955
he special senses allow us to view and hear what is
going on around us, to maintain our balance, and
to communicate effectively with others. This chapter
focuses on the eye and disorders of vision; the ear and
disorders of hearing; and the vestibular system and dis-
orders of equilibrium and balance.
The Eye and Disorders of Vision
There are 286 million people worldwide who are visu-
ally impaired—38 million are blind and 248 million have
partial vision loss that cannot be corrected.
1
Disorders
of vision can result from a number of conditions includ-
ing those that affect the lens (cataract), retina (retinopa-
thy and macular degeneration), and intraocular pressure
(glaucoma) (Fig. 38-1).
General Structure of the Eye
The optic globe, commonly called the
eyeball,
is a
remarkably mobile, nearly spherical structure contained
in a pyramid-shaped cavity of the skull called the
orbit.
The eyeball is composed of three layers: an outer layer,
which includes the white, opaque sclera and the transpar-
ent cornea; a middle vascular layer called the
uvea
, which
includes the choroid, ciliary body, and iris; and an inner
neural layer, which includes an outer pigment epithelium
and an inner neural retina (Fig. 38-2).
2
Exposed sur-
faces of the eyes are protected by the eyelids, which are
mucous membrane–lined skin flaps that provide a means
for shutting out most light. Tears bathe the anterior sur-
face of the eye, keeping the conjunctiva and corneal epi-
thelium moist and washing away foreign material.
T
Disorders of
Special Sensory
Function: Vision,
Hearing, and
Vestibular
Function
38
C h a p t e r
The Eye and Disorders of Vision
General Structure of the Eye
Disorders of the Conjunctiva and Cornea
Conjunctivitis
Corneal Trauma
Keratitis
Disorders of the Lens
Disorders of Refraction
Disorders of Accommodation
Cataracts
Disorders of the Retina
Retinal Blood Supply
Retinopathies
Retinal Detachment
Macular Degeneration
Disorders of Intraocular Pressure
Open-Angle Glaucoma
Angle-Closure Glaucoma
Congenital and Infantile Glaucoma
Disorders of Neural Pathways and Cortical Centers
Disorders of the Optic Pathways
Visual Field Defects
The Extraocular Eye Muscles and Disorders
of Eye Movement
Strabismus
Amblyopia
The Ear and Disorders of Auditory Function
Disorders of the External Ear
Impacted Cerumen
Otitis Externa
Disorders of the Middle Ear and Eustachian Tube
Eustachian Tube Disorders
Otitis Media
Otosclerosis
Disorders of Inner Ear and Central Auditory Pathways
Tinnitus
Central Auditory Pathway Disorders
Hearing Loss
Conductive Hearing Loss
Sensorineural Hearing Loss
Diagnosis and Treatment of Hearing Loss
Hearing Loss in Infants and Children
Hearing Loss in the Elderly
The Vestibular System and Disorders of Equilibrium
The Vestibular System
Nystagmus
Vertigo
Disorders of Peripheral Vestibular Function
Benign Paroxysmal Positional Vertigo
Acute Vestibular Neuronitis
Ménière Disease
Disorders of Central Vestibular Function
Tests of Vestibular Function
Treatment of Vestibular Disorders
