Optic Nerve Disorder

An optic nerve is a group of nerve fibres that carry visual signals. There are two optic nerve bundles connecting the back of each eye (retina) with the brain. Optic nerve disorders occur due to damage to the optic nerves. Some optic nerve disorders can lead to vision loss. The severity and type of vision loss depend on the site where the damage occurs. The vision loss due to optic nerve disorders follows a specific pattern. The three types of vision loss patterns due to optic nerve disorders are: 

1. If the optic nerve on one of the sides gets damaged, vision loss will occur on the damaged side.
2. Damage to the optic chiasm (space behind the eye where the optic nerves meet) causes vision loss in the outer part of both the eyes.
3. Damage to the optic pathway from optic chiasm and visual cortex (the region of the brain that processes visual information) causes vision loss on one side of the visual field from both the eyes.

Signs and symptoms can vary with the type of optic nerve disorder. These signs can be temporary or permanent. You might experience the following:

1. Pain in the eye
2. Headache
3. Blurry vision
4. Seeing halos around light 
5. Colour blindness
6. Nausea and vomiting 
7. Complete or partial vision loss
8. Night blindness 
9. Tinnitus (ringing in your ears)
10. Peripheral vision loss

Damage to the optic nerve can be due to a variety of reasons such as compression of the optic nerve, infection, inflammation, glaucoma, cancer, trauma, and interruption of blood circulation to the optic nerve.  

There are different types of optic nerve disorders. Various optic nerve disorders have different causes; these are: 

1. Optic neuritis: It is caused due to inflammation (swelling) of the optic nerve. This inflammation can be due to certain infections or immunological conditions like multiple sclerosis (MS).  
2. Glaucoma: Glaucoma is caused due to pressure build-up due to fluid accumulation inside the eyes that damages the optic nerves.  
3. Optic nerve atrophy: Optic nerve atrophy (decrease in size) is caused due to damage to the optic nerve. This optic nerve damage can have many causes like trauma, exposure to toxic substances, disease, or poor blood flow to the eye. 
4. Optic nerve head drusen: Optic nerve head drusen are caused due to the build-up of protein and calcium salts in the optic nerve over time.
5. Anterior ischaemic optic neuropathy: It occurs due to the loss of blood flow to the optic nerve. This condition can cause sudden vision loss. 
6. Birth abnormalities: Babies born with abnormalities in their optic nerves have poor vision. 
7. Optic nerve coloboma: It is an inherited condition that causes one or both optic nerves to not develop as they should. 
8. Optic nerve gliomas: Gliomas are tumour growths on the optic nerves. These tumours are not cancerous and affect people who have neurofibromatosis type 1 (NF 1).
9. Papilledema: Pressure causes the optic nerve to swell. This pressure can be due to traumatic brain injury, meningitis, brain tumour, or another problem. 
10. Optic nerve meningiomas: These are slow-growing tumours that can cause severe vision loss. 
11. Devic’s disease: Devic’s disease (neuromyelitis optica) is a disease condition where the immune system starts attacking the host’s optic nerves and spinal cord.

 

Risk factors for optic neuritis are:

1. People living in higher altitudes
2. People with a history of multiple sclerosis
3. Caucasian people

Risk factors associated with glaucoma are:

1. People aged 60 years or older
2. People of African-American descent 
3. Family history of glaucoma 
4. Decreased corneal thickness 
5. High fluid pressure inside the eye

Diagnosis of optic nerve disorders can be made by clinical examinations, which include:

Optic nerve imaging 

Your doctor might use one of these optic nerve imaging techniques to look for nerve disorders. 

1. Optical Coherence Tomography (OCT): It creates a three-dimensional (3D) representation of the optic nerve. In addition, it is capable of directly measuring the thickness of the nerve fibre layer. 
2. The Nerve Fiber Analyzer: Laser light is used to measure the thickness of the nerve fibre layer. This layer can give essential clues to the doctor about glaucoma.
3. The Heidelberg Retina Tomograph (HRT): This technique uses a special laser to get a 3D high-resolution image of the optic nerve. This test gives an idea about the extent of nerve fibre loss or damage.

Dilated eye exam

Here, the doctor checks for vision problems that make it hard to see. The doctor will then give you some eye drops to dilate the eye and check for eye diseases.

Ophthalmoscopy

This test allows your ophthalmologist (eye doctor) to examine the back of your eyes.

Magnetic resonance imaging (MRI) 

Your eye doctor might use imaging techniques like an MRI scan that uses the magnetic field to create detailed images of the organs.

 

1. Treatment for Optic Nerve Disorders includes the following:
   1. Antibiotic medicines to control the infection 
   2. Controlling health conditions like diabetes, blood pressure, and obesity 
   3. Corticosteroids 
   4. Avoiding alcohol 
   5. Abscesses drainage 
   6. Vitamin supplements 
   7. Vision aids 
   8. Optic nerve decompression
2. Treatment of Glaucoma involves:
   1. Medication that causes the eye to make less fluid or medicine that lowers the pressure by draining the fluid from the eye. 
3. Optic neuritis does not usually require treatment and is resolved on its own within a few weeks. The vision also returns to normal. This is the case when the optic neuritis is not caused due to any other health condition. In some cases, your doctor might inject medication (steroid) into your vein to fasten the vision improvement and reduce the swelling.
4. There are no treatment options for Optic Nerve Atrophy.
5. Optic nerve head drusen do not require any treatment. Patients usually have a good visual prognosis.

Following these steps can help prevent the optic nerve disorders: 

1. Maintaining a healthy weight through a good diet and exercise 
2. Getting regular eye examinations 
3. Managing conditions that affect the vision, for example, diabetes and high blood pressure   
4. Avoiding or quitting smoking as smoking increases the risk of nerve damage and other vision problems. 
5. Wearing sunglasses and eye-protective gear when engaging in sports or activities that might affect the eye.

Optic nerve damage is the cause of optic nerve disorders. If this nerve damage is left untreated, it can cause 

1. Permanent vision loss
2. Decreased vision quality 
3. Disability 
4. Brain damage from encephalitis, brain tumour or haemorrhage
5. Poor quality of life

You should seek medical help from a doctor if you notice the following symptoms:

1. Long-term headaches 
2. Pain in the eye
3. Changes in eyesight, such as blurry vision, double vision, or vision loss.
4. Seizures 
5. Lethargy 
6. Slurred speech
7. Confusion
8. Change in level of consciousness