The retina consists of light-sensitive tissue at the back of the eye which discerns light and color. In rare cases, babies are born with a retinal disorder known as congenital stationary night blindness (CSNB). This means that they struggle to see and identify objects in low light, particularly at night. Whilst the condition is present from birth, it remains stationary, so there is no deterioration as sufferers grow older.
Problems with Congenital Stationary Night Blindness
People with CSNB generally have no vision problems during the day. However, at night, CSNB sufferers may be affected by a range of factors such as:
– unable to distinguish road signs
– unable to see stars
– greater risk of falling over objects
It is recommended that people with this disorder do not drive or work in poor light at night.
There are two types of CSNB, known as complete and incomplete. Those with the complete type may have greater difficulty with identifying colours. Those with the incomplete type can suffer from another eye disorder called nearsightedness.
Causes of Congenital Stationary Night Blindness
The specialized light receptor cells in the retina are called rods. Rods are responsible for sending visual signals from the eye to the brain in dim light. Proteins produced by particular genes are found in these rods. CSNB sufferers have mutations within these genes creating a disruption to normal signalling between the rod cells and the brain. As a result, poor visual perception in low light occurs.
There are at least ten different genes which are associated with this disorder. The condition can be inherited in three ways:
Autosomal dominant: One parent will have CSNB. Both sexes are susceptible.
Autosomal recessive: Usually parents will be unaffected by this trait as it can skip generations. Both sexes are susceptible.
X linked recessive: Mostly males are affected. Usually the mother will not have CSNB as it skips generations. The trait is not passed from father to son.
There is no known cure for this disorder, although trials have been conducted with various supplements. Sufferers usually seek to manage the condition and avoid tasks or situations which may put them in danger. Those who live in well-lit urban areas often report few limitations caused by CSNB. It is not common to include this condition in a genetic testing regimen unless it is known within a family’s medical history.