Mydriasis

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. " ... 

The alkaloid is principally used in medicine to cause dilatation of the pupil of the eye (mydriasis), due to paralysis of the circular muscle of the ns. The accommodation is also paralysed as a result of action on the ciliary muscle (cycloplegia). Atropine is also used in conditions where... 

Tropacocaine (Benzoyl-i/r-tropine). This resembles cocaine in action, but produces local anaesthesia more rapidly and for a shorter time and causes little or no mydriasis. 

Neither tropine nor 4-tropine is mydriatic, though the former is stated to produce mydriasis in cats when injected in large doses. The pharmacological properties of these two bases have been compared by Hazard, who points out that these cis-trans isomerides show qualitative differences in pharmacological action, whereas among optical isomerides there are usually only quantitative differences in activity. It has been stated that rabbits are immune from poisoning by belladonna and, in that connection,... 

These results indicate that in these new ester mydriatics, the structural factors, which influence the development of this type of pharmacological action are similar to those made evident by the chemical investigations of Jowett and Pyman and the pharmacological work of Marshall, Dale, Laidlaw and Cushny on the tropeines. The nature of the basic component is obviously important since mydriasis is produced by simple bases such as ephedrine. As regards the nature of the esterifying acid, Jowett and Pyman drew the following conclusions — ... 

Sympathomimetic. A drug that produces effects similar to stimulating the sympathetic nervous system, that is, increased blood pressure, dilated bronchi, and mydriasis. 

Mydriasis, tachycardia, twitching, tremor, restlessness, irritability, anxiety, anorexia... 

Central nervous sysfe/n-dreamless sleep, drowsiness atropine may produce mild stimulation in some patients e-mydriasis (dilatation of the pupil), cydoplegia (paralysis of accommodation or inability to focus the eye)... 

Eyes—blurred vision, mydriasis, photophobia, cycloplegia, increased ocular tension... 

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). 

These drugs dilate the pupil (mydriasis), constrict superficial blood vessels of the sclera, and decrease the formation of aqueous humor. Depending on the specific drug and strength, these dru may be used before eye surgery in the treatment of glaucoma, for relief of minor eye irritation, and to dilate the pupil for examination of the eye... 

Cycloplegic mydriatics cause mydriasis and cyclople-gia (paralysis of the ciliary muscle, resulting in an inability to focus the eye). These drugs (see Chap. 25) are used in the treatment of inflammatory conditions of the iris and uveal tract of the eye and for examination of the eye... 

Adverse reactions include transitory stinging on initial instillation, blurring of vision, mydriasis, increased redness, irritation, discomfort, and increased IOP. Systemic adverse reactions include headache, browache, palpitations, tachycardia, arrhythmias, hypertension, myocardial infarction, and stroke. 

Tachycardia, hypertension, tachypnea, mydriasis, lacrima-tion, diaphoresis, rhinorrhea, piloerection, vomiting, diarrhea, yawning, muscle cramps, irritability, and anxiety... 

Myoclonus (inducible or spontaneous), muscular hypertonicity, shivering, tremor, akathesia, tachycardia, mydriasis, and ocular clonus... 

Monitor for adverse effects of medications, such as atropine (dry mouth, mydriasis, urinary retention, and tachycardia). 

Ipratropium is the most commonly used anticholinergic for treating bronchoconstriction in asthma. It is available as an MDI and solution for nebulization. Ipratropium has an onset of action of approximately 30 minutes and a duration of action of 4 to 8 hours. Care should be taken not to spray the metered-dose inhaler into or allow the nebulized solution to get in the patient s eyes, as it can cause mydriasis and blurred vision. 

Acute pain may cause hypertension, tachycardia, diaphoresis, mydriasis, and pallor. 

Suicide risk even in patients without psychiatric disease Avoid in uncontrolled narrow-angle glaucoma (causes mydriasis) Hepatotoxic avoid in alcoholics even if signs/symptoms of hepatic disease are absent. 

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... 

Use of diethylpropion for a period longer than 3 months is associated with an increased risk for development of pulmonary hypertension. When used as directed, reported common central nervous system adverse effects included overstimulation, restlessness, dizziness, insomnia, euphoria, dysphoria, tremor, headache, jitteriness, anxiety, nervousness, depression, drowsiness, malaise, mydriasis, and blurred vision. In addition, diethylpropion can decrease seizure threshold, subsequently increasing a patient s risk for an epileptic event. Other organ systems also can adversely be affected, resulting in tachycardia, elevated blood pressure, palpitations, dry mouth, abdominal discomfort, constipation,... 

Inspection of the retina during an ophthalmoscopic examination is greatly facilitated by mydriasis, or the dilation of the pupil. Parasympathetic stimulation of the circular muscle layer in the iris causes contraction and a decrease in the diameter of the pupil. Administration of a muscarinic receptor antagonist such as atropine or scopolamine prevents this smooth muscle contraction. As a result, sympathetic stimulation of the radial muscle layer is unopposed, causing an increase in the diameter of the pupil. These agents are given in the form of eye drops that act locally and limit the possibility of systemic side effects. 

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