Routine eye exams should always include a pressure check which is the basic Glaucoma test. The most accurate way of evaluating the intraocular pressure is with the Goldman Applanation method. That requires eye drops and the use of an applanator with a cobalt blue light. The most common method is the non-contact tonometer which is the ” air puff” test. It is easy and quick, but not as accurate as the applanation. If the pressure is close to or above 21 mm, then a closer look is indicated because there is an increased chance that there may be a problem.
The next part of the exam is to look at the optic nerve. Normal nerves should have a yellowish pinkish appearance and the central cup part should not be more then 30% of the overall optic nerve. If it is and there is a vertical elongation to the cup, then additional testing must be done. Next up would be a visual field test. This involves following a light and using ones’ peripheral vision to see other spots. This evaluates the neurological integrity of the nerve. If there are glaucomatous field and nerve changes then there will first be an increase in the natural blind spot followed by arcuate “scotomas” or blind areas surrounding the central vision. These are clear indications of a positive diagnosis of Glaucoma. Confirmation of the disease is made with a GDX, which is an instrument that actually maps out the optic nerve changes and spots areas that are in danger.
There are several types of Glaucoma, the most common type being Chronic Open Angle. There is also a Narrow Angle type which is most common in farsighted patients. Diseases like Diabetes can cause the disorder as well by increasing blood vessel growth into the angle that drains the fluid from the eye. That is most dangerous and is called Neovascular Glaucoma and follows Rubeosis which is blood vessel growth in the iris of the eye. Trauma can cause the disease by recessing the iris resulting in scar tissue. That is called Angle Recession Glaucoma. Finally, there is Pigmentary Glaucoma which results from pigment leaching out of the iris and blocking the drainage area. This has a very strong genetic component and is the most difficult to treat.
The key issue with Glaucoma evaluation is to know the signs of early disease and treating it appropriately. All too often the early signals are missed and damage to the nerve occurs. The increase in pressure results in a decrease in blood flow to the nerve resulting in death to the tissue. Thus, the new treatment methods focus on vascular sparing to keep the blood flowing to the nerve. As a practitioner, even questionable pressures or optic nerves should be tested further and we must not assume that things are normal. Proper follow up is a must and patient compliance must be carefully evaluated.