Optic Disk Swelling

A doctor checks into the eye with an ophthalmoscope when there are regular complaints of headache, nausea or vomiting. This is to check for the appearance of the optic nerve and the blood vessels that pass through the eye. Swelling of the optic nerve is called Papilledema.

The optic nerve is a thick cord that connects the back of each eyeball and its retina to the brain. The cerebral spinal fluid protects the nerve between the brain and eye. Even if there is a slight increase in the pressure of this fluid, due to swelling in the brain, the optic nerve can get compressed around its whole circumference in a choking manner. The optic nerve can bulge whenever it develops inflammation on its own - causing Papilledema.

Such swelling of the optic nerve head can also be caused due to intracranial pressure. This could be due to an underlying brain tumor or brain infection such as abscess, meningitis or encephalitis. In fact many who are diagnosed with brain tumors exhibit Papilledema. Sometimes this can be caused due to high blood pressure.

Causes of Papilledema :

• Tumor of the Brain, Skull, Spinal column or cord, optic nerve
  
• Hydrocephalus - accumulation of cerebrospinal fluid within the skull
  
• Intracranial infections such as encephalitis, meningitis
  
• Abscess - Accumulation of Pus, Hemorrhage or trauma to the head
  
• Craniosynostosis - Abnormal closure of the skull bones
  

Symptoms of Papilledema :

• Headaches - especially the types which become severe on awakening; headaches that become exacerbated by coughing or holding breath
  
• Nausea and Vomiting
  
• Changes in vision manifesting in the form of double vision, flickering, transient blurring or graying
  

Pseudo tumor cerebri or benign intracranial hypertension is one condition which can cause increased pressure in the cerebral spinal fluid. This is caused when the body makes too much spinal fluid. This is common in women especially who are obese and of child bearing age, and at such times when the body is adjusting to hormone changes such as pregnancy, the first menstrual period or menopause. It is better to go in immediately for neuro-imaging and MRI to check the cerebral cenous sinuses. A lumbar puncture could be done to check the opening pressure as well as CSF (cerebro spinal fluid) test, Fluorescein Angiography - an eye test specifically intended to check the blood flow in the Retina and Choroid, if there is diagnostic uncertainty. In some cases ultrasonography and Retinal Tomography may be used to get 3D data and image.

Although a swollen optic nerve tends to improve over a period of time, it may take months for complete restoration of normal vision. Doctors usually treat with intravenous steroid drugs but this process may have little effect on vision in some cases, although it may help to improve overall health.

Fluorescein Angiography

Fluorescein Angiography is a diagnostic test that aids visualization of the blood circulation in the retina and choroid. Fluorescein is a water-soluble dye that is injected into a vein in the patient's arm. It travels through the blood vessels of the body thereby aiding multiple photographing of the retina. The images obtained help in detecting any swelling or leakage in the blood vessels. The patient's eyes are dilated with mydriatic eye drops so that photographs of the inside of the eye can be taken.

Some patients may notice skin rash, itching or allergic reaction to the dye. Nausea or vomiting may be noticed. But this non-invasive test can usually be safely repeated. Abnormal results of fluorescein angiography test may indicate diabetic retinopathy, macular degeneration, or cancer. Ischaemia or edema in the retina circulation can be detected with the help of fluorescein angiography.

Vitamin A

Vitamin A is a fat soluble vitamin which is derived from beta carotene which plays a significant role in the process of vision and other important metabolic pathways pertaining to cell division and genetic expression. The significant forms of vitamin A include retinol, retinal, retinoic acid and retinyl esters. There are approximately six hundred derivatives of beta carotenes and the most important form is retinol.

Functions of Vitamin A

Vitamin A is essential for many metabolic pathways in the body. It is the chief requirement for the function of the rhodopsin protein located in the retina to absorb light and to differentiate functions of the cornea and the conjunctival membranes. Vitamin A is essential for normal functioning of the retina. Apart from this, vitamin A plays a significant role in immune system functions, cell signaling and cellular communication and reproduction. The functions and pathways associated with vitamin A are directly related to the functionality of vital organs such as heart, brain, lungs, liver and kidneys. Hence vitamin A is also known as an important antioxidant. Besides it is required for the growth and differentiation of epithelial tissue, normal growth of bone and embryonic development. Most of our body's Vitamin A is stored in the liver in the form of retinyl esters.

Vitamin A Deficiency: Poor adaptation of vision to darkness or what is known as night blindness is an early symptom that may be followed by degenerative changes in the retina. Degenerative changes in eyes and skin are commonly observed in vitamin A deficiency. The predominant form of vitamin A deficiency is Nyctalopia or night blindness. This occurs as result of retinol imbalance which is the chief derivative of vitamin A. In third-world, vitamin A deficiency is the primary cause of blindness. Pregnant and lactating women, premature children, children living in rural areas of developing countries and patients who have a history of liver diseases such cirrhosis and cystic fibrosis are most susceptible to Vitamin A deficiency. Severe or prolonged deficiency may lead to dry eye or Xerophthalmia (dryness in conjunctiva and cornea of the eye) that can result in corneal ulcers, inflammation, ridge formation, scarring and eventually blindness. Xerophthalmia is due to lacrimal gland dysfunction. Other associated conditions include keratomalacia and follicular hyperkeratosis. Another important consequence of Vitamin A deficiency is acquired immunodeficiency disease, with an increased incidence of death related to infectious diseases. Vitamin A deficiency is associated with increased disease progression and mortality in HIV patients.

World Health Organization (WHO) Recommendations for Vitamin A:
Supplementation may be required in cases where the blood Vitamin A level falls below 20 µg/dL.
Severe deficiency is < 10 µg/dL

Food sources and recommended dietary allowance

Vitamin A is naturally available in dairy products such as milk, cheese, curd, cream. Meat products like liver and fish oil and leafy vegetables are excellent sources of vitamin A. Other sources include pumpkin, potatoes, broccoli, cereals, beans and cow peas. Studies indicate that the intensity of the fruit or vegetable color is directly proportional to the amount of vitamin A present in it. The recommended intake of vitamin A per day for children 500 micrograms, males 1000 micrograms and females 800 micrograms respectively.

RDAs (recommended dietary allowance) for vitamin A are given as mcg of retinol activity equivalents (RAE) to account for the different bioactivities of retinol and provitamin A carotenoids. FDA may introduce new labeling regulations in the near future which may result in listing Vitamin A with RAE values rather than in IU.
The following table shows conversion rates of mcg of RAE (retinol activity equivalents):

• 1 IU retinol = 0.3 mcg RAE
  
• 1 IU beta carotene from dietary supplements = 0.15 mcg RAE
  
• 1 IU beta carotene from food = 0.05 mcg RAE
  
• 1 IU alpha carotene or beta-cryptoxanthin = 0.025 mcg RAE
  

Essentially all dietary sources of vitamin A are converted into retinol by the body: 1 mcg of physiologically available retinol is equivalent to the following amounts from dietary sources:

• 1 mcg of retinol
  
• 12 mcg of beta carotene
  
• 24 mcg of alpha carotene or beta cryptoxanthin
  

Hypervitaminosis A: Vitamin A in excess can be toxic. According to WHO, values in excess of 120 µg/dL is Hypervitaminosis A. Chronic vitamin A over dosage may be a serious issue in normal adults who take more than 15 mg per day and in children who take more than 6 mg per day of vitamin A over a period of several months. Symptoms can include :

• Dry skin
  
• Cheilosis
  
• Glossitis
  
• Hypercalcemia
  
• Hyperlipidemia
  
• Amenorrhea
  
• Liver fibrosis with portal hypertension
  
• pseudotumor cerebri
  
• increased intracranial pressure and Papilledema
  
• lymph node enlargement
  

Other than that some symptoms such as pain, vomiting, alopecia and bone demineralization may result due to excessive intake of Vitamin A. In pregnant women, an over dose of Vitamin A over a period of time may result in spontaneous abortions or Congenital malformations, craniofacial abnormalities and valvular heart disease in the baby.

However, unlike preformed Vitamin A, beta-carotene is not known to be teratogenic (reproductive toxicity). Even a relatively large supplemental doses of beta carotene or eating carotenoid rich food for long duration need not result in toxicity always. Rarely a reversible condition known as carotenodermia - where the skin turns yellow/orange might be the result of long term over dosage of beta carotene.