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Top-Ten from the Second Meeting of the Optometric Glaucoma Society
December 3, 2003, Dallas, Texas, USA
Mike Patella and Murray Fingeret
The 2003 meeting of the OGS was convened in honor of Anders Heijl. Lecturers included Heijl, Paul Palmberg, Richard Parrish, Thom Freddo, Chris Johnson, William Swanson, Ron Harwerth, Shaban Demirel, Mitchell Dul, Leo Semes, Robert Feldmann, Murray Fingeret, and Mike Patella. Special guest was John Lynn.
Highlights were as follows:
- Aqueous flare associated with medications suppressing aqueous inflow may not result from breakdown of the blood-aqueous barrier as has been assumed, but instead may occur through a physiological concentration effect. It may be useful to make clinical distinctions between flare that is pathological versus flare that is physiological. Proteins delivered to the iris root and the ciliary body band by this shunt pathway may contribute to aqueous outflow resistance.
- In the EMGT Study, the average glaucoma patient was approximately 70 years old at the time of diagnosis. With a remaining life expectancy of 12 years, he/she would on average lose 4.2 dB during his/her remaining lifetime (if progression is linear). This suggests that the average newly-diagnosed 70-year-old patient would not be expected ever to develop visual impairment unless the visual field at diagnosis showed an MD of »-10 dB or worse in the better eye. Nevertheless, an important minority of EMGT patients progressed very quickly, with significant and reproducible progression being noted in as little as six months. This corresponded to perimetric losses of 3.8 dB/year. In this scenario a patient could progress from mild to severe damage within four years, suggesting that it may be beneficial to perform more intensive follow-up testing of newly diagnosed patients in the first one to two years of therapy. If stability is noted, then the rate of follow-up testing might be significantly reduced relative to current practice.
- In the EMGT Study, progression was more common in patients with higher IOP, in older patients, in patients with more advanced baseline damage, and in individuals with exfoliation glaucoma.
- Zippy Estimation of Sequential Thresholds (ZEST) is an accurate, efficient, and reproducible threshold test strategy which is used with the recently-introduced FDT Matrix perimeter. ZEST has greater consistency of testing time, irrespective of visual field status. In order to document glaucomatous progression, more sensitive tests with lower variability are needed.
- The Glaucoma Progression Analysis (GPA) tool highlights visual field changes from baseline that exceed the test-retest variability empirically found in a large clinical sample of glaucoma patients. Expected variability strongly depends upon overall visual field status, test point location, and local defect depth.
- There are few studies that have looked at the impact of glaucoma visual impairment and its effect over time. Additional studies are needed to understand the risk of blindness due to glaucoma.
- Untreated OHTS patients with both corneal thicknesses in the lower tertile, and either a higher range of uncorrected Goldmann IOP (>26 mmHg) or a larger vertical C/D, had a five-year progression risk of 22-36%. This suggests that, in these categories, the number needed to treat over such a follow-up period could be as low as three to five, assuming highly effective treatment. Ocular hypertensive patients should usually participate in any decision to treat or not to treat, especially in high-risk categories.
- Plots of functional and structural losses on equal scales suggest that functional loss occurs at least as soon as structural loss in early glaucoma.
- In macular perimetry of patients with advanced glaucoma, diffuse loss and test-retest variability were quite similar for both Full Threshold and SITA algorithms. Both pupillary dilation and the use of a size V stimulus can reduce perimetric test-retest variability in macular test points that have low threshold sensitivity.
- Glaucomatous neural losses are predictable from visual sensitivity measurements by clinical perimetry in both monkeys and patients, although the variance of the structure-function relationship is larger in patients than in monkeys. The observed differences between experimental and clinical glaucoma suggests that the reduced precision in patients is related to difficulties in obtaining postmortem perimetry data and retinal tissue rather than the fundamental structure-function relationship.
