When the IOP is under good control on only one, or sometimes two, well-tolerated topical medications, and glaucomatous damage is mild, most surgeons prefer a cataract extraction alone. IOP during the cataract surgery may fluctuate, but it usually stays within physiologic levels, and this fluctuation may be lessened by using an anterior chamber maintainer (10).
However, cataract extraction with a posterior chamber intraocular lens (PC IOL) implantation can be associated with a significant IOP rise during the early postoperative course in patients with preexisting glaucoma, especially with older extracapsular techniques (11,12,13,14,15,16), or when viscoelastic is not removed from the eye completely. Although outflow facility seems to improve after phacoemulsification (17), the IOP can still be significantly elevated within the first 24 hours, and possibly the highest level of IOP may occur within 2 hours postoperatively (18). After extracapsular cataract extraction (ECCE) (13) or phacoemulsification (17) with PC IOL implantation in patients with glaucoma, more than half may have IOP greater than 25 mm Hg, or even 35 mm Hg (19), indicating the need for close monitoring and prophylactic medical treatment to prevent postoperative IOP spikes.
When ECCE has been compared to phacoemulsification, a significant increase in IOP during the first 5 to 7 hours after surgery has been found in both groups, with better IOP control seen after phacoemulsification using sutureless scleral tunnel (16). Using an anterior chamber maintainer instead of viscoelastic for lens implantation has been associated with a lower IOP on the first postoperative day (20). Although the pressure can usually be brought under control within the first few postoperative days, patients with advanced glaucomatous damage before surgery may suffer additional, irreversible loss of vision during this time. Therefore, moderate-to-advanced glaucomatous optic atrophy and visual field loss may argue against cataract surgery alone, despite the preoperative level of IOP, although the risk may be less with phacoemulsification techniques and thorough removal of viscoelastic from the eye.
Conversely, one study found that an IOP spike greater than 30 mm Hg was almost 3 times more common in eyes that had a combined procedure than in the eyes that had phacoemulsification alone (21).
Several studies have also looked at the IOP course in the intermediate and late postoperative periods following cataract surgery in patients with preexisting glaucoma. In general, the extracapsular techniques with PC IOLs were shown to be tolerated better than intracapsular procedures (12), although postoperative glaucoma control could be a problem with either technique. During the first 2 to 4 months after extracapsular surgery, many glaucoma patients will have pressures above the preoperative baseline, whereas the IOP in others may be unchanged or even improved (22,23,24). Patients with preexisting open-angle glaucoma were found to have a small reduction in mean IOP and to require fewer medications 1 to 2 years after extracapsular cataract surgery (25,26,27). A similar trend has been seen in glaucoma patients following phacoemulsification and IOL implantation (28,29,30), in patients with pseudoexfoliation (31), and in patients without glaucoma (32).
The reasons for IOP lowering after phacoemulsification are not clear, but one proposed hypothesis suggests an induction of a potential stress response in the trabecular meshwork by the ultrasound (33). Anterior chamber depth increased after cataract extraction with PC IOL implantation in patients with angle closure glaucoma and open-angle glaucoma (34), and IOP was well controlled in most cases (35). However, this trend generally reverses with time (36). Cataract surgery alone should not be relied upon as a means of treating uncontrolled glaucoma. However, as stated, when the IOP is well controlled on a low dose of well-tolerated medication with mild glaucomatous damage, cataract surgery alone, especially small-incision phacoemulsification with PC IOL implantation, may be a reasonable choice.
