Eyes are said to be the windows to a person’s soul. It shows a person’s emotions and thoughts when a person reacts to different things. In 2012, an article appeared in the Scientific American where a doctor shared his view on pupil dilation as an effect of processing of information in the nervous system.
The eyes do not only convey a person’s emotions. It also acts as a gateway to his state of health. Doctor’s would look the person’s eyes when health is being examined. The changes in a person’s eyes show whether he is intoxicated or has used a substance. The changes may include the constriction or widening of the pupil, the color of the eyes and its movement.
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Why Do Pupils Dilate and Move?
The pupil is the round black opening located at the center of the iris and functions as an entrance for light to enter the eyes to process sight. It’s compared to a camera’s aperture as it controls how much light can enter the eye. The pupils dilate when a person sees something that stimulates his senses or when there is low light.
Its expansion or constriction is controlled by the muscles in the iris, namely the iris sphincter and the iris dilator. Smaller pupil limits the light’s passage, while expanded pupils allow more light to reach the retina to help the person see even when it is dark.
The normal pupils’ size ranges from 2.0 to 4.0 millimeters when it is bright and 4.0 to 8.0 mm when it is dark. When a dilated pupil (mydriasis) does not react to light it is called a “fixed dilated” pupil.
Aside from dilation, eyes also exhibit various movements depending on the stimuli. Nystagmus or the involuntary movement of the eyes can either be horizontal (side to side), vertical (up and down), or rotary. It can also happen in both eyes and only one. There are also two types of nystagmus – congenital and acquired.
When a person has no congenital problem to cause an infantile nystagmus syndrome, he could still have acquired nystagmus that can occur after taking medication. Usually, when a person takes a medicine for seizure or is sedated due to a drug or excessive alcohol intake, nystagmus may occur.
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Which Drugs Can Cause Dilated Pupils?
Different drugs cause different eye responses. Both prescription and non-prescription medicines can cause the eyes’ pupils to dilate. So it is not only illicit drugs which can affect the pupils’ dilation. The following may also affect the eyes’ ability to react to light:
Medicine for motion sickness
Drugs for seizures
Parkinson’s disease medications
Botox and other drugs with botulinum toxin
But what are the illicit drugs which can particular be tied to pupil dilation?
Police officers also evaluate the pupil size in order to detect drug impairment. In a study in 2011, the changes in the appearance of the eyes are among the most definitive ways considered when checking whether a teenager is using illicit drugs. Both bloodshot eyes and widely dilated pupils indicate drug use.
The common signs that can be seen on the eye of a person using alcohol or substance include:
Constricted or dilated pupils
Rapid and involuntary movement of the eyeballs, or nystagmus
Enlarged pupils are among the withdrawal symptoms of a person with alcohol use disorder. Based on the 2011 study, the pupillary dilatation also indicates that the teenager is on cocaine, amphetamine or a hallucinogenic.
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Here are some drugs that cause the pupils to dilate:
Central nervous system stimulant (CNS) – CNS stimulants are used to treat narcolepsy or excessive sleepiness and attention deficit disorder. This type of drug includes amphetamines, methamphetamine, and cocaine.
Amphetamines – Amphetamines are stimulant drugs that have similar effects to cocaine. It causes the release of neurotransmitters dopamine and norepinephrine. Its effects can last for several hours.
Methamphetamine – Its chemical composition is similar to amphetamine but methamphetamine, also called meth, gets to the brain quickly. Both amphetamines and methamphetamine are classified as Schedule II or drugs that are accepted for medical uses but are also highly addictive.
Cocaine – Cocaine is regarded as a highly addictive drug that produces an immense feeling of pleasure. However, unlike the effect of amphetamines, cocaine’s effects only last less than an hour.
Heroin – Heroin comes from morphine which is taken from the seed pod of poppy plants grown in various parts of the country. It is highly addictive, more potent than morphine, and it makes the user feel the pleasurable sensation often referred to as “rush.”
Hallucinogens – Hallucinogenic drugs is another group of illicit drugs which changes the person’s thoughts, feelings, and perceptions. It includes LSD, mescaline, PCP, and magic mushrooms or psilocybin (magic mushrooms). This type of drug affects the brain’s serotonin receptors and causes pupil dilation.
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