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What Are Cycloplegics?

B. Chisholm
B. Chisholm

Cycloplegics are medications, usually in the form of eye drops, which cause cycloplegia, which is paralysis of the ciliary muscle in the eye. This stops accommodation of the eye, that is focusing for vision at different distances. There are a number of drugs which are cycloplegics including atropine, homatropine, cyclopentolate and tropicamide, all of which differ slightly in potency, onset and duration of action. They are available in most countries by prescription only and trade names may differ from country to country, according to manufacturer.

The mechanism of action of cycloplegics is by their blocking action on the muscarinic receptors in the eye. These receptors are involved in the ocular muscle action so, by blocking them, the cycloplegics prevent the muscles from moving. This not only causes cycloplegia, but also mydriasis, which is dilation of the pupil. The different cycloplegics have different potency with regards to both cycloplegia and mydriasis.

Cycloplegics usually come in the form of eye drops.
Cycloplegics usually come in the form of eye drops.

The choice of which of the cycloplegics is used will be made by the doctor, according to the indication for which it is being used. Most commonly they are used to make examination of the eye easy. They may also be used to treat uveitis, a swelling or inflammatory condition of the eye, and to prepare the eye for ophthalmic surgery.

Atropine, homatropine, cyclopentolate and tropicamide all have a slightly different onset of action and their duration of action, both on the pupil and the ciliary muscle differ. The treating doctor will prescribe the most suitable agent on a case-by-case basis. In the case of atropine, the usual dosage regimen for acute inflammatory conditions is instillation three times daily and for preparation before a procedure, the drops may be given less frequently for a couple of days before. The prescribed dose should never be exceeded.

It's possible for cycloplegics to interact negatively with other prescription medications.
It's possible for cycloplegics to interact negatively with other prescription medications.

As with any medication, cycloplegics may cause unwanted side effects. These are mainly local effects, due to the topical nature of eye drops, but systemic effects have also been reported. Local adverse effects which have been reported include irritation or burning of the eyes and allergic conjunctivitis. Systemic effects may include flushing, increased heart beat and confusion.

The tip of an eye-drop container can become contaminated if it comes in contact with skin, eyes or other surfaces.
The tip of an eye-drop container can become contaminated if it comes in contact with skin, eyes or other surfaces.

As with any medication, cycloplegics may interact with others, including prescribed, over-the-counter, homeopathic and complementary medicines, so these should be disclosed to the prescribing doctor. The cycloplegics may be contraindicated in people with some underlying clinical conditions, so these should also be discussed with the doctor. They may increase the intra-ocular pressure, so it may be contraindicated in patients with glaucoma.

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    • Cycloplegics usually come in the form of eye drops.
      By: apops
      Cycloplegics usually come in the form of eye drops.
    • It's possible for cycloplegics to interact negatively with other prescription medications.
      By: Rob Byron
      It's possible for cycloplegics to interact negatively with other prescription medications.
    • The tip of an eye-drop container can become contaminated if it comes in contact with skin, eyes or other surfaces.
      By: design56
      The tip of an eye-drop container can become contaminated if it comes in contact with skin, eyes or other surfaces.
    • In most countries, cycloplegics are available only by prescription.
      By: FotolEdhar
      In most countries, cycloplegics are available only by prescription.
    • Using cycloplegics may increase intra-ocular pressure in some patients.
      By: Hunor Kristo
      Using cycloplegics may increase intra-ocular pressure in some patients.
    • Eye irritation is a possible side effect of cycloplegics.
      By: Rob hyrons
      Eye irritation is a possible side effect of cycloplegics.
    • Cycloplegics may cause irritation or burning of the eyes and allergic conjunctivitis.
      By: GVictoria
      Cycloplegics may cause irritation or burning of the eyes and allergic conjunctivitis.