PHARMACOLOGY OF THE EYE

Prepared By :

Dr./ Rehab LashinePharmacology Department

Physiological Anatomy of the Eye

THE ANT.CHAMBER OF THE EYE

The Ciliary Body

The Pupil

Pupillary Muscles

Mydriasis

Miosis

Effect of Miosis and Mydriasis on Acquous Humor Drainage

Accomodation

Autonomic Nerve supply of the Eye

Parasympathetic:

1- Bl.Vs. …Conjuctival VD ( Oculomotor)

2- Ciliary mm.. (Accomodation) (Oculomotor)

3- Sphincter pupillae(Miosis) (Oculomotor)

4- Increased lacrimation…..7th vranial n.(N.B.: Stim. Of the nic. Rec. causes twitches of

eye lid mm.)

•Sympathetic1- Bl.Vs.( Conjunctival VC)………α1

2- Dilator Pupillae ( Mydriasis)…….. α1

3- Levator palpebrae & Muller’s m.(Exophthalmus & widening of the palpebral fissure)…..

4- Ciliary mm (relaxation)……. β2

5- Lacrimal glands (lacrimation)……… α1

6- α & β rec. in the Bl.vs. of the ciliary processes….help in regulation of aqueous humour formation

Light Reflex

Corneal Reflex

Drugs Acting on the Eye

I- Drugs affecting the size of the pupil:MioticsMydriatics

II- Drugs Affecting Accomodation….Cycloplegics

III- Drugs affecting the IOP (intraocular pressure)

IV- Local Anesthetics

V- Antiallergic agents

VI- TTT of Eye Infection

Miotics

M3 rec.: Parasympathomimeticsα1 blockers:

Sympatholytics(e.g.Phenoxybenzamine)

Central : Morphine ( ↑oculomotor nucleus)

USES:-Glaucoma-Counteract action of mydriasis- To break adhesions

Mydriatics Active:

- Sympathomimetics….(Mydriasis without Cycloplegia or loss of light reflex)

- Local anesthetics…..(Cocaine) (Mydriasis without Cycloplegia or loss of light reflex ).

Passive: - Anticholinergics……(Mydriasis with Cycloplegia & loss of light

reflex) except Eucatropine (doesn’t cause cycloplegia).

Ganglion Blockers …...(Mydriasis with Cycloplegia ) Central

USES:Fundus Exam, Therapy of acute Iritis, Breaking Adhesions

Drugs Affecting Accomodation

Drugs causing Accomodation to near objects:

- stim. of ciliary mm: Parasympathomimetics

Cycloplegics: drugs causing paralysis of ciliary mm…..loss of accomodation…fixation of vision for far vision: Parasympatholytics (EXCEPT EUCATROPINE)

N.B:.Sympathomimetic mydriatics are safely

used in adults > 40 years in whom Atropine have the risk of causing dangerous rise in IOP.

Therapeutic uses of Cycloplegic drugs:1- Ttt of Iridicyclitis2- Ttt of choroiditis3- Measurement of refractive errors

Drug Therapy of Primary Open Angle (chronic simple) Glaucoma

A) Miotics: They act mainly by↑ the acqueous outflow.

1- Direct : pilocarpine.

2- Indirect: choline esterase inhibitors

B) Sympathomimetics: ↓ acq.humour production, & ↑ outflow

C) Β-adrenoceptor blocking agents: ↓ acq.humour production…….Timolol, befunolol

D) Oral Agents: Carbonic Anhydrase inhibitors. ↓ acq.humour production…..Acetazolamide

Drug Therapy of acute angle closed (congestive) glaucoma

Dehydrating agents: IV infusion Of Hypertonic solution ( Mannitol, Glycerol)

Oral Acetazolamide

Topical miotics: e.g.: pilocarpine

Analgesics: pethidine or morphine (for pain)

Drug used in treating inflammatory and allergic eye conditions

1- Conjunctivitis: can be ttted by:A- Penicillin G, chloramphenicol ( Acute purulent

conj.)

B- Sulphacetamide (eye drops)..for trachoma

C- Tetracycline ….for chronic follicular conjunctivitis

D- Vidarabine, or Acyclovir for Herpes simplex keratitis

E- Topical steroids for chronis puppillary conj.

Drug used in treating inflammatory and allergic eye conditions( Cont.)

2- Glucocorticoids: to suppress inf., and allergy

3- Topical Antihistaminics: (eye drops), in allergies

4- Sodium cromoglycate: ( for ttt. Of spring catarrh, vernal keratoconjunctivitis)

5- Astringents : Zinc Sulphate ( angular conj.)

Harmful drugs for the Eye1- Drugs that ↑ IOP: A- Mydriatic cycloplegics, tricyclic antidepressants B- Chronic steroid use

2- Cataractogenic drugs: steroids, phenothiazines, heavy metals…

3- Drug-induced retionopathies: ethanol, methano, indomethacin,steroids

4- Drugs causing corneal deposits: Amiodarone, chloroquine…

5- Oculomucocutaneous syndrome ( Conj. Fibrosis, corneal opacities,and dimnished tear secretion) e practolol

6- O2 : 40 % for prolonged periods in premature infants causes Retrolental fiboplasia

Experiment