Collaborative Initial Glaucoma Treatment Study: Results

The Collaborative Initial Glaucoma Treatment Study (CIGTS) asked a simple question: in newly diagnosed open-angle glaucoma, should treatment start with drops or with trabeculectomy?

It randomized 607 patients to either approach and followed them for up to nine years.

It measured the field, the acuity, and the quality of life (see the references).

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Design of the Collaborative Initial Glaucoma Treatment Study

Patients were aged 25 to 75 years with newly diagnosed open-angle glaucoma and a field defect in at least one eye.

One group received stepped medical therapy, starting with one drug and adding more, with laser and surgery as later steps.

Also, the other group had a trabeculectomy at the start, with antimetabolites allowed.

Collaborative Initial Glaucoma Treatment Study: Pressure Results

Surgery lowered the pressure more than drops, with average values of about 14 to 15 mmHg in the surgery group against 17 to 18 mmHg in the medication group over the follow-up period (see the references).

The pressure difference was stable, and both groups reached a level considered safe in most patients.

Visual Field Results

Over nine years, field loss was small and the same in both groups on average (see the references).

In addition, patients with more advanced loss at baseline had a faster loss, and black participants and those with diabetes had more progression in the medical arm.

Collaborative Initial Glaucoma Treatment Study: Acuity, Cataract and Symptoms

• Cataract developed more often after surgery
• Local eye symptoms were higher in the first years after surgery
• Quality of life scores were similar in the two groups in the long term
• Visual acuity loss was small and no larger in one arm than the other in later analyses

The surgery arm had complications such as bleb problems, and the drug arm had side effects and the burden of daily drops.

What the Findings Mean

Both approaches protect the field in early to moderate disease, and the choice can reflect the patient’s priorities, the risk of surgery, and the ability to use drops.

Surgery has a stronger pressure effect, which can matter for patients with high pressures or advanced disease at diagnosis.

Collaborative Initial Glaucoma Treatment Study: Limits of the Study

• It ran before laser trabeculoplasty and minimally invasive surgery became common first steps
• Drug regimens differ from current prostaglandin-based practice (see primary open-angle glaucoma)
• Patients with very advanced glaucoma were excluded
• Quality of life tools were limited

Practical Use

Start most patients with drops or laser, and reserve primary surgery for those with advanced disease, very high pressures, or a poor ability to use drops.

Discuss the lifelong aspect of treatment, and review the target when the field changes.

Collaborative Initial Glaucoma Treatment Study: An Example Case

A 48-year-old man with newly diagnosed glaucoma has a pressure of 34 mmHg and moderate field loss in both eyes.

After a discussion of the CIGTS findings, which showed a larger pressure drop with surgery and similar field outcomes, he chooses a trabeculectomy in the worse eye, because he works long shifts and has trouble keeping up with drops.

The pressure drops to 11 mmHg, and he later needs cataract surgery, as the study would predict.

How to Explain the Study

Explain that two sensible ways to start were compared, that the fields were similar after years, and that surgery gave a lower pressure but more early discomfort and cataract.

Present the options with their pros and cons and let the patient choose.

Questions Patients Ask

• Which is safer? Drops have fewer immediate risks, and surgery has more early risks.
• Will I need drops after surgery? Some patients do, and many do not.
• Does surgery cure glaucoma? No, it lowers pressure and the disease still needs monitoring.

What Came After

Selective laser trabeculoplasty and minimally invasive glaucoma surgery have been added as first steps, and the LiGHT trial found laser to be a good first treatment.

Patients with advanced glaucoma or those with poor adherence may still be offered early surgery.

Key Points to Remember

Surgery gave lower pressures, medicine gave fewer early complications, and fields were similar after years.

The quality of life scores were close, with more eye symptoms early after surgery.

Cataract was more frequent after trabeculectomy, and the choice should reflect the patient’s job, health, and wishes.

Patients with severe disease at diagnosis need individual planning.

Use in Clinical Practice

Ask about work, travel, and the ability to instill drops before choosing the first step, and record the discussion in the chart.

Revisit the choice at each visit, since circumstances and the stage of disease change.

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References

1. Musch DC, Gillespie BW, Lichter PR, Niziol LM, Janz NK. Visual field progression in the Collaborative Initial Glaucoma Treatment Study: the impact of treatment and other baseline factors. Ophthalmology. 2009;116:200-207.
2. Lichter PR, Musch DC, Gillespie BW, et al. Interim clinical outcomes in the Collaborative Initial Glaucoma Treatment Study comparing initial treatment randomized to medications or surgery. Ophthalmology. 2001;108:1943-1953.
3. Musch DC, Lichter PR, Guire KE, Standardi CL. The Collaborative Initial Glaucoma Treatment Study: study design, methods, and baseline characteristics of enrolled patients. Ophthalmology. 1999;106:653-662.
4. American Academy of Ophthalmology. Basic and Clinical Science Course, Section 10: Glaucoma. AAO; current edition.