glaucoma
5 LESSONS in Glaucoma Management
New technology has advanced our understanding of this disease, but the old standards still apply.
JOSEPH SOWKA, O.D., F.A.A.O., DIPL

Optometric Management is proud to present this installment in our series of articles on glaucoma that have been planned in partnership with the Optometric Glaucoma Society (OGS). The Society has provided OM with expert authors who will discuss therapies, epidemiology, diagnostic equipment and other current issues in glaucoma management. For additional information on the Society, contact the OGS through the Web site optometricglaucomasociety.org. The views expressed in this article are the author's and do not necessarily represent the views of the OGS or Optometric Management.

When I agreed to write this article, I had an idea in mind. As it turns out, this idea was, by my own estimation, a bad one. Suddenly, I had a commitment, but no idea. So I thought about what I have been passionate about in glaucoma and I realized that I have been sharing the same things with my students and residents over and over again in my Glaucoma Service at Nova Southeastern University. Suddenly, I had a new idea: to review some fundamental lessons in glaucoma that we as practitioners often forget.

Figure 1: New onset disc hemorrhage inferior temporal in a non-compliant patient previously diagnosed with ocular hypertension. These changes indicate conversion to glaucoma despite a normal visual field.

LESSON 1: Minimum equipment needs

Today we have an impressive array of technologies with which to diagnose and monitor patients. However, we must not forget the basics. If we have good fundamentals, then we can deliver good care to glaucoma patients. So, what is the minimum amount of equipment necessary to not only meet the standard of care, but actually give good care to patients? I believe that every office needs an applanation tonometer, a threshold perimeter, a gonioscopic lens and a lens that allows stereoscopic evaluation of the optic disc. This collection not only meets the minimum standard of care, but in my opinion, also allows us to give excellent care to patients with glaucoma. Not using this basic array of equipment can put you and your patients at risk.

Now, beyond the basic equipment mentioned above, a pachymeter will enhance your ability to manage glaucoma patients. If you want to specialize further, the addition of a fundus camera that allows quality disc photographs (preferably stereoscopic) will boost your practice to the next level. Adding a diagnostic laser such as ocular coherence tomography (OCT, Stratus), laser polarimetry (GDx VCC, Carl Zeiss Meditec) or scanning laser tomography (HRT3, Heidelberg Engineering), will raise your practice to an elite level.

LESSON 2: Gonioscopy is important

Clearly, one of the most neglected procedures in glaucoma management is gonioscopy. There are a number of reasons that O.D.s shy away from this procedure. As optometry students, we disliked practicing the procedure and disliked undergoing it ourselves even more. For many, this prejudice remains. They feel that it's inconvenient for the patient because it's uncomfortable, or inconvenient for their practice because it takes too long to perform. Some may be unsure of the anatomy. I have seen practitioners get lost in closed angles and angles with minimal trabecular meshwork pigmentation and end up misjudging the angle anatomy. The only way to improve one's ability is to do the procedure frequently.

Make no mistake: Gonioscopy is vitally important. You can't accurately diagnose and categorize any glaucoma, primary or secondary, open angle or closed, without knowing the status of the angle.

Case in point

A patient recently presented to my office with complaints of an uncomfortable right eye for several weeks duration. He had a history of "laser surgery for glaucoma" in the right eye many years ago. He was using a topical beta-blocker and carbonic anhydrase inhibitor randomly and occasionally in each eye. His vision was NLP OD and 20/20 OS. He had a patent laser peripheral iridotomy (LPI) and microcystic edema of the cornea in the right eye. His IOP measured 62mm Hg OD and 25mm Hg OS. Gonioscopically, he had no angle structures visible in the right eye and only minimal trabecular meshwork in one quadrant in the left eye. Clearly, he had chronic angle closure glaucoma OU. Because the right eye was blind, my goal was to reduce IOP and manage pain, which I accomplished through compliance and adjustments in topical therapy. The larger concern was the visually functional right eye that also suffered from chronic angle closure. He underwent LPI OS with no changes to the angle anatomy, indicating a plateau iris syndrome rather than pupil block. He subsequently underwent successful laser peripheral iridoplasty.

What lessons can be learned here? Clearly, if I had not performed gonioscopy, I would not have been able to properly manage the patient. It is possible to have angle closure in the face of a patent LPI. Patients with LPI need ongoing gonioscopy. In fact, not only does every glaucoma patient need gonioscopy as part of the initial diagnostic work-up, but also on a yearly basis. Every year I have several patients who convert from open to closed angle glaucoma. Proper laser intervention effectively assists in their management.

LESSON 3: The camera is your friend

Figures 2 and 3: Disc progression superiorly and inferiorly in a poorly controlled patient with glaucoma. Subtle differences are noted only through photographic comparisons between an early image (top) and a later one (bottom).

One of the most underutilized tools in glaucoma management is disc photography. Of course, many O.D.s take disc photos. However, the key is to use photos in both the diagnosis and judgment of progression.

Frequently, patients' inability to maintain steady fixation can hinder careful study of the disc. In such cases, photography is invaluable. However, it's of no use to take photos and simply file them in a patient's chart. You must study and interpret them. Remember, you're not just billing for the technical photography, but also for your interpretation. Insurers mandate that there be written interpretation of photographs (as well as visual fields and diagnostic lasers) within patient charts. Take care to examine the neuroretinal rim, para- papillary atrophy and nerve fiber layer. Often, you can more readily identify subtle nerve fiber layer defects or disc hemorrhages on a disc photo.

Disc photography is one of the most valuable methods for identifying disease progression. In the Ocular Hypertension Treatment Study (OHTS), the majority of patients reached a study endpoint by converting to glaucoma not by a change in the visual field, but a change in the optic disc. Certainly, for ocular hypertensive patients, serial disc analysis is one of the most important procedures in management.

Case in point

A middle-aged female was initially diagnosed with ocular hypertension. I felt that she would benefit from prophylactic therapy. However, she was frequently non-compliant with therapy and negligent with visits. When looking at the disc photos taken roughly two years apart, it's clear that there is a new onset nerve fiber layer defect and a disc hemorrhage. (See figure 1.) The patient's visual fields remain normal at this time. However, clearly her disease has progressed and I have now diagnosed her with glaucoma.

In my glaucoma practice, I dilate and take stereoscopic disc photographs for glaucoma patients annually. I also painstakingly study the discs and compare them with photos from previous years in order to identify any changes. I don't need to do this while a patient is in the office, and in fact, I typically do not. This careful analysis is likely the only way that you can identify changes occurring to the disc over time. Comparing written cup-to-disc ratios is meaningless. Looking at a patient live and comparing what you see with a picture is better, but still not very sensitive. Comparing one picture with another is the best way to judge disc progression outside of scanning laser evaluation. We hope not to see disc changes in the glaucoma population we manage, but it does happen. (See figure 2.)

Learning to critically examine an optic nerve and decide if it is normal or glaucomatous is challenging. In my experience, it typically takes years to develop this ability. However, this is a skill worth mastering. As clinicians, we need to be able to decide if a patient has glaucoma or not based upon disc and nerve fiber layer evaluation. Carefully evaluating patient photos and making annual comparisons has helped me the most in developing my "disc reading" skills.

LESSON 4: Be objective

We diagnose glaucoma by examining and considering the IOP, disc and nerve fiber layer, visual field, anterior chamber angle, and performing other advanced structural tests. While we must consider every possible facet, it's crucial to examine everything as objectively as possible; that is, to examine the disc and interpret the visual fields and diagnostic lasers without prejudice. When presented with a GDx VCC, OCT, HRT, or visual field, I interpret the test independent of other factors and determine whether it is normal or abnormal. Then I consider this information within the entire clinical context of that particular patient. I don't want to presuppose a patient has glaucoma because that may induce me to "interpret" the tests as abnormal. Judge and interpret the information as objectively as possible, then put the information into the proper clinical context in order to make the best possible decisions.

LESSON 5: Use diagnostic lasers wisely

The advent of the OCT, GDx VCC and HRT have helped make us better diagnosticians. However, always remember that they are but a piece of information that you must use wisely and appropriately. Never should we base a diagnosis solely upon information from one technology or only one aspect of a printout from a diagnostic laser. While many want to rely upon the new diagnostic technology to actually give a diagnosis, we must abandon this strategy in favor a more holistic approach to interpretation and use in diagnosis. Remember, no technology is going to make a diagnosis. The diagnostic lasers simply, accurately tell us how the topography of the optic disc or thickness of the nerve fiber layer departs from the normal population in that instrument's database. You as the clinician must decide, in your own clinical experience, if the patient's departure from the instrument's normative database represents an anatomic anomaly or if the results indicate a clinical abnormality. In order to do this, you must look at all aspects of the printout, compare it with your clinical experience, then combine this information with everything else you learned from the patient's examination.

Case in point

In my role as a consultant for a diagnostic laser, I received a phone call from an ophthalmologist seeking my opinion. One of his patients demonstrated an increase in the GDx VCC Nerve Fiber Indicator (NFI) parameter from one year to the next. Based upon this sole change, he was planning on performing a trabeculectomy on the patient. He wanted to know if the magnitude of change in this one parameter was adequately diagnostic of progression and if I agreed that surgery was appropriate. Clearly, there was not enough information for me (or him, either) to make such a judgment. I tried to explain my holistic approach to interpretation and suggested that he delay surgery in order to collect more information.

The information and technology to diagnose and manage glaucoma patients is continually evolving. While you must keep up with this evolution, please do not forget some simple rules that have, up to now, allowed us to provide excellent care for our glaucoma patients.

Disclosure: Dr. Sowka is a member of the Speaker Bureau for Alcon laboratories and is a paid consultant for Carl Zeiss Meditec.