In this issue of the Journal , Drs. Slabaugh, Bojikian, Moore, and Chen report the effects of phacoemulsification cataract surgery on intraocular pressure in their patients with medically-controlled open-angle glaucoma. Ophthalmologists are keenly interested in this topic for many reasons. Cataract and glaucoma are leading causes of global blindness. Also, these conditions are interrelated in several ways that impact clinical management. Cataract may affect the monitoring of glaucoma progression. Patients with glaucoma may have risk factors for cataract surgery, including small pupil and weak zonules. Medical and surgical therapy for glaucoma may influence cataract progression. Moreover, cataract surgery may alter intraocular pressure and, thus, influence the management of glaucoma.

Why do we need more information about this topic? After all, evidence-based analysis and reviews about the topic have appeared. Numerous articles have been published about the topic of coexisting cataract and glaucoma, dating back to the use of intracapsular and extracapsular cataract surgery. Despite prior reports, new information based on well-characterized patients (such as those described by Slabaugh et al) can provide new insights about the topic. In addition, clinical management of cataract and glaucoma has continued to change as techniques evolve and improve. The pace of innovation and improvement of cataract surgical techniques has been steady for decades. For this reason, the topic of management of cataract and glaucoma is a moving target, which requires updated information at intervals over time.

In their study, Slabaugh and colleagues found a modest reduction of intraocular pressure after phacoemulsification in glaucoma patients, decreasing on average by 1.8 mm Hg at 1 year after surgery, from a preoperative mean intraocular pressure of 16.3 ± 3.6 mm Hg. Other studies have found varying reductions of intraocular pressure after cataract surgery in glaucoma patients. An explanation for at least some of this variability of results is described by Slabaugh and colleagues: a higher preoperative intraocular pressure was associated with a greater reduction of intraocular pressure. According to their results, the intraocular-pressure–lowering response after cataract surgery varies, in part, with the magnitude of the preoperative intraocular pressure. Similarly, a retrospective review of 588 eyes treated with phacoemulsification and intraocular lens implantation found an association between greater postoperative intraocular pressure reduction and higher presurgical intraocular pressure.

For decades, treatment by cataract surgery alone has been recommended for patients with cataract, mild glaucoma damage, and well-controlled intraocular pressure. In this setting, any reduction of intraocular pressure is an incidental benefit of cataract surgery, but it is not likely to have an important role in the management of glaucoma for these patients. In these patients, prior cataract surgery does not interfere with glaucoma surgery performed at a later time. Current cataract surgical techniques with clear cornea incisions spare the conjunctiva from surgical trauma and scarring, which does not interfere with subsequent glaucoma surgical procedures.

Patients with narrow angles or angle-closure glaucoma may experience a pronounced reduction of intraocular pressure after phacoemulsification cataract surgery. In patients with angle-closure glaucoma treated with phacoemulsification cataract surgery, long-term reduction of intraocular pressure and decreased need for pressure-lowering medications may be achieved, likely due to changes in the anterior chamber angle occurring after phacoemulsification of the lens. Although greater reduction of intraocular pressure was observed in patients with deeper anterior chamber angle depth in the study by Slabaugh and colleagues, a potentially different effect in patients with narrow or closed angles would not have been identified because of the exclusion of such patients from this study.

Should cataract extraction by phacoemulsification be considered a therapeutic option for patients with coexisting cataract and glaucoma? The study by Slabaugh and colleagues provides enlightening information related to this question, which may make clinicians less sanguine about recommending phacoemulsification alone in their patients with open-angle glaucoma. In their patients with medically controlled open-angle glaucoma at 1 year after phacoemulsification surgery, 38% had worsening intraocular pressure control, including 24% who needed additional medications or laser treatments. In contrast, at 1 year after treatment of 801 patients with open-angle glaucoma or ocular hypertension by topical prostaglandin therapy, 9% of subjects were nonresponders, with less than 3 mm Hg reduction of intraocular pressure. In patients with open-angle glaucoma, 18% of patients required treatment with 1 additional medication at 1 year after selective laser trabeculoplasty, whereas less than 5% of patients in the Advanced Glaucoma Intervention Study (AGIS) trial met criteria for failure at 1 year after trabeculectomy as the first, second or third intervention. By this comparison, phacoemulsification cataract surgery appears to be less effective than conventional medical, laser or incisional surgical therapy for treatment of open-angle glaucoma.

When considering cataract surgery as “therapy” for glaucoma, the magnitude of the effect and the duration of the effect are considerations. Evidence-based analysis has shown an estimated 2 to 4 mm Hg reduction of intraocular pressure after cataract surgery alone, but strong evidence for sustained long-term pressure control was found only in patients who were treated with combined cataract extraction and trabeculectomy. Previous studies have shown that the reduction of intraocular pressure is greatest at 1 year after cataract surgery, and thereafter the intraocular pressure tends to return to baseline levels over several years. Interpretation of these results has varied, with 1 study suggesting that phacoemulsification may help to prevent and treat glaucoma, and another evidence-based review concluding that there is no strong evidence to suggest that lens extraction represents a clinically useful treatment for primary open-angle glaucoma.

For many years, patients with cataract and advanced glaucomatous optic nerve damage or visual field loss have been considered candidates for combined surgery rather than cataract surgery alone. The concept has been that patients with advanced glaucoma may be at risk for further damage with marked elevation of the intraocular pressure during the perioperative or the late postoperative period. An evidence-based review in 2002 found insufficient evidence to determine the short-term impact of phacoemulsification on intraocular pressure in glaucoma patients. A more recent study of 310 eyes found intraocular pressure greater than 30 mm Hg on the first postoperative day in 8.1% of normal eyes and 15.6% of eyes with glaucoma. When evaluating patients with advanced glaucoma damage, surgeons may be encouraged to recommend cataract surgery alone over combined cataract surgery and trabeculectomy if they perceive cataract surgery to be safe and to have a low likelihood of transient or sustained elevation of intraocular pressure. The choice of combined vs cataract surgery alone is controversial for patients with advanced glaucoma, but the study by Slabaugh and colleagues did not report intraocular pressure measurements during the perioperative period and does not guide clinicians with new information concerning this debate.

Congratulations to Dr. Slabaugh and colleagues for providing new evidence about the modest reduction of intraocular pressure after phacoemulsification cataract surgery in medically-controlled open-angle glaucoma patients. Their study provides useful information to help interpret the variability of reduction of intraocular pressure that has been documented in previous studies of patients with coexisting cataract and glaucoma who have been treated with phacoemulsification cataract extraction. Also, clinicians will be interested in their results as they contemplate the therapeutic benefit or lack thereof after phacoemulsification cataract surgery in their patients with glaucoma.