3. Mydriasis
Mydriasis occurs when an individual’s
pupils (the black opening in the center
of the eye that regulates light entry),
become dilated, or larger. Although
this occurs as a normal response to
light, mydriasis may also occur as a
result of other, less common,
underlying causes.
4. The pupil functions as the part of the
eye that regulates the amount of light
that enters the eye at any given
moment. When there are low amounts
of light in the environment, such as at
nighttime, the pupil usually dilates in
order to bring in more light for
increased vividity. This phenomenon is
called mydriasis. Conversely, when
there are high amounts of bright light
in the environment, such as during
daytime, the pupil typically constricts,
or gets smaller, in order to protect the
back of the eye from excessive light
damage. When the pupil constricts, it
is called miosis.
5. CAUSES
Although mydriasis is a normal occurrence, prolonged or inappropriate mydriasis can be indicative of an underlying cause. Potential causes
of unusual mydriasis include injury to the muscles or nerves of the eye, traumatic brain injury, increased levels of oxytocin, and side effects of
certain recreational drugs or prescribed medications. Additionally, there are also certain conditions that may result in mydriasis.
Brain or eye injury, most often due to trauma, may damage the nerves that control the size of the pupil. Traumatic brain injury, usually
caused by a stroke, tumor, or head injury, can increase the intracranial pressure (pressure around the brain), potentially resulting
in mydriasis. Traumatic brain injury can also damage the oculomotor nerve which innervates, or sends signals, to constrict the pupil. Damage
to the oculomotor nerve can result in a blown pupil and consequent mydriasis. This may affect both or just one eye and is usually considered
a medical emergency. Additionally, damage to the pupillary sphincter, a muscle located in the iris (the colored part of the eye that controls
the size of the pupil) can affect one’s typical response to light and result in mydriasis.
Another potential cause of mydriasis is increased oxytocin production. Oxytocin is a hormone produced in the body which is normally
released during exercise and during physical interactions with others. Recent research has shown that increased oxytocin levels may
temporarily cause mild to moderate mydriasis.
Conditions that can cause mydriasis include benign episodic unilateral mydriasis and Adie syndrome. Benign episodic
unilateral mydriasis causes temporary mydriasis of one eye. The condition is typically accompanied with other signs and symptoms,
including headaches, eye pain, light sensitivity, nausea, and blurred vision. Adie Syndrome can cause mydriasis of either one or both eyes,
although it most commonly affects just one. It is typically accompanied with pupils that constrict slowly in bright light and diminished deep
tendon reflexes, usually of the Achilles tendon, located in the lower legs. Though these conditions are usually not dangerous, an exam to
assess an individual’s eye health and nervous system is often necessary to rule out any harmful underlying causes.
Certain recreational drugs can also result in mydriasis. Stimulants, including cocaine, methamphetamines, and ecstasy, as well as certain
hallucinogens, including LSD and psilocybin mushrooms, have effects on the brain that can cause dilated pupils as a side effect.
Finally, a variety of medications, such as mydriatics and anticholinergics, among several others, can also lead to mydriasis.
6. Which medications cause mydriasis?
The most common medications that can cause mydriasis are anticholinergics and mydriatics.
Anticholinergics inhibit specific hormones, or chemical signals, from entering the eye and
can result in mydriasis as a side effect. Examples of anticholinergics include atropine, used
primarily to increase an individual’s heart rate, and scopolamine, commonly prescribed
for motion sickness. Other common side effects of anticholinergics include constipation,
decreased sweating, increased heart rate, and decreased saliva production.
Unlike anticholinergics, mydriatics are specific medications used to intentionally dilate an
individual’s pupils. Mydriatics, such as tropicamide, allow healthcare practitioners to take a
deeper look at the structures of the internal eye. Effects of mydriatics typically last about
four to eight hours and during this time, the individual may be sensitive to bright light.
Other groups of medications that may cause mydriasis as a side effect include selective
serotonin reuptake inhibitors (SSRIs), GABA receptor agonists, and adrenergic agonists.
7. How does mydriasis cause
glaucoma?
Mydriasis is a risk factor for angle closure glaucoma in certain
individuals. This is most commonly seen in those with “narrow
angles”, which refers to an unusually narrow angle between the outer
edge of the iris and the cornea (the clear part of the eye that covers
the front of the eye).
Glaucoma is a group of eye disorders associated with the destruction
of the optic nerve, a cranial nerve that innervates the eye. While open
angle glaucoma is slowly progressive, angle closure glaucoma is
characterized by a sudden onset of pain in the eye often accompanied
with headache, blurry vision, and halos appearing around lights.
Angle closure glaucoma is caused by a blockage that prevents
the aqueous humor (the clear fluid in the space in the front of the eye)
from draining. This ultimately results in increased pressure in the eye,
also called increased intraocular pressure. With “narrow
angles”, mydriasis can cause a closure of the angle and thus may play
a role in the development of angle closure glaucoma.
8. How is mydriasis treated?
Mydriasis is treated by diagnosing
and treating the underlying cause.
Seeking immediate medical attention
is important with unusual or
prolonged mydriasis, as prompt
intervention may be necessary in
more serious causes, such
as traumatic brain injury.
9. What are the most important facts
to know about mydriasis?
Mydriasis refers to the dilation of the pupil, which normally
occurs in response to low amounts of light in the
environment. In some cases, prolonged mydriasis occurs
when an individual’s pupil remains dilated regardless of the
amount of light in the environment. This phenomenon may
be caused by injury to the muscles and nerves of the
eye, traumatic brain injury, increased levels of oxytocin,
benign episodic unilateral mydriasis, or side effects of
recreational drugs or prescribed medications. Mydriasis may
contribute to the possible development of angle closure
glaucoma due to its effect on “narrow angles” of the eye.
Treatment for mydriasis depends on the underlying cause.
11. Nystagmus
People with nystagmus can’t control their eye
movements. Their eyes move rapidly and
uncontrollably in an up and down, side to side or
circular motion. Nystagmus may be passed down
from your parents, or it may be caused by another
health issue. The condition can be managed with
glasses or contact lenses or rarely, surgery.
Nystagmus (ni-stag-muhs) is a condition in which
your eyes make rapid, repetitive, uncontrolled
movements — such as up and down (vertical
nystagmus), side to side (horizontal nystagmus) or in
a circle (rotary nystagmus). These eye movements
can cause problems with your vision, depth
perception, balance and coordination.
12. Babies with this condition start to show symptoms
between six weeks and three months of age. This type
of nystagmus is congenital, meaning people are born
with it. In some cases, it’s passed down to children from
their parents, but the exact cause isn’t always clear.
Children with congenital nystagmus usually have it in
both eyes. The main symptom is blurry vision.
Congenital nystagmus
Acquired nystagmus
Unlike congenital nystagmus, acquired nystagmus develops
later in life. The condition is usually caused by an underlying
health condition or drugs. Adults with acquired nystagmus
describe their vision as “shaky.”
13. Symptoms and
Causes
Nystagmus symptoms can affect
one or both eyes. Some of the most
common warning signs include:
•Uncontrollable eye movement.
•Shaky or blurry vision.
•Balance problems.
•Dizziness.
•Light sensitivity.
•Nighttime vision problems.
14. How do you get
nystagmus
•Retina or optic nerve disorders.
•Underdeveloped control over eye
movements.
•Inner ear conditions, such as Meniere’s
disease.
•Stroke.
•Head trauma.
•Diseases of the central nervous system.
•Albinism (lack of pigmentation in the skin).
•Multiple sclerosis (MS).
•Certain medications, such as antiseizure
drugs.
Your brain controls your eye movement. When you move your head, your eyes move automatically to adjust.
This stabilizes the image and helps you see clearly. In individuals with nystagmus, the areas of the brain that
control eye movements don’t work properly.
Nystagmus could indicate another eye problem, or it could be associated with another medical condition.
Nystagmus causes and risk factors include:
15. • A neurological examination.
• Eye-movement recordings.
• An ear exam.
• Imaging tests, such as CT
scans or MRI, to capture
pictures of your brain.
Tests
16. Clearer vision can help slow the rapid eye movements
associated with nystagmus. As a result, symptoms can
be successfully managed with eyeglasses or contact
lenses.
Glasses or contact lenses
Medications
Some medications can reduce nystagmus symptoms in
adults, such as gabapentin (antiseizure), baclofen (muscle
relaxant) and onabotulinumtoxina (Botox®). These
medications aren't used in children with nystagmus.
TREATMENT
17. In rare instances, eye muscle surgery may be
recommended. During this procedure, your surgeon
repositions the muscles that move the eyes. This type of
surgery doesn’t cure nystagmus, but it allows you to
keep your head in a more comfortable position, thereby
limiting eye movement.
Eye muscle surgery
Vision correction surgery
If you have nystagmus and are nearsighted, laser vision
correction surgery — such as LASIK — may be beneficial.
While laser eye surgery doesn’t cure nystagmus, it improves
your vision. As a result, nystagmus symptoms may be
reduced.
19. Papilledema
People with nystagmus can’t control their eye
movements. Their eyes move rapidly and
uncontrollably in an up and down, side to side or
circular motion. Nystagmus may be passed down
from your parents, or it may be caused by another
health issue. The condition can be managed with
glasses or contact lenses or rarely, surgery.
Nystagmus (ni-stag-muhs) is a condition in which
your eyes make rapid, repetitive, uncontrolled
movements — such as up and down (vertical
nystagmus), side to side (horizontal nystagmus) or in
a circle (rotary nystagmus). These eye movements
can cause problems with your vision, depth
perception, balance and coordination.
Editor's Notes
endocrinológicas después de la obesidad, diabetes mellitus tipo 2 e hiperlipidemia.
