
Cycloplegic drugs are formulated in the form of eye drops . In fact, to perform their function avoiding systemic effects, they must be administered locally by eye .
For the execution of diagnostic tests, these drugs are generally administered by the doctor or by the health personnel before the beginning of the specialist visit. Depending on the cycloplegic drug used and the type of examination to be performed, the drops must be instilled in the eyes from 10-20 minutes up to an hour before the start of the examination, in single administration or in repeated administrations. However, in some cases it may be necessary to start the treatment a few days earlier, directly at home by the same patient, in order to achieve the highest possible degree of cycloplegia.
For the use of cycloplegic drugs in the home by patients, a doctor's prescription is required. In fact, they can be purchased in pharmacies only upon presentation of a specific medical prescription (generally repeatable). The indications regarding dosage and instructions for use must be provided by the doctor. If this is not the case, it is necessary to follow the instructions on the leaflet of the medicine to be used.
Of course, the use of cycloplegic drugs is only local and in no case should they be ingested.
Side effects
Side effects induced by Cicloplegic drugs
Generally, cycloplegic drugs are well tolerated and do not cause significant side effects. Clearly, the inability to focus on the nearest objects is a natural consequence of the cycloplegia and mydriasis they induced.
However, as with any other medicine, cycloplegic drugs also have the potential to induce side effects. The most common are: transient eye irritation, slight increase in eye pressure and photophobia.
Other reported side effects, whose frequency however is not known, consist of:
- Headache;
- Dry mouth;
- Loss of appetite;
- Drowsiness;
- agitation;
- Confusion;
- Tachycardia;
- Urinary retention.
Furthermore, in the event of prolonged use and / or excessive doses of cycloplegic drugs, it is possible to experience systemic toxicity, especially in children. In such a situation, it is essential to contact the doctor immediately and go to the nearest emergency room.
Finally, we must not forget the possibility of allergic reactions occurring in sensitive individuals.
Pregnancy and breastfeeding
Can Cicloplegic drugs be used in pregnancy and during breastfeeding?
Since cycloplegic drugs are administered via the eye and are hardly systemically absorbed, their use can usually be carried out - when strictly necessary - even during pregnancy or lactation, provided it is under the supervision of a doctor. Therefore, before using or before receiving these medications from your doctor, it is always good to inform them of your pregnancy or breastfeeding condition.
Contraindications
When Cicloplegic Drugs Should Not Be Used
The use of cycloplegic drugs for the induction of cycloplegia and mydriasis is not indicated in the following cases:
- Allergy known to the active ingredient and / or to any of the excipients contained within the medicinal product to be used;
- In patients suffering from closed-angle glaucoma;
- In patients with a tendency to intraocular hypertension;
- In children under the age of three.
Please note
For complete information on use, dosage, use during pregnancy and lactation, side effects and contraindications of cycloplegic drugs, it is advisable to consult the package insert of the medicinal product prescribed by the doctor.
