The stage of the glaucoma is on the y axis, and the life expectancy is on the x axis. The slope and the curve of each of the individual lines are determined and graphed in different ways:
• Dotted lines indicate that the slope and the curve have been determined by plotting the results of serial studies, such as repeated disc photographs taken yearly or repeated visual field examinations.
• Solid lines depict the clinical course as described in the patient's history.
• Dashed lines are extrapolations that are presumed to represent what will happen. These hypothetical, extrapolated future courses are based on the nature of the previous courses and on knowledge of what has happened since a known point in time.
This illustration shows the courses of seven different patients with different manifestations of glaucoma:
• A patient at point A has minimal glaucoma and about one third of his or her life still to live.
• A patient at point B has advanced glaucoma and has about one third of his or her life still to live.
• A patient at point C has very early glaucoma and only a few years to live.
• A patient at point D has advanced glaucoma and only a few years to live.
• Patient no. 1, considered at point A has one third of his or her life to live and is in an early stage of glaucoma. About one third of his or her life earlier, this patient was noted to have elevated pressure and followed without treatment. The patient continued to be followed without treatment and no damage to the optic nerve or visual field was ever noted. It is reasonable to assume that, if the patient continues to have intraocular pressures around the same level as those noted initially, he or she will probably follow the course described by line 1 and will die without any evidence of glaucoma damage.
• Patient no. 2, also considered at point A, (i.e., having minimal damage with one third of his or her life left to live). In this case, however, the patient's intraocular pressure rose continuously, and the patient was noted to develop early disc and field damage, which then continued at the rate depicted by the dashed line 2. This patient, if untreated, would develop definite asymptomatic damage. However, the patient would have no functional loss at the time of his or her death.
• Patients nos. 3 and 4, at point B: Both have advanced glaucoma and one third of their lives left to live. However, patient no. 3 is deteriorating rapidly and will be blind long before he or she dies, whereas patient no. 4, who had a blow to the eye as a child and lost vision to a steroid-induced glaucoma at that time, has had stable vision for most of his or her life, and it is reasonable to expect that it will continue to be stable.
• Patients at points C and D both have only a few years to live, but those at point C (like patients nos. 1 and 2 at point A) have minimal damage, and those at point D (like patient no. 4 at point B) have marked damage.
• Patient no. 5 started with a clinical course similar to that of patient no. 3 (advanced glaucoma and deteriorating rapidly), but around the midpoint of his or her life, the glaucoma became less severe. Nevertheless, this patient will be blind at the time of his or her death unless there is effective intervention. Compare with patient no. 4, who at point D has the same life expectancy and the same amount of damage as patient no. 5 (only a few years to live and advanced glaucoma). Patient no. 4, however, has a stable clinical course and does not appear to need a change in therapy. In contrast, patient no. 5 needs urgent lowering of intraocular pressure.
• Patient no. 6, at around point C, also has only a few years of life remaining but has a glaucoma that is getting worse a little bit more slowly than that affecting patients no. 2 and 5. However, because patient no. 6 has so little damage to start with, no treatment is necessary, even though he or she is getting worse. Even without treatment, he or she will not have enough damage or visual loss from glaucoma at the time of death that he or she will have any awareness of being sick and will have no limitation in function.
• Patient no. 7 at point C has only a few years left to live but has a type of glaucoma that is deteriorating so rapidly that even though he or she has only a short period to live, he or she will be blind well before the time of death.
Using the glaucoma graph to define and characterize the nature of the clinical course helps the physician and patient to understand that
• Patients nos. 1, 4, and 6 do not need any treatment at all; patient no. 1 will never develop damage, patient no. 4 has marked damage but it is not getting worse, and patient no. 6 is getting worse so slowly that it will not interfere with his or her life.
• Patients nos. 3, 5, and 7 need treatment urgently to prevent them from becoming totally blind before the time of their deaths.
• Patient no. 2: The need for treatment is controversial. Because this patient would never develop glaucoma, perhaps he or she should not be treated at all. But because he or she would develop some damage, those who want to prevent any damage at all would advise therapy.