Cataract and Glaucoma: What Happens When You Have Both?

Understanding Both Conditions

Cataracts and glaucoma are the two most prevalent sight-threatening conditions in Australia, and both become increasingly common from the age of 60 onwards. While they are distinct diseases affecting different parts of the eye, they frequently coexist — and managing one inevitably affects the other.

A cataractis a clouding of the eye’s natural lens, causing blurred or dim vision that worsens progressively over months to years. Treatment is surgical: the cloudy lens is removed and replaced with a clear artificial intraocular lens (IOL).

Glaucoma is a group of conditions characterised by damage to the optic nerve, most commonly from elevated intraocular pressure (IOP). It is often asymptomatic until significant vision loss has occurred, affecting peripheral vision first. Management ranges from eye drops to laser to surgery, depending on severity.

How Cataracts and Glaucoma Interact

When a patient has both conditions, surgical planning requires careful thought. Several interactions are clinically important:

• Angle-closure risk: As the crystalline lens enlarges with age, it can narrow the drainage angle of the eye. In patients with narrow-angle or angle-closure glaucoma, removing the thick cataract often dramatically opens the drainage angle, providing meaningful IOP reduction as a direct result of the cataract extraction alone.
• IOP monitoring: Patients on glaucoma drops must continue their medications around the time of cataract surgery as directed. IOP can fluctuate in the early post-operative period, and closer monitoring is warranted.
• Intraoperative floppy iris syndrome (IFIS): Certain glaucoma medications — particularly alpha-agonist drops such as brimonidine — can cause the iris to become flaccid during surgery, making the procedure more challenging. Your surgeon will ask about all eye drops in advance so appropriate steps can be taken.
• Advanced glaucoma and IOL selection: Where there is significant optic nerve damage, visual field loss may persist after cataract surgery regardless of how successful the lens exchange is. Setting realistic expectations is an important part of the pre-operative discussion.

Combined Cataract Surgery and MIGS

For patients with mild-to-moderate open-angle glaucoma requiring better IOP control, combining phacoemulsification with a MIGS procedure is an efficient and effective approach. The most commonly used MIGS devices in Australia include:

• iStent inject W— two tiny titanium stents placed in the trabecular meshwork to create a bypass for aqueous drainage.
• Hydrus microstent— a small scaffold that scaffolds Schlemm’s canal, improving aqueous outflow over a larger arc.

Both devices are implanted through the same corneal incision used for cataract surgery, adding only a few minutes to the procedure. Evidence from randomised controlled trials demonstrates that combined cataract–MIGS surgery achieves greater IOP reduction than cataract surgery alone, and significantly reduces the number of glaucoma drops patients need post-operatively.

Pre-operative assessment for combined surgery should include optical coherence tomography (OCT) of the optic nerve and retinal nerve fibre layer, as well as automated visual field testing, to establish a baseline and guide surgical planning.

Cataract Alone vs Combined Cataract & MIGS

Conclusion

Having both cataracts and glaucoma is common, and the coexistence of these conditions need not mean two separate surgical episodes. For many patients, combining phacoemulsification with a MIGS procedure delivers improved vision and better IOP control in a single, safe procedure. The key is thorough pre-operative assessment — including optic nerve imaging and visual field testing — to match the surgical approach to the severity of your glaucoma.

Frequently Asked Questions