Rare Pulmonology News

Disease Profile

Keratoconus

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

Unknown

Age of onset

#N/A

ICD-10

#N/A

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

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Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

Noninflammatory corneal thining; KC

Categories

Eye diseases

Summary

Keratoconus is the degeneration of the structure of the cornea, which is the clear tissue covering the front of the eye. In this condition, the shape of the cornea slowly changes from the normal round shape to a cone shape. Most people who develop keratoconus start out nearsighted, which tends to become worse over time. The earliest symptom is a slight blurring of vision that cannot be corrected with glasses. Over time, there may be eye halos, glare, or other night vision problems.The cause is unknown, but the tendency to develop keratoconus is probably present from birth. Keratoconus is thought to involve a defect in collagen, the tissue that makes up most of the cornea. Some researchers believe that allergy and eye rubbing may play a role.[1] Treatment for keratoconus depends on the severity of your condition and how quickly the condition is progressing. Mild to moderate keratoconus can be treated with eyeglasses or contact lenses. In some people the cornea becomes scarred or wearing contact lenses becomes difficult. In these cases, surgery might be necessary.[2]

Symptoms

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
Percent of people who have these symptoms is not available through HPO
Astigmatism
Abnormal curving of the cornea or lens of the eye
0000483
Autosomal dominant inheritance
0000006
Keratoconus
Bulging cornea
0000563
Young adult onset
0011462

Cause

The exact cause of keratoconus is unknown. Both genetic and environmental factors may play a role in the development of keratoconus.

The genetic factors involve abnormalities in the structure of collagen, which result in a weak and flexible cornea. Keratoconus is more common in people with Down syndrome, Marfan syndrome, and Leber congenital amaurosis, and certain genetic conditions. In these cases, the cause depends on the specific condition.[3] 

Environmental factors may include living in sunny, hot areas of the world, while eye-rubbing is a major behavioral factor in the disease. Malfunctioning enzymes that normally help maintain the health of the cornea may play a role. All of these factors contribute to the main problem in keratoconus, which is the defective collagen structure that results in thinning and irregularity of the cornea. Keratoconus occurs more frequently in patients with atopy (asthma and eczema) or severe ocular allergies. It may also be linked to hormonal factors because it is more frequent during puberty and also may progress during pregnancy.[3]

Treatment

Treatment depends on the severity of the keratoconus symptoms and may include: :[4][5]

  • Eyeglasses and contact lens: During early stages, vision can be corrected with eyeglasses. As the condition progresses, rigid contacts may need to be worn so that light entering the eye is refracted evenly and vision is not distorted. You should also refrain from rubbing your eyes, as this can aggravate the thin corneal tissue and make symptoms worse. 
  • Laser: Laser can improve corneal abrasions and contact lens tolerance.
  • Implants: Keratoconus can also be treated with Intacs, which are small curved implantable corneal devices that can reshape the cornea. Intacs are FDA approved and can help flatten the steep cornea found in keratoconus. 
  • Collagen: Collagen cross-linking is a new treatment that uses a special laser and eyedrops to promote “cross-linking” or strengthening of the collagen fibers that make up the cornea. This treatment may flatten or stiffen the cornea, preventing further protrusion. 
  • Corneal transplant: When good vision is no longer possible with other treatments, a corneal transplant may be recommended. This surgery is only necessary in about 10 percent to 20 percent of patients with keratoconus. In a corneal transplant, the diseased cornea is removed and replaced with a healthy donor cornea. A transplanted cornea heals slowly. It can take up to a year or more to recover good vision after corneal transplantation. Usually contact lenses are needed afterwards. 
  • Deep Anterior Lamellar Keratoplasty: With this procedure, only the front and middle layers of the cornea are transplanted. The benefits of this transplant over the “full” cornea transplant is a much faster healing period and less risk of rejection.

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

Organizations

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
  • The Merck Manuals Online Medical Library provides information on this condition for patients and caregivers.
  • The National Eye Institute (NEI) was established by Congress in 1968 to protect and prolong the vision of the American people. Click on the link to view information on this topic.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

    In-Depth Information

    • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
    • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
    • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
    • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
    • PubMed is a searchable database of medical literature and lists journal articles that discuss Keratoconus. Click on the link to view a sample search on this topic.

      References

      1. Vorvick LJ & Lusby FW. Keratoconus. MedlinePlus. 2014; https://www.nlm.nih.gov/medlineplus/ency/article/001013.htm.
      2. Keratoconus Treatment. Mayo Clinic. January 30, 2016; https://www.mayoclinic.org/diseases-conditions/keratoconus/diagnosis-treatment/treatment/txc-20180387.
      3. Keratoconus treatment. American Academy of Ophthalmology. March, 2015; https://www.aao.org/eye-health/diseases/keratoconus-treatment.
      4. How is keratoconus treated?. WebMD. 2015; https://www.webmd.com/eye-health/eye-health-keratoconus?page=2#3.
      5. Keratoconus treatment. American Academy of Ophthalmology. 2015; https://www.aao.org/eye-health/diseases/keratoconus-treatment.

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