The pupils are the black sphere that is in the central part of the color zone of the eye, the iris and its function is to dilate or contract to control the amount of light that enters the eye.
Sometimes, the pupils can present problems that prevent them from contracting or dilating, when they remain dilated, this condition is known by the name of mydriasis o dilated pupils.
The pupils, like the diaphragm of a photography camera, open or dilate automatically when the person is in a dimly lit area. Now, there are also certain conditions in which the eye reacts to stimuli that dilate the pupil and that have nothing to do with the absence of lighting, and may be physiological, pharmacological or pathological.
En Área Oftalmológica Avanzada We explain what mydriasis is, causes and treatment.
What is mydriasis?
Mydriasis is the permanence of the dilated pupils when they should be contracted, even when in a lighted environment, quite the opposite of the myosis or punctate pupils.
This occurs when the muscles of the iris are unable to close the pupil.
To dilate the pupil, the radial muscles of the iris and is controlled through the sympathetic system, while to contract the pupil the circular muscles of the iris o pupillary Sphincter, through the parasympathetic system.
The pupil is the space that remains in the center of the iris and is responsible for controlling the amount of light that penetrates the eyeball and reaches the retina, essential to obtain a good vision (for example, to avoid glare). The pupils normally dilate in low light conditions, so that more amount of light to the eye y images can be formed correctly on the retina. Under normal conditions, the pupillary dynamics, size and dilation speed of both eyes, is similar and symmetrical.
Types of mydriasis
Next we explain the most frequent types of mydriasis that we find in ophthalmology:
physiological mydriasis
Dilation of the pupils (mydriasis) in a low-light environment is a normal process in healthy eyes. Physiological mydriasis is the process by which both pupils dilate symmetrically in both eyes in low-light environments.
Episodic benign unilateral mydriasis
It is identified by a clear asymmetry between both pupils or anisocoria, one being dilated while the other remains at its normal size. This is a rare type of mydriasis that occurs especially in patients with migraines, parasympathetic deficit or sympathetic hyperactivity in the iris. It is very common in cases of major stress as in students at the time of final exams, or work stress.
Symmetric areactive mydriasis
The pupils remain dilated in a bright environment or even when we stimulate a light directly on the eye (photomotor test). One of the main causes of symmetric arreactive mydriasis is brain damage caused, in many cases, by cardiorespiratory arrest or strong trauma where we can make a first assessment of the brain status of the injured person.
Asymmetric areactive mydriasis
In this case we have a pupil that reacts normally to light stimuli while in the other eye a dilated, mydriatic pupil is observed that does not respond to light. This is mainly due to traumatic causes (a blow to the head that injured the pupillary sphincter muscle), brain tumors that affect only one hemisphere or after an inflammatory eye disease (uveitis) or acute intraocular hypertension (angle-closure glaucoma) that left the pupil attached to crystalline in mydriasis (posterior synechiae).
Bilateral mydriasis
It is generally caused by a process of intoxication caused by the ingestion of methanol, drugs, opiates or toxins that cause cholinergic activity. Some other causes that can be associated with bilateral mydriasis are hypothermia and lesions in the middle of the cerebral pons.
Causes of the most common dilated pupils
Now that we know what mydriasis is and how it occurs, it is important to know its main causes:
ambient light
The most normal cause of dilated pupils is the absence of light in certain places and situations. The pupil dilates as an automatic reaction in order to see properly.
emotional state
Few people realize that the pupils dilate during an intense emotional state. Nervous breakdowns, fear and enthusiasm are some emotions that can cause sudden mydriasis.
certain drugs
The consumption of anticholinergic drugs blocks the transmission of some chemicals to the eyes and dilates the pupils. Similarly, the ophthalmologist uses drugs (cycloplegic eye drops, atropine, among others), to dilate the pupils and be able to explore the fundus or before certain surgeries such as cataracts or retinal detachment.
drugs or alcohol
The consumption of alcoholic beverages and narcotic substances can cause dilated pupils for several hours. Drugs that cause mydriasis include cocaine, ecstasy, THC, methamphetamines, and hallucinogens.
Drugs affect serotonin receptors and can increase or decrease the production of this transmitter, causing dilated pupils as a consequence.
Management
When mydriasis has no apparent cause, a neurological or brain condition may be suspected that is permanently stimulating pupil dilation.
Some non-ophthalmological diseases can significantly affect the layers of the eye and their proper functioning.
Among the latests Moravia's compositions diseases that can cause mydriasis as a side effect, we find:
- Cerebral haemorrhage.
- Stroke
- eye tumor or in the brain.
- Trigeminal nerve injury.
- Trauma or collateral damage due to glaucoma.
Transmission
If dilated pupils appear as an abnormal reaction that persists despite being in a brightly lit place, it is important to see an ophthalmologist immediately.
In a case of permanent mydriasis, the most important thing is to detect the cause that is generating this abnormal and involuntary reaction, since it can be dangerous conditions such as a stroke.
The treatment of mydriasis will depend on the cause that is affecting the ocular structure.
As long as the person has dilated pupils, it is important to use sunglasses, not to expose themselves to sunlight and not to drive.
From a purely ophthalmological point of view, in cases of severe mydriasis, we can carry out specific treatments to close the pupil. You can make a surgery to selectively close the pupil diameter, adjusting the amount of light that enters the eye, an intervention we call Pupiloplasty.
En Área Oftalmológica Avanzada We have the best human and technological team to attend to visual health. Do not hesitate to contact us, we are happy to assist you!
