Night blindness, congenital stationary

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Congenital Stationary Night Blindness (CSNB)
Specialty	Ophthalmology
Symptoms	Difficulty seeing in low light or darkness, normal daytime vision
Usual onset	At birth
Duration	Lifelong
Types	Type 1 (CSNB1), Type 2 (CSNB2), and other variants
Causes	Genetic mutations
Risk factors	Family history of the condition
Diagnostic method	Electroretinogram (ERG), genetic testing
Differential diagnosis	Retinitis Pigmentosa, Vitamin A deficiency
Treatment	No cure, management focuses on coping strategies
Prognosis	Stable, does not worsen over time

Congenital Stationary Night Blindness (CSNB) is a rare, non-progressive eye disorder present from birth characterized by an inability or difficulty to see in low light or darkness, while daytime vision remains normal. CSNB is caused by genetic mutations affecting the function of the retina, the light-sensitive layer of cells at the back of the eye. This condition is classified into two main types, Type 1 (CSNB1) and Type 2 (CSNB2), based on the genetic cause and the pattern of vision impairment. Other less common variants also exist.

Symptoms and Signs

The primary symptom of CSNB is difficulty seeing in low light or darkness, whereas vision in well-lit conditions is typically unaffected. Individuals may also experience nearsightedness, misalignment of the eyes, and involuntary eye movements. The severity of symptoms can vary among affected individuals.

Causes

CSNB is caused by mutations in various genes that are important for the normal function of the retina. These mutations affect the photoreceptor cells or the signal transmission from these cells to the brain. CSNB1 is usually associated with mutations in genes responsible for the function of rod cells, which are photoreceptor cells that function in low light. CSNB2 and other variants typically involve mutations that affect the function of both rod and cone cells, the latter being responsible for color vision and detailed vision in bright light.

Diagnosis

Diagnosis of CSNB involves a thorough clinical examination, including a detailed family history and visual function tests. The most definitive test is an Electroretinogram (ERG), which measures the electrical responses of the retina to light and can distinguish between different types of night blindness. Genetic testing may also be conducted to identify specific mutations.

Treatment

There is no cure for CSNB, and treatment focuses on managing symptoms and improving quality of life. This may include the use of low-vision aids, such as specialized glasses or magnifiers, and adopting coping strategies for low-light environments. Genetic counseling may be recommended for affected individuals and their families.

Epidemiology

The prevalence of CSNB is not well-documented, but it is considered a rare condition. Both males and females can be affected, although some forms of CSNB, such as CSNB1, are more common in males due to X-linked inheritance patterns.

See Also

• Retinal diseases
• Genetic disorders
• Visual impairment

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