Early glaucoma intervention delays progression

By Sean Henahan

MALMÖ - The long-awaited results of the Early Manifest Glaucoma Trial (EMGT) at last confirm that treatments targeting intraocular pressure (IOP) reduction delay the disease's progression - at least for some patients.

Beginning in 1993, the EMGT randomised 255 patients from Malmö and Helsingborg in Sweden who were in the early stages of open-angle glaucoma to either no initial treatment or treatment with laser trabeculectomy and IOP-lowering medication (Betaxolol).

The active treatment group saw an average 25% drop in IOP. Long-term follow-up showed a marked advantage for treated patients, who went an average of 66 months before developing signs of increased glaucomatous damage compared to the control group which showed signs of advancing disease after an average of 48 months.
Progression was also less frequent in the treatment group with 45% developing signs of glaucoma compared to 62% of untreated patients.

The patients, who had a median age of 68 years, were examined every three months for an average of six years. These comprehensive examinations included Humphrey Full Threshold 30-2 visual field tests and tonometry at every visit, and optic disc photography every six months.
Patients in the control group whose glaucoma progressed were immediately offered treatment.

The treatment effects were seen in all age groups and in both high- and normal-tension glaucoma, and among eyes with greater or less amounts of visual field loss, reported Anders Heijl MD, PhD in the journal Archives of Ophthalmology.
"These results strongly support the body of evidence suggesting that immediate treatment of early stage open-angle glaucoma will slow the disease progression," said Paul Sieving MD, PhD, Director of the National Eye Institute (NEI), co-sponsor of the study.

All patients in the study had newly detected, previously untreated open-angle glaucoma. Most were recruited from a population-based screening of more than 44,000 elderly citizens. Patients with mean IOP above 30 mm Hg were specifically excluded from the study.

Other exclusion criteria included advanced visual field defects, visual acuity worse than 20/40 or any condition which would preclude perimetric evaluation or optic disc photography.

"The EMGT data has important clinical implications. The results not only confirm previous beliefs that IOP reduction is beneficial but also provide new knowledge on rates of disease progression, with and without treatment, in patients with various characteristics.

"Our results therefore strengthen the rationale for current standard clinical management," the researchers said.
Dr Heijl noted that inter-patient variability was very large. Thus, as many as 30% of treated patients progress after only four years and some untreated patients remained stable throughout the study.

"The study findings support the medical community's growing contention that glaucoma treatment should be tailored to the individual needs of the patient. One option could include no initial treatment, but subsequent treatment if the disease progresses.
"Many glaucoma medicines have side effects, so the decision not to treat the disease in its early stage - but closely monitor patients - can postpone or obviate the need for medications in selected patients," Dr Heijl said.
Side effects associated with treatment included redness, dryness, erythema and blurred vision.

Data monitoring revealed a surprise, a considerably higher rate of nuclear opacities of LOCS II Grade II or above in the treatment group.
Six patients in the treatment group required cataract surgery compared to two in the control group. Glaucoma filtering surgery and topical irreversible cholinesterase inhibitors have both been associated with an increased cataract incidence in previous studies.

The EMGT results come not long after the results of the Ocular Hypertension Treatment Study (OHTS), another landmark glaucoma trial. That five-year, 22-centre study enrolled 1,636 patients with elevated intraocular pressure (IOP) but no signs of optic nerve damage.

Half of the patients followed a daily drop regimen while the other half received no treatment other than regular monitoring. The eye drop regimens reduced the development of open-angle glaucoma by more than 50% compared to controls.
"The EMGT was designed to answer conclusively the question whether treatment actually made a difference.

"Coming on the heels of other clinical trial reports, the EMGT results can be seen as part of a significant evolution in our knowledge of glaucoma management," wrote Paul R. Lichter MD, University of Michigan, in an accompanying editorial. The complete EMGT report (and Dr Lichter's commentary) appear in the Archives of Ophthalmology (2002;120: 1268-1279; 1371-1372). The complete text is available online at archophthalmol.com.

 

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