No. The defects occur after the increase pressure in your eye causes permanent damage to your vision. Usually you lose the peripheral vision. When it is bad you feel like looking through a tunnel when your peripheral vision is gone.
Not always. Some glaucoma patients display damage to the optic nerve inside the eye before the visual field is affected.
Good question! Glaucoma is a progressive optic neuropathy. What that means, is that it continues to get worse and cause more loss of vision. The visual field defects, once present, only continue to get worse. That is why the treatment is so important for holding on what you have.
No. Defects someone would notice in daily life would be late in the disease. Specialized visual field tests can show defects much sooner but still after damage has occurred. More specialized testing such as optical tomography can detect changes much sooner (ie, before visual field defects) and with appropriate treatment help preserve the vision.
No. Sometimes the elevated pressure will "eat away" at the myelin in the optic nerve causing an increase in the cup disc ratio before field damage occurs. This can give the patient a false sense of security and lead to noncompliance and subsequent damage.
Frequently. Changes in the field of vision are one of the hallmarks of the diagnosis of glaucoma. The aim of treatment is to prevent this from happening and also to prevent it when present from progressing. Some cases are detected early when other changes hint strongly that glaucoma could be a problem, and so field defects might not have occurred yet in such cases.
In advanced glaucoma. Glaucoma is a condition that is related to an increase in eye pressure. Over time, the optic nerve gets damaged and you start to lose peripheral vision (which shows up as field defects). So, initially you may have a normal field, but if left untreated, you will have field defects which are permanent.
Yes. By definition, glaucoma is a group of diseases which causes characteristic optic nerve damage with corresponding visual field defects. These defects are not always symptomatic to the patient and may only be detectable through special testing.
Hopefully not. Glaucoma is diagnosed by a number of parameters of which the visual field is one. The goal of treatment is to prevent progression and this usually happens with good treatment. But sometimes a field defect is the clue to the presence of the condition, and changes in the field can be a clue to advancement of the therapy needed to treat the glaucoma.