Vision/Hearing Disorders

• Vision


  Occurs because light rays reflect from an object through the cornea, aqueous humors, lenses, & vitreous humors to the retina
• Retina


  • Studded with rods and cones
  • Fovea is an area of closely packed cones on the retinas where the color is best perceived
• Stereopsis


  Depth perception, or the ability to locate an object in space relative to other objects
• Stereo-fly or random dot test


  A simple test for dot perception
• Accommodation


  The adjustment the eye makes when focusing on a close image

  
• Refractive errors


  • Hyperopia (vision is blurry at a close range)
  • Myopia (the light rays focus at the point in front of the retina)

  
• Laser in Situ Keratomileusis (LASIK)


  A laser surgery for correction of refractive errors
• Astigmatism


  Congenital or acquired unevenness of the curvature of the cornea
• Nystagmus


  Rapid irregular movement, either vertically or horizontally
• Amblyopia


  Lazy eye or subnormal vision in one eye; the child may be using one eye for vision while "resting" the other eye

  
• Color vision deficit (color blindness)


  The inability to perceive color correctly due to the absence of one of the sets of cones of the retina that perceive red, green, or blue

  
• Coloboma


  Congenital incomplete closure of the facial cleft
• Hypertelorism


  A congenital condition involving abnormally wide-spaced eyes, associated with chromosomal abnormalities like Waardenburg's syndrome

  
• Hypertelorism signs


  • White forelock of hair
  • Different-colored irises
  • Eyebrows that tend to grow together in the center line
  • Can hear no sound - need close follow-up to determine whether cochlear implants or hearing aids can provide ability to hear
• Ptosis


  Inability to raise the upper eyelid normally so the eyelid always remains slightly closed

  
• Myasthenia gravis must always be ruled out as a cause of bilateral ptosis
• Strabismus


  Unequally aligned eyes (cross-eyes) caused by unbalanced muscle control

  
• Eye muscle actions and innervation


  • Superior rectus: turns eye up & medially, innervated by oculomotor (3rd CN)
  • Medial rectus: turns eye inward, innervated by oculomotor (3rd CN)
  • Inferior rectus: turns eye down & medially, innervated by oculomotor (3rd CN)
  • Lateral rectus: turns eye out, innervated by abducens (6th CN)
  • Superior oblique: turns eye down & laterally, innervated by trochlear (4th CN)
  • Inferior oblique: turns eye up & laterally, innervated by oculomotor (3rd CN)

  
• Strabismus deviations


  • Exotropia - eye turning out
  • Esotropia - eye turning in
  • Hypertropia - eye turning up

  
• Stye


  Infection of a ciliary gland (a modified sweat gland) that enters into the hair follicle at the lid margin, most commonly caused by Staphylococcus
• Chalazion


  Low-grade granulation tissue tumor of the meibomian, or tarsal, gland on the eyelid, cause unknown but may be a result of a low grade infection produced by retained secretion in the gland
• Blepharitis marginalis


  Inflammation of the eyelid margin, usually a local infection caused by staphylococcus possibly an extension of seborrheic dermatitis (cradle cap)

  
• Conjunctivitis


  Inflammation of the conjunctiva, causes are numerous, including bacteria (most serious - ophthalmia neonatorum [exposure to gonococcus bacillus])
• Inclusion blennorrhea


  Caused by Chlamydia organism, any free discharge of mucus
• Acute catarrhal conjunctivitis


  Commonly called "pinkeye", usually caused by a virus or irritation from foreign body, most frequently caused by Hemophilus influenzae, Streptococcus pneumoniae
• Herpetic conjunctivitis


  Herpes simplex viral infection (may occur along with development of facial herpes lesion)
• Allergic conjunctivitis


  Hypersensitivity to specific allergen, usually seasonal
• Differentiation of common types of conjunctivitis


  • Viral: itching minimal, hyperemia generalized, tearing profuse, exudation minimal, preauricular adenopathy common, stained scrapings show monocytes
  • Bacterial: itching minimal, hyperemia generalized, tearing moderate, exudation profuse, preauricular adenopathy uncommon, stained scrapings show bacteria, PMNs
  • Chlamydial: itching minimal, hyperemia generalized, tearing moderate, exudation profuse, preauricular adenopathy common only in inclusion conjunctivitis, stained scrapings show PMNs, plasma cells, inclusion bodies
  • Allergic: itching severe, hyperemia generalized, tearing moderate, exudation minimal, preauricular adenopathy none, stained scrapings show eosinophils
• Keratitis


  Inflammation and infection of the superficial layers of the cornea, may accompany or be a complication of conjunctivitis, may result when a foreign body strikes the cornea, with the invading organism fungal, bacterial, or viral
• Periorbital cellulitis


  Infection of subcutaneous tissue most often caused by extension of a superficial infection after an open break in the skin, such as a mosquito bite or scratch near the eye
• Dacryostenosis


  Blockage of the nasolacrimal duct, primarily in newborns because of a membrane obscuring distal end of duct or plugging by epithelial debris
• Normal tear drainage
• Types of eye infections


  • Fungal
  • Bacterial
  • Viral
• Signs and symptoms of keratitis


  • Acute pain
  • Tearing
  • Photophobia
  • Redness
• Keratitis: Treatment


  1. Referral to ophthalmologist for therapy

  2. Infection could lead to corneal scarring, resulting in vision impairment
• In keratitis, light rays are unable to enter the eye normally
• Periorbital Cellulitis: Signs and Symptoms


  • Swelling around and in the eye with possible damage to eye globe or optic nerve

  
• Periorbital Cellulitis: Treatment


  IV antibiotic therapy
• Dacryostenosis


  Blockage of the nasolacrimal duct; primarily in newborns because of a membrane obscuring distal end of duct or plugging by epithelial debris
• Dacryostenosis: Signs and Symptoms


  • Painless lump in the inner canthus
  • Tearing
  • Usually unilateral