Ophthalmology

What is Aniridia?

What is Aniridia?

Aniridia is when the center of the eyeball appears to be missing.  This is called the iris. Although the iris is not really missing, they look like it is entirely black and appears to be a large black iris.  When in fact it is the muscles that control the iris to get big or small are missing.  There is only a dense ribbon of material around what would be the iris.

  • What causes Aniridia?
  • Diagnosis
  • Treatment of Aniridia
  • Conclusion

 

aniridia

 

Aniridia is in two forms.  One is inherited trait and the other is called sporadic.   Other names for this are Autosomal Dominant and Autosomal Recessive. Autosomal is a reference to chromosome pairs.    Aniridia can be found in either form of chromosome patterns.  This does not include the chromosomes that decide a baby’s sex.  The inherited form causes and leads to vision problems.  It usually appears as a deformity in both eyes. There are some people appear to be missing a fraction of the iris.  This is usually seen as the iris being lopsided, misshaped, or appears to look like cataracts.  The iris may also look as though it is raised away from the white of the eye. A child’s cornea is usually found to be smaller than most people who do not have the affliction.  The iris may also become almost transparent.  A person is generally diagnosed with Aniridia at birth. 

Aniridia is a very uncommon disorder.  There is only one child out of every half million that is born with this condition.   In some races it may not be diagnosed until a complete eye exam is performed in early child development or as an adult.  To a trained professional he/she will notice at least one sign of this illness being present.  The most obvious is when there appears to be no iris.  Another complaint is vision problems.  A patient with Aniridia usually has twenty fifty eye sight and may be as bad as twenty two hundred.  Perfect vision is twenty twenty.  These problems will affect child development.  Eye and hand coordination is impacted greatly.  This is because the center of the eye is what helps differentiate detail.  When the eye muscle does not work properly, then there are vision problems.   People with Aniridia are light sensitive.  This means that bright light, such as the sun, causes physical pain. When the dominant gene is present the person is not likely to develop any other physical or mental limitations.  However when the gene is recessive other medical problems will arise as the child develops.  Have you ever looked at someone in the eyes when talking to them and their eyes appear to shift quickly from side to side?  This is a sign of Aniridia.  There are other conditions that are often present in patients with Aniridia.  The conditions that are commonly found in children are retardation, learning disorders, and Gillespie Syndrome.

Video of Aniridia

 

What causes Aniridia?

Why does Aniridia develop in some unborn children and not in others?  It has been noted that inherited genes is sometimes the culprit.  This is the inherited form of Aniridia.  Unless a special genetic test is done while the mother is pregnant, the parents do not know about this disease being present until after the baby is born.  Early intervention is the best way to attempt to give the child the best advantage in life.  This intervention begins when a child is born with Aniridia.  Inherited Aniridia happens when several genes do not develop properly, deformed, or missing.  A common term in the medical community is atypical colobomata.  It is when soft tissue in a fetus does not develop or close properly.

Sporadic Aniridia is when chromosomes for whatever reason are malformed or simply missing part of their makeup.  Aniridia causes damage to the optic nerve. This is what usually causes the eyes to look like they are wobbly.  Lazy eye syndrome is also a cause of the optic nerve not developing correctly or completely.  Chromosomes and genes are what make up our DNA.   The particular chromosomes involved are chromosome 11 and the other is on part of 2p.  When it is inherited there is a possibility of half the children of the parents who have it, will actually develop Aniridia.

The lens can appear to be dislocated.  It’s a disorder known by the name Ectopia lentis. The sporadic development of Aniridia is unknown.  There has not been any significant study that will or has shown why this happens. This Sporadic Aniridia is a major sign in children who have some form of kidney cancer. This is also called renal failure.  It correspondingly affects the urinary tract and genitalia.  It has also been linked to mentally retarded children/adults.  Improper development of the optic nerve also happens in AniridiaAniridia is associated with other ophthalmic diseases.  Glaucoma is a symptom of this birth defect.  It happens when pressure in the eye gets too high. The pressure in the eye can build over time.  This pressure causes nerve damage.  Have you ever gone to an eye doctor and had air blown into your eye?  This is a pressure test to determine if the patient has glaucoma.  Cataracts, albinism (this is when the iris has absolutely no color), optic hypoplasia, and an immature optic nerve are classic signs of AniridiaAniridia can be a symptom for other conditions.  They are known as WAGR and Gillespie Syndrome.  WAGR is an abbreviation of Wilm tumour, Aniridia, Genitourinary, and Retardation.  Other conditions that are present in Aniridia are cloudy retina, small retina, immature retina, a squint, and being cross eyed.

There is no way to completely prevent Aniridia from developing.  The best parents can do is have gene testing done before deciding to have a child.  This is not a true preventative, but it will show the chances of the baby having this disorder.  The parents can then make informed decisions about having offspring.

There are have been a few small studies showing a connection between Aniridia and the following complaints of loss of smell sensation, difficulty in remembering single words but understanding their meaning, and signs of glucose intolerance.  Glucose intolerance is a sign of diabetes developing in the near future.

Diagnosis

There are several techniques that are used today to find any abnormalities in the eye.  The slit lamp exam, iris fluorescein angiography, high frequency ultrasound bio microscopy, and optical coherence tomography.  The use of the slit lamp test is to decipher whether the iris is partially missing or completely missing.  This test can find if glaucoma is present also.  The Iris test finds subtle irregularities in the iris. The high frequency ultrasound test is used to find the degree of damage that is in the cornea. Optical coherence test is useful in locating the opaqueness of the iris and determining how bad it is.  Aniridia has common signs that can be seen by the naked eye.  You cannot miss the obvious signs of lack of color in the iris or the lens being dislocated.  Aniridia can be diagnosed and treatment plans developed as early as two days after birth.  The treatment plan will continue into the child’s adult life.   An eye doctor will take special pictures of the inside of the eye to monitor any changes.  This is especially important for children with this disorder.  There is a stain test that can be performed in order to identify Aniridia.   Children that have complications related to Aniridia are at a high risk of developing kidney failure.  It has been proven in children with Aniridia, which they are at a high risk of developing WAGR.  This is highly linked to kidney failure later in life.  The earlier the disorder is found the longer the life span is possible.  The progression of the health of the eyes is not good when it entails hypoplasia.  Hypoplasia is when the eye is not developed completely.

 

Treatment of Aniridia

Unfortunately at this time there are no current treatments available that will cure Aniridia. One common treatment is cataract surgery.  This is only done when there is a significant loss of sight that is due to the clouding on the iris.  Aniridia may cause photophobia.  Photophobia is a high sensitivity to light.  Some treatments available are tinted eye glasses and tinted contact lenses.  It is very important to have regular checkups in order to monitor this condition.  Any major changes can then be dealt with before more damage is caused.  Seeking help from a specialist is the best way to get direction on how to deal with the effects of Aniridia.  The specialized doctor will be able to offer the best form of counseling.  Whether this effects one eye or both, it is very important to use eye protection.  In the case of only one eye having problems, you must wear glasses suited for your daily activities.  This includes wearing glasses as a child in order to eliminate or reduce rapid eye movement.  Prescription eye glasses are best suited to accomplish this outcome by helping the eye to not strain. However, glasses are not used when there is damage to the cornea.  Controlling the pressure inside the eye is necessary for anyone who suffers from Aniridia.  There are a few ways of accomplishing this treatment plan.  There is a procedure called corneal transplant.  But in patients who suffer from Aniridia, this transplant is most often not successful.  Beta-blockers, Miotics, and topical medicines are common treatment options. Prescription eye drops are frequently used when the pressure in the eye is high in order to facilitate lowering that pressure.

When a child is diagnosed with WAGR, it is important to have routine exams performed usually at three month intervals.  During these examinations an ultrasound should be performed.  This is in order to catch the development of tumors at the earliest stage possible.  It has not been decided at what point this test should stop being done.  A general consensus is at around of age seven it is a safe time to discontinue or reduce the amount of ultrasounds performed.  Most children will have been diagnosed with WAGR before their eighth birthday.  There is only one case where this has been diagnosed in an adult at the age of twenty five.  It appears that regular exams and ultrasounds should continue in patients that are at risk of developing Wilms Tumours disease.  It would not to be at such a frequent interval as it is for children eight and below.  Adults with Aniridia should have routine exams performed as they normally would for physicals.

Surgery is only an option in specific cases.  For instance, if cataracts are present then surgery is done to remove the cataract.  Recently there has become available the use of lasers to perform this type of surgery.  Replacing the iris with an artificial one has been done after removing the cataract.  Now there is stem cell replacement therapy that is being done with great outcomes.

 

Conclusion

As with any disorder, prevention is always the best policy.  Although it may not be completely preventable, Aniridia can be reduced.  Consistent monitoring of the presence of pressure in the eye is very helpful. Very routine eye examines are important in children who suffer from Aniridia.  This is especially important if there has been any sign of renal abnormalities.  If it is not watched closely this pressure will build on the inside of the eye and lead to severe blindness.  This could require surgery.  In another situation it may lead to the need of surgery to the cornea.  This could result in the need for a corneal graft.  For the parents of a newly diagnosed child, or an adult experiencing problems associated with Aniridia, there are a number of support groups available.  These types of groups help deal with the good and bad of caring for someone with this disorder.  For parents that were not prepared for this outcome of the pregnancy, it serves as an educational tool.  For someone who is having trouble dealing with the various social effects this has on their life, this kind of support system is very helpful.

We will be expanding on this important topic in future articles. While I recommend you to register to download an e-book: “Adult Prevention Guide” for better health, a FREE

Click here for PDF

We welcome your comments at the end of the article.
The Team Manager Web Diseases

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Glaucoma

Glaucoma is an eye disorder that is more prevalent in people older than 40 years of age. It is characterized by increased intraocular pressure and can develop into complete blindness in later stages. Glaucoma is the third most common age-related eye disease and the second leading cause of blindness in adults in the United States. There is no cure for glaucoma, but the disease can be controlled. Once glaucoma occurs, the patient will always have it and must follow a treatment regimen to maintain stable intraocular eye pressures.

  • What is glaucoma?
  • What are the causes of glaucoma?
  • What are the stages of glaucoma development?
  • What are the risk factors of glaucoma?
  • How is glaucoma diagnosed?
  • What are the signs and symptoms of glaucoma?
  • What are the types of glaucoma?
  • What are the treatment options for glaucoma?
  • What medicines are prescribed for glaucoma?
  • What are the surgical procedures for glaucoma?
  • Patient Teachings

Eye with Glaucoma

What is glaucoma?

Glaucoma refers to a group of diseases characterized by abnormal pressure within the eyeball. This pressure is called the intraocular pressure (IOP). An increase in the IOP (normal is  10-21 mm Hg) will cause damage to the cells of the optic nerve, the structure responsible for transmitting visual information from the eye to the brain. Previously, increased intraocular pressure is the main reason for the occurrence of glaucoma. Though the condition will definitely damage the optic nerve, not all cases of glaucoma are linked to increased intraocular pressure. Some of these cases are due to an abnormal or poor regulation of blood flow to the optic nerve and these patients will have a normal intraocular pressure.

What are the causes of glaucoma?

There are two accepted theories regarding how increased IOP damages the optic nerve in glaucoma.

  1. Direct mechanical theory suggests that high IOP damages the retinal layer as it passes through the optic nerve head.
  2. Indirect ischemic theory suggests that high IOP compresses the microcirculation in the optic nerve head, resulting in cell injury and death.

Some glaucomas appear as exclusively mechanical, and some are exclusively ischemic types. Typically, most cases are a combination of both. Regardless of the cause of damage, glaucomatous changes typically evolve through clearly discernible stages.

What are the stages of glaucoma development?

The following chart illustrates the different stages of glaucoma development:

 

Stages of Glaucoma

Stages of Glaucoma

 

What are the risk factors of glaucoma?

  • Family history of glaucoma
  • Thin cornea
  • African American race
  • Older age
  • Diabetes mellitus
  • Cardiovascular disease
  • Migraine syndromes
  • Nearsightedness (myopia)
  • Eye trauma
  • Prolonged use of topical or systemic corticosteroids

How is glaucoma diagnosed?

There are four ways to diagnose glaucoma and each test or procedure will help the physician arrive to a final diagnosis:

  • Tonometry to measure the IOP
    • Applanation tonometry uses a tiny instrument to apply pressure to the anesthetized cornea.
    • Noncontact tonometry is performed with a tonometer mounted on a slit-lamp microscope using a warm puff of air that flattens an anesthetized area of the cornea to obtain a pressure reading.
    • In contact tonometry, the instrument is placed directly on the anesthetized cornea to measure eye pressure.
    • Tonometry is not adequate to detect glaucoma alone
  • Ophthalmoscopy to inspect the optic nerve.
    • The optic nerve is examined with an ophthalmoscope through dilated pupils, visual field examination looks for loss of peripheral vision, and the angle where the iris meets the cornea is checked.
  • Gonioscopy to examine the filtration angle of the anterior chamber.
    • This is an examination of the front part of the eye to check the angle where the iris meets the cornea; it is used to distinguish between open-angle glaucoma and closed-angle glaucoma
  • Perimetry to assess the visual fields.
    • As the optic nerve damage increases, visual perception in the area is lost. The localized areas of visual loss (ie, scotomas) represent loss of retinal sensitivity and nerve fiber damage and are measured and mapped by perimetry.
    • The results are mapped on a graph.
    • In patients with glaucoma, the graph has a distinct pattern that is different from other ocular diseases and is useful in establishing the diagnosis.

What are the signs and symptoms of glaucoma?

Persons suffering from glaucoma may not know that they have already the condition until they have felt some changes in their vision. Some would have severe and throbbing headache, blurred vision or “halos” around lights, difficulty focusing, difficulty adjusting eyes in low lighting, loss of peripheral vision, and aching or discomfort around the eyes.

The signs and symptoms may also differ to the type of glaucoma.

What are the types of glaucoma?

Opthalmologists will classify the type of glaucoma according to types:

  1. Primary glaucoma
    • Open-angle glaucoma
    • Acute angle-closure glaucoma
  2. Secondary glaucoma may be caused by some infections, tumors, or even injuries.
  3. Congenital glaucoma is due to some developmental abnormalities.

Primary Open-Angle Glaucoma (POAG)

In PAOG, optic nerve damage is chronic and progressive. It is characterized with visual field defects, an IOP of >21 mm Hg (or may have fluctuating IOPs). At first, the person may not know that he is already developing the medical condition. There are usually no symptoms but a possible ocular pain, headache, and seeing halos are prevalent.

Angle-Closure (Pupillary Block) Glaucoma (AAOG)

As the name suggests, there is complete or partial closure of the angle at the junction where the iris meets the cornea. This closure can create an obstruction in aqueous humor outflow thus resulting to an increased IOP. This is considered a medical emergency because as sudden as it develops, it can lead to partial or total blindness if not treated.

Clinical manifestations of AAOG will include periocular pain and the conjunctiva appears inflammed (conjunctival hyperemia) or sometimes referred to as “red eye”. The pain can be associated to further symptoms of nausea and vomiting, decreased heart rate, and profuse sweating. The person will also complain of rapidly progressive visual impairment as the IOP increases. When examined, the pupil appears vertically oval and is fixed in a semi-dilated position.

What are treatment options for glaucoma?

At this time, there is no treatment for glaucoma. Treatment focuses on pharmacologic therapy, laser procedures, surgery, or a combination of these approaches, all of which have potential complications and side effects. The object is to achieve the greatest benefit at the least risk, cost, and inconvenience to the patient. Although treatment cannot reverse optic nerve damage, further damage can be controlled. The goal is to maintain an IOP within a range unlikely to cause further damage.

What medicines are prescribed for glaucoma?

Before the patient is given a drug to help in managing problems in glaucoma, the following principles need to be considered:

  • Periodic follow-up examinations are essential to monitor IOP, the appearance of the optic nerve, the visual fields, and side effects of medications.
  • Therapy takes into account the patient’s health and stage of glaucoma. Comfort, affordability, convenience, lifestyle, and personality are factors to consider in the patient’s adherence to the medical regimen.
  • The patient is usually started on the lowest dose of topical medication and then advanced to increased concentrations until the desired IOP level is reached and maintained.
  • One eye is treated first, with the other eye used as a control in determining the efficacy of the medication; once efficacy has been established, treatment of the other eye is started.
  • If the IOP is elevated in both eyes, both are treated.
  • When results are not satisfactory, a new medication is substituted.
  • The main markers of the efficacy of the medication in glaucoma control are lowering of the IOP to the target pressure, appearance of the optic nerve head, and the visual field.

Cholinergics (miotics)

  • Examples: pilocarpine, carbachol
  • Action: Increases aqueous fluid outflow by contracting the ciliary muscle and causing miosis (constriction of the pupil) and opening of trabecular meshwork
  • Side effects: Periorbital pain, blurry vision, difficulty seeing in the dark

Adrenergic agonists

  • Examples: dipivefrin, epinephrine
  • Action: Reduces production of aqueous humor and increases outflow
  • Side effects: Eye redness and burning; can have systemic effects, including palpitations, elevated blood pressure, tremor, headaches, and anxiety

Beta-blockers

  • Examples: betaxolol, timolol
  • Action: Decreases aqueous humor production
  • Side effects: Can have systemic effects, including bradycardia, exacerbation of pulmonary disease, and hypotension

Alpha-adrenergic agonists

  • Examples: apraclonidine, brimonidine
  • Action: Decreases aqueous humor production
  • Side effects: Eye redness, dry mouth and nasal passages

Carbonic anhydrase inhibitors

  • Examples: acetazolamide, methazolamide, dorzolamide
  • Action: Decreases aqueous humor production
  • Side effects: Oral medications (acetazolamide and methazolamide) associated with serious side effects, including anaphylactic reactions, electrolyte loss, depression, lethargy, gastrointestinal upset, impotence, and weight loss; side effects of topical form (dorzolamide) include topical allergy

Prostaglandin analogs

  • Examples: latanoprost, bimatoprost
  • Action: Increases uveoscleral outflow
  • Side effects: Darkening of the iris, conjunctival redness, possible rash

What are the surgical procedures for glaucoma?

Surgery is indicated if medications no longer able to control the flow of aqueous humor. Surgery focuses on creating an area for the aqueous humor to flow freely, thus preventing increased IOP.

For AACG, laser peripheral iridotomy or surgical iridectomy is performed. Laser iridotomy is a noninvasive procedure utilizing a laser to remove a portion of the iris, thus allowing aqueous fluid to flow through the area. Prophylactic iridotomy may be performed on the other eye to prevent AACG. POAG is treated with argon laser trabeculoplasty (noninvasive laser beam creates openings in trabecular meshwork), trabeculectomy (part of iris and trabecular meshwork removed), or cyclocryotherapy (cryoprobe destroys part of ciliary body)

Patient Teachings

Medications and surgical interventions do not treat glaucoma. It is important that the person will have awareness of this condition and learn how to monitor his/her IOP. The following teaching points will help in the continuing care for glaucoma:

  • Know your intraocular pressure (IOP) measurement and the desired range.
  • Be informed about the extent of your vision loss and optic nerve damage.
  • Keep a record of your eye pressure measurements and visual field test results to monitor your own progress.
  • Review all your medications (including over-the-counter and herbal medications) with your ophthalmologist, and mention any side effects each time you visit.
  • Ask about potential side effects and drug interactions of your eye medications.
  • Ask whether generic or less costly forms of your eye medications are available.
  • Review the dosing schedule with your ophthalmologist and inform him or her if you have trouble following the schedule.
  • Participate in the decision-making process. Let your doctor know what dosing schedule works for you and other preferences regarding your eye care.
  • Have the nurse observe you instilling eye medication to determine whether you are administering it properly.
  • Be aware that glaucoma medications can cause adverse effects if used inappropriately.
  • Eye drops are to be administered as prescribed, not when eyes feel irritated.
  • Ask your ophthalmologist to send a report to your doctor after each appointment.
  • Keep all follow-up appointments

References:

gonioscopy. (n.d.) WordNet 3.0, Farlex clipart collection. (2003-2008). Retrieved April 22 2013 from http://www.thefreedictionary.com/gonioscopy

We will be expanding on this important topic in future articles. While I recommend you to register to download an e-book: “Adult Prevention Guide” for better health, a FREE

Click here for PDF

We welcome your comments at the end of the article.

 

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