Cataract and glaucoma are both common in the elderly and often coexist in the same eye. Cataract surgery aims to restore vision, while glaucoma surgery aims to lower intraocular pressure to prevent progression of visual field damage. Combined surgery addresses both conditions in a single procedure.
Cataract surgery alone may achieve a mild intraocular pressure reduction of less than 2 mmHg on average. The effect may be greater in cases with high preoperative intraocular pressure or angle-closure components, but in open-angle glaucoma, one should not rely solely on cataract surgery for intraocular pressure lowering. 1, 3)
The essence of combined surgery is the decision of whether to perform “vision-improving surgery” and “pressure-lowering surgery” at the same time. While it avoids two separate surgeries, it requires simultaneous management of postoperative inflammation, intraocular pressure fluctuations, and effects on the filtering bleb.
QIf a glaucoma patient undergoes cataract surgery, can intraocular pressure decrease?
A
It can decrease, but often only mildly. A relatively larger decrease can be expected in cases of pseudoexfoliation glaucoma, high preoperative intraocular pressure, or angle-closure components. However, in open-angle glaucoma with a low target intraocular pressure, cataract surgery alone is often insufficient.
When dealing with both cataracts and glaucoma, it is easier to understand by categorizing based on the required level of intraocular pressure reduction rather than starting from the surgical procedure name.
The indication for combined surgery is not determined solely by the presence of cataract. It is necessary to confirm how much intraocular pressure needs to be lowered, how much visual field remains, and whether future glaucoma surgery should be preserved.
Glaucoma-side evaluation
Intraocular pressure and target pressure: Check whether current eye drops are sufficient and how much pressure needs to be lowered after surgery.
Visual field and optic nerve: In cases with progression threatening central vision, transient intraocular pressure fluctuations tend to be problematic.
Angle findings: Check whether the angle is open or closed, the extent of peripheral anterior synechiae, and whether the angle is suitable for MIGS.
Conjunctival condition: If filtration surgery or tube shunt may be performed in the future, prioritize conjunctival preservation.
Cataract side evaluation
Main cause of vision loss: Differentiate whether it is due to cataract or glaucomatous visual field damage.
Surgical difficulty: Pseudoexfoliation, zonular weakness, mature cataract, and poor pupillary dilation increase the risk of intraoperative complications.
Intraocular lens selection: In advanced glaucoma, consider the impact on contrast sensitivity and visual field testing, and be cautious with multifocal intraocular lenses.
Postoperative intraocular pressure spike: In glaucomatous eyes, residual viscoelastic material, inflammation, and steroid response can easily cause postoperative IOP elevation.
MIGS (minimally invasive glaucoma surgery) is a group of surgeries that improve aqueous humor outflow while reducing invasiveness and complication risks compared to traditional filtration surgery. It is often considered for mild to moderate open-angle glaucoma because it can be easily performed at the same time as cataract surgery.
Trabeculotomy is an outflow reconstruction surgery that reduces resistance around the trabecular meshwork and Schlemm’s canal, the exit points for aqueous humor. In recent years, minimally invasive methods performed from inside the eye have increased, becoming one of the main concepts of MIGS.
This page focuses on MIGS and trabeculotomy as concepts for considering combined cataract surgery. See the articles below for details on surgical classification, devices, indications, complications, and treatment outcomes.
The method of performing phacoemulsification and trabeculectomy simultaneously is called phacotrabeculectomy. It aims for visual recovery and IOP reduction in a single surgery, but long-term bleb outcomes may be inferior to filtration surgery alone, so indications should be carefully determined. 4, 5)
Cataract surgery and trabeculectomy are performed through the same conjunctival and scleral side.
Surgery time can be shortened easily
Conjunctival manipulation and inflammation can affect the filtering bleb
Separate incision method
Cataract surgery is performed via a temporal corneal incision, and trabeculectomy is performed superiorly.
The superior conjunctiva is relatively easy to preserve.
Increases surgeon position changes and operation time
Both are effective for lowering intraocular pressure, and the long-term outcomes depend on patient background and the surgeon’s technique. The actual decision-making factors include how much of the superior conjunctiva to preserve, whether the surgical field for cataract surgery is easily secured, and where to create the filtering bleb.
In trabeculectomy, mitomycin C (MMC) and other agents may be used to suppress subconjunctival scarring. While MMC helps lower intraocular pressure, it can increase the risks of hypotony, bleb leakage, bleb infection, and endophthalmitis, so postoperative follow-up including bleb management is important. 5)
6. When Considering Combined Use of a Drainage Device
Glaucoma drainage devices are considered for refractory glaucoma where trabeculectomy is unlikely to succeed. In eyes with prior filtering surgery, severe conjunctival scarring, uveitic glaucoma, or neovascular glaucoma, there is an option to implant the device simultaneously with cataract surgery.
When performed concurrently with cataract surgery, comprehensive consideration of corneal endothelium, anterior chamber depth, tube position, and inflammation management is necessary. This should be understood as an individually designed surgery for refractory cases, rather than a routine combined cataract and glaucoma procedure.
After surgery, it is necessary to monitor not only visual acuity recovery but also intraocular pressure stability, inflammation, filtering bleb, and anterior chamber depth simultaneously.
Intraocular pressure spike: Can occur due to residual viscoelastic material, inflammation, or steroid response. Early detection is important in glaucoma eyes.
Filtering bleb function: In cases with combined trabeculectomy, check bleb height, vascularity, leakage, and overfiltration.
IOL power error: Myopic surprise has been reported in hypotonous eyes after filtering surgery.
Eye drop management: In cases with combined MIGS, determine whether glaucoma eye drops can be reduced based on postoperative intraocular pressure.
QAre there any problems if cataract surgery is performed after filtering surgery?
A
Cataract surgery after trabeculectomy may reduce filtering bleb function and affect intraocular pressure control. In patients with low preoperative intraocular pressure, myopic surprise has been reported. The timing of cataract surgery should be determined based on bleb stability, target intraocular pressure, and degree of visual impairment.
QIf cataract surgery and MIGS are performed simultaneously, will future filtering surgery be unnecessary?
A
It is not necessarily unnecessary. MIGS is an option for mild to moderate cases to reduce the burden of eye drops or aim for moderate intraocular pressure reduction, and may be insufficient when low target intraocular pressure is needed for advanced glaucoma. However, because it preserves the conjunctiva, it tends to leave room for future trabeculectomy or drainage device surgery.
In combined cataract and glaucoma surgery, not only the conventional “cataract surgery + trabeculectomy” but also the option of cataract surgery + MIGS is expected to gain further prominence in the future. The reason is that it can be performed through the same small incision as cataract surgery, allows for faster postoperative recovery, and can intervene in both intraocular pressure and the number of eye drops while preserving the conjunctiva.
On the other hand, MIGS does not completely replace filtration surgery. The actual goal of combined surgery is to clarify for each patient which of the following to prioritize: “visual recovery,” “intraocular pressure reduction,” “reduction of eye drop burden,” or “preservation of future surgical options.”
American Academy of Ophthalmology. Cataract in the Adult Eye Preferred Practice Pattern. PIIS0161642021007508.pdf. 2021.
European Glaucoma Society. Terminology and Guidelines for Glaucoma, 5th Edition. Br J Ophthalmol. 2025. doi:10.1136/bjophthalmol-2025-egsguidelines.
American Academy of Ophthalmology. Primary Open-Angle Glaucoma Preferred Practice Pattern. Primary Open-Angle Glaucoma PPP.pdf. 2020.
Zhang ML, Hirunyachote P, Jampel H. Combined surgery versus cataract surgery alone for eyes with cataract and glaucoma. Cochrane Database Syst Rev. 2015:CD008671.
Jampel HD, Friedman DS, Lubomski LH, et al. Effect of technique on intraocular pressure after combined cataract and glaucoma surgery: An evidence-based review. Ophthalmology. 2002;109:2215-2224.
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