Jerome , a a 45 year old man came to the Eye Clinic complaining of pressure abov

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Answer:

Optic Chiasma

Human brain is divided into three regions

1. Fore Brain

2. Mid Brain

3. Hind Brain

Fore brain is further classified into:

The main parts of diencephalon are epithalamus, thalamus and hypothalamus.

Epithalamus: it is not formed of any nervous tissue and is thin by nature. Anterior part of epithalamus gets folded to form anterior choroid plexus. Behind the epithalamus is present a short stalk like structure called the pineal stalk which bears the Pineal body at its tip and it is responsible for the release of a hormone; melatonin.

Thalamus: Thalamus is located superior to the mid brain and is composed mainly of the grey matter.

Hypothalamus: Hypothalamus is the lowermost part of the diencephalon which is also considered to control the release of the hormones.

The optic nerves which comes from the eyes forms a crossing in front of the hypothalamus. This crossing is called as the optic chiasma.

Significance of optic chiasma:

Optic chiasma is present in all the vertebrates; hence it is considered to play a very important role in the evolution.

Optic chiasma; which is a crossing of the optic nerves helps in regulating the vision as directed by the brain.

Since an X-shaped structure is formed; the nerves from the left eye goes to the right part of the brain and vice versa. The optic nerves originate from the retina of the eyes and enter to the lobes of the brain in the opposite direction.

There are so many factors which can lead to a number of diseases related to the optic chiasma. They are-

However among all of them, the most potent and common factor responsible for the disease in the optic chaisma is due to the tumor in the pituitary gland.

Pituitary gland is connected to the hypothalamus by a stalk like structure called infundibulum. Also the movement of the molecules between the hypothalamus and the pituitary gland occurs through a hypophyseal portal system. When tumor arises or originates in the pituitary gland; through the hypophyseal portal system it reaches the hypothalamus. Due to extreme high rate of cell division; it posess an immense pressure over the optic chaisma too.

Due to the extreme pressure posed by the cancerous cells over the optic chaisma; the functioning of the chaisma gets impaired and it could lead to many problems like-

Loss in the visual field: Visual field refers to the complete area of our vision. With continuous and constant pressure over the optic chiasma, there takes place a damage to the available area thus leading to blindness

Blurred vision: If the pressure applied is not very high, it results in the blurred image formation.

Nystagmus: Depending on the position of an object; whether they are moving or they are still, our eyes too moves and likewise it results in the effective image formation;. However in persons characterized with a condition on Nystagmus; the change in the position of the eyes does not occur depending on the location of objects. This thus impacts their vision. Also the eyes keeps on rotating and moving and likewise a blurred image is formed.

Bitemporal hemianopsia: This condition is also known as bitemporal heteronymous hemianopsia or the bitemporal hemianopia. This results in partial blindness due to the loss in vision of both the right and the left visual fields in their outer half.

Thus these are some of the vital consequences which may arise due to the pressure generated over the optic chaisma as a result of the tumor of the pituitary-hypothalamus glands.

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