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Ametropic Amblyopia

Disease Details

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Description: Ametropic amblyopia is a vision development disorder where one or both eyes have a significant refractive error, such as myopia, hyperopia, or astigmatism, leading to poor vision development despite corrective lenses.
Type: Ametropic amblyopia primarily results from uncorrected refractive errors and is not typically associated with a specific pattern of genetic transmission. It generally arises due to differences in visual input between the eyes during early development, which leads to reduced visual acuity in one eye. The condition itself is not inherited, although the refractive errors leading to it can have a genetic component.
Signs And Symptoms: Many people with amblyopia, especially those who only have a mild form, are not aware they have the condition until tested at older ages, since the vision in their stronger eye is normal. People with amblyopia typically have poor stereo vision, since it requires both eyes. They further may have, on the affected eye, poor pattern recognition, poor visual acuity, and low sensitivity to contrast and motion.Amblyopia is characterized by several functional abnormalities in spatial vision, including reductions in visual acuity, contrast sensitivity function, and vernier acuity, as well as spatial distortion, abnormal spatial interactions, and impaired contour detection. In addition, individuals with amblyopia have binocular abnormalities such as impaired stereoacuity (stereoscopic acuity) and abnormal binocular summation. Also, central vision in amblyopes is more crowded than central vision in normal observers.These deficits are usually specific to the amblyopic eye. Subclinical deficits of the "better" eye have also been demonstrated.People with amblyopia also have problems of binocular vision such as limited stereoscopic depth perception and usually have difficulty seeing the three-dimensional images in hidden stereoscopic displays such as autostereograms. Perception of depth, from monocular cues such as size, perspective, and motion parallax remains normal.
Prognosis: For ametropic amblyopia, the prognosis largely depends on the age at which treatment begins and the severity of the condition. Early diagnosis and appropriate intervention, typically during childhood, can significantly improve vision and may lead to near-normal vision. However, untreated or late-diagnosed cases may result in permanent visual impairment. Prompt correction of refractive errors and consistent visual therapy are crucial for a favorable outcome.
Onset: Ametropic amblyopia typically has its onset during early childhood. It occurs when there is a significant difference in the refractive errors (such as myopia, hyperopia, or astigmatism) between the two eyes, leading to poor visual development in one eye if not corrected.
Prevalence: Ametropic amblyopia is a specific type of amblyopia caused by uncorrected refractive errors in both eyes. Its prevalence varies widely depending on the population and methodologies used in studies, but it generally affects around 1-2% of children. Early detection and appropriate correction of refractive errors can help prevent this condition.
Epidemiology: Amblyopia occurs in 2–5% of the population in Western countries. In the UK, 90% of visual health appointments in the child concern amblyopia.Depending on the chosen criterion for diagnosis, 1–4% of the children have amblyopia.
Intractability: Ametropic amblyopia, also known as refractive amblyopia, is not inherently intractable. It is a treatable condition, especially when intervention occurs early. Treatment typically involves the correction of refractive errors with glasses or contact lenses, and may include patching or atropine drops to encourage use of the amblyopic eye. Early diagnosis and consistent treatment are key to improving visual outcomes.
Disease Severity: Ametropic amblyopia is a type of amblyopia (commonly known as "lazy eye") caused by significant differences in prescription (refractive errors) between the two eyes. This condition can lead to poor vision in the affected eye if not adequately corrected during childhood.

Disease Severity: The severity of ametropic amblyopia can vary depending on how early it is detected and treated. If left untreated, it can result in significant and permanent vision impairment in the affected eye. Early intervention typically includes corrective lenses and sometimes vision therapy, which can greatly improve outcomes.
Healthcare Professionals: Disease Ontology ID - DOID:10377
Pathophysiology: Amblyopia is a developmental problem in the brain, not any intrinsic, organic neurological problem in the eyeball (although organic problems can lead to amblyopia which can continue to exist after the organic problem has resolved by medical intervention).
The part of the brain receiving images from the affected eye is not stimulated properly and does not develop to its full visual potential. This has been confirmed by direct brain examination. David H. Hubel and Torsten Wiesel won the Nobel Prize in Physiology or Medicine in 1981 for their work in showing the extent of the damage to ocular dominance columns produced in kittens by sufficient visual deprivation during the so-called "critical period". The maximum "critical period" in humans is from birth to two years old.
Carrier Status: Ametropic amblyopia is not a condition that is related to carrier status, as it is not a genetic disease that follows Mendelian inheritance patterns. Rather, it results from significant refractive errors, such as myopia, hyperopia, or astigmatism, that are uneven between the two eyes or are left uncorrected during early childhood.
Mechanism: Ametropic amblyopia, also known as refractive amblyopia, occurs due to unequal refractive errors between the eyes.

**Mechanism:**
It arises when one eye has a significantly different refractive error (such as myopia, hyperopia, or astigmatism) compared to the other. This discrepancy leads to one eye providing a consistently blurred image to the brain, which then favors the clearer images from the stronger eye. Over time, the brain relies more on the stronger eye, resulting in the weaker eye not developing proper visual acuity.

**Molecular Mechanisms:**
The exact molecular mechanisms involved in ametropic amblyopia are not fully elucidated but are believed to involve neuroplastic changes in the visual cortex of the brain. Key points include:

- **Synaptic Plasticity:** Synaptic connections in the visual pathways may be altered due to the imbalance in visual input, leading to reduced synaptic efficacy in the eye with the poorer image quality.

- **Neurotransmitter Modulation:** Changes in levels and activity of neurotransmitters, such as glutamate and gamma-aminobutyric acid (GABA), could affect synaptic strength and visual signal processing.

- **Gene Expression:** Differential expression of genes regulating synaptic growth, connection strength, and neuroplasticity might contribute to the under-development of the visual cortex associated with the amblyopic eye.

Understanding these molecular pathways is crucial for developing targeted therapies and interventions to treat or mitigate the effects of amblyopia.
Treatment: Treatment of strabismic or anisometropic amblyopia consists of correcting the optical deficit (wearing the necessary spectacle prescription) and often forcing use of the amblyopic eye, by patching the good eye, or instilling topical atropine in the good eye, or both.: 130 Atropine appears to result in similar outcomes to patching. If there is overpatching or overpenalizing the good eye when treating amblyopia, "reverse amblyopia" can result. Eye patching is usually done on a part-time schedule of about 4–6 hours a day. Treatment is continued as long as vision improves. It is not worthwhile continuing to patch for more than 6 months if no improvement continues.Deprivation amblyopia is treated by removing the opacity as soon as possible followed by patching or penalizing the good eye to encourage the use of the amblyopic eye. The earlier the treatment is initiated, the easier and faster the treatment is and the less psychologically damaging. Also, the chance of achieving 20/20 vision is greater if treatment is initiated early.One of the German public health insurance providers, Barmer, has changed its policy to cover, as of 1 April 2014, the cost of software for amblyopic children whose condition did not improve through patching. The app offers dedicated eye exercises that the patient performs while wearing an eyepatch.Evidence for vision therapy is unclear as of 2011.
Compassionate Use Treatment: Ametropic amblyopia, often referred to as "lazy eye," is usually treated through conventional methods such as corrective lenses, patching, or atropine drops. In terms of compassionate use, off-label, or experimental treatments, the following approaches could be considered:

1. **Compassionate Use Treatment**:
Compassionate use generally refers to the use of new, unapproved treatments for serious diseases. For ametropic amblyopia, compassionate use might not be as common, but individualized care plans could include specialized vision therapy or customized corrective lenses.

2. **Off-label Treatments**:
- **Atropine Drops**: Although primarily used for penalization therapy in amblyopia, the dosage and frequency might be adjusted from the standard recommendations based on the patient's specific needs.
- **Bifocals or Multifocal Lenses**: These are sometimes prescribed off-label to help manage the accommodation issues in children with amblyopia.

3. **Experimental Treatments**:
- **Perceptual Learning Software**: Various computer-based programs are being explored to enhance visual processing and improve visual acuity.
- **Virtual Reality (VR) Therapy**: Emerging studies are examining the role of VR games designed to stimulate both eyes and encourage binocular vision.
- **Pharmacological Agents**: Some research is looking into medications that may help enhance neural plasticity and improve vision outcomes, although these are still in experimental stages.

Before considering any new or experimental treatment, it is essential to consult with an ophthalmologist or pediatric ophthalmologist who specializes in treating amblyopia.
Lifestyle Recommendations: Ametropic amblyopia, a form of lazy eye caused by significant refractive errors, can benefit from the following lifestyle recommendations:

1. **Eye Exercises**: Regularly perform exercises designed to improve eye coordination and strength, such as focusing on near and distant objects.

2. **Proper Eyewear**: Consistently wear prescribed glasses or contact lenses to correct refractive errors and ensure optimal vision.

3. **Regular Eye Check-ups**: Schedule frequent visits to an eye care professional to monitor vision and make necessary adjustments to prescriptions.

4. **Limit Screen Time**: Reduce the amount of time spent on screens to minimize eye strain and support overall eye health.

5. **Healthy Diet**: Maintain a balanced diet rich in vitamins A, C, and E, as well as omega-3 fatty acids, to support eye health.

6. **Adequate Lighting**: Ensure good lighting when reading or doing close-up work to reduce eye strain.

Following these recommendations can help manage ametropic amblyopia and support better visual health.
Medication: Ametropic amblyopia, often referred to as "lazy eye," is typically not treated with medication. The primary treatments involve corrective measures such as prescription glasses or contact lenses to correct the refractive error. Additionally, other interventions like patching the stronger eye, atropine drops in the stronger eye, and vision therapy exercises may be recommended to improve the visual performance of the affected eye.
Repurposable Drugs: There are no specific repurposable drugs that are currently established for the treatment of ametropic amblyopia. The primary treatments for amblyopia, including the ametropic type, typically involve optical correction (using glasses or contact lenses), occlusion therapy (patching the stronger eye), or pharmacologic penalization (using atropine drops in the stronger eye) to encourage the use of the amblyopic eye. Research continues to explore potential pharmaceutical interventions, but as of now, none are widely accepted or used in clinical practice.
Metabolites: Ametropic amblyopia does not have specific metabolites directly associated with the condition. This type of amblyopia is caused by significant refractive error differences between the eyes, leading to poor visual development in the affected eye. It is a functional visual impairment rather than a metabolic or biochemical disorder. Consequently, there are no identified metabolites directly linked to ametropic amblyopia.
Nutraceuticals: Ametropic amblyopia, often resulting from significant refractive errors, is typically managed with corrective lenses, vision therapy, or sometimes patching. Nutraceuticals (food-derived substances with health benefits) are not standard treatments for this condition.
Peptides: For ametropic amblyopia, peptides or nanotechnology-based solutions are not commonly referenced in standard treatments or research literature. Typical management involves corrective lenses, occlusion therapy (patching the stronger eye to stimulate the weaker eye), and vision therapy exercises.