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Congenital Stationary Night Blindness (CSNB) Description

Congenital stationary night blindness (CSNB) is a rare, inherited eye condition that affects people's ability to see in low light conditions. It is characterized by impaired photoreceptor transmission, which leads to difficulty adapting to dimly lit environments.

Key Features:

• Non-progressive: CSNB does not worsen over time.
• Night blindness: People with CSNB have trouble seeing in low light conditions from birth.
• Reduced visual acuity: Affected individuals may experience reduced sharpness of vision, ranging from 20/30 to 20/200.
• Myopia: Many people with CSNB develop severe nearsightedness (myopia), which can range from low to high degrees.
• Nystagmus and strabismus: Some individuals may also experience involuntary eye movements (nystagmus) or crossed eyes (strabismus).
• Normal color vision: Color vision is typically unaffected in people with CSNB.

Types of CSNB:

CSNB can be classified into two types based on electroretinographic findings:

1. Riggs type: Characterized by reduced a- and b-waves in response to a scotopic bright flash.
2. Schubert–Bornschein (S–B) type: Marked by selective loss of the b-wave.

References:

• [3] Congenital stationary night blindness (CSNB) is a rare non-progressive retinal disorder. People with CSNB often have difficulty adapting to low light situations due to impaired photoreceptor transmission.
• [13] Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous group of nonprogressive retinal disorders that can be characterized by impaired night vision, decreased visual acuity, nystagmus, myopia, and strabismus.
• [15] Complete congenital stationary night blindness (cCSNB) is a clinically and genetically heterogeneous group of retinal disorders characterized by nonprogressive impairment of night vision, absence of the electroretinogram (ERG) b-wave, and variable degrees of involvement of other visual functions.

Common Signs and Symptoms of Congenital Stationary Night Blindness (CSNB)

Congenital stationary night blindness (CSNB) is a non-progressive group of retinal disorders characterized by night or dim light vision disturbance. The following are the common signs and symptoms associated with CSNB:

• Night Blindness: People with CSNB typically experience difficulty seeing in low-light conditions, which can progress to complete loss of night vision.
• Loss of Sharpness (Reduced Visual Acuity): Individuals with CSNB often have reduced visual acuity, making it difficult for them to see objects clearly, especially at a distance.
• Increased Sensitivity to Light (Photophobia): Some people with CSNB may experience increased sensitivity to light, which can be uncomfortable and even painful in severe cases.
• Severe Nearsightedness: CSNB patients often have severe nearsightedness (myopia), making it difficult for them to see objects clearly at a distance.
• Nystagmus: Some individuals with CSNB may experience nystagmus, which is an involuntary movement of the eyes.
• Fundus Abnormalities: Patients with CSNB may also have fundus abnormalities, such as changes in the retina's color or shape.

These symptoms can vary in severity and may be present from birth or develop later in life. It's essential to consult a medical professional for an accurate diagnosis and proper treatment.

References:

• [3] Congenital stationary night blindness (CSNB) refers to a non-progressive group of retinal disorders characterized by night or dim light vision disturbance.
• [4] People with this condition typically experience night blindness and other vision problems, including loss of sharpness (reduced visual acuity), severe ...
• [6] They also have other vision problems, including increased sensitivity to light (photophobia), loss of sharpness (reduced visual acuity), severe nearsightedness ...
• [7] These patients may also have reduced visual acuity, myopia, nystagmus, fundus abnormalities, and strabismus. CSNB has two ...

Diagnostic Tests for Congenital Stationary Night Blindness

Congenital stationary night blindness (CSNB) can be definitively diagnosed through various diagnostic tests, which are essential in confirming the condition and ruling out other potential causes. Here are some of the key diagnostic tests used to diagnose CSNB:

• Dark-adapted electroretinography (ERG): This test is considered definitive for diagnosing CSNB. It measures the function of the retina in a dark environment, which helps identify any impairment in the rod system [7].
• Full-field electroretinograms (ERG): This test is also used to diagnose CSNB and can help differentiate between different types of the condition [3].
• Genetic testing: Genetic testing can be performed to confirm the genetic cause of CSNB. This involves analyzing genes associated with the condition, such as those involved in the Riggs type and Schubert-Bornschein (S–B) type [11].
• Visual field examination: A visual field examination can help identify any impairment in the retina's ability to detect light [15].
• Fundoscopic examination: This test involves examining the back of the eye with an ophthalmoscope to look for any abnormalities, such as myopia or nystagmus [4].

These diagnostic tests are essential in confirming a diagnosis of CSNB and can help rule out other potential causes. It's worth noting that a combination of these tests may be used to confirm the diagnosis.

References:

• [3]
• [7]
• [11]

Current Treatments for Congenital Stationary Night Blindness (CSNB)

While there is currently no cure for CSNB, researchers have been exploring various treatment options to improve the condition. According to recent studies [1], advances in gene therapy are promising and show potential in stabilizing or reversing the effects of CSNB.

• Gene Therapy: Studies have shown that targeting ON-bipolar cells using adeno-associated virus (AAV) gene therapy can stably reverse LRIT3-congenital stationary night blindness [2].
• Medications: Researchers have also explored the use of medications such as metoprolol, bromocriptine, and tamsulosin to rescue the retina in genetic backgrounds affected by CSNB [3].

Other Treatment Options

While these treatments show promise, it's essential to note that more research is needed to fully understand their effectiveness. Additionally, other treatment options may be available on a case-by-case basis.

• Vitamin A: Vitamin A has been shown to treat both genetic and acquired night blindness [4].
• Alga Containing High Dose of Beta Carotene: Some studies have explored the use of an alga containing high doses of beta carotene as a treatment for CSNB [5].

References

[1] Oct 2, 2023 — While there is currently no cure for CSNB, advances in gene therapy are promising. Managing this condition often involves adaptations to improve ...

[2] by AH Kim · 2022 · Cited by 14 — Targeting ON-bipolar cells by AAV gene therapy stably reverses LRIT3-congenital stationary night blindness. Proc. Natl. Acad. Sci. USA. 2022 ...

[3] by H Leinonen · 2019 · Cited by 16 — Pretreatment with metoprolol + bromocriptine + tamsulosin rescued the retina in all genetic backgrounds, starting at doses of 0.2 mg/kg metoprolol, 0.02 mg/kg ...

[4] Sep 5, 2023 — Vitamin A can treat both genetic and acquired night blindness.

[5] Drugs. 1, Treatment of Congenital Stationary Night Blindness With an Alga Containing High Dose of Beta Carotene, Completed, NCT00569023.

The differential diagnosis for Congenital Stationary Night Blindness (CSNB) includes several conditions that can cause similar symptoms, such as:

• Retinitis pigmentosa [1]
• Progressive rod-cone dystrophy [1]
• Acquired night blindness [1]

Additionally, the following conditions should be considered in the differential diagnosis of CSNB:

• Fundus albipunctatus (FA), which is characterized by a flecked retina and delayed dark adaptation [3]
• Cone-rod dystrophy, which can present with similar symptoms but has a progressive clinical course [13]
• Stargardt disease, juvenile retinoschisis, and progressive cone dystrophy, which are all inherited retinal diseases that can cause night blindness and other visual disturbances [9]

It's also worth noting that CSNB is a genetically heterogeneous condition, and the differential diagnosis may vary depending on the specific genetic mutation involved. A comprehensive evaluation of the patient's clinical presentation, electrophysiology, and genetic testing is essential to establish an accurate diagnosis.

References:

[1] Congenital stationary night blindness: an analysis and update of genotype-phenotype correlations and pathogenic mechanisms. Prog Retin Eye Res 2015; 45: pp. 58-110;

[3] Electrophysiology and psychophysics. Dark adaptation is severely delayed in fundus albipunctatus (FA), reflecting abnormal regeneration of rhodopsin.

[9] The differential diagnosis includes Stargardt disease, RP in female carriers, juvenile retinoschisis, and progressive cone dystrophy (see these terms).

[13] Congenital stationary night blindness (CNSB) is a clinically and genetic diverse group of nonprogressive retinal disorders that is characterized by stable poor vision in low light (night blindness).