Chapter 19

Visual and Auditory Systems

Objectives List both trade and generic drug names

covered in this chapter. Describe the functions of the eyes and ears. List the major components of the eyes and

ears. Explain the drug action of the medications

listed.

Objectives (cont’d)

Describe what causes glaucoma. Describe the different types of conjunctivitis

and their treatments. List the various infections that affect the eyes

and ears. Explain how medications work to relieve

glaucoma.

Introduction Five main senses of body system are sight,

hearing, touch, smell, taste. Two senses that can change life dramatically

are seeing and hearing. Equilibrium is another sense that plays a

role in the ability to balance.

The Eyes (Opthalmic System)

Eyes link outside world to the mind. Images translate into impulses that create

lasting memories in the mind. Three different levels of eye specialists:

Opticians make lenses.Optometrists perform eye exams.Ophthalmologists are medical doctors.

Anatomy of the Eye Eyebrows shade eyes from light. Eyelashes (more than 2000) catch debris,

keep eyes moist, shade the eyes. Orbit is bony socket that holds the eye. Eye position able to rotate 100 degrees

laterally.

Anatomy of the Eye (cont’d)

Eyelids:Eyelids have four layers (outer skin, muscles,

connective tissue, conjunctiva.Layers allow the eyes to open and close.

Blinking protects eyes from foreign objects. Lacrimal fluid cleanses the eye.

Anatomy of the Eye (cont’d) Conjunctiva is thin transparent layer, mucous

membrane, covers anterior eyelids and sclera.

Lacrimal gland, in orbit, secretes tear into eye; has ducts to nasal cavity.

Lysozyme is enzyme in tears with antimicrobial properties.

Anatomy of the Eye (cont’d)

Anatomy of the Eye (cont’d)

Cornea: transparent cover allows light into the eye Connective tissue covered with thin epithelial

layer No blood vessels—nourished by aqueous

humor (tissue fluid) and oxygen Nerve fibers sensitive to pain

Anatomy of the Eye (cont’d)

Sclera:Attached to cornea; wraps around back of

eyeballWhite portion of eye: many fibers and muscles

with opening for optic nerve Optic nerve sends images to brain for

interpretation

Anatomy of the Eye (cont’d)

Choroid coat: layer inside sclera Fovea: innermost layer where sharpest

vision occurs Sclera joins with iris and ciliary body in front

of eye Iris: colored part of eye to filter light

Anatomy of the Eye (cont’d) Posterior cavity: largest space in eye;

surrounded by lens, ciliary body, retina Ciliary body: forms ring around front of eye;

holds lens in place Vitreous body: holds shape and form of eye Vitreous humor: nourishes and cleanses eye

Anatomy of the Eye (cont’d)

Retina:Thin layer; contains layers of neurons, nerves,

pigmented epithelium, membranous tissuesReceptor cells responsible for vision

Six muscles responsible for eye movements

Eye Muscles and Direction of Movement

Anatomy of the Eye (cont’d)

Pupil:Dilates (mydriasis) when focusing on distant

figure or darknessConstricts (miosis) in extreme light

Aqueous humor provides the nutrients and oxygen to maintain lens and cornea.

Anatomy of the Eye (cont’d) Aqueous humor:

Accumulates; must be released to maintain pressure

Canal of Schlemm: ducts used to release aqueous humor

Retina contains nerve endings to transmit electrical impulses to brain.

Vision Retina contains rods and cones responsible

for vision. Rods: sight in dim light; produce black and

white images. Cones detect color. Rods and cones synapse with nerve endings;

signals sent through optic nerve to brain. Occipital lobe—visual interpretation.

Conditions That Affect the Eye

New developments/treatments:Laser surgery-correct visionLens implantation—for blindness

Conditions: glaucoma, conjunctivitis, congestion of eye, viral and bacterial infections

Allergies With allergies,eyes become itchy, red and

watery. Treatment includes: avoiding irritants, getting

allergy shots, mast cell stabilizers, antihistamines, and decongestants.

Drug Treatment for Allergies Mast cell stabilizers: prevent allergy cells

from opening and releasing chemicals that cause inflammation.Solutions, suspensions, systemic agents

Antihistamines and decongestantsalleviate symptoms of and inflammation.

Corticosteroids: relieve inflammation.

Conjunctivitis Conjunctivitis known as “pink eye.” Is common in daycare centers; contagious. Is acute inflammation of the conjunctiva. Causes include: viral, bacterial, fungal,

allergies. Symptoms include: inflammation, itching,

burning, white mucus. Wash hands and avoid touching the eyes.

Drug Treatment for Conjunctivitis No treatment for viral infection; antibiotics for

bacterial infection Antiinfectives: vidarabine, natamycin,

gentamicin, ciprofloxacin Ophthalmic sulfonamides Aminoglycosides Macrolides

Cataracts Cataracts are characterized by a film over

the eyes.Vision becomes blurred; can lead to blindness.

Cause: formation of protein buildup onto the lens.

Eyeglasses/contacts can clear up vision problems.

Surgery

Cataracts (cont’d)

Mydriatic-cycloplegic drugs used to dilate eyesAtropine, cyclopentolate, homatropine

tropicamide

Glaucoma Pressure within the eyes is higher than

normal (increased ocular pressure [IOP]). Two causes: overproduction of aqueous

humor; blocked ducts that drain excess aqueous humor.

Left untreated, causes blindness. Types of glaucoma include primary, acute

congestive, and chronic simple.

Drug Treatment for Glaucoma β-adrenergic blockers: lower intraocular

pressure Carbonic anhydrase inhibitors Miotics: reduce intraocular pressure Sympathomimetics: decrease aqueous

humor Prostaglandin agonists: increase outflow of

aqueous humor

Blindness Blindness is partial or total lack of vision.

Blindness has many causes. Macular degeneration - only peripheral vision Retinitis pigmentosa: field of vision is limited

to a small circular opening in the middle. Most common treatment: eyeglasses.

Blindness (cont’d)

Corneal transplant—may correct blindness. Stem cell transplant—may reverse blindness.

Miscellaneous Ophthalmic Agents

Artificial tears bought OTC. Used to relieve dry eyes, irritation. Ingredients include: sodium chloride, buffers

to adjust pH, additives to prolong effects. Dosage form is solution. Comes in various strengths, combinations.

Miscellaneous Ophthalmic Agents (cont’d)

All contain sodium chloride and all used for same reasons.

Artificial tear inserts available by prescriptions for dry eye syndrome, severe keratoconjunctivitis.

Artificial Tears ProductsTrade Name Manufacturer IngredientsTear Drop Parmed Polyvinyl alcohol, NaCl, EDTA, benzalkonium ClArtificial Tears Various mfg Polyvinyl alcohol, povidone, NaCl,

chlorbutanolCellufresh Allergan Carboxymethylcellulose, NaCl, KCl, Na lactateRefresh Allergan Polyvinyl alcohol, povidone, NaClJust Tears Blairex Benzalkonium Cl, EDTA, polyvinyl alcohol, NaClMurine Ross Polyvinyl alcohol, povidone, benzalkonium Cl, dextrose, EDTA, NaCl, sodium bicarbonate, sodium phosphateRestasis Allergan Cyclosporine, glycerin, polysorbate,, carbomer, purified water, sodium hydroxide

The Ears (Auditory System) Human ear responsible for hearing, balance,

equilibrium, communication skills. Ear is composed of three sections: external,

middle, inner. External ear—auricle; composed of cartilage

and skin; entrance for sound waves.

Anatomy of the Ear

External Ear Auditory canal: about 1 inch long; leads to

tympanic membrane (eardrum). There are two major functions of tympanic

membrane: protection of middle ear from foreign objects; transmission of sounds to middle ear.

Sounds transmitted by vibrations. Cerumen is wax substance produced by

glands.

Middle Ear Vibration carried to middle ear. Cavity (space) contains bony structures

(ossicles): malleus, incus, stapes. Ossicles connected to each other. Eustacian tube:

Eustacian tube eads to nasopharynx.It equalizes pressure between outside and inside

atmosphere.

Inner Ear Stapes continues transfer of sound to inner

ear. Fluid-filled cavity—labyrinth; comprise many

components that process and transmit audible sounds via nerve impulses to brain.

There are two areas: perilymph, membrane division.

Inner Ear (cont’d)

Three main areas of the inner ear include:CochleaVestibuleSemicircular canal

Conditions Affecting the Ear Various conditions affect quality of hearing:

infections, ear wax accumulation, damage to eardrum, genetic defects.

Most infections are viral but may lead to bacterial infection as well.

Deafness Causes include: aging, heredity, infections,

loud noises, medications, trauma. Loud noises break hair-like structures in

middle ear; do not regenerate No medication available—hearing aids,

implants.

Otitis Media Otitis media is infection of the middle ear

associated with inflammation of eustachian tube.

Sore throat—can lead to middle ear infection—often seen in children.

For reoccurring infections, insertion of small tubes by physicians to drain middle ear.

Drug Treatment for Otitis Media Antiinfectives: treat infection

Antibiotics if infection is severe: amoxicillin or sulfamethoxazole/trimethoprim

Antihistamines, decongestants, and analgesics: treat symptoms

Cerumen Buildup Excessive wax builds up or dries—impedes

hearing quality. Doctor removes wax buildup. Irrigation kit includes saline solution and ear

syringe. Other treatments include: mineral oil,

glycerin, or hydrogen peroxide in the ear to soften the wax.

Ototoxicity Ototoxicity caused by some drugs. Tinnitus—buzzing or ringing in ears—if

untreated leads to permanent ear damage. Balance may also be affected. Prognosis: some cases reverse themselves;

others cause permanent hearing loss.

Miscellaneous Otic Preparations

Bacterial infections treated with bactericidal or bacteriostatic preparations.

All ear agents—combinations—antibiotics, steroids, ear wax removers.