Retina – what it is responsible for in the eye and what diseases threaten it

The retina is the inner membrane (also known as the nerve or sensory membrane) of the eyeball wall. There are 3 different types of nerve cells in the retina that perform different tasks:

• Visual cells, called photoreceptor cells, are divided into rod cells (responsible for twilight vision)and cone cells (responsible for daytime vision and color recognition),
• Bipolar cells – one of the protuberances of the bipolar cell receives stimulation from the cone or rod cell, and the other protuberance connects to the ganglion cell, which constitutes the third neuron,
• Ganglion cells – ganglion cell protrusions form a layer of nerve fibers in the retina, which converge to form the optic nerve that connects the retina to the brain.

The area of the retina where the nerve fibers converge is visible on the fundus of the eye as the optic nerve disc. Close to it is the macula.

Photoreceptors, i.e. rods and cones, contain visual pigments and, in addition, adhere to the pigment epithelium, the cells of which are filled with melanin (this pigment absorbs light not absorbed by visual pigments, and this prevents back reflection of light). It is the photoreceptors that are responsible for converting light energy into electrical energy: via the neuronal pathway, electrical stimuli enter the brain, where the images we see are formed – it is not the eye that sees, but the brain. When any step in this transmission process is disrupted, vision abnormalities occur.

These abnormalities, which can be the first symptoms of retinal diseases, take the form of:

• gloom,
• Tingles (dots, spots, threads) in the visual field,
• light flashes,
• discontinuity of the observed lines ,
• eye pain.