Night Blindness

(Nyctalopia)By Kevin J Ambadan

Definition

Derived from Greek words: nykt = ‘night’ & alaos = ‘blindness’

It is a condition in which it difficult or impossible to see in relatively low light.

Symptom of several eye diseases.

EtiologyNight Blindness may exist from birth or be caused by injury or malnutrition (for example, vitamin A deificiency).

Causes:• Vitamin A deficiency• Retinitis Pigmentosa & other tapetoretinal

degenerations• Congenital night blindness• Pathological myopia• Peripheral cortical cataract & Corneal opacities• Advanced Primary open angle glaucoma

Vitamin A Deficiency

Inhibits the production of rhodopsin (the eye pigment responsible for sensing low light situations) found in the retina, composed of retinal (active form of Vitamin A)

The decreased amount of rhodopsin in the eye implies that there is inadequate retinal to bind to opsin. Therefore, night blindness results.

Retinitis Pigmentosa

A disorder in which the rod cells in the retina gradually lose their to respond to the light.

Patients suffering from this genetic condition have progressive nyctalopia and eventually their daytime vision may also be affected (Hamarlopia).

Congenital Stationary Night Blindness

It is a rare X-linked non-progressive retinal disorder.

Caused by malfunction in neurotransmission from rods to bipolar cells in the retina.

Also known as Oguchi’s disease.

Peripheral Cortical Cataract

The outer area of the retina is made up of more rods than cones.

As rods are responsible for vision in dim light, loss of peripheral vision often results in night blindness.

TreatmentTREAT THE UNDERLYING CAUSE!!!!

The treatment method depends on the cause of the night blindness:• Vitamin A deficiency - treated by giving

Vitamin A supplement• Retinitis Pigmentosa – not completely

curable, but the rate of progression of this disease can be reduced by intake of vitamin A supplements and surgeries (retinal transplant)

Treatment• Myopia – use of corrective glasses or

lenses or refractive surgery• Glaucoma – switching of glaucoma

medicines may help• Peripheral Cataract – Cataract surgeries• Oguchi’s Disease – incurable

The end