L. Jay Katz, MD: When caring for patients with ocular hypertension, how important is it to examine structure with imaging or disc photography as opposed to testing visual fields?
Ronald L. Gross, MD: Both are important. The Ocular Hypertension Treatment Study (OHTS) found that the first sign of glaucomatous damage in the majority of subjects was structural, but in a substantial number of subjects, about a third, an abnormal visual field was the first sign.1 In general, we believe the nerve changes before the field, but in some cases, that is not true. For that reason, we must follow both structure and function.
Dr. Katz: How often do you see patients who have glaucoma?
Dr. Gross: It is important to set a good baseline, particularly for visual field testing, which should be done fairly quickly. That usually takes at least two reliable visual field tests. As for analyzing structure, it is important to have an objective record, such as optic nerve photographs or image analysis. Once we have obtained good baseline data, we usually repeat the testing for the average patient once a year.
Dr. Katz: Do you use standard white-on-white perimetry, or do you sometimes use other types of visual field analysis?
Dr. Gross: Typically, we use the Swedish interactive threshold algorithm (SITA) standard 24-2 field. We have found that short-wavelength automated perimetry (SWAP), which is blue-on-yellow, is not as useful as we once thought it was, since similar numbers of patients show abnormalities earlier in SWAP and standardized automated perimetry. For that reason, we depend on white-on-white. Some of the newer technologies, such as frequency doubling, may be useful, and some data suggest it detects defects earlier. We do not have a large amount of data, however, to tell us exactly where it fits into our evaluation.
Dr. Katz: Based on the OHTS, we could use an algorithm to help predict the risk of glaucoma development over 5 years. Do you use the algorithm and discuss it with your patients?
Dr. Gross: In general, I do not calculate a specific number for a patient, but the idea of a risk analysis is important. Understanding that older patients, patients with higher pressures, and those with thinner corneas have the highest risk of developing glaucoma and then determining low, medium, or high risk for an individual patient are helpful. Often, patients will decide if treatment is appropriate, but their decision may well be influenced by their risk.
Dr. Katz: I do not use the algorithm, either; I use the same risk factors in determining the relative risk of disease progression. I agree that it is critically important for patients to have a role in the decision-making process, but they rely a great deal on us for advice. How do you come to common ground in terms of pushing in one direction or the other—treatment versus observation—to reach a decision with a patient who is a glaucoma suspect?
Dr. Gross: We would all like to say we do not have a bias, but I admit I do. In general, the lower the risk is, the more I am biased toward watching the patient. The higher the risk is, the more I favor treatment. Regardless of their decision, it is most important that patients continue to be observed.
Dr. Katz: Suppose a patient appears to have a very low risk, say 5% over 5 years, but chooses treatment to feel more comfortable about lowering his or her pressure. What is your opinion of that choice?
Dr. Gross: I think that is perfectly reasonable. Conversely, I may have a patient with pressures in the 30s who chooses to be observed. I may be worried, but if I have talked to him or her and he or she understands the risks and chooses to be observed, I think it is his or her personal choice.
Dr. Katz: When you start therapy, what treatment path do you choose, and how effective is that for this population?
Dr. Gross: I tell patients that lowering IOP is the only treatment that has been proven effective in studies and that we usually can do that with drops.2-4 I mention that we have surgeries that can accomplish the same thing, but for most patients, medications are the first choice.
Dr. Katz: Let's discuss the normal-tension glaucoma patients, the other side of the coin. These are people who have pressures in the so-called normal or average range, and they have progressive visual field loss and changes in their optic nerve heads. Has your approach to managing these patients changed based on recent information?
Dr. Gross: When taking care of these patients, we must answer some difficult questions: Is this glaucoma? Does this patient need to be treated? Are there other factors in play? We have good data from the Collaborative Normal- Tension Glaucoma Study that we should lower the IOP.5 In doing so, however, we often must consider other factors, such as perfusion pressure, diastolic blood pressure, and cardiac arrhythmias, to name a few. We need to determine if those are present and if they are, if we can do something about them to improve the patient's status. On the other hand, we need to consider if there is something we can do to affect the health of the optic nerve and the neurons of the retinal ganglion layer. We have some new data from the Low-Tension Glaucoma Treatment Study (LoGTS), which has looked at this question in a scientific way for the first time.6
The LoGTS was a randomized, prospective, multicenter trial that examined timolol versus brimonidine as monotherapy for patients with low-tension glaucoma. These patients' pressures were in the teens and rarely, if ever, elevated. Much to the surprise of many of us, visual field analyses by several methodologies showed substantially better preservation of the visual field in the brimonidine group than in the timolol group, even though these agents are equivalent in their ability to lower IOP.
Lowering pressure is important, and prostaglandin analogues are still more efficacious in general than other classes, but given the results of this study, we may need to consider the role of brimonidine in our normal-tension patients.
Dr. Katz: What would you do if you learned your patient had extremely low diastolic blood pressure and was taking blood pressure medication?
Dr. Gross: This is an easier case, because we can ask the internist if the patient's regimen can be modified to avoid very low blood pressures, which may be affecting his glaucoma. Often more frustrating is the patient who has low blood pressure and is not being treated for hypertension. That can be much more difficult to address.
Dr. Katz: Do you ever advocate for 24-hour blood pressure monitors for these types of patients?
Dr. Gross: It is not a routine test that I do, but in isolated instances with progression without an explanation or evidence of systemic hypotension, it may be helpful.
Dr. Katz: Every patient is different. In a typical patient, what is maximum medical therapy, and how can we enhance adherence in the day-to-day management of glaucoma?
Dr. Gross: Unfortunately, we do not have a good way toassess adherence. In general, I assume it is probably a lot worse than patients tell us or than we think it is. Something we can do to improve adherence is simplify medication regimens as much as possible—limit the number of bottles patients use and limit the number of instillations per day— to make them more manageable.
Maximum medical therapy is different for every patient, but in general, if a patient is using a prostaglandin analogue and a fixed-combination drop, then he is using three classes of medication and two bottles. We know that adding a fourth class (and a third bottle) will not add much in the way of efficacy. For the average patient, that may well represent maximum medical therapy. What do you think?
Dr. Katz: Because of the cost issue, the side effect profile, and the limited additivity of using multiple medications, I think two bottles, maybe three, is the maximum from which most patients will benefit. So, I agree with you. I think there are some general principles that we can follow in caring for our patients, and you summarized them very nicely. In closing, I would add we do need some general guidelines for caring for our patients with glaucoma, but we still must individualize care. That is where our abilities as clinicians come through, in deciding on the best approach after discussion with the patient.
- Kass MA, Heuer DK, Higginbotham EJ, et al. The Ocular Hypertension Treatment Study: A randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120:701-713.
- Feiner L, Piltz-Seymour JR; Collaborative Initial Glaucoma Treatment Study Group. Collaborative Initial Glaucoma Treatment Study: a summary of results to date. Curr Opin Ophthalmol. 2003;14:106-111.
- The AGIS Investigators. The Advanced Glaucoma Intervention Study (AGIS): 7. The relationship between control of intraocular pressure and visual field deterioration. Am J Ophthalmol. 2000;130:429-440.
- Heijl A, Leske MC, Bengtsson B, et al.; Early Manifest Glaucoma Trial Group. Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial. Arch Ophthalmol. 2002;120:1268-1279.
- Collaborative Normal-Tension Glaucoma Study Group. Comparison of glaucomatous progression between untreated patients with normal-tension glaucoma and patients with therapeutically reduced intraocular pressures. Am J Ophthalmol. 1998;126:487-497.
- Krupin T, Liebmann JM, Greenfield DS, et al.; Low-Pressure Glaucoma Study Group. A randomized trial of brimonidine versus timolol in preserving visual function: results from the Low-Pressure Glaucoma Treatment Study. Am J Ophthalmol. 2011;151:671-681.
