Case Report: Glaucoma Progression Analysis

Optometric Management, Jul 2006 by Fingeret, Murray

This 77-year-old African American man was diagnosed with primary open-angle glaucoma in 1996. At the time of diagnosis, intraocular pressures (IOPs) in each eye were elevated (maximum IOP OD 28 mm Hg; OS 25 mm Hg) with damage confined to the right eye. Corneal thickness measurements were 525 µm OD, 523 µm OS, and gonioscopy revealed wide open angles OU.

The patient was prescribed latanoprost (Xalatan) in each eye once daily at bedtime, which lowered his IOPs to approximately 16 mm Hg to 18 mm Hg in each eye. The initial visual field (9/25/1996) for the right eye showed an inferior partial arcuate scotoma with excellent reliability (Figure 1A), while the left field showed mild diffuse loss (Figure 1B).

The patient was lost to follow-up for 2 years, during which time he did not use his glaucoma medications. Therapy was reinstituted and a field performed on 9/30/1998, which showed field loss in the right eye had increased in size (Figure 1A) with a full inferior arcuate scotoma now apparent. The left eye's field was considered within normal limits.

The patient was then followed with fields performed annually, with the mean deviations (MDs) graphed on the bottom of the first page (Figure 1A, 1B). In Figure 1A, two OD baseline fields are plotted using the Glaucoma Progression Analysis (GPA). Follow-up fields can then be compared to an average of the two baseline fields. Note the MD regression analysis of all the fields at the bottom of the first page. All fields show reliability indices that are well within acceptable limits. The second field (1998) shows fewer significant points on the total deviation maps and reduced MD loss relative to the first field, probably due to learning effects.

The patient was followed over time, with the IOPs remaining stable in the mid-to-high teens using latanoprost only. Looking at the progression analysis plot for the right eye (far right side of Figure 2A), for the 1999 field, three points are flagged with an X, which indicates these points are so deeply damaged that the significance of further change could not be determined. Also, two points are flagged with an open triangle, indicating they have become significantly worse relative to baseline.

The progression analysis plot for the right field performed in 2000 showed one point had worsened on two consecutive fields (as seen by the half-filled triangle) and two points had worsened on this field only. The 2001 field shows that the same point that had worsened in 2000 has continued to show change (noted now on two consecutive fields). Also, for this field, several additional points are flagged as getting worse for the first time. Looking at the regression analysis slope for the right eye (lower part of Figure 1A), the points are moving downward indicating that the MD is getting worse. Looking at the individual test results, the MD has changed from -9.24 dB in 1996 to -11.88 in 2001. This trend, indicating worsening, cannot be explained on the basis of developing cataracts as the visual acuities and lens assessment were unchanged.

The 2002 field, again reliable, shows progression is continuing although the MD is slightly improved (Figure 3A). Five points in the lower field have now shown significant change in two successive fields, as compared to the baseline field, and the message "Possible Progression" is seen on the printout. The last field of this set for the right eye from 2003, confirms progression. Five points have shown significant change three fields in a row, and one point has shown significant change in two consecutive fields. The message on the field reads "Likely Progression," as based upon criteria developed for the Early Manifest Glaucoma Trial.

Of particular interest in this series of fields in the right eye is that with visual inspection, the number of points flagged does not appear to have changed from prior fields. What has changed is that the defect, while similar in size going back to 2001, has gotten denser or deeper. This is why the progression analysis symbols are flagged.

The left eye's visual fields remained relatively full until 2002, at which time several points are flagged as getting worse for the first time. The field repeated in 2003 now shows the hallmarks of a superior partial arcuate scotoma. Only one point flagged in 2002 is repeatable although several other points are now flagged. The suspicion is that the left field is getting worse. This field needs to be repeated to confirm the change.

In summary, visual field progression has been confirmed for the right eye, with suspicious loss in the left eye. The therapeutic regimen for this patient needs to be reevaluated. The single field printout for the last field in the series (2003) (Figures 4A and B) summarizes the data, alerting the clinician to the number of fields that have been performed along with the dates. The box on the right side of the printout using the GPA symbols shows that in the right eye, several points have gotten progressively worse, and that "Likely Progression" has occurred. The left single field analysis (Figure 4B) shows superior partial arcuate loss, possibly getting worse.