UNIT 25 MIOTICS, MYDRIATICS AND

Structure
25.0 Objectives
25.1 Introduction
25.2 Description of Drngs

25.2.1 Miotics
25.2.2 Mydriatics
25.2.3 Mydriatics and Cycloplegics

25.3 Let Us Sum Up
25.4 Answers to Check Your Progress

25.0 OBJECTIVES
After completing this unit, you should be able to understand:
@ different diagnostic and therapeutic drugs like miotics, ‘mydiiatics and

cycloplegics;
@ the doses and duration of action of these drugs;
@ side effects of these drugs along with their contraindications; and
0 the newer drugs that are coming to the market regularly.

251 INTRODUCTION
Miotics are drugs that cause construction of pupil.
The commonly used miotics belong to two groups, parasympatl~o~nin~ettihcast
stimulate sphincter pupillae, or sy.,-;;atholytics that constrict pupil by relaxing
dilator pupillae muscle.
Mydriatics are drugs that dilate the pupil while cycloplegics are agents that cause
paralysis of ciliary muscle (paralysis of accomm~dation), Mydriatics usually
produce paralysis of ciliary muscle to a, greater or lesser degree.

Currently two classes of diugs, adrenergics and parasympatholytics, are available
for mydriatic purpose. For most dilation procedures the adrenergic or
anticholinergic agents can be used either alone or in combinatio~lf or inaxiinum
mydriasis. Agents used topically in the eye for the purpose of inhibiting
accommodation are termed cycloplegics. Their primary use is for cycloplegic
refraction and the treatment of uveitis. Since these agents also illhibit action of
the iiis sphincter muscle they are effective mydriatics and are coinmonly used for
routine pupillarj7 tiilarion.
All these h g s w hen instilled into the conjunctival sac are rapidly absorbed
through the cornea and become effective in the eye.

25,2 DESCRIPTION OF DRUGS
In this unit you will study the diagnostic and therapeutic drugs in details. They
include miotics, mydriatics and cycloplegies.

25.2.1 Miotics
Miotics are drugs that cause constriction of pupil. These are used in the
management of glaucomas and the treatment of esotropias and accommodation
insufficiency.

Pilocarpine I

~iloca$ine is a direct acting parasympathomimetic drug, which duplicates the
inuscarinic effects of acetylcholine, but has no nicotinic effects. Pilocarpine
stimulates secretory glands and s~noolhm uscles, but has 110 effect on striated
muscles. Pilocarpine nitrate, a sterile ophthalmic solution is available as 1 per cent,
2 per cent or 4 per cent drops. Pilocarpine is effective in the treatment of
glaucoma by improving the facility of outflow (by contraction of cilia~ym uscle)
and by decreasing aqueous secretion. Onset of rniosis occurs within 10-30 lninutes
and lasts for 4-8 hours following topical application.

Indications and Usage
Pilocarpine is indicated for:
e The control of intra-ocular pressure in angle closure glaucoma.
9 Emergency relief of mydiiasis in an acutely glaucomalous situation.
9 To reverse mydriasis caused by a cycloplegic agent.
@ In the treatment of accommodative strabismus.
@ Controversial role in the treatment of hyphaema.
9 After cataract extraction in cases of iiltra capsular cataract extraction. ,

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Contraindications
Pilocarpine is contraindicated in persons showing ‘hypersensitivity to any of its
components. It is also contraindicated in anterior uveitis.

Warnings
Pilocarpine is readily absorbed systemically on topical application. Excessive
application may elicit toxicity symptonls in some iildividuals (manifested as
salivation, lacriination, sweating, nausea, vomiting and dimllbea, bronchiolar
spasin and pulmonary edeina can occur).

Precautions
Pilocarpine has been reported to cause retinal’ detachment in individuals with
pre-existing retinal diseases or predisposed to retinal tears. Safety and
effectiveness in children have not been established.

Adverse Reaction !I
Include visual blul-ring due to miosis and accoinlnodative spasm, poor dark
adaptation caused by the failure of the pupil to dilate in reduced illumination and
conjunctival hyperemia. Miotics have been reported to cause lens opacities in
susceptible individuals after prolonged use. Allergic blepharo-conjunctivitis, ocular
pseudopeinphigoid, corneal epithelial staining iind vascularisation, atypical band
keratopathy, iris hyperemia and epithelial cyst formation have been reported in
some patients.

Dosage and Administration
* To aid in emergency miosis, 1 to 2 drops of one of the higher concentrations I

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should be used. I

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The dosage and strength required to reverse mydiiasis depends on the
. cycloplegic used. . i

The drops are used bd – qid in the treatment of angle closure glaucoma,

Carbachol
Carbachol is a cholinergic prepared as a sterile topical ophthalmic solution.
Carbachol is a direct acting parasympathomimetic that is sometimes used when

y or resistance to pilocarpine develops. Unlike pilocarpine, carbachol has both
nicotinic and muscarinic actions. It is available as 0.75 per cent to 3 per cent
drops.

It is a cholinergic (parasympatl~omimetic)a gent. Carbachol has a double action, it
not only stimulates the motor end plate of the muscle cell, as do all cholinesters,
but it also partially inhibits cholinesterase.

Indications and Usage
For lowering intra-ocular pressure in the treatment of glaucoma.

Miolics are contraindicated where constriction is undesirable such as acute iritis.
It is also contraindicated in those patients showing hypersensitivity to any
component of this preparation.

Warnings
The preparation is for topical use’only and not for injection. Carbachol should
be used with caution in the presence of corneal abrasion to avoid excessive
penetration that can produce systemic toxicity and in patients with acute cardiac
failure, bronchial asthma, active peptic ulcer, hyperthyroidism, gastrointestinal
spasm, urinary tract obstruction and Parkinson’s disease. As with all miotics,
retina! detachment has been reported when used in certain susceptible
individuals.

Avoid over dosage. The rniosis usually causes difficulty in dark adaptation.
Patient should be advised to exercise caution in night hiving and other hazardous
occupations in ,poor light.

Adverse Reaction .
This preparation is capable of producing sys.temic symptoins of a cholinesterase
inliibitor even when the epithelium is intact. Transient ciliary and conjunctival
injection, headache and ciliary spasm with resultant temporary decrease of visual
acuity may occur. Salivation, syncope, cardiac arrhythmia, gastrointestinal
.cramping, vomiting, asthma and diarrhoea may occur. I

Dosage and Administration
It is administered three to four times per day.

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Phospholine Iodide
Phospholine iodide is available in the following concentrations: 0.03 per cent,
0.06 per cent, !0.125 per cent, 0.25 per cent.

Phospholine iodide is a long acting cholinesterase inhibitor for topical use that
enhances the effect of endogenously liberated acetylcholine of iris, ciliary muscle * I

and other parasympathetically innervated struct~ireso f the eye. It thereby causes
rrriosis, increase in facility of aqueous humor, fall in intra-ocular pressure and

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potentiation of accommodation.
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~ , Indications and Uses
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, I In Glaucoma- chronic open angle glaucoma, sub-acute or chronic angle closure I

, 252 gla~icomaa fter iridectomy or where surgery is refused or contraindicated.
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Miotiw. Mydrlolics and
Cycioplegies

e Active uveal inflammation.
Most cases of angle closure glaucoma due to the possibility of increasing
angle block.

@ Hypersensitivity to the active or inactive ingredients.

Adverse Reaction
0 Stinging, burning, lacrimation, lid muscle twitching, conjunctival and ciliary

redness, browache, induced myopia with visual blurring may occur.
@ Activation of latent iritis or uveitis may occur.
@ Tris cysts may form and, if treatment is continued, may enlarge and obscure

vision. This occurrence is more frequent in children.
Prolonged use may cause conjui~ctivalt hickening, obstruction of nasolacrimal
canals.
Lens opacities, paradoxical increase in inha-ocular pressure.

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Dosage and Administration
Early chronic glaucoma, 0.03 per cent instilled twice a day. Refrigerated aqueocs
solution shows a drop in potency within four weeks.

Physostigmine Sulphate ,
Physostigmine is an alkaloid obtained from the seeds of physostignline venenosum.
T t is an iildirectly acting parasympathornimetic agent. It is available as a solution
of 0.25 per cent, 0.5 per cent and .O per cent and an ointment containing 2 per
cent of the drug. It is a reversible anlicholine-esterase. The mechanism of action
involves inhibition of choline-esterase with consequent accumulation of
acetylcholine at the neuromuscular junctions.

Indications
It can be used in conjunction with pilocarpine in the treatment of acute glaucoma,
in angle closure glaucoma and in diagnosis and treatment of myasthenia gravis.

Contraindicatio~ts
Hypersensitivity to the drug and conditions predisposing to retinal detachment.

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Adverse Reaction
These include twitching, irritation and allergic reaction. Depigrnentation of the lid
s)cin has been noted in some patients with the use as an ointment.

‘Dosage and Administration
It is administered every 4 to 6 hours,

25.2.2 Mydriatics +

Mydriatics are drugs that cause dilatation of pupit. ,
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Phenylephrine Hydrochloride a

, Phenylephrine hydrochloride 5 per cent and 10 per cent ophthalmic solution is I

primarily a direct acting drug that stimulates the alpha-receptors of those structu~~s
innervated by the post ganglionic sympathetic nerve fibres. It also causes blanching ,

of the conjunctival vessels. It is a mydriatic with no cycloplegic effect.

~Indicatioisa nd Uses I

Although the mydriasis produced by 2.5 per cent phenylephrine alone is generally I

not adequate for detailed examination of the retinal periphery, it is often sufficient 253

Basic Ocular Sciences for viewing the poste ior pole. Mydriasis produced is not accompanied by
cycloplegia. It is a fast acting mydriatic.

One drop of 2.5 per cent phenylephrine causing >5 mmHg iise in IOP has been
used as a provocativer test for diagnosis of angle closure glaucoma.

It is used in diagnosis of ptosis of Homer’s syndrome as it responds to the
instillation of 0.125 per cent phenylephrine drops. The diagnosis of Horner’s
syndrome can also be established as 1.0 per cent phenylephrine causes dilation of
a hon~er’sp upil but not of a normal pupil.

Contraindications
Angle closure glaucoma.
Hypertensive patients: Phenylephrine is a powerful vasocollstrictor and is
absorbed systemically when applied topically to the eye.

9. 10 per cent Phenylephine is contraindicated in infants.
Q In patients receiving reserpine, guanethidine and tricyclic antidepressants,

phenylephrine is contraindicated because of their increased susceptibility to
vasopressor action.
In eyes where corneal epithelium is denuded it may cause corneal clouding.

@ Persons with a known hypersensitivity to any component.

Adverse Effects
Ophthalmic: Mild stinging on initial instillation, rebound conjunctival congestion
on prolonged use, and rebound rniosis may occur in some elderly patients and
subsequent instillation may produce less mydriasis.

Systemic: The major difficulty in using this drug is the possibility of
inducing systemic hypertension, tachycardia. Headache or browache may
occur. Episodes of myocardial infarction and arrhythmias in elderly patients
are reported.

Stability: One other disadvantage is relatively short shelf life as once the
bpttle is opened Pheilylephrine rapidly oxidizes, which makes it less
effec;ive.

Dosage and Administration
Topically 1 or 2 drops into the conjunctiva of each eye for refraction, in
conjunction with some cycloplegic of choice. Maximum dilation with
phenyleplvine alone occurs within 15-60 minutes. The pupil size returns to
normal within 4-6 hours. Initial instillation of a topical anaesthetic before
phenyepwne prevents the stinging caused by phenylephrine and enhances
pupillary dilation.

In premature infants for dilation, 2.5 per cent phenylephrine is used in conjunction
with 0.2 per cent cyclopentolate or 0.5 per cent tropicarnide.

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25.2.3 Mydriatics and Cycloplegics

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Cycloplegics are drugs that cause paralysis of ciliary muscles, i.e., cause relaxation
of accommodation. i
Atropine Sulphate
Atropine sulphate is an anti-cholinergic prepared as a sterile topical ophthalmic
solution and ointment supplied in three strengths: 0.5 per cent, 1 per cent and .

3.0 per cent. Intramuscular injections are available as 0.3, 0.4 and 0.6 mg/ml
254 preparations.

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Mechanism of Action Miotics, Mydriatics and
Cycloplegles

Atropine sulphate is a naturally occurring alkaloid that acts directly on the
muscarinic receptors of structure innervated by the post-ganglionic parasympathetic
fibres, It does not reduce liberation of acetylcholine, but tissues are rendered
insensitive to it. It is the competitive inhibitor of the muscarinic action of
acetylcholine and is the strongest of the’ drug available for cycloplegic purposes. It
causes mydriasis and cycloplegia by paralysing sphincter pupillae and ciliary
muscle respectively.

Indicatioizs and Usage
e It is used for mydriasis and cycloplegia (in young patients in which

accomodation is very active).
e Pupillary dilation in inflammatory conditions of the iris (to prevent pain,

release synechiae and give rest to inflamed tissue).
‘ In ciliary block glaucoma.

u It is used to prevent undue vagal response in tensilon test.
s Amblyopia therapy (penalisation)

In cases of accomodative spasm.
@ Pre and post operatively in many intra-ocular surgeries,

Contraindications
Contraindicated in persons with primary glaucoma or a tendency towards glaucoma
e.g., narrow anterior chamber angle and in those persons showing hypersensitivity
to any component of this preparation. .
Subluxated lens (lens may dislocate into anterior chamber and cause pupillary
block glaucoma.
Precautions
Atropine solution should not be used in children as it causes systemic absorption
through nasolacrimal mucosa.
To avoid excessive systemic absorption the lacriinal sac should be compressed for
one minute after instillation.

Adverse Reaction
Local: Atropine can cause allergic responses, usually wound the eyelids and
conjunctiva. The allergic responses include redness and crusty flaking of the
eyelid margins, dryness and wrinkling of the skin around the eyelids and injected
bulbar conjunctiva with some watery discharge. Blurred vision and photophobia are
consequent to the cycloplegic and mydriatic effect of atropine. I

Systemic: Dryness of skin and mouth, tachycardia, irritability or delirium, flushiag
of face, skin rash, abdominal distension in infants and hyperpyrexia may occur in

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children. Severe reactions are manifested by hypotension with progressive
respiratoiy depression. The elderly are more susceptible to a~~ticholinergtiocx icity I

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like cognitive impairment and delirium.
Plasma concentrations peak after 10 rnin of topical application. Two drops of

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1 per cent solution contain 1 mg of the drug which is twice the preoperative I

injectable dose.
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Dosage and Administration
Because of a long duration of its effect and delay in the onset of action it is not i

routinely used for office procedures.

Children: For refraction, administer 1 per cent ointment to each eye, thrice ddly
for three days prior to examination, 255

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Basic Ocular Sciences Hornatropine Hydrobromide

Homatropine 2 per cent sterile ophthalmic solution was the first anti-cholinergic to
be developed specifically as an alte~nativet o atropine.

It is a synthetic anti-cholinergic agent that directly blocks the muscarinic action of
acetylcholine, causing mydriasis and cycloplegia. Its effect generally lasts longer
than those of either cyclopentolate or tro~icamideb ut it is not necessarily more
effective. Homatropine is therefore not conlmonly used as a diagnostic agent,
however its relatively long lasting effect makes it valuable in the treatment of
anterior ocular inflammations such as iritis.

Indications and Usage
As a moderately long acting mydriatic and cycloplegic agent for cycloplegic
refraction and in the treatment of inflammatory condition of the uveal tract. It is
inferior to atropine for penalization therapy of amblyopia.

Contraindications
In persons with a tendency of occludable angles.
It should not be used in patients who have shown allergy to atropine.

Patient Warning
rur.

Patient should be advised not to drive or engage in other hazardous activities while
pupils are dilated. Caution also in pregnant and lactating mothers.

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Adverse Reaction
Adverse reactions are similar to atropine but much less in frequency. Prolonged
use may produce local irritation characterized by follicular conjunctivitis, vascular
congestion, edema, exudate and an eczematous dermatitis.

Dosage and Administration
For refraction instill one or two drops topically in the eye(s). May be repealed in
5 to 10 minutes if necessary.

Cyclopentolate Hydrochloride
Cyclopentolate 1 per cent is an anticholinergic prepared as a sterile ophthalmic
solution. Also available as 0.5 per cent and 2 per cent solution.

Cyclopentolate is an effective antimuscarinic agent and the cycloplegic of choice
for children under age 12 and for youths between 12 and 20 when latent hyperopia
or accommodative esotropia is suspected. Its cycloplegic efficacy is greater than

a hornatropine.. Also used for pre and post-operative states when mydriasis is
required and when a short acting mydriatic ~ ~ c l o ~is ln~eed~edi cin the therapy of

, iridocyclitis. Unlike atropine and homatropine onset of mnhximum cycloplegia
approximates the onset of maximum mydriasis.

It can also be used in patients with central lenlicirlar changes, if they feel better
with mydriasis, till the patient is ready for surgery.

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Contraindications . I
Angle closure glaucoma and in patients with hypersensitivity to the drug. 1
Cyclopentolate is also not recommended for children with emotional problems

I I since it can have marked central nervous system effects that may be increased in .
256 susceptible youngsters,

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Dosage and Admiitistration Miotics, Mydriatics and
Cycloplegies

One drop followed by second drop in 5 minutes or as desired by the physician.
Complete recovery usually occurs in 24 hours.

Adverse Reaction

Local: 1ncreaGd intra-ocular pressure, blurred vision, and photophobia.

Systemic: psychotic reactions, behavioural disturbances, seizures, disorientation and
cardio-respiratory collapse in children have been reported. Dryness of the mouth,
tachycardia, headache or allergic reaction may occur. Because toxic reactions
occur with multiple installations of 1 per cent solution, the smallest dose should be
used.

Management of over dosage in life threatening tpxicity includes slow injection of
physostigrnine intravenously.

Tropicamide is one of the no st commonly used anti-cholinergic mydriatic because
of its powerful mydriatic effects, rapid onset of action and low incidence .of side
effects. It is available as 0.5 per cent or 1 per cent eye drops.

Tropicamide acts by blocking muscaranic acetylcholine receptors. The stronger
preparation (1 per cent) also paralyses accomTnodation. The 0.5 per cent strength
may be useful in producing mydriasis with #onlys light cycloplegia.

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Zndicatiorzs and Usage

For mydriasis and cycloplegia, for diagnostic procedures and when a short acting
mydriatic is needed for some pre and post-operative stages. Unlike atropine,
homatropine and cyclopentolate, pupillary dilation with tropicamide is less
dependent on iris pigmentation. For premature infants a combination of 2.5 per
cent phenylephine and 0.5 per cent tropicanlide is recommended because tlie latter
alone fails to dilate adequately.

Contraindications I

Contraindicated in angle closure glaucoma and in persons showing hypersensitivity
to ady component of this preparation.

Precautions

In the elderly and others where increased intra~ocularp ressure may be
encountered, mydriatics and cycloplegics should be used with caution. This
preparation may cause CNS disturbances that inay be dangerous in infants and
children.

Patient should be advised not to drive or engage in other hazardous activities while
pupils are dilated,

Dosage and ~dministration

One or two drops of 1 per cent solution in each eye 2 to 3 times at 5 minutes
intervals or as directed by the physician.

Adverse Reaction

Local: Stinging sensation. I

Systemic: Rarely in children, confusion or fiyperactivity may occur. 257

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sC ………..
Basic Ocular ~clences

Check Yoar Progress
1) What are miotics and mydriatics?

…………………..*……..~.*…….*……………..~……………..I….**…..*……..11……………. …6

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2) Name at least three mydriatics and cycloplegics.

………………………………………………………………………………………………………………….
3) ‘ Which i s only rnydriatic?

………………………………………………………………………………………………………………….
4) Which cycloplegic is used in children with squint?

25.3 LET US SUM UP
In this unit you have learnt that mydriatics are the drugs, which produce dilatation .
of the pupil, and cyclopegics x e the agents that cause paralysis of the ciliary ,

muscle (paralysis of accommodation). You have also learned that mydsiatics
usually produce paralysis of the ciliary muscle in greater or lesser degree. All
these drugs when instilled into the conjunctival sac are rapialy absorbed through
the cornea and become effective in the inner eye.

The mydriatics may be divided into two groups: (a) Para-sympatholytics, and
(b) Sympathornirnetics. The parasynlpatholytic agents block the action of the
parasympathetic nervous system. You lcnow hat acetylcholine is the ne~lrohumoral
transmitter at the receptor site, and all the drugs in this group act by competing
with Acetylcholine. As a result, due to unopposed action of dilator pupillae
myd~iasisa nd cycloplegia are produced.

In next unit you will study the antiglaiicoma drugs.

25.4 ANSWERS TO CHECPC YOUR PROGRESS
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1) The drugs that constrict the pupil are cillled rniotics and which dilate the
pupil are called mydiiatics.

2) Atropine, Hornatropine and Tropicanlide
3) Phenylephiine
4) Atropine

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