How to Diagnose Scotoma

Scotoma is derived from the Greek word for darkness and refers to any blind spot in someone's vision surrounded by an area of relatively normal vision. It is a condition rather than a disease and may not even be abnormal. In fact, all mammalian eyes have a scotoma where the optic nerve exits the retina. The following steps will show how to diagnose a scotoma.

Instructions

• 1

  Demonstrate the presence of the normal scotoma. Close one eye and look straight ahead with the open eye. Hold a small object such as your thumb about 15 degrees to the side opposite the closed eye. The object will seem to disappear when you move it into the blind spot. This area is about 5 by 7 degrees.

• 2

  Identify the specific type of abnormal scotomas with a general vision test. Scotomas are classified according to the area of the vision loss. Central scotomas affect the central vision and hemianopic scotomas are a loss of the majority of the central vision. Peripheral scotomas are a loss of vision at the edge of the visual field.

• 3

  Determine the presence of diseases that cause scotomas. Diseases that affect macula of the retina are the most likely to result in blind spots and these are most commonly demyelinating diseases such as multiple sclerosis.

• 4

  Observe biochemical causes of scotomas. These most often include poisoning from alcohol and quinine, in addition to a deficiency of vitamin A.

• 5

  Diagnose additional causes of scotomas. They also may result in a range of strokes and brain injuries. Tumors that compress the optic nerve or blood supply for the eye, most often arising from the pituitary gland, also may cause scotomas.