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Keratoconus

Disease Details

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Description: Keratoconus is a progressive eye disease where the cornea thins and bulges into a cone-like shape, causing distorted vision.
Type: Keratoconus is a degenerative eye disease affecting the cornea. Its genetic transmission is typically considered complex and multifactorial, involving various genetic and environmental factors. While the exact pattern is not fully understood, there is evidence suggesting autosomal dominant inheritance with variable expressivity in some cases.
Signs And Symptoms: People with early keratoconus often notice a minor blurring or distortion of their vision, as well as an increased sensitivity to light, and visit their clinician seeking corrective lenses for reading or driving. At early stages, the symptoms of keratoconus may be no different from those of any other refractive defect of the eye. As the disease progresses, vision deteriorates, sometimes rapidly due to irregular astigmatism. Visual acuity becomes impaired at all distances, and night vision is often poor. Some individuals have vision in one eye that is markedly worse than the other eye. The disease is often bilateral, though asymmetrical. Some develop photophobia (sensitivity to bright light), eye strain from squinting in order to read, or itching in the eye, but there is normally little or no sensation of pain. It may cause luminous objects to appear as cylindrical pipes with the same intensity at all points.

The classic symptom of keratoconus is the perception of multiple "ghost" images, known as monocular polyopia. This effect is most clearly seen with a high contrast field, such as a point of light on a dark background. Instead of seeing just one point, a person with keratoconus sees many images of the point, spread out in a chaotic pattern. This pattern does not typically change from day to day, but over time, it often takes on new forms. People also commonly notice streaking and flaring distortion around light sources. Some even notice the images moving relative to one another in time with their heartbeat.
The predominant optical aberration of the eye in keratoconus is coma. The visual distortion experienced by the person comes from two sources, one being the irregular deformation of the surface of the cornea, and the other being scarring that occurs on its exposed highpoints. These factors act to form regions on the cornea that map an image to different locations on the retina. The effect can worsen in low light conditions, as the dark-adapted pupil dilates to expose more of the irregular surface of the cornea.
Prognosis: Patients with keratoconus typically present initially with mild astigmatism and myopia, commonly at the onset of puberty, and are diagnosed by the late teenage years or early 20s. The disease can, however, present or progress at any age; in rare cases, keratoconus can present in children or not until later adulthood. A diagnosis of the disease at an early age may indicate a greater risk of severity in later life. Patients' vision will seem to fluctuate over a period of months, driving them to change lens prescriptions frequently, but as the condition worsens, contact lenses are required in the majority of cases. The course of the disorder can be quite variable, with some patients remaining stable for years or indefinitely, while others progress rapidly or experience occasional exacerbations over a long and otherwise steady course. Most commonly, keratoconus progresses for a period of 10 to 20 years before the course of the disease generally ceases in the third and fourth decades of life.
Onset: The onset of keratoconus typically occurs during adolescence or early adulthood, usually between the ages of 10 and 25. However, it can sometimes start at a younger or older age. The condition tends to progress over a period of 10 to 20 years before stabilizing. The exact cause of keratoconus is not well understood, but it is believed to result from a combination of genetic, environmental, and cellular factors.
Prevalence: Keratoconus is a progressive eye disease where the cornea thins and begins to bulge into a cone-like shape. The prevalence of keratoconus is estimated to be approximately 1 in 2,000 individuals, although more recent studies suggest it could be as high as 1 in 375 in certain populations due to improved diagnostic techniques.
Epidemiology: The National Eye Institute reports keratoconus is the most common corneal dystrophy in the United States, affecting about one in 2,000 Americans, but some reports place the figure as high as one in 500. In the pediatric populations, ages three to 18, the prevalence of keratoconus was found to be as high as one in 334 children. The inconsistency may be due to variations in diagnostic criteria, with some cases of severe astigmatism interpreted as those of keratoconus, and vice versa. A long-term study found a mean incidence rate of 2.0 new cases per 100,000 population per year. Some studies have suggested a higher prevalence amongst females, or that people of South Asian ethnicity are 4.4 times as likely to develop keratoconus as Caucasians, and are also more likely to be affected with the condition earlier.Keratoconus is normally bilateral (affecting both eyes) although the distortion is usually asymmetric and is rarely completely identical in both corneas. Unilateral cases tend to be uncommon, and may in fact be very rare if a very mild condition in the better eye is simply below the limit of clinical detection. It is common for keratoconus to be diagnosed first in one eye and not until later in the other. As the condition then progresses in both eyes, the vision in the earlier-diagnosed eye will often remain poorer than that in its fellow.
Intractability: Keratoconus is generally considered a progressive and chronic eye condition that can be challenging to manage and treat, but it is not necessarily intractable. Early and moderate stages of keratoconus can be managed with corrective lenses such as glasses or specially designed contact lenses. Advanced cases may require surgical interventions, such as corneal cross-linking to halt progression, or corneal transplants to restore vision. While the condition can be difficult to control, especially in advanced stages, treatment options are available to manage and improve patient outcomes.
Disease Severity: Disease severity in keratoconus can be categorized as mild, moderate, or severe. This classification is based on the degree of corneal thinning and steepening, distortion, visual acuity, and other diagnostic measures such as corneal topography and pachymetry. Early detection and management are crucial to slow progression and optimize visual outcomes.
Healthcare Professionals: Disease Ontology ID - DOID:10126
Pathophysiology: Despite considerable research, the cause of keratoconus remains unclear. Several sources suggest that keratoconus likely arises from a number of different factors: genetic, environmental or cellular, any of which may form the trigger for the onset of the disease. Once initiated, the disease normally develops by progressive dissolution of Bowman's layer, which lies between the corneal epithelium and stroma. As the two come into contact, cellular and structural changes in the cornea adversely affect its integrity and lead to the bulging and scarring characteristic of the disorder. Within any individual keratoconic cornea, regions of degenerative thinning coexisting with regions undergoing wound healing may be found. Scarring appears to be an aspect of the corneal degradation; however, a recent, large, multicenter study suggests abrasion by contact lenses may increase the likelihood of this finding by a factor over two.A number of studies have indicated keratoconic corneas show signs of increased activity by proteases, a class of enzymes that break some of the collagen cross-linkages in the stroma, with a simultaneous reduced expression of protease inhibitors. Other studies have suggested that reduced activity by the enzyme aldehyde dehydrogenase may be responsible for a build-up of free radicals and oxidising species in the cornea. Whatever the pathogenetical process, the damage caused by activity within the cornea likely results in a reduction in its thickness and biomechanical strength. At an ultrastructural level the weakening of the corneal tissue is associated with a disruption of the regular arrangement of the collagen layers and collagen fibril orientation. While keratoconus is considered a noninflammatory disorder, one study shows wearing rigid contact lenses by people leads to overexpression of proinflammatory cytokines, such as IL-6, TNF-alpha, ICAM-1, and VCAM-1 in the tear fluid.A genetic predisposition to keratoconus has been observed, with the disease running in certain families, and incidences reported of concordance in identical twins. The frequency of occurrence in close family members is not clearly defined, though it is known to be considerably higher than that in the general population, and studies have obtained estimates ranging between 6% and 19%. Two studies involving isolated, largely homogenetic communities have contrarily mapped putative gene locations to chromosomes 16q and 20q. Most genetic studies agree on an autosomal dominant model of inheritance. A rare, autosomal dominant form of severe keratoconus with anterior polar cataract is caused by a mutation in the seed region of mir-184, a microRNA that is highly expressed in the cornea and anterior lens. Keratoconus is diagnosed more often in people with Down's syndrome, though the reasons for this link have not yet been determined.Researches also have shed light on the role of hormones in the pathophysiology of keratoconus. Hormones such as androgen, prolactin, estrogen and progesterone have been shown to influence corneal biomechanics and tissue remodeling, potentially affecting the integrity of the cornea in individuals predisposed to keratoconus. Moreover, fluctuations in hormonal levels during puberty and pregnancy have been associated with the onset or exacerbation of keratoconus in some cases.
Keratoconus has been associated with atopic diseases, which include asthma, allergies, and eczema, and it is not uncommon for several or all of these diseases to affect one person. Keratoconus is also associated with Alport syndrome, Down syndrome and Marfan syndrome. A number of studies suggest vigorous eye rubbing contributes to the progression of keratoconus, and people should be discouraged from the practice. Keratoconus differs from ectasia, which is caused by LASIK eye surgery. Post-LASIK Ectasia has been associated with the excessive removal of the eye's stromal bed tissue during surgery.
Carrier Status: Keratoconus is not typically described in terms of carrier status because it is not a simple Mendelian genetic condition. It involves multifactorial inheritance with environmental and genetic factors contributing to its development. There is no "carrier" state like there is for recessive genetic disorders. Instead, those with a family history of keratoconus may have an increased risk of developing the condition.

Nan: Unspecified or irrelevant. If "nan" refers to information not available, it is likely meant to not apply in this context.
Mechanism: Keratoconus is a progressive eye disease where the cornea thins and bulges into a cone-like shape, causing visual distortion.

**Mechanism:**
- Structural weakening of the corneal tissue leads to its thinning and protrusion.
- This deformation causes irregular astigmatism and myopia, resulting in blurred and distorted vision.
- The exact cause is not fully understood, but it is believed to involve both genetic and environmental factors.

**Molecular Mechanisms:**
- Abnormal collagen cross-linking in the corneal stroma reduces the mechanical strength of the cornea.
- Increased activity of proteolytic enzymes like matrix metalloproteinases (MMPs) leads to degradation of the extracellular matrix.
- Oxidative stress results in damage to corneal cells and tissues.
- Changes in the expression of specific genes involved in collagen synthesis and repair processes are observed, indicating genetic predispositions.
- Dysfunction in the balance of molecules that regulate apoptosis (cell death) and wound healing contributes to the disease progression.
Treatment: Keratoconus is a progressive eye disease where the cornea thins and begins to bulge into a cone-like shape, distorting vision. Treatments for keratoconus include:

1. **Eyeglasses or Soft Contact Lenses:** Used in mild cases to correct vision.
2. **Rigid Gas Permeable (RGP) Contact Lenses:** Provide a more stable and uniform refractive surface.
3. **Scleral and Semi-Scleral Lenses:** Larger lenses that vault over the cornea to improve vision and comfort.
4. **Corneal Cross-Linking:** A procedure that strengthens corneal tissue to halt progression. It involves applying riboflavin (vitamin B2) drops to the cornea, followed by exposure to ultraviolet (UV) light.
5. **Intacs:** Small, crescent-shaped plastic inserts placed in the cornea to flatten its shape and improve vision.
6. **Topography-Guided Custom Ablation:** A laser procedure that reshapes the cornea to restore a more regular surface.
7. **Corneal Transplant:** In severe cases, partial or full-thickness corneal transplant may be needed.

It's important for individuals with keratoconus to be regularly monitored by an eye care professional to manage and adjust treatment as the disease progresses.
Compassionate Use Treatment: For keratoconus, compassionate use or experimental treatments include:

1. **Corneal Cross-Linking (CXL)**: While it's an approved treatment in many regions, its use was initially experimental. It involves applying riboflavin (vitamin B2) drops to the eye and then activating them with ultraviolet (UV) light to strengthen corneal tissue.

2. **Topography-Guided Photorefractive Keratectomy (TG-PRK)**: This procedure aims to reshape the cornea and improve its symmetry, often used in conjunction with CXL to optimize results.

3. **Intracorneal Ring Segments (ICRS)**: These small, crescent-shaped implants are inserted into the cornea to flatten its shape and improve vision. Their use can be considered off-label or experimental, depending on the specific type and region.

4. **Customized Contact Lenses**: While not a surgical treatment, the development of advanced scleral lenses and other customized contacts often falls under experimental efforts to manage keratoconus more effectively.

5. **Gene Therapy and Stem Cell Therapy**: These are still in early experimental stages and aim to address the underlying causes of keratoconus at the cellular level.

These treatments are typically considered for patients who do not respond well to conventional therapies and require careful evaluation by a medical professional.
Lifestyle Recommendations: For keratoconus, consider these lifestyle recommendations:

1. **Eye Protection**: Avoid rubbing your eyes, as it can worsen the condition.
2. **Visual Aids**: Use prescribed contact lenses or glasses. Rigid gas-permeable (RGP) lenses can be particularly helpful.
3. **UV Protection**: Wear sunglasses to protect your eyes from harmful UV rays.
4. **Healthy Diet**: Maintain a balanced diet rich in vitamins and antioxidants beneficial for eye health, such as Vitamins A, C, E, and zinc.
5. **Regular Check-ups**: Schedule consistent visits to your eye specialist to monitor the progression and adjust treatment as needed.
6. **Avoid Smoking**: Smoking can contribute to eye problems; quitting can help preserve your vision.
7. **Manage Allergies**: If you have allergies, manage them properly to prevent eye irritation and rubbing.

Contact your healthcare provider for specific recommendations tailored to your condition.
Medication: Keratoconus does not have a specific medication to stop or reverse the condition. However, management strategies include:

1. **Corneal Collagen Cross-Linking (CXL)**: This procedure strengthens the cornea by using ultraviolet (UV) light and riboflavin (vitamin B2) to increase the cross-links between collagen fibers.

2. **Eyeglasses or Contact Lenses**: In the early stages, vision can be corrected with glasses or soft contact lenses. As the condition progresses, specialized hard contact lenses, such as rigid gas permeable (RGP) lenses, may be required.

3. **Intacs**: These are corneal implants that can help to flatten the curvature of the cornea, improving vision and possibly delaying the need for a corneal transplant.

4. **Corneal Transplant**: In advanced cases, a corneal transplant may be necessary if other treatments are ineffective.

Patients with keratoconus should have regular follow-ups with their eye specialist to monitor the progression and adjust treatment as necessary.
Repurposable Drugs: For keratoconus, there are no widely recognized repurposable drugs currently approved for reversing or significantly slowing the progression of the condition. Management primarily involves the use of specialty contact lenses and surgical interventions such as corneal cross-linking, which strengthens the cornea.

If you're looking at experimental treatments or less common drugs currently being studied, some have looked into the potential of medications like doxycycline (for its anti-collagenase activity), but these are not standard treatments.

Always consult a healthcare provider for the most current and personalized medical advice.
Metabolites: Keratoconus is a progressive eye disorder that affects the cornea. Metabolomic studies have identified various metabolites that could be associated with the condition, such as abnormal levels of oxidative stress markers, altered amino acid profiles, and changes in lipid metabolites. These aberrations suggest disturbances in metabolic pathways, highlighting the significance of oxidative damage and inflammatory processes in the pathophysiology of keratoconus.
Nutraceuticals: Nutraceuticals are food-derived products that offer health benefits and potentially provide a therapeutic effect. For keratoconus, some studies suggest that certain nutrients could support corneal health:

1. **Antioxidants**: They're believed to protect corneal cells from oxidative stress. Vitamin C, vitamin E, and beta-carotene are common antioxidants.
2. **Omega-3 Fatty Acids**: Found in fish oil, they have anti-inflammatory properties that may benefit ocular health.
3. **Lutein and Zeaxanthin**: Carotenoids found in green leafy vegetables and other foods, they might help protect the eyes from damage caused by light exposure.

While evidence on the effectiveness of these nutraceuticals in directly treating keratoconus is still limited, they are generally considered supportive for overall eye health. Always consult with a healthcare provider before starting any new supplement regimen.
Peptides: Keratoconus is a progressive eye condition in which the cornea thins and bulges outward into a cone-like shape, causing visual distortion. Regarding peptides and nanotechnology, research is ongoing to explore their potential therapeutic roles. Peptides might be studied for their ability to strengthen corneal tissue or reduce oxidative stress. Nanotechnology approaches are being investigated for targeted drug delivery systems to improve treatment efficacy and minimize side effects. These areas of research aim to develop advanced treatments for managing or potentially halting the progression of keratoconus.