Take Glaucoma Progression Monitoring To the Next Level

Newer diagnostic tools can aid management.

By Lawrence Stone, MD, and Matin Babaev

After we diagnose glaucoma or identify a glaucoma suspect, the next phase of care involves monitoring the patient for worsening of the visual field or optic nerve status — that is, progression. While comparisons of serial 24° or 30° threshold tests are valuable, they require us to scrutinize sheets of paper or scroll through multiple computer images to match up corresponding points.

For anatomical testing such as retinal nerve fiber layer (RNFL) analysis, comparing a multitude of studies and determining if a clinically significant change has occurred is also problematic. In a busy office, it can be frustrating to review and accurately analyze all this material.

At our office, we've used the Humphrey Field Analyzer guided progression analysis (HFA GPA) and Cirrus HDOCT guided progression analysis (GPA) of the RNFL, both manufactured by Carl Zeiss Meditec, to make the task of monitoring glaucoma patients for progression faster and more accurate.

Many devices from other manufacturers also feature progression analysis programs. However, ophthalmologists often do not use or underutilize these functions and features. Whether the treatment goal is to alter therapy in patients who are progressing, or maintain the same treatment for stable patients, these modalities can reduce chair time and enhance the patient's acceptance of treatment recommendations.

The printouts are easy for patients to understand. For the HFA GPA, the two studies I show patients most often are the visual field index (VFI) and the probability analysis. For the RNFL GPA, the RNFL change map and the various thickness maps are all useful. When the data points form a horizontal line, this has a certain “wow factor” as patients can see for themselves that their condition is stable. I'll punctuate the consultation with comments highlighting the benefits of treatment and encouraging continued compliance.

Guided Progression Analysis

HFA GPA software differentiates statistically significant progression of visual field loss from random variability. The analysis is based upon knowledge of the variability found at various stages of glaucomatous visual field loss. The GPA also provides a trend analysis of the patient's overall visual field. If the slope of the trend line changes significantly, the physician must rule out glaucomatous progression. Five studies are necessary for the GPA to generate a change analysis.

The HFA GPA analyzes and condenses test results onto a one- or two-page report. The first two tests establish the patient's baseline fields. Then the GPA picks up areas of visual field loss over multiple tests and gives probability percentages indicated by triangles. An open triangle indicates P <5% for one test from baseline; a half black triangle indicates P <5% for two tests from baseline; and a black triangle reports P <5% comparison of three consecutive tests P <5% from baseline. The GPA will compare identical test strategies, such as SITA FAST with SITA FAST, or SITA Standard with SITA Standard, but cannot intermix those studies. So it is imperative the office use the same testing strategy from test to test.

OCT RNFL Analysis

The Cirrus OCT matches blood vessels of the optic nerve and other landmarks to achieve registration from one test to another, allowing serial comparison of RNFL images.

Like the HFA, the OCT employs a GPA that can aid in the identification of glaucomatous progression through RNFL thickness event and trend analysis. Event analysis assesses change from baseline compared to expected variability. If change is outside the range of expected variability, it is identified as progression. Trend analysis looks at the rate of change over time, using linear regression to determine rate of change. At least three tests are required (the first two are baseline) to generate change data.

The following two patients who received treatment at our office illustrate how ophthalmologists can use these modalities in monitoring glaucomatous progression.

Case History One (RB)

RB is 86-year-old woman with COAG, s/p left filtering procedure. She is taking Travatan-Z (travoprost 0.4%, Alcon) in the right eye and artificial tears in both eyes. Intraocular pressures are 17 mm Hg OD and 10 mm Hg OS. Pressures in the right eye had been higher over the past few visits.

In the right eye, the HFA GPA single-field analysis (Figure 1) showed a superior nasal visual field loss with possible progression. The probability analysis showed P <5% for="" two="" consecutive="" tests="" from="" baseline="" for="" 3="" points="" (indicated="" by="" half-filled="">

Figure 1. Guided progression analysis showed a superior nasal visual field loss with possible progression. The half-filled triangles indicate the probability analysis showed P < 5% for two consecutive tests from baseline.

GPA of RNFL testing OD (Figure 2) showed an evolving bundle defect in the inferior-temporal quadrant. The location of the RNFL defect is consistent with the superior nasal visual field defect.

Figure 2. Guided progression analysis of RNFL testing in the right eye showed an evolving bundle defect in the inferior-temporal quadrant consistent with the superior nasal visual field defect.

In the left eye, HFA GPA summary (Figure 3) mirrored the patient's clinical course. From 2004 to 2005, the field dramatically worsened, necessitating filtering surgery in 2005. Since her surgery, the field has remained stable, as the VFI chart shows.

Figure 3. In the left eye, the RNFL GPA summary mirrored the patient's clinical course, which has remained stable since filtering surgery in 2005.

Case History Two (PF)

The patient is an 80-year-old bilateral pseudophake with COAG. Visual acuity is 20/20 in both eyes. IOPs have been well maintained on Lumigan 0.1% (bimatoprost, Allergan) and Trusopt (dorzolamide, Merck).

Over the past six years, both the RNFL GPA and the HFA GPA have shown no changes from baseline OU.

Review of the single-field GPA in the right eye (Figure 4) confirmed no progression. The printout presented a probability analysis based upon comparison with the baseline studies.

Figure 4. Review of the single-field GPA in the right eye confirmed no progression, with the printout showing a probability analysis based upon comparison with the baseline studies.

The GPA RNFL (Figure 5) in the right eye showed no RNFL progression.

Figure 5. The GPA RNFL in the right eye showed no RNFL progression.

Discussion of Cases

In the first case history, the HFA GPA found possible progression in the superior-temporal quadrant, and RNFL GPA showed nerve fiber bundle thinning in corresponding inferior nasal bundle. With these findings in hand and an up drift in the patient's IOP readings, I prescribed adjunctive therapy.

In case two, analyses of both GPA modalities confirmed that no progression had occurred. My review of the tests took about a minute. I showed the printouts to the patient, who was also quickly able to ascertain that her condition was stable.

A Matter of Routine

Every physician will develop his or her own routine in terms of how often to utilize various tests. Insurance reimbursement may come into play in determining how many studies per year are performed. In my practice, I find the additional information saves significant chair time and enhances the patient's experience. Demystifying the progression analysis decision-making process by showing the patient his or her test results fosters confidence in my care.

However, guided progression analysis of visual fields and RNFL findings in monitoring for progression are not the be-all and end-all. Ophthalmologists must still look at the optic nerve head periodically for cupping changes. I utilize stereo photography, which I project into my exam rooms through our electronic medical records. I do stereo analysis of the optic disk when patients are dilated, about once or twice a year. With my photography technique, stereo photographs underestimate the degree of cupping compared to my 90 D slit lamp examination. I take this into account if I'm comparing the 90 D exam to the photography.

Aside from whether or not progression has occurred, there are other reasons why changes in therapy might be needed — insurance plan mandates, medication side effects or costs, and up drifts in pressure above target ranges being the most common.

Ophthalmologists with sizable numbers of glaucoma patients should consider incorporating progression analysis programs into their office routine. OM

Lawrence Stone, MD, is in private practice in Chicago and a founding partner of Stone Eye Center LLC. He has written and lectured extensively on the topic of early glaucoma detection. He has no relevant disclosures to report. Matin Babaev served a summer internship with Dr. Stone.