Progress in glaucoma: early detection, new treatments, less blindness.

“Eyes that have a field defect at the start of treatment are more likely to progress to blindness than are eyes in which treatment is started. . . with no field defect.” Morton Grant’s observations on the long-term outcome of glaucoma, published in 1982, have been confirmed by Chen in the reprinted section. Similar to a study by Hattenhauer which found that patients with damage had a higher probability of becoming blind than patients with high pressures but no damage, Chen found that patients with worse initial visual field loss were significantly more likely to develop blindness. Chen found a lower probability of blindness than the previous study, and points out that the advent of computerized perimetry has resulted in finding visual field defects earlier than the manual techniques of the Goldmann or tangent screen perimeters. Chen used the Humphrey automated perimeter, including the sensitive techniques of corrected pattern standard deviation (CPSD) and the Glaucoma Hemifield Test. These detect scotomas earlier than the arcuate scotomas or nasal steps characteristic of manual perimetry used by Grant and by Hattenhauer. Progress continues, however. Even since Chen’s cohort of patients was diagnosed, newer, more sensitive techniques have become available. Short wavelength automated perimetry (SWAP) finds defects sooner than the standard white-onwhite perimetry used by Chen. In the foreseeable future, even more sensitive techniques may become standard of care, such as quantitative analysis of the optic disc and retinal nerve fiber layer. In keeping with earlier detection of glaucomatous damage, Chen reports lower rates of blindness in those with glaucomatous damage at the time of diagnosis than Hattenhauer. Of interest, Chen’s rate was similar to the group treated for ocular hypertensives in Hattenhauer’s study. Differences in study design make exact comparisons difficult: Chen studied patients from a University glaucoma specialty practice; unlike the Hattenhauer study, which was community-based and not confined to glaucoma specialists. Comparison of blindness rates from these two studies with other reports of blindness from glaucoma must keep in mind differing definitions of blindness: the American definition includes visual field loss and central acuity;while other studies use the World Health Organization criteria, which uses only visual acuity. In addition to earlier detection of glaucoma, improved treatments have probably decreased the probability of blindness. Newer medications, such as the prostaglandin analogs, are not only more effective in lowering intraocular pressure, but also have fewer side effects. This improved therapeutic index makes it likely that the medications will be used sooner and more often in patients already under treatment. Ultimately more patients with “borderline” disease may be started on treatment when the treatment has few side effects. Chen’s finding that some glaucoma patients became blind despite treatment, especially those with pre-existing damage at the time of diagnosis, mirror several recent studies. Both the Collaborative Initial Glaucoma Treatment Study (CIGTS) and the Advanced Glaucoma Intervention Study (AGIS) studied patients with glaucomatous damage. CIGTS found 11% of patients progressed after 5 years, while AGIS found an 18% probability of progression after 5 years. In contrast, the Ocular Hypertension Treatment Study, which enrolled patients without damage, found 4% of patients to progress after 5 years. Common to all of these studies is the fact that some patients with glaucoma remain stable while others, receiving similar treatment and pressure lowering, progress. This points out the role of the ophthalmologist, to “find and fix”: find the subgroup of patients progressing despite treatment; and, fix the situation by lowering the intraocular pressure enough to halt progression. If glaucomatous progression is not responded to by adequate pressure lowering, progression can continue. Chen honestly reports that the group going blind did not have significantly lower mean pressures on treatment than the group retaining vision. As technology advances, previous studies can appear outdated. Although the OHTS used standard Humphrey perimetry to confirm normal visual fields upon entry to the study, testing of some of the same patients with the newer SWAP technique of perimetry found 20% to have abnormal visual fields (CA Johnson; Invest Ophthalmol Vis Sci 2002; (ARVO suppl):86) The trabeculectomy technique used by both the CIGITS and AGIS studies was standard of care at the time, however, more recent studies using antifibrotic agents find increased success rates and lower intraocular pressures. Corneal thickness was not measured in Chen’s study, CIGTS, AGIS, nor the Collaborative Normal Supported in part by an unrestricted grant from Research to Prevent Blindness, Inc, New York, New York.