Cycloplegia

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Cycloplegia

Cycloplegia is paralysis

Paralysis

Paralysis is the complete loss of muscle function for one or more muscle groups. Paralysis can cause loss of feeling or loss of mobility in the affected area....
of the ciliary muscle

Ciliary muscle

The ciliary muscle is a muscle in the eye that controls the eye's accommodation for viewing objects at varying distances....
of the eye

Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
, resulting in a loss of accommodation

Accommodation (eye)

Accommodation is the process by which the :eye increases optical power to maintain a clear image on an object as it draws near the eye. The young human eye can change focus from distance to 7 cm from the eye in 350 milliseconds....
.

iris is the heavily pigmented colored part of the eye. It has a contractile diaphragm in front of the lens with a central opening called the pupil. It is located between the lens and the cornea, and is attached radially to the ciliary body and the cornea via ligaments called pectinate ligaments.

The iris contains two sets of muscles:

The muscles regulate the amount of light entering the eye.

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Encyclopedia

Cycloplegia is paralysis

Paralysis

Paralysis is the complete loss of muscle function for one or more muscle groups. Paralysis can cause loss of feeling or loss of mobility in the affected area....
of the ciliary muscle

Ciliary muscle

The ciliary muscle is a muscle in the eye that controls the eye's accommodation for viewing objects at varying distances....
of the eye

Eye

Accommodation (eye)

Anatomy

The iris is the heavily pigmented colored part of the eye. It has a contractile diaphragm in front of the lens with a central opening called the pupil. It is located between the lens and the cornea, and is attached radially to the ciliary body and the cornea via ligaments called pectinate ligaments.

The iris contains two sets of muscles:

a radial group for enlargement of the pupil (dilator pupillae)
a circular group set to decrease pupil size on contraction (sphincter pupillae).

The muscles regulate the amount of light entering the eye. The sphincter pupillae is stimulated through muscarinic receptors by the parasympathetic nervous system. The dilator pupillae is stimulated through adrenergic receptors by the sympathetic

Sympathetic

The word sympathetic means different things in different contexts.* In neurology and neuroscience, the sympathetic nervous system is a part of the autonomic nervous system....
nervous system.

Photophobia

Destruction of the sphincter pupillae from any cause can result in a permanent condition, called "photophobia

Photophobia

Photophobia is a symptom of excessive sensitivity to light and the aversion to sunlight or well-lit places. In medical terms it is not fear, but an experience of discomfort or pain to the eyes due to light exposure....
." Light entering an eye with a paralyzed or destroyed sphincter will result in severe pain, because the pupil can not be made smaller.

Cycloplegic drugs

Cycloplegic drugs are generally muscarinic receptor blockers. These include atropine

Atropine

Atropine is a tropane alkaloid extracted from deadly nightshade , jimsonweed , Mandrake and other plants of the family Solanaceae. It is a secondary metabolite of these plants and serves as a hard drug with a wide variety of effects....
, cyclopentolate

Cyclopentolate

Cyclopentolateis a mydriatic and cycloplegia agent commonly used during pediatric eye examinations. Cyclopentolate is also administered as an atropine substitute to reverse muscarinic and CNS effects of indirect cholinomimetic administration....
, homatropine

Homatropine

Homatropine is an anticholinergic medication that inhibits muscarinic acetylcholine receptors and thus the parasympathetic nervous system. It is used in eye drops as a cycloplegic, to temporarily paralyze accommodation , and as a mydriatic, to dilate the pupil....
, scopolamine

Scopolamine

Scopolamine, known by the names levo-duboisine and hyoscine, is a tropane alkaloid Medication with muscarinic antagonist effects. It is obtained from plants of the family Solanaceae , such as henbane, jimson weed and Angel's Trumpets , and corkwood ....
and tropicamide

Tropicamide

Tropicamide is a muscarinic anticholinergic.Other brand names include Mydriacyl....
. They are indicated for use in cycloplegic refraction

Refraction

Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one optical medium to another....
s and the treatment of uveitis

Uveitis

Uveitis specifically refers to inflammation of the middle layer of the eye, termed the "uvea" but in common usage may refer to any inflammatory process involving the interior of the eye, with inflammation specifically of the uvea termed iridocyclitis....
. Many cycloplegics are also mydriatic

Mydriasis

Mydriasis is an excessive dilation of the pupil due to disease, Physical trauma, or the use of drugs. Normally, the pupil dilates in the dark and constriction in the light to improve vividity at night and to protect the retina from sunlight damage during the day....
(pupil dilating) agents and are used as such during ophthalmoscopic examinations

Eye examination

An eye examination is a battery of tests performed by an optometrist or ophthalmologist assessing Visual perception and ability to Focus on and discern objects, as well as other tests and examinations pertaining to the eyes....
to better visualize the retina

Retina

The vertebrate retina is a light sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera....
.

When cycloplegic drugs are used to dilate the pupil, the pupil in the normal eye regains its function when the drugs are metabolized or carried away. Some cycloplegic drugs can cause dilation of the pupil for several days. Usually the ones used by ophthalmologists or optometrists wear off in hours, but when the patient leaves the office strong sunglasses are provided for comfort. Anyone who has had their retina examined with the prior use of cycloplegic drugs is aware of this phenomenon.