Causes of Cornea disorders
Cornea disorders Causes: Book Excerpts
Related information on causes of Cornea disorders:
As with all medical conditions,
there may be many causal factors.
Further relevant information on causes of Cornea disorders may be found in:
Causes of Cornea disorders: Online Medical Books
16 MEDICAL BOOKS ONLINE!
Review excerpts from medical books online, free, without registration,
for more information about the causes of Cornea disorders.
Corneal reflex, absent:
Medical causes
(Handbook of Signs & Symptoms (Third Edition))
Acoustic neuroma.
Acoustic neuroma affects the trigeminal nerve, causing a diminished or absent corneal reflex, tinnitus, and unilateral hearing impairment. Facial palsy and anesthesia, palate weakness, and signs of cerebellar dysfunction (ataxia, nystagmus) may result if the tumor impinges on the adjacent cranial nerves, brain stem, and cerebellum.
Bell's palsy.
A common cause of diminished or absent corneal reflex, Bell's palsy causes paralysis of CN VII. It can also produce complete hemifacial weakness or paralysis and drooling on the affected side, which also sags and appears masklike. The eye on this side can't be shut and tears constantly.
Brain stem infarction or injury.
An absent corneal reflex can occur on the side opposite the lesion when infarction or injury affects CN V or VII or their connection in the central trigeminal tract. Associated findings include a decreased level of consciousness, dysphagia, dysarthria, contralateral limb weakness, and early signs and symptoms of increased intracranial pressure, such as a headache and vomiting.
With massive brain stem infarction or injury, the patient also displays respiratory changes, such as apneustic breathing or periods of apnea; bilateral pupillary dilation or constriction with decreased responsiveness to light; rising systolic blood pressure; a widening pulse pressure; bradycardia; and coma.
Guillain-Barré syndrome.
With this polyneuropathic disorder, a diminished or absent corneal reflex accompanies ipsilateral loss of facial muscle control. Muscle weakness, the dominant neurologic sign of this disorder, typically starts in the legs, and then extends to the arms and facial nerves within 72 hours. Other findings include dysarthria, dysphagia, paresthesia, respiratory muscle paralysis, respiratory insufficiency, orthostatic hypotension, incontinence, diaphoresis, and tachycardia.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Signs & Symptoms (Third Edition), 2006
Corneal abrasion:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
A corneal abrasion usually results from a foreign body, such as a cinder or a piece of dust, dirt, or grit that becomes embedded under the eyelid. Even if the foreign body is washed out by tears, it may still injure the cornea. Small pieces of metal that get in the eyes of workers who don’t wear protective glasses quickly form a rust ring on the cornea and cause corneal abrasion. Such abrasions also commonly occur in the eyes of people who fall asleep wearing hard contact lenses or whose lenses aren’t fitted properly.
A corneal scratch produced by a fingernail, a piece of paper, or other organic substance may cause a persistent lesion. The epithelium doesn’t always heal properly, and a recurrent corneal erosion may develop, with delayed effects more severe than the original injury.
In the United States, corneal abrasions are a common ophthalmologic cause of emergency department visits. Incidence is highest among younger, physically active individuals; corneal abrasions are rare in elderly people.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Corneal ulcers:
Causes
(Professional Guide to Diseases (Eighth Edition))
Corneal ulcers generally result from protozoan, bacterial, viral, or fungal infections. Common bacterial sources include Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus viridans, Streptococcus (Diplococcus) pneumoniae, and Moraxella liquefaciens; viral sources comprise herpes simplex type 1, variola, vaccinia, and varicella-zoster viruses; and common fungal sources are Candida, Fusarium, and Cephalosporium.
Other causes include trauma, exposure, reactions to bacterial infections, toxins, trichiasis, entropion, allergens, and wearing of contact lenses. (See What happens in corneal ulceration.) Tuberculoprotein causes a classic phlyctenular keratoconjunctivitis, vitamin A deficiency results in xerophthalmia, and fifth cranial nerve lesions lead to neurotropic ulcers.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Corneal reflex, absent:
Medical causes
(Professional Guide to Signs & Symptoms (Fifth Edition))
Acoustic neuroma
This tumor affects the trigeminal nerve, causing a diminished or absent corneal reflex, tinnitus, and unilateral hearing impairment. Facial palsy and anesthesia, palate weakness, and signs of cerebellar dysfunction (ataxia, nystagmus) may result if the tumor impinges on the adjacent cranial nerves, brain stem, and cerebellum.
Bell’s palsy
A common cause of diminished or absent corneal reflex, Bell’s palsy causes paralysis of cranial nerve VII. It can also produce complete hemifacial weakness or paralysis and drooling on the affected side. The affected side also sags and appears masklike. The eye on this side can’t be shut and tears constantly.
Brain stem infarction or injury
An absent corneal reflex can occur on the side opposite the lesion when a brain stem infarction or injury affects cranial nerve V or VII or their connection in the central trigeminal tract. Associated findings include decreased level of consciousness, dysphagia, dysarthria, contralateral limb weakness, and early signs and symptoms of increased intracranial pressure, such as headache and vomiting.
In a massive brain stem infarction or injury, the patient also displays respiratory changes, such as apneustic breathing or periods of apnea; bilateral pupillary dilation or constriction with decreased responsiveness to light; rising systolic blood pressure; widening pulse pressure; bradycardia; and coma.
Guillain-Barré syndrome
In this polyneuropathic disorder, a diminished or absent corneal reflex accompanies ipsilateral loss of facial muscle control. Muscle weakness, the primary neurologic sign of this disorder, typically starts in the legs, then extends to the arms and facial nerves within 72 hours. Other findings include dysarthria, dysphagia, paresthesia, respiratory muscle paralysis, respiratory insufficiency, orthostatic hypotension, incontinence, diaphoresis, and tachycardia.
Herpetic keratoconjunctivitis
This disorder may cause corneal anesthesia, usually unilaterally. Other findings include regional adenopathy, blepharitis, and vesicles on the eyelid.
Trigeminal neuralgia (tic douloureux)
A diminished or absent corneal reflex may stem from a superior maxillary lesion that affects the ophthalmic branch. The patient with trigeminal neuralgia characteristically experiences sudden bursts of intense pain or shooting sensations, lasting from 1 to 15 minutes, in one of the divisions of the trigeminal nerve, primarily the superior mandibular or maxillary division. An attack may be triggered by local stimulation, such as a light touch to the cheeks, exposure to hot or cold temperatures, or eating or drinking hot or cold food or beverages. Areas around the patient’s nose and mouth may be hypersensitive.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Signs & Symptoms (Fifth Edition), 2006
Corneal abrasion:
Causes
(Handbook of Diseases)
A corneal abrasion usually results from a foreign body, such as a cinder or a piece of dust, dirt, or grit, which becomes embedded under the eyelid. Even if the foreign body is washed out by tears, it may still injure the cornea.
A small piece of metal that gets in the eyes of workers who don’t wear protective glasses quickly forms an abrasion and then forms a rust ring on the cornea. Abrasions also commonly occur in the eyes of people who fall asleep wearing hard contact lenses. A corneal scratch produced by a fingernail, a piece of paper, or another organic substance may cause a persistent lesion. The epithelium doesn’t always heal properly, and a recurrent corneal erosion may develop, with delayed effects more severe than those of the original injury.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Diseases, 2003
Corneal ulcers:
Causes
(Handbook of Diseases)
Corneal ulcers generally result from bacterial, protozoan, viral, or fungal infections. Common bacterial sources include Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus viridans, Streptococcus (Diplococcus) pneumoniae, and Moraxella liquefaciens; viral sources, herpes simplex type 1, and varicella-zoster viruses; and common fungi, such as Candida, Fusarium, and Cephalosporium.
Other causes include trauma, exposure, reactions to bacterial infections, toxins, and allergens. Tuberculoprotein causes a classic phlyctenular keratoconjunctivitis; vitamin A deficiency results in xerophthalmia; and fifth cranial nerve lesions result in neurotropic ulcers.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Diseases, 2003
Corneal reflex, absent:
Medical causes
(Nursing: Interpreting Signs and Symptoms)
Acoustic neuroma.Acoustic neuroma affects the trigeminal nerve, causing a diminished or absent corneal reflex, tinnitus, and unilateral hearing impairment. Facial palsy and anesthesia, palate weakness, and signs of cerebellar dysfunction (for example, ataxia or nystagmus) may result if the tumor impinges on the adjacent cranial nerves, brain stem, and cerebellum.
Bell's palsy.A common cause of diminished or absent corneal reflex, Bell's palsy causes paralysis of CN VII. It can also produce complete hemifacial weakness or paralysis and drooling on the affected side, which also sags and appears masklike. The eye on this side can't be shut and tears constantly.
Brain stem infarction or injury.An absent corneal reflex can occur on the side opposite the lesion when infarction or injury affects CN V or VII or their connection in the central trigeminal tract. Associated findings include a decreased level of consciousness, dysphagia, dysarthria, contralateral limb weakness, and early signs and symptoms of increased intracranial pressure, such as a headache and vomiting.
With massive brain stem infarction or injury, the patient also displays respiratory changes, such as apneustic breathing or periods of apnea; bilateral pupillary dilation or constriction with decreased responsiveness to light; rising systolic blood pressure; a widening pulse pressure; bradycardia; and coma.
Guillain-Barré syndrome.With this polyneuropathic disorder, a diminished or absent corneal reflex accompanies ipsilateral loss of facial muscle control. Muscle weakness, the dominant neurologic sign of this disorder, typically starts in the legs, and then extends to the arms and facial nerves within 72 hours. Other findings include dysarthria, dysphagia, paresthesia, respiratory muscle paralysis, respiratory insufficiency, orthostatic hypotension, incontinence, diaphoresis, and tachycardia.
» READ BOOK EXCERPT ONLINE »
Source: Nursing: Interpreting Signs and Symptoms, 2007
When you reach a certain age, it's usually clear that your vision isn't as sharp as it used to be. Learn how surgery for the cloudy lens of a...
Aging can often mean losing the ability to read up close. But does that mean a life of looking for lost glasses? Learn what other options are...
Sexual contact can sometimes result in problems. An unwanted pregnancy or sexually transmitted diseases may be some of those consequences. But by...
Health insurance is important to everyone, especially people with chronic conditions like Crohn's disease and ulcerative colitis. Tune in to...
See full list of 4 related videos
» Next page: Symptoms of Cornea disorders
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
