Night blindness: causes, symptoms, diagnosis, treatment

Congenital inpatient night blindness, or niktalopia (lack of night vision) is a non-progressive disease caused by dysfunction of the rod system. Histological examination of structural changes in photoreceptors is not detected. The results of electrophysiological studies confirm the presence of a primary defect in the outer plexiform (synaptic) layer, since the normal rod signal does not reach bipolar cells. There are different types of stationary night blindness, which are differentiated by ERG.

Congenital stationary night blindness with a normal fundus is characterized by different types of inheritance: autosomal dominant, autosomal recessive and linked to the X chromosome.

Normal ocular fundus

1. Autosomal dominant congenital niktalopia (type Nugare): insignificant pathology in cone electro-retinograms and subnormal rod electroretinogram.
2. Autosomal dominant stationary nictalopia without myopia (type Riggs): normal cone electro-retinogram.
3. Autosomal recessive or X-linked chromosome niktalopiya with myopia (type Schubert-Bornschein).

Congenital inpatient night blindness with changes in the fundus. This form of the disease includes Ogushi's disease - a disease with an autosomal recessive type of inheritance, which differs from stationary congenital night blindness by changes in the fundus, manifested by a yellowish metallic sheen, more pronounced in the posterior pole. The macular area and vessels on this background look relief. After 3 hours of dark adaptation, the fundus becomes normal (Mitsuo phenomenon). After the light adaptation, the fundus again slowly acquires a metallic luster. In the study of dark adaptation, a noticeable elongation of the rod threshold is revealed in normal cone adaptation. Concentration and kinetics of rhodopsin are normal.

With changes in the fundus

1. Ogushi's disease is an autosomal recessive disease characterized by an elongation of the period of dark adaptation to 2-12 hours to achieve normal rod-like thresholds. Change in the color of the fundus from a golden brown color with light adaptation to normal in a state of tempo adaptation (phenomenon Mizuo).
2. The "white-spot" fundus is an autosomal recessive disease characterized by multiple small white-yellow dots at the posterior pole with an intact fovea and extension to the periphery. Blood vessels, the optic nerve disk, peripheral fields and visual acuity remain normal, electroretinogram and electrooculogram can be pathological during routine investigation and normal with long-term adaptation.

The white eye fundus (fundus albi punctatus) is compared with the starry sky at night, as on the middle periphery of the fundus and in the macular area are regularly located a myriad of whitish small delicate spots. Disease with autosomal recessive type of inheritance. On the PHAG, focal regions of hyperfluorescence not associated with white spots, which are not visible on angiograms, are revealed.

In contrast to other forms of stationary night blindness in the white-spot eye, a slowing of the regeneration of the visual pigment in both sticks and cones was noted. The amplitude of photographic and scotopic a- and b-waves of ERG is reduced under standard recording conditions. After several hours of dark adaptation, the scotopic response of ERG slowly returns to normal.

[1], [2]