Sensory Disorders



Sensory Disorders





CATARACT

Acataract is a gradually developing opacity of the lens or lens capsule. Light shining through the cornea is blocked by this opacity, and a blurred image is cast onto the retina. As a result, the brain interprets a hazy image. Cataracts commonly occur bilaterally, and each progresses independently. Exceptions are traumatic cataracts, which are usually unilateral, and congenital cataracts, which may remain stationary.



Causes



  • Aging


  • Trauma, foreign body injury


  • Exposure to ionizing radiation or infrared rays


  • Exposure to ultraviolet radiation


  • Drugs that are toxic to the lens, such as prednisone, ergot alkaloids, dinitrophenol, naphthalene, phenothiazines, or pilocarpine


  • Genetic abnormalities


  • Infection such as maternal rubella during the first trimester of pregnancy


  • Maternal malnutrition


  • Metabolic disease, such as diabetes mellitus or hypothyroidism


  • Myotonic dystrophy


  • Uveitis, glaucoma, retinitis pigmentosa, or retinal detachment


  • Atopic dermatitis







CLEFT LIP AND CLEFT PALATE

Cleft lip and cleft palate — an opening in the lip or palate — may occur separately or in combination. Cleft lip and cleft palate are twice as common in males as in females; isolated cleft palate is more common in females.


Causes



  • Isolated birth defect: normal development of orofacial structures disrupted by a combination of genetic and environmental factors


  • Part of a chromosomal or Mendelian syndrome (cleft defects are associated with over 300 syndromes)


  • Exposures to specific teratogens during fetal development








CONJUNCTIVITIS

Conjunctivitis (also known as pinkeye) is characterized by hyperemia of the conjunctiva. The three main types of conjunctivitis are infectious, allergic, and chemical. This disorder usually occurs as a benign, self-limiting condition; it may also be chronic, possibly indicating degenerative changes or damage from repeated acute attacks. Epidemic keratoconjunctivitis is an acute, highly contagious viral conjunctivitis. Careful handwashing is essential to prevent the spread of conjunctivitis.


Causes


Infectious Conjunctivitis

Most commonly by:



  • bacterial — Staphylococcus aureus, Streptococcus pneumoniae, Neisseria gonorrhoeae, Neisseria meningitidis


  • chlamydial — Chlamydia trachomatis (inclusion conjunctivitis)


  • viral — adenovirus types 3, 7, and 8; herpes simplex 1; coxsackie; varicella zoster.


Allergic Conjunctivitis

Hypersensitivity to:



  • pollen, grass, unknown seasonal allergens (vernal conjunctivitis), or animals


  • topical medications, cosmetics, or fabrics


  • air pollutants or smoke


  • contact lenses or solutions


Chemical Conjunctivitis

Chemical reaction to:



  • environmental irritants (wind, dust, smoke, swimming pool chlorine)


  • occupational irritants (acids, alkalies)







CORNEAL ULCER

Corneal ulcers produce corneal scarring or perforation and are a major cause of blindness worldwide. They occur in the central or marginal areas of the cornea, vary in shape and size, and may be singular or multiple. Marginal ulcers are the most common form. Prompt treatment (within hours of onset) and referral to an ophthalmologist are imperative to prevent visual impairment.


Causes


Protozoan Infection



  • Acanthamoeba


Bacterial Infections



  • Staphylococcus aureus


  • Pseudomonas aeruginosa


  • Streptococcus viridans


  • Streptococcus (Diplococcus) pneumoniae


  • Moraxella liquefaciens


Viral Infections



  • Herpes simplex 1


  • Variola


  • Vaccinia


  • Varicella zoster


Fungal Infections



  • Candida


  • Fusarium


  • Acremonium


Other



  • Trauma


  • Exposure reactions to bacterial infections, toxins, trichiasis, entropion, allergens, or contact lenses


  • Vitamin A deficiency (xerophthalmia)


  • Fifth cranial nerve lesions (neurotropic ulcers)







ECTROPION AND ENTROPION

Ectropion, the outward turning or eversion of the eyelid, may be congenital or acquired. Acquired ectropion may be involutional, paralytic, cicatricial, or mechanical. Involutional ectropion is the most common form and usually stems from age-related weakness in the lid. Paralytic ectropion may occur with seventh cranial nerve palsy from diverse causes, such as Bell’s palsy, tumors, herpes zoster oticus, and infiltrations or tumors of the parotid gland. Cicatricial ectropion results from scarring of the anterior lamella from facial burns, trauma, chronic dermatitis, or excessive skin excision with blepharoplasty. Mechanical ectropion can occur with lid tumors that cause the lower eyelid to evert.

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Sep 22, 2018 | Posted by in ANATOMY | Comments Off on Sensory Disorders
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