“Glaucoma” is the term used to describe a group of eye diseases that share the following characteristics: progressive, structural damage to the optic nerve, often but not always associated with an increase of internal eye pressure, resulting in a progressive and characteristic pattern of visual field (peripheral and then central vision) loss.
The most important test for uncovering glaucoma is examination of the optic nerve by use of one or several different lighted instruments that give the doctor a three-dimensional view of the shape and size of the nerve. This is best performed through an enlarged (dilated) pupil. The eye doctor evaluates the optic nerve for glaucomatous ‘cupping,’ that is, structural deformation (physical damage) to the nerve.
Internal eye pressure, called ’intra-ocular pressure,’ is an important but often misunderstood element in the diagnosis of glaucoma. Most cases of glaucoma are associated with (not necessarily caused by) elevated intra-ocular pressure, but some cases are not (between 5% and 20% of patients with definite glaucoma have eye pressures which fall within the ‘normal range.’) Furthermore, many people have intra-ocular pressure above the ‘normal range’ (some well above normal) yet do not show any signs of optic nerve damage from glaucoma. This is key; without optic nerve damage, there is no glaucoma. In years past, high intra-ocular pressure was considered the necessary and sufficient cause of all glaucoma. We now know this is not true.
Some optic nerves are better able to tolerate elevated eye pressure than are others. For some optic nerves, even ‘normal’ eye pressure is sufficient to cause damage. This variable tolerance of intra-ocular pressure is thought to be due to (1) genetic factors and (2) the quality of circulation (blood flow) to the optic nerve, both of which vary from person to person. This second factor may explain why diabetics are more susceptible to glaucoma, as the micro- and macro-vascular effects of hyperglycemia, insulin resistance/hyperinsulinemia and/or abnormal blood lipids impair the quality of ocular circulation.
Diabetes affects every part of the eye, not just the retina. Presenting critical information about seven different kinds of diabetic eye disease as well as important steps all diabetics must take to preserve vision, Dr. Chous clearly and comprehensively guides you through the fundamentals of good diabetes management and great eye care. Written by an eye doctor, diabetes educator and patient advocate, this book is dedicated to helping you or someone you love avoid blindness and other complications by taking charge of your diabetes. See his book at http://www.diabeticeyes.com.