Essential of Human Diseases & Conditions-Chapter 5

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Vision requires:

light stimulus
relay of light/image to the retina
stimulation of rods and cones in the retina
nerve impulses conducted to brain

Signs and symptoms that need medical attention:

visual disturbances
unequal pupils or sudden loss of vision
persistent pain
itching or burning in or around the eyes
swollen, red eyelids
redness of the eyes
drainage or exudate
involuntary eye movements

Hyperopia (Farsightedness)

light focused behind the retina, which impairs near vision

Myopia (Nearsightedness)

light focused in front of the retina, which impairs far vision


light focused unevenly onto the retina, which causes blurred areas


eye cannot focus quickly to accommodate changes in distance


involuntary, repetitive, rhythmic movements of one or both eyes

Eye lid disorders caused by inflammation, infection, or other condition include:

Hordeolum (stye)
Chalazion (stye)


inflammation of the conjunctiva in one or both eyes
Mucous discharge from the eye
can be caused by viral or bacterial infection
highly contagious
commonly called "pink eye"


cloudy area in the lens
opacity blocks light from reaching retina
usually develop slowly
gradual reduction of vision


damage to the optic nerve caused by elevated intraocular pressure
open-angle vs. closed-angle
One of the major cause of blindness
more common after age 60, but can occur at any age
more common with nearsightedness

Macular Degeneration

progressive deterioration in retina
may start with mild distortion of central vision and progress to complete loss
usually both eyes are affected
leads to central vision blindness

Diabetic Retinopathy

caused by small hemorrhages and newly formed vessels in the retina
decreased visual clarity
usually both eyes are affected
major cause of blindness

Retinal Detachment

separation of the retina from the choroid
usually sudden and painless
early symptoms are seeing light flashes and floaters
more common with nearsightedness
results in blindness if untreated

Other common conditions that can affect the eye include:

corneal abrasion or ulcer

Cancer of the Eye

benign or malignant neoplasms
usually metastases from other primary cancer
retinoblastoma is most common primary malignancy of the eye in children
Ocular melanoma is the most common ocular tumor in adults

Hearing requires:

vibratory or sound stimulus
relay of sound/vibration to inner ear
stimulation of tiny hairs in cochlea
nerve impulses conducted to brain

Signs and symptoms that need medical attention:

hearing loss
ear pain or pressure
ringing or buzzing noise (tinnitus)
vertigo or dizziness
nausea and vomiting

Disorders of Conduction

impacted cerumen
infective otitis externa
swimmer's ear
otitis media

Infective Otitis Externa

Inflammation of external ear canal with signs and symptoms of:
pain, often severe
red, swollen canal
drainage, watery or purulent
hearing loss

Otitis Media

Inflammation of the middle ear with signs and symptoms of:
feeling of fullness or pressure
impaired hearing
pain, often severe
drainage, watery or purulent
nausea and vomiting

Ménière Disease

chronic disease of the inner ear
syndrome includes: vertigo, tinnitus, progressive hearing loss and sensation of pressure
sudden onset of episodes (vertigo, tinnitus, etc.)
duration of hours to days
treatment is symptomatic relief, not curative


inflammation of labyrinth usually from viral or bacterial infection; can result from meningitis
ruptured tympanic membrane
tear or injury resulting from pressure, untreated middle ear infection, force or trauma


cyst of infected skin cells within middle ear that erodes the cavity and ossicles


inflammation of the mastoid bone from untreated acute otitis media or associated with cholesteatoma

Sensorineural Hearing Loss

nerve impulses not transmitted to the brain due to damage to the cochlea or auditory nerve
hearing loss can result from loud music, industrial noise, nearby explosion, medications, the aging process, and certain other causes
irreversible, so prevention is essential

Benign Paroxysmal Positional Vertigo (BPPV)

A disorder of the vestibular system
Symptoms include a spinning sensation, nausea, vomiting, involuntary eye movements, and unsteady gait
Medications and positional head exercises may help reduce symptoms

Cancer of the Ear

benign or malignant tumors
may originate from any part of the ear
metastases from other primary cancer
acoustic neuroma: a common tumor that surrounds eighth cranial nerve; usually benign, but may be recurrent

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