What is Aniridia?
Aniridia is an eye condition named after its most obvious symptom. Aniridia literally means "without irises" (the colored part of the eye) People with Aniridia have an enlarged pupil, so their eyes appear black. Aniridia is a developmental disorder; the eye stops growing properly early in pregnancy, which can cause problems in the eye later in life. The following conditions may be present at birth, or may develop later in life:
Glaucoma (increased pressure within the eye). People with Aniridia have a particularly high risk of developing glaucoma, and it may be very difficult to treat. Regular testing should begin at birth.
Cataracts (areas of clouding in the lens of the eye) Often present at birth. If cataracts interfere with vision, they may require surgical removal.
Macular or Foveal Hypoplasia (underdevelopment of the fovea or macular region of the retina) Macular hypoplasia is a frequent cause of poor vision.
Aniridic keratopathy (also called "corneal pannus," it is a clouding of the cornea of the eye caused by an overgrowth of blood vessels). Keratopathy may be noted in childhood or adolescence, but typically progresses between the ages of 20 and 40. The risk of developing this problem is increased by eye surgery.
Nystagmus is an involuntary eye movement. It is extremely common in people with aniridia. The degree and direction of eye movement can vary greatly from person to person.
Ptosis is an abnormally low position (drooping) of the upper eyelid. Ptosis occurs when the muscle that usually raises the eyelid is not strong enough to do so. Ptosis is sometimes associated with aniridia. It may be present at birth, or noted within the first few months of life. Ptosis may also occur as a side effect of Vincristine, a drug commonly used to treat Wilms tumor. If necessary, ptosis can be treated with surgery.
Can My Baby See?
Lack of an iris alone does not cause blindness. Functional vision in an individual will depend on the type and degree of other conditions, such as the development of the macula, the presence of cataracts, or the degree of glaucoma. The amount of functional vision can vary dramatically between individuals, but most people with Aniridia have visual acuities in the 20/80 to 20/200 range. Visual Acuity, (the ability to see) is measured in the following way:
20/20 = what the average person can see at 20 feet, the individual being tested sees at 20 feet. 20/80 = what the average person can see at 80 feet, the individual being tested can only see at 20 feet. 20/200 = what the average person can see at 200 feet the individual being tested can only see at 20 feet. Whether a baby can see can usually be determined fairly early in life by their interest in lights, objects, and faces, and their willingness to follow these objects of interest from side to side. Facial expression also suggests active vision.
But while parents of typically-sighted children usually note these early signs of vision in infants 2 weeks to 3 months of age, it is not unusual for babies with aniridia to begin to display them at a much later age. Parents of children with aniridia often say that their child seemed to "wake up" visually as late as 6 to 9 months of age.
Because it is likely that your child will have some vision, it's important to provide many opportunities for them to use the vision they have. There are many books and resources to assist parents with activities which will encourage their child with low vision to develop to their full potential.
What is Photophobia? How Can I Help My Child With This Problem?
Photophobia is common in people with aniridia. Photophobia literally means "fear of light." It is not a true phobia, but a medical condition in which a person feels discomfort or pain in the eye when bright light is present. People with aniridia may experience this discomfort in sunlight or indoors. In the normal eye, the irises provide protection against the sun. Since studies have shown that too much sunlight on the retina may increase the risk for cataracts in all humans, people with aniridia must be particularly careful to protect their eyes when outside.
Small children with aniridia seem to have an especially difficult problem with sensitivity to light. This difficulty seems to lessen as they grow older, perhaps because they learn other ways to control the amount of light that enters the eye by squinting. Artificial (indoor) light is not harmful to people with aniridia, and is usually not bright enough to be uncomfortable, so it is not necessary to darken indoor lights for a child with aniridia. When out of doors - even on cloudy days - dark sunglasses and a hat are important for both protection from ultraviolet rays and for comfort and safety.
What about Glasses?
One of the first questions families ask about their child with aniridia is whether prescription glasses would be helpful for them. To answer this question, it is important to understand how prescription lenses work. Glasses correct vision when the eye is "near-sighted" or "farsighted" (or a combination of these). These problems are the result of the front of the eye being slightly shorter, longer, or more irregularly shaped than is normal. This irregular shape distorts light as it comes into the eye, and causes blurred vision. Placing a lens in front of the eye corrects the distortion, and allows vision to be clear.
Some people with aniridia are near-sighted or far-sighted, and glasses can improve that aspect of their vision. However, most people with aniridia have decreased vision as a result of abnormalities at the back of the eye, in the fovea or macula. These abnormalities cannot be corrected with glasses.
Contact Lenses
In years past, special contact lenses were often prescribed for people with aniridia. These contact lenses had an artificial iris painted on them, and were thought to help decrease glare. In more recent times, dark tinted contact lenses have been used for the same reason. New research on aniridia shows that the aniridic cornea lacks certain important cells, called "limbal cells," which allow normal regeneration and repair. Without these cells, the aniridic cornea does not heal well after surgery, and can become scarred and opaque even when no surgery has been done. This scarring is called "aniridic keratopathy," or sometimes, "corneal pannus." Because of this poor healing ability of the cornea, the use of contact lenses of any kind is now discouraged except in certain cases.
What is the difference between an Optometrist and an Ophthalmologist?
An optometrist is not a medical doctor, but is a doctor of optometry (O.D.). Optometrists diagnose vision problems and eye disease, prescribe eyeglasses and contact lenses, and prescribe drugs to treat eye disorders. They cannot perform surgery, but they often provide patients with pre- and post surgical care. Sometimes ophthalmologists and optometrists work in the same practice and co-manage patients.
An ophthalmologist is a physician who specializes in the medical and surgical care of the eyes and visual system and in the prevention of eye disease and injury. They provide a full spectrum of care including routine eye exams, diagnosis and medical treatment of eye disorders and diseases, prescriptions for eyeglasses, surgery, and management of eye problems that are caused by systemic illnesses.
Eye Care Basics
Infants with aniridia should be referred for care by an ophthalmologist as soon as possible after diagnosis.
Eye Care for the infant or child with aniridia should include:
1.) Examinations approximately every 3 to 6 months --more often if complications such as glaucoma are identified.
2.) Thorough examination of all the structures of the eye. This examination may require EUA (Exam Under Anesthesia) during infancy and at periodic intervals throughout early childhood.
3.) Ocular photographs at the initial visit or EUA, if possible, and repeated if and when ocular changes occur.
4.) Tests for refraction (near or farsightedness) intraocular pressures, eye alignment, muscle strength, and other tests as necessary.
Your child’s ophthalmologist should also discuss with you: the importance of protecting your child’s eyes from sunlight, signs and symptoms of infection, glaucoma, and whom to call if you have questions or suspect a problem.
Eye drops
Sometimes infants and children with aniridia require eye drops for infections or glaucoma. Because of the sensitivity and decreased healing ability of the aniridic cornea, you may want to remind your eye doctor that all eye drops should be preservative-free whenever possible.
There are several ways to instill eye drops with a minimum of fuss. Here are some suggestions from other parents:
1) Infants – wrap in a towel or blanket (to keep arms/hands down) Place child on his back on the floor, facing away from you, with his head between your knees. This will allow you to keep him from turning his head, while still having both hands free.
2) Place a drop in the corner of (closed) eye. Wait…when child opens the eye, the drop will go in.
3) Another method: instead of trying to push the eyelid up, try pulling the lower eyelid down. Place the drop inside the "pouch" created in the lowered lid, and release.
Frequently Asked Questions
Peter Netland, MD, PhD University of Tennessee Medical Group, Inc.
How often should an ophthalmologist examine a child with aniridia?
In a child with aniridia without glaucoma, follow-up approximately once to twice a year would be ideal. In a child with aniridia and glaucoma, the frequency of visits would be increased to approximately two to three times a year. If there are problems controlling the glaucoma, the follow-up visits would be more frequent, with the exact frequency depending on the severity of the clinical situation.
What tests is the ophthalmologist likely to perform?
The most likely tests are measurement of the intraocular pressure and an examination of the front of the eye. When possible, the vision would also be measured on a routine basis. On occasion, the retina and the optic nerve will be examined. Genetic testing and other laboratory testing may be obtained in conjunction with the pediatrician.
What is an EUA and why is it necessary? How frequently should it be performed?
An EUA is an "examination under anesthesia." In many instances, the child can be examined in the office, without anesthesia. Sometimes, sedation with chloral hydrate can be performed in an examination room in the office or close to the office. Chloral hydrate is a short-acting medication that allows a short period of sedation. Occasionally, both an office examination or one utilizing chloral hydrate is insufficient, and it may be necessary to perform an examination under anesthesia. In this situation, general anesthesia is administered and the child needs to be monitored for breathing. This can oftentimes be performed with a mask, but sometimes an endotracheal tube is used. Examination under anesthesia almost always allows a more thorough examination. The intraocular pressure and anterior part of the eye can be examined very thoroughly, including gonioscopy. In gonioscopy, the anterior chamber angle where the fluid exits inside the eye can be examined. The lens can be examined, as well as the fundus (retina). As part of the fundus examination, a thorough examination of the optic nerve can be performed. It is also possible to obtain a refraction with retinoscopy, or perform B-scan ultrasonography, photography or other diagnostic tests. This can allow a very thorough assessment of any problems with the eye.
What kinds of complications are most likely associated with infants and aniridia?
Decreased vision may occur from different causes. Sometimes, the retina is not well developed, and this can lead to reduced vision and nystagmus. Sometimes, glaucoma can occur and this can cause problems with the vision. Also, corneal problems can occur that can affect the vision.
How important is the physician’s previous experience with aniridia? When is it necessary to see a specialist?
Prior experience with aniridia patients is always useful to a physician when treating new patients with aniridia. However, in straightforward patients, a conscientious ophthalmologist can monitor a patient with aniridia well, even if they have had only limited experience with this disease. As the problems become more complicated, it is helpful to see a specialist. Oftentimes, these specialists may have seen more patients with aniridia in the past. Problems such as glaucoma or corneal problems requiring surgery often require specialist treatment. It is very helpful, to maintain the relationship with a pediatric ophthalmologist or a general ophthalmologist. In many instances, these doctors will be able to help maintain vision, monitoring for "lazy eye", change of glasses or other problems.
Some children take medications for behavioral conditions or other medical issues. Are there any medications to watch out for?
Most of the medications for behavioral problems have little or no effect on the eye. Interestingly, drugs like clonidine may actually lower the intraocular pressure. Medications with labeling indicating caution in glaucoma patients do not apply to the aniridia patients. For example, certain flu or cold medications may be labeled for caution, due to a potential problem in elderly patients predisposed to angle-closure glaucoma. Check with your physician to be sure about specific medications, but in general, most of these do not have any adverse effects.
Are there surgical procedures that can prevent glaucoma? How effective are they, and what are the risks?
Most procedures are used to treat glaucoma after it has been diagnosed. Glaucoma may occur in up to half the children with aniridia. There is a preventative surgery, pioneered by Dr. David Walton. The treatment involves the use of goniotomy, which surgically incises the drainage part of the eye and opens closed areas. This approach requires detailed examination and close monitoring, and can be helpful in avoiding glaucoma associated with aniridia.
Are there any warning signs that parents can look for to tell whether their child is developing glaucoma?
Eye discoloration can be a clue, if corneal edema causes some bluish-white discoloration of the cornea. Otherwise, it is unlikely that any color change will tip off the parent to the potential presence of a problem. Decreased vision can be another clue that may indicate the onset of glaucoma. Other classical signs of glaucoma include tearing and photophobia, but these may not be observed in the child. Most times, the problem is detected during a routine monitoring visit. However, if there is any suspicion of a problem or a persistent change, do not hesitate to contact an ophthalmologist.
How common are retinal detachments in aniridic patients?
Aniridia itself probably does not cause retinal detachments. However, aniridic patients may have risk factors for retinal detachments, including high myopia (nearsightedness). Also, a small percentage of individuals will develop this problem, whether or not they have aniridia. If there are any symptoms of retinal detachment, including flashes of light or new floaters, or areas of loss of peripheral vision, it is important to have a complete eye examination. The ophthalmologist can quickly detect whether or not there is a retinal detachment by examination in the office.
Does retinal detachment affect both eyes?
Retinal detachment is not common in either eye. When it does occur, it usually affects one eye. However, in unusual cases, both eyes can be affected.
Are there any tests that can be done to detect retinal detachment?
An office examination remains the best way to detect retinal detachment, even in the early stages. The ophthalmologist can examine the retina with special lenses and an indirect ophthalmoscope. Also, he or she may use the slit lamp examination with lenses to examine the back of the eye. This simple office examination can usually show the signs of retinal detachment. When the view of the back of the eye is not clear, it may be helpful to perform an ultrasound, to demonstrate whether or not the retina is detached.
What procedures can be done for retinal detachment, and what are the success rates of these procedures?
There are many surgical options for retinal reattachment. There are no medical treatments for this condition. The surgical choices include placing a buckle on the outside of the eye to bend the sclera, so that the retina can reattach. Other choices include filling the eye with gas or fluid to press down the retina. Often, laser or freezing treatments are used to help seal the retina down after it is reattached. The success rate is very high for reattaching the retina. Unfortunately, in some instances, the retina does not function as well. This is more common if the central part of the retina (the macula) is detached prior to the reattachment procedure. Other problems can develop post-operatively. Sometimes, there is persistent fluid, which can be further treated. Sometimes, there is scarring, which may also require further surgical treatment. Fortunately, in many instances, the vision returns close to the baseline vision. Therefore, this surgery is well worthwhile, and should be undertaken to preserve the vision if retinal detachment occurs.
How should intraocular pressure (also called IOP, a test for glaucoma) be measured in infants?
(answered by John Kim, MD, Cornea and External Disease Fellow, Cincinnati Eye Institute)
In regards to IOP measurements in infants, certainly IOP's measured on an awake, cooperative infant would be ideal, but is very difficult to obtain. It may be tried while the infant is taking a bottle or while sleeping. If the child his struggling with the exam, the IOP reading would most likely be falsely elevated. For an EUA, most general anesthetics tend to decrease IOP's except for succinylcholine and ketamine. I've enclosed information from a table for your reference:
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