User:Shannonchan futurepharmd/Congenital blindness

Lead
Congenital blindness refers to blindness present at birth. Congenital blindness is sometimes interchangeably used with "Childhood Blindness." However, current literature has various definitions of both terms. Childhood blindness encompasses multiple diseases and conditions present in ages up to 16 years old, which can result in permanent blindness or severe visual impairment over time Congenital blindness is a hereditary disease and can be treated by gene therapy. Visual loss in children or infants can occur either at the prenatal stage (during the time of conception or intrauterine period) or postnatal stage (immediately after birth). There are multiple possible causes of congenital blindness. In general, 60% of congenital blindness cases are contributed from prenatal stage and 40% are contributed from inherited disease. However, most of the congenital blindness cases show that it can be avoidable or preventable with early treatment.

[Insert overview about epidemiology]

Signs and Symptoms
There are two categories in which the signs of congenital blindness can be classified. The first category pertains to consistently poor vision, such as the not displaying preferential looking when presented with high-contrast visual stimuli. The second category encompasses severe ocular anomalies, such as Anophthalmos (born with only one eye or lost both eyes), Microphthalmos (underdevelopment of one or both eyes), and Coloboma (a portion of tissue missing in the eye(s)).

Complications
== Causes ==

Prenatal Causes of Childhood Blindness

 * Premature Birth
 * Refractive error
 * Congenital cataract
 * Retinopathy of prematurity (ROP)
 * Infection
 * Congenital toxoplasmosis
 * Congenital cytomegalovirus infection
 * Vitamin A deficiency

Genetic Mutations
Gene alterations leading to retinal dystrophies or congenital malformations may cause congenital and childhood blindness. Examples of these include:

Celestenoelle.bustria (talk) 06:50, 30 July 2023 (UTC) Celestenoelle.bustria (talk) 06:50, 30 July 2023 (UTC)
 * Microphthalmia
 * Anophthalmia
 * Coloboma
 * Leber's congenital amaurosis (LCA) is a collection of inherited, degenerative eye disorders that can reduce the strength of visual clarity or sharpness in infants and can cause childhood blindness. These eye disorders are mostly autosomal recessive diseases, and diagnoses of LCA are linked to multiple gene variants, including the Retinal pigment epithelium-specific 65 kDa (RPE65) gene. The RPE65 protein is essential in the process of vision, as it contributes to the regeneration process of the visual pigment rhodopsin. During the normal visual cycle, all-trans-retinyl palmitate, a stored form of vitamin A, binds and activates retinoid isomerohydrolase. This enzyme converts all-trans-retinyl palmitate into 11-cis-retinol, which is further oxidized into 11-cis-retinal. This compound binds with apo-rhodopsin to become rhodopsin, concluding the visual cycle. The RPE65 protein binds with all-trans-retinyl palmitate and helps bring it to isomerohydrolase. RPE65-associated LCA is characterized by dysfunctional isomerization activity and early-onset blindness.
 * Retinoblastoma is the most common intraocular malignancy present in children younger than 5 years old. The eye cancer can be passed down genetically as an autosomal dominant condition.

Postnatal Causes of Childhood Blindness

 * Measles


 * Infection (such as Ophtalmia neonatorum)

Pathophysiology
== Screening == As per the CDC recommendations, newborns should undergo an eye examination while they are still in the hospital nursery. It is equally important to continue monitoring their eyes and vision system throughout their childhood and adolescence.

The following methods are used to test infant's vision:

Diagnosis
Vision develops rapidly during a child's first year of life, which can make it difficult to determine level of vision impairment early on. However, pediatric nurses, medical officers and pediatricians trained in eye screening detect small or large eyeballs, nystagmus, strabismus, “white pupils” and birth defects like coloboma and aniridia. Pregnant individuals from families with a history of congenital blindness are closely monitored and encouraged to perform genetic testing in order to identify possible gene mutations in their offspring.

Prevention
== Gene Therapy Treatment == Gene therapy treatment is done in the outpatient setting. Patients visit the hospital for the treatment, then return home. Patients do not need to be strictly monitored or stay in the hospital. The gene therapy treatment is in vivo which involves the use of a delivery vector to transmit the therapeutic gene into the targeted cells. The delivery vector uses a recombinant adeno-associated virus (AAV) carrying the RPE65 gene (AAV2-hRPE65v2). The procedure is a single injection of the AAV2-hRPE65v2 therapeutic gene into the unilateral subretinal of the eye. Gene therapy can only improve eye vision but cannot cure the condition. The therapeutic gene, Voretigene neparvovec (Luxturna), was the first gene therapy approved by FDA for inherited diseases.

===Epidemiology ===