Miosis

A special feature of the iris is its autonomic innervation. Sympathetic activation widens the aperture of the iris whereas impulses from the parasympa thetic nervous system decrease the aperture size. Therefore adrenergic agonists and anticholinergic compounds both increase the aperture of the iris, i.e., cause mydriasis, and antiadrenergic and cholinergic agonists decrease it, i.e., cause miosis. The iris can thus be considered an excellent mirror reflecting the balance of the autonomic nervous system in the body. " ... 

White has shown that the lysergic acids themselves exhibit weakly some, but not all, of the types of activity characteristic of the alkaloids of higher molecular weight. Both acids produce a slight transitory cyanosis of the cockscomb and cause ataxia and delayed miosis in the cat and also relax the isolated rabbit intestine. On the whole, lysergic acid appeared more active than the isomeride. 

Mu Morphine-like supraspinal analgesia, respiratory and physical depression, miosis, reduced Gl motility... 

RISK FDR INJURY. Narcotics may produce orthostatic hypotension, which in turn results in dizziness. The nurse should assist the patient with ambulatory activities and with rising slowly from a sitting or lying position. Miosis (pinpoint pupils) may occur with the administration of some narcotics and is most pronounced with morphine, hydro mo rpho ne, and hydrochlorides of opium alkaloids. Miosis decreases the ability to see in dim light. The nurse keeps the room well lit during daytime hours and advises the patient to seek assistance when getting out of bed at night. 

Dapiprazole acts by blocking die a-adrenergic receptor in smootii muscle and produces miosis through an effect on the dilator muscle of the iris. The drug is used primarily after ophtiialmic examinations to reverse the diagnostic mydriasis (dilation of the pupil). 

Major gastrointestinal effects include decreased gut motility and changes in secretion of gastric and intestinal fluids. Morphine and most p receptor agonists cause pupillary constriction. Some tolerance to this effect may develop, but addicts with high opioid levels will still have miosis. Respiratory depression is the usual cause of death from opioid overdose. 

Neurological signs nystagmus, miosis, blurred vision, tremor, slurred speech, dystonia, convulsion, amnesia, confusion, peripheral numbness... 

Ocular Effects. Pinpoint pupils (miosis) have been observed in individuals following acute exposure to methyl parathion. Electroretinographic changes have been reported in mice following intraperitoneal injection of 1.5 mg of methyl parathion. These changes were a direct effect of methyl parathion on... 

Ocular Effects. One study reported that seven children exposed to methyl parathion by inhalation, oral, and possibly dermal routes exhibited pinpoint pupils (miosis) (Dean et al. 1984). This effect is a consequence of the effects on the autonomic nervous system. No other studies were located regarding ocular effects in humans or animals after inhalation exposure to methyl parathion. 

Neurological effects related to cholinesterase depression occurred in seven children acutely exposed to methyl parathion by inhalation as well as orally and dermally (Dean et al. 1984). The children were admitted to a local hospital with signs and symptoms of lethargy, increased salivation, increased respiratory secretions, and miosis. Two of the children were in respiratory arrest. Two children died within several days of each other. All of the children had depressed plasma and erythrocyte cholinesterase levels (Table 3-2). These effects are similar to those occurring in methyl parathion intoxication by other routes (see Sections 3.2.2.4 and 3.2.3.4). Three adults exposed in the same incident had normal plasma (apart from one female) and red blood cell cholinesterase, and urinary levels of 4-nitrophenol (0.46-12.7 ppm) as high as some of the ill children. 

Clinical signs and symptoms of toxicity are related to the overstimulation of muscarinic, nicotinic, and central nervous system receptors in the nervous system. Muscarinic receptors are those activated by the alkaloid drug muscarine. These receptors are under the control of the parasympathetic nervous system, and their hyperactivity results in respiratory and gastrointestinal dysfunction, incontinence, salivation, bradycardia, miosis, and sweating. Nicotinic receptors are those activated by nicotine. Hyperactivity of these receptors results in muscle fasciculations even greater stimulation results in blockade and muscle paralysis (Lefkowitz et al. 1996 Tafliri and Roberts 1987). Hyperactivity of central nervous system receptors results in the frank neurological signs of confusion, ataxia, dizziness, incoordination, and slurred speech, which are manifestations of acute intoxication. Muscarine and nicotine are not... 

Ocular effects include conjunctival reddening, a slight miosis, and decreased intraocular pressure Cardiovascular tachycardia and vasodilation combined with orthostatic hypotension in high doses... 

Patients who are acutely intoxicated with an opioid usually present with miosis, euphoria, slow breathing and slow heart rate, low blood pressure, and constipation. Seizures may occur with certain agents such as meperidine (Demerol ). It is critically important to monitor patients carefully to avoid cardiac/ respiratory depression and death from an excessive dose of opioids. One strategy is to reverse the intoxication by utilizing naloxone (Narcan ) 0.4 to 2 mg IV every 2 to 3 minutes up to 10 mg. Alternatively, the IM/SC route may be used if IV access is not available. Because naloxone is shorter-acting than most abused opioids, it may need to be readministered at periodic intervals otherwise the patient could lapse into cardiopulmonary arrest after a symptom-free interval of reversed... 

Medications with anticholinergic properties induce mydriasis, which can lead to angle closure in pupillary block and plateau iris. Pupillary block may also be induced by drugs that cause miosis.12... 

The adverse effects of pilocarpine are caused by the induction of miosis. The contraction of the ciliary muscle causes the lens to displace forward, which can lead to accommodation spasm, myopia, and brow ache. Pupillary constriction can also affect night vision. Pilocarpine should be avoided in patients with severe myopia, as it increases the risk of developing retinal detachment. Systemic effects may occur at higher concentrations and include, nausea, vomiting, diarrhea, and bradycardia. 

Eye Contact Flush eyes immediately with water for 10-15 min, then don a respiratory protective mask. Although miosis may be an early sign of agent exposure, do not administer an injection when miosis is the only sign present seek medical attention immediately. 

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