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Achromatopsia

Disease Details

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Description: Achromatopsia is a congenital or acquired condition characterized by a total absence of color vision, causing individuals to see only in shades of gray.
Type: Achromatopsia is typically transmitted in an autosomal recessive manner.
Signs And Symptoms: The five symptoms associated with achromatopsia are:
Color blindness – usually monochromacy
Reduced visual acuity – uncorrectable with lenses
Hemeralopia – with the subject exhibiting photophobia
Nystagmus
Iris operating abnormalitiesThe syndrome is typically first noticed in children around six months of age due to their photophobia or their nystagmus. The nystagmus becomes less noticeable with age but the other symptoms of the syndrome become more relevant as school age approaches. Visual acuity and stability of the eye motions generally improve during the first six to seven years of life – but remain near 20/200. Otherwise the syndrome is considered stationary and does not worsen with age.If the light level during testing is optimized, achromats may achieve corrected visual acuity of 20/100 to 20/150 at lower light levels, regardless of the absence of color. The fundus of the eye appears completely normal.Achromatopsia can be classified as complete or incomplete. In general, symptoms of incomplete achromatopsia are attenuated versions of those of complete achromatopsia. Individuals with incomplete achromatopsia have reduced visual acuity with or without nystagmus or photophobia. Incomplete achromats show only partial impairment of cone cell function.
Prognosis: Achromatopsia is a rare, hereditary vision disorder characterized by the complete absence of color vision, along with other visual impairments such as light sensitivity (photophobia), reduced visual acuity, and nystagmus (involuntary eye movements). The prognosis for individuals with achromatopsia involves lifelong challenges related to these visual limitations. While the condition remains stable and generally does not worsen over time, there is currently no cure. Management typically focuses on coping strategies and visual aids to improve quality of life. Research, including gene therapy, is ongoing to explore potential treatments.
Onset: Achromatopsia typically has an onset at birth or early infancy. It is a congenital condition that affects the cone cells in the retina, leading to color blindness, reduced visual acuity, and sensitivity to light. Symptoms are usually noticeable in infants and will persist throughout life.
Prevalence: Achromatopsia is a rare genetic vision disorder. The prevalence is estimated to be approximately 1 in 30,000 to 50,000 individuals worldwide.
Epidemiology: Achromatopsia is a relatively uncommon disorder, with a prevalence of 1 in 30,000 people.However, on the small Micronesian atoll of Pingelap, approximately five percent of the atoll's 3,000 inhabitants are affected. This is the result of a population bottleneck caused by a typhoon and ensuing famine in the 1770s, which killed all but about twenty islanders, including one who was heterozygous for achromatopsia.The people of this region have termed achromatopsia "maskun", which literally means "not see" in Pingelapese. This unusual population drew neurologist Oliver Sacks to the island for which he wrote his 1997 book, The Island of the Colorblind.
Intractability: Achromatopsia is currently considered an intractable disease. It is a rare, hereditary vision disorder characterized by a complete absence of color vision, light sensitivity, and reduced visual acuity. As of now, there is no cure or fully effective treatment for achromatopsia, although research and experimental therapies, including gene therapy, are being explored.
Disease Severity: Achromatopsia is a non-progressive congenital disorder typically categorized as severe. It results in a complete absence of color vision, accompanied by other visual impairments such as light sensitivity (photophobia), nystagmus (involuntary eye movement), and reduced visual acuity. The condition significantly impacts daily life due to the inability to perceive colors and the associated visual difficulties.
Healthcare Professionals: Disease Ontology ID - DOID:13911
Pathophysiology: The hemeralopic aspect of achromatopsia can be diagnosed non-invasively using electroretinography. The response at low (scotopic) and median (mesopic) light levels will be normal but the response under high light level (photopic) conditions will be absent. The mesopic level is approximately a hundred times lower than the clinical level used for the typical high level electroretinogram. When as described; the condition is due to a saturation in the neural portion of the retina and not due to the absence of the photoreceptors per se.In general, the molecular pathomechanism of achromatopsia is either the inability to properly control or respond to altered levels of cGMP; particularly important in visual perception as its level controls the opening of cyclic nucleotide-gated ion channels (CNGs). Decreasing the concentration of cGMP results in closure of CNGs and resulting hyperpolarization and cessation of glutamate release. Native retinal CNGs are composed of 2 α- and 2 β-subunits, which are CNGA3 and CNGB3, respectively, in cone cells. When expressed alone, CNGB3 cannot produce functional channels, whereas this is not the case for CNGA3. Coassembly of CNGA3 and CNGB3 produces channels with altered membrane expression, ion permeability (Na+ vs. K+ and Ca2+), relative efficacy of cAMP/cGMP activation, decreased outward rectification, current flickering, and sensitivity to block by L-cis-diltiazem.Mutations tend to result in the loss of CNGB3 function or gain of function—often increased affinity for cGMP—of CNGA3. cGMP levels are controlled by the activity of the cone cell transducin, GNAT2. Mutations in GNAT2 tend to result in a truncated and, presumably, non-functional protein, thereby preventing alteration of cGMP levels by photons. There is a positive correlation between the severity of mutations in these proteins and the completeness of the achromatopsia phenotype.Molecular diagnosis can be established by identification of biallelic variants in the causative genes. Molecular genetic testing approaches used in achromatopsia can include targeted analysis for the common CNGB3 variant c.1148delC (p.Thr383IlefsTer13), use of a multigenerational panel, or comprehensive genomic testing.
Carrier Status: Achromatopsia is an inherited condition characterized by a lack of color vision, among other vision problems. The condition is typically inherited in an autosomal recessive manner. This means that a person must inherit two copies of the mutated gene, one from each parent, to be affected by the condition. A carrier, who has only one copy of the mutated gene, usually does not exhibit symptoms of achromatopsia but can pass the gene to their offspring.
Mechanism: Achromatopsia is a congenital condition characterized by complete color blindness, alongside other visual impairments such as light sensitivity and reduced sharpness of vision. The condition primarily involves dysfunctions in the cone cells of the retina, which are responsible for color vision.

**Molecular Mechanisms:**
Achromatopsia is typically caused by mutations in one of several genes that play crucial roles in the functionality of cone cells. The most commonly affected genes include CNGA3, CNGB3, GNAT2, PDE6C, and PDE6H:

1. **CNGA3 and CNGB3**: These genes encode subunits of the cone photoreceptor cyclic nucleotide-gated (CNG) channels. Mutations in these genes impair the normal functioning of the CNG channels, which are essential for the phototransduction cascade—the process by which light is converted into electrical signals in the retina.

2. **GNAT2**: This gene encodes the alpha subunit of cone transducin, a protein involved in the phototransduction pathway. Mutations in GNAT2 disrupt the normal signaling process within cone cells.

3. **PDE6C and PDE6H**: These genes encode subunits of cone phosphodiesterase (PDE), an enzyme crucial for the degradation of cyclic GMP, a secondary messenger in the phototransduction pathway. Mutations in these genes lead to a failure in regulating cyclic GMP levels, resulting in impaired cone cell function.

The malfunctioning of any of these components impairs the cones' ability to process light, leading to the symptoms observed in achromatopsia.
Treatment: Achromatopsia currently has no cure. However, treatments focus on managing symptoms. These can include:

1. **Tinted Lenses or Glasses:** To reduce light sensitivity and improve contrast.
2. **Adaptive Devices:** Such as magnifiers and text-to-speech software.
3. **Gene Therapy:** Experimental treatments are being researched to address genetic causes.

Regular consultation with an ophthalmologist specialized in low vision is recommended to tailor these treatments to individual needs.
Compassionate Use Treatment: Achromatopsia is a rare, inherited vision disorder characterized by the absence or malfunctioning of cone cells in the retina, leading to complete color blindness, reduced visual acuity, and light sensitivity. As of now, there is no FDA-approved treatment for achromatopsia, but several experimental and compassionate-use treatments are being investigated:

1. **Gene Therapy**: This approach aims to correct the genetic defects causing achromatopsia. Experimental gene therapies, such as AGTC's and MeiraGTx's clinical trials involving AAV vectors to deliver functional copies of mutated genes like CNGA3 or CNGB3, are underway.

2. **Retinal Implants**: Some experimental treatments involve retinal implants that can potentially restore some vision functions by bypassing damaged photoreceptors.

3. **Pharmacological Agents**: Research is ongoing into drugs that might partially compensate for the defective cones or enhance the function of the remaining rods and cones.

4. **Vision Aids**: Although not a cure, certain visual aids like tinted glasses or contact lenses can help reduce light sensitivity and improve visual comfort.

These treatments are still in the clinical trial phase or under compassionate use protocols and are not widely available. Patients interested in these options should consult with their healthcare provider to explore participation in clinical trials or access to experimental treatments.
Lifestyle Recommendations: Achromatopsia is a non-progressive and hereditary visual disorder that affects the perception of color, often accompanied by other symptoms such as light sensitivity (photophobia) and reduced visual acuity. Here are some lifestyle recommendations for individuals with achromatopsia:

1. **Sun Protection**: Wear wide-brimmed hats and high-quality sunglasses with UV protection to manage light sensitivity and reduce glare.

2. **Adaptive Devices**: Use specialized optical devices such as tinted contact lenses or red-tinted glasses to enhance visual comfort and contrast.

3. **Low Vision Aids**: Utilize magnifying devices, large-print reading materials, and electronic visual aids to assist with reading and other close-up tasks.

4. **Lighting Adjustments**: Optimize indoor lighting by using adjustable lamps and avoiding direct sunlight. Task lighting can help reduce eye strain.

5. **Technology**: Employ screen readers, text-to-speech software, and high-contrast settings on digital devices to facilitate daily tasks such as reading and navigating.

6. **Education and Support**: Seek out support from visual impairment organizations and communities, and consider joining support groups to share experiences and coping strategies.

7. **Routine Eye Care**: Maintain regular check-ups with an ophthalmologist or optometrist to monitor eye health and adapt strategies as needed.

8. **Safe Mobility**: Ensure a safe environment by removing hazards and using clear, high-contrast markings on stairs, doorways, and other critical areas.

9. **Adaptive Education Techniques**: Work with educators to implement learning strategies and tools that accommodate visual limitations, ensuring access to resources and materials.

By integrating these recommendations, individuals with achromatopsia can improve their quality of life and manage their symptoms more effectively.
Medication: Achromatopsia is a rare, inherited vision disorder characterized by the inability to perceive colors. There is currently no cure or specific medication approved to treat achromatopsia. Management typically focuses on supportive measures such as using tinted glasses or contact lenses to reduce light sensitivity and enhance visual comfort. Low-vision aids and adaptive devices may also be beneficial. Genetic research and clinical trials are ongoing to explore potential future treatments.
Repurposable Drugs: Achromatopsia is a rare, inherited vision disorder characterized by the partial or total absence of color vision. Currently, there are no widely accepted repurposable drugs for treating achromatopsia. Research is ongoing to develop effective treatments, including gene therapy approaches. Management typically focuses on symptomatic relief, such as the use of tinted lenses to reduce light sensitivity.
Metabolites: Achromatopsia is a rare, non-progressive visual disorder characterized by partial or complete absence of color vision, sensitivity to light (photophobia), and nystagmus. There are no specific metabolites associated with achromatopsia itself, as it is primarily a genetic condition caused by mutations in specific genes such as CNGA3, CNGB3, GNAT2, PDE6C, and PDE6H that affect the function of cone cells in the retina. "Nan" does not appear to be relevant to achromatopsia in this context. If it refers to a specific concept or term, please provide additional details.
Nutraceuticals: There is currently insufficient evidence to support the efficacy of nutraceuticals in the treatment of achromatopsia. This condition is primarily a genetic disorder affecting cone cells in the retina, leading to color blindness, light sensitivity, and poor visual acuity. Nutraceuticals, including vitamins, minerals, and other dietary supplements, have not been proven to restore normal cone function or correct the underlying genetic defects associated with achromatopsia.
Peptides: Achromatopsia is a medical condition characterized by the inability to perceive colors, leading to complete color blindness. It is a hereditary condition related to mutations in specific genes affecting the cone cells in the retina.

Peptides: Research in achromatopsia has not prominently focused on peptides as a therapeutic approach. Most current treatments and research are directed toward gene therapy, vision aids, and adaptive strategies to manage the condition.

Nan: The term "nan" is unclear in this context. If "nan" refers to nanotechnology, researchers are exploring its potential applications in ophthalmology, such as targeted drug delivery and advanced imaging techniques. However, specific therapies using nanotechnology for achromatopsia are still in experimental stages.