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Aniridia is a rare congenital condition characterized by the underdevelopment in the iris of the eye.
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How many people have aniridia?
Aniridia is a rare genetic disorder estimated to affect about 1 in 50,000 to 100,000 people worldwide. The exact number of individuals with aniridia can vary due to underdiagnosis and regional differences in healthcare access.
Can a person have a black iris?
Yes, even though having black irises is extremely rare. Some people mistake very dark brown eyes for being black eyes (irises). This dark brown color comes from a condition called aniridia, where the color of the iris is very close to the color of the pupil.
What is the main function of the pupil of the eye?
The pupil serves two important functions - to control the illumination in the eye, and to improve the optical quality of the image on the retina. The first function is obvious - the smaller the hole, the less light gets in. It therefore serves to regulate the light level within the retina. The second function is very important because as the pupil gets larger, more aberrations are created and the image on the retina gets "messier". People with no iris (aniridia) have very poor visual acuity because the eye can't get a sharp image, both because there is to much light (over-saturation) and because there are lots of optical aberrations present. One final function of the pupil is to increase depth of focus, similar to an aperture stop on a camera. This basically increases the range (distance) over which things appear sharp.
Wilms tumor?
DefinitionWilms tumor is a type of kidney cancer that occurs in children.Alternative NamesNephroblastoma; Kidney tumorCauses, incidence, and risk factorsWilms tumor is the most common form of childhood kidney cancer. The exact cause of this tumor in most children is unknown.A missing iris of the eye (aniridia) is a birth defect that is sometimes associated with Wilms tumor. Other birth defects linked to this type of kidney cancer include certain urinary tract problems and enlargement of one side of the body, a condition called hemihypertrophy.It is more common among some siblings and twins, which suggests a possible genetic cause.The disease occurs in about 1 out of 200,000 to 250,000 children. It usually strikes when a child is about 3 years old. It rarely develops after age 8.SymptomsAbdominal painConstipationFeverGeneral discomfort or uneasiness (malaise)High blood pressureIncreased growth on only one side of the bodyLoss of appetiteNauseaSwelling in the abdomen (abdominal hernia or mass)VomitingNote: Abnormal urine color may also be associated with this disease.Signs and testsSpecial emphasis is placed on the history and physical exam. The doctor may ask if you have a family history of cancer and look for associated birth defects in the child.A physical examination reveals an abdominal mass. High blood pressure may also be present.Blood in the urine occurs in less than 25% of children.Tests include:Abdominal ultrasoundAbdominal x-rayBUNChest x-rayComplete blood count (may show anemia)CreatinineCreatinine clearanceCT scan of the abdomenIntravenous pyelogramUrinalysisOther tests may be required to determine if the tumor has spread.TreatmentIf your child is diagnosed with this condition, avoid prodding or pushing on the child's belly area, and use care during bathing and handling to avoid injury to the tumor site.The first step in treatment is to stage the tumor. Staging helps doctors determine how far the cancer has spread and to plan for the best treatment. Surgery to remove the tumor is scheduled as soon as possible. Surrounding tissues and organs may also need to be removed if the tumor has spread.Radiation therapy and chemotherapy will often be started after surgery, depending on the stage of the tumor.Expectations (prognosis)Children whose tumor has not spread have a 90% cure rate with appropriate treatment.ComplicationsThe tumor may become quite large, but usually remains self-enclosed. Spread of the tumor to the lungs, liver, bone, or brain is the most worrisome complication.High blood pressure and kidney damage may occur as the result of the tumor or its treatment.Removal of Wilms tumor from both kidneys may affect kidney function.Calling your health care providerCall your health care provider if you discover a lump in your child's abdomen, blood in the urine, or other symptoms of Wilms tumor.Call your health care provider if your child is being treated for this condition and symptoms get worse or new symptoms develop, particularly cough, chest pain, weight loss, or persistent fevers.PreventionFor children with a known high risk of Wilms tumor, screening with ultrasound of the kidneys may be recommended.ReferencesKim S, Chung DH. Pediatric solid malignancies: neuroblastoma and Wilms' tumor. Surg Clin North Am. 2006;86(2):469-487.Jaffe N, Huff V. Neoplasms of the kidney. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 499.
