Cataract Surgery in Patients with Glaucoma: Open Angle, Narrow Angles, and What to Expect

Glaucoma and cataract frequently coexist in older patients. Both are common after the age of 60 and both affect vision, often making it difficult to know how much each condition is contributing to a patient's visual symptoms. The surgical management of cataract in a patient with glaucoma raises several specific questions: what visual improvement can be expected given the degree of glaucomatous damage, will cataract surgery help lower intraocular pressure, which intraocular lens is most appropriate, and how does a history of long-term glaucoma drops affect the surgical planning? For patients with narrow angles or primary angle closure, cataract removal also has important implications for angle anatomy and the risk of future angle closure events. This post addresses each of these questions with reference to the published evidence. For a general overview of cataract surgery in Melbourne covering what to expect from the process and how to evaluate a surgeon, see our companion guide.

Does cataract surgery lower intraocular pressure in open angle glaucoma?

Phacoemulsification has a measurable intraocular pressure (IOP) lowering effect in patients with open angle glaucoma. This effect is mediated by several mechanisms including widening of the anterior chamber angle when the relatively thick cataractous lens is replaced with a thin intraocular lens, traction on the ciliary body via the zonules altering aqueous dynamics, and changes in trabecular meshwork function related to the surgical inflammatory response.

A systematic review and meta-analysis published in the Journal of Glaucoma in August 2024 found that cataract surgery meaningfully lowers IOP in patients with primary open angle glaucoma, exfoliative glaucoma, and ocular hypertension at 12 months after surgery. The review noted that the full IOP-lowering effect of phacoemulsification is partially masked by concurrent topical glaucoma medications and that the true effect may be greater than measured values suggest (Journal of Glaucoma 2024;33(8):576-586. doi: 10.1097/IJG.0000000000002386).

A prospective multicentre Australian study published in PubMed following 171 POAG patients over a mean of 4.8 years found that cataract surgery reduced mean IOP by 2.22 mmHg, with 34 percent of eyes achieving a reduction of at least 3 mmHg. This was a real-world study with matched controls providing high-quality evidence for the IOP-lowering effect in an Australian population (PubMed 32031310).

A 2023 prospective study comparing IOP changes in normotensive and open angle glaucoma patients following phacoemulsification found that at six months postoperatively, the IOP reduction was significantly greater in eyes with open angle glaucoma compared with normotensive controls (5.3 mmHg versus 1.6 mmHg respectively), confirming that glaucomatous eyes benefit more from the IOP-lowering effect of cataract surgery than eyes without glaucoma (PMC10083030).

The clinical implication is that cataract surgery may provide a modest but meaningful IOP reduction that supplements medical management in patients with open angle glaucoma. It is not a substitute for glaucoma treatment but may reduce the medication burden or improve IOP control in some patients.

Visual outcomes: how glaucoma severity affects the expected result

The visual outcome after cataract surgery in glaucoma patients depends critically on the degree of existing glaucomatous optic nerve damage. Removing the cataract improves the optical quality of the image reaching the retina, but the optic nerve's ability to transmit that signal to the brain is limited by the extent of glaucomatous damage. A patient with significant visual field loss from glaucoma will not recover that field through cataract surgery.

Mild glaucoma with minimal field loss: patients in this group can expect visual outcomes comparable to patients without glaucoma. The cataract is likely the primary cause of their visual symptoms and removal provides significant improvement.

Moderate glaucoma with established field defects: visual improvement after cataract surgery is expected but the final visual acuity is limited by the optic nerve damage. Patients should understand that cataract removal will improve image clarity and potentially measured visual acuity, but established field defects will remain. An improvement in the patient's functional vision may be meaningful even if the measured visual acuity change is modest.

Advanced glaucoma with severe field loss or significant optic nerve damage: expectations must be set very carefully. If the central field is preserved, cataract removal may provide meaningful improvement in visual acuity. If the central field is involved, the improvement from cataract surgery may be minimal. Electrophysiological or potential acuity testing can help estimate likely visual benefit before proceeding.

Patients with advanced glaucoma must also understand that postoperative IOP spikes, which can occur in the first few days after cataract surgery, carry a higher risk of accelerating optic nerve damage. This is managed with careful perioperative IOP monitoring and appropriate prophylactic pressure-lowering treatment after surgery.

Glaucoma drops, preservative toxicity, and ocular surface disease

One of the most clinically important and underappreciated aspects of cataract surgery planning in glaucoma patients is the effect of long-term preserved glaucoma drops on the ocular surface and its implications for biometry accuracy.

Most topical glaucoma medications contain the preservative benzalkonium chloride (BAK). BAK exerts detergent and surfactant effects on cell membranes that are effective at maintaining sterility of the drop formulation but are toxic to the corneal epithelium, conjunctival goblet cells, and the tear film with prolonged chronic exposure. Studies have linked higher BAK concentrations and greater cumulative exposure to tear film instability, loss of goblet cells, disruption of the corneal epithelial barrier, and conjunctival inflammation. These effects are clinically significant in patients on multiple glaucoma drops or those who have been on preserved therapy for many years.

Ocular surface disease caused by preservative toxicity produces dry eye symptoms and corneal surface irregularity. This has a direct and clinically significant impact on the accuracy of biometry and IOL power calculation before cataract surgery. The corneal curvature measurement used in IOL power calculation is derived from the anterior corneal surface. An irregular or unstable tear film produces irregular and variable keratometry readings, leading to less accurate IOL power calculation and a higher risk of postoperative refractive surprise. A 2024 systematic review published in PMC confirmed that the tear film plays an important role in the optical quality of the cornea's refractive power and that interferometry assessing tear film stability is relevant to ensuring reliable IOL power calculation in patients with ocular surface disease (PMC12735008).

The practical implications for cataract surgery planning in glaucoma patients include:

Pre-operative ocular surface assessment is mandatory. Tear film break-up time, corneal staining, and goblet cell status should be assessed before biometry. Patients with significant OSD should have the surface treated before measurements are taken.

Switching to preservative-free glaucoma formulations before surgery improves measurement accuracy. Where preservative-free alternatives exist for the patient's current glaucoma medications, switching four to eight weeks before planned biometry allows the corneal surface to recover and produces more reliable measurements.

Multiple biometry measurements on different occasions should be taken in patients with significant OSD to assess reproducibility. Inconsistent keratometry readings signal an unstable tear film and unreliable measurements.

IOL power calculation targets should take the surface disease into account. In patients with significant corneal irregularity from preservative toxicity, targeting a slightly myopic outcome provides a buffer against refractive surprise.

IOL selection in patients with open angle glaucoma

The choice of intraocular lens in patients with open angle glaucoma requires careful consideration of the same contrast sensitivity issues that apply to patients with macular degeneration, with some additional glaucoma-specific factors.

Diffractive trifocal and multifocal lenses are relatively contraindicated in patients with significant glaucoma. Glaucoma causes characteristic loss of contrast sensitivity, particularly at mid and high spatial frequencies, before measurable loss of Snellen visual acuity. Diffractive IOLs further reduce contrast sensitivity by splitting light across multiple focal zones. The combination of glaucoma-related and diffractive-IOL-related contrast loss can produce poor functional vision even with adequate measured acuity, and the halos and glare from diffractive lenses are more noticeable and less neuroadaptable in an eye with glaucomatous contrast sensitivity loss.

The American Academy of Ophthalmology advises that multifocal and EDOF lenses are generally not recommended for patients with vision loss from glaucoma or other eye diseases. For a complete guide to IOL types and patient selection criteria, see our premium IOL guide Australia.

Monofocal lenses are the standard recommendation for patients with moderate or advanced glaucoma. A monofocal lens maximises optical efficiency and contrast at the chosen focal distance.

For patients with early mild glaucoma where contrast sensitivity is relatively preserved, a non-diffractive EDOF lens may be considered on an individual basis. The non-diffractive design avoids the contrast penalty of diffractive optics while providing extended intermediate range. This remains a nuanced decision requiring careful assessment of glaucoma severity and the patient's visual priorities.

Toric lenses for astigmatism correction are appropriate in glaucoma patients and do not carry the contrast sensitivity concerns of diffractive designs.

Occludable angles and primary angle closure: why cataract surgery is particularly beneficial

For patients with narrow angles, occludable angles, or primary angle closure disease, cataract surgery has a much more substantial and clinically important role than in open angle glaucoma. The anatomical basis for this is straightforward: the crystalline lens in angle closure eyes is relatively thick and anteriorly positioned, contributing to or causing the angle narrowing. Removing the lens and replacing it with a thin intraocular lens dramatically deepens the anterior chamber and widens the angle, often eliminating the angle closure mechanism entirely.

The evidence for IOP reduction after cataract surgery in angle closure disease is compelling and substantially greater than in open angle glaucoma. A review of evidence across the spectrum of angle closure disease found that phacoemulsification achieved a 13 percent IOP reduction in primary open angle glaucoma, versus approximately 30 percent IOP reduction and 53 percent decrease in the number of medications required in primary angle closure glaucoma. In acute angle closure, IOP reduction following cataract surgery was approximately 71 percent, with almost no need for postoperative medications.

A retrospective study of 55 eyes with primary angle closure published in PubMed found a statistically significant median reduction in IOP of 3 mmHg at 7.2 months after cataract extraction, with on average one less glaucoma medication required postoperatively. Patients with greater preoperative IOP and more extensive peripheral anterior synechiae achieved greater IOP reduction (PubMed 21623222).

The EAGLE trial, a prospective multicentre randomised trial comparing early cataract surgery with laser peripheral iridotomy and medications in primary angle closure, found that the cataract surgery group had significantly better outcomes including lower IOP, higher quality of life, and lower medication use over a period of up to 10 years. This trial established early cataract extraction as the preferred treatment for primary angle closure disease.

For patients with occludable angles who have a mild but visually symptomatic cataract, proceeding with cataract surgery is often the most logical management decision. Rather than performing a laser peripheral iridotomy as a temporising measure, removing the lens directly addresses the anatomical mechanism of angle closure.

Why cataract surgery does not eliminate the glaucoma risk entirely in angle closure eyes

While cataract surgery dramatically improves the angle anatomy in eyes with angle closure disease, it is important for patients to understand two specific limitations:

First, open angle glaucoma remains possible after cataract surgery. Cataract surgery addresses the angle closure component of the disease by widening the angle and eliminating pupillary block, but it does not protect against primary open angle glaucoma, normal tension glaucoma, or other forms of open angle disease. The trabecular meshwork function that determines the resistance to aqueous outflow in open angle glaucoma is unaffected by lens removal. Patients who have had cataract surgery for angle closure disease still require ongoing glaucoma monitoring.

Second, peripheral anterior synechiae (PAS) that formed during the angle closure process may cause permanent damage to the trabecular meshwork. PAS are areas where the iris has become adherent to the trabecular meshwork during episodes of angle closure, physically blocking aqueous outflow at those locations. When PAS formation is extensive, the damaged trabecular meshwork segments may continue to cause elevated IOP even after the angle has been widened by cataract surgery. The greater the extent of PAS formation before surgery, the more likely residual trabecular meshwork damage is to cause ongoing IOP elevation postoperatively. This is why early treatment of angle closure disease, before extensive PAS have formed, produces the most complete IOP normalisation after cataract surgery.

The important clinical message is that cataract surgery is an excellent and evidence-based treatment for angle closure disease that can dramatically improve IOP control and reduce medication burden. However it does not cure glaucoma, does not reverse existing optic nerve damage, and does not eliminate the need for ongoing glaucoma monitoring. Patients should understand that postoperative glaucoma surveillance remains necessary regardless of how well the angle anatomy improves.

GPs and optometrists referring patients with coexisting glaucoma and cataract can find referral information for optometrists on this site. For information on cataract surgery costs and Medicare rebates, see our cost guide.

Arranging an assessment

If you have been diagnosed with glaucoma or narrow angles and have been told you also have a cataract, a combined assessment by a surgeon experienced in both conditions is appropriate. The timing of cataract surgery, the choice of intraocular lens, the management of glaucoma medications before surgery, and the decision about combined cataract and glaucoma procedures all require subspecialty assessment.

I consult at Northern Eye Consultants, Northpark Private Hospital, Bundoora, and at Bass Coast Eye Centre, Wonthaggi. A referral from your GP or optometrist is required. Referrals can be addressed to Dr Ross MacIntyre at either location.

Contact Northern Eye Consultants to arrange an appointment. For referral information for GPs and optometrists, visit the Northern Eye Consultants for-referrers page. Information on the range of glaucoma services at Northern Eye Consultants is also available. Further information on cataract surgery Melbourne including a published five-year surgical outcomes audit is available at drmacintyre.com.

References

1. The Effect of Phacoemulsification on the Intraocular Pressure of Patients With Open Angle Glaucoma: A Systematic Review and Meta-Analysis. Journal of Glaucoma. 2024;33(8):576-586. https://doi.org/10.1097/IJG.0000000000002386
2. Effect of phacoemulsification cataract surgery on intraocular pressure in early glaucoma: A prospective multi-site study. PubMed 32031310. https://pubmed.ncbi.nlm.nih.gov/32031310/
3. Impact of Cataract Surgery on IOP and Ocular Structures in Normotensive Patients and Primary and Exfoliation Open-Angle Glaucoma Patients. PMC10083030. https://pmc.ncbi.nlm.nih.gov/articles/PMC10083030/
4. The impact of preservatives on the ocular surface in patients with ocular hypertension or glaucoma. Ophthalmology Times. https://www.ophthalmologytimes.com/view/the-impact-of-preservatives-on-the-ocular-surface-in-patients-with-ocular-hypertension-or-glaucoma
5. Ocular Surface Parameters in Glaucoma Patients Treated with Topical Prostaglandin Analogs. PMC12735008. https://pmc.ncbi.nlm.nih.gov/articles/PMC12735008/
6. Clinical outcomes after lens extraction for visually significant cataract in eyes with primary angle closure. PubMed 21623222. https://pubmed.ncbi.nlm.nih.gov/21623222/
7. Lens Extraction in Angle-Closure Glaucoma. Glaucoma Today. https://glaucomatoday.com/articles/2015-mar-apr/lens-extraction-in-angle-closure-glaucoma
8. AAO 2024: Early cataract extraction for angle closure glaucoma. Ophthalmology Times. https://www.ophthalmologytimes.com/view/aao-2024-early-cataract-extraction-for-angle-closure-glaucoma
9. American Academy of Ophthalmology. Factors to Consider in Choosing an IOL for Cataract Surgery. https://www.aao.org/eye-health/tips-prevention/best-artificial-lens-implant-iol-cataract-surgery