Cataracts and glaucoma are two common age-related eye conditions that often occur together. Cataracts involve the clouding of the eye’s natural lens, which impairs vision. Glaucoma is a progressive disease that damages the optic nerve, typically due to elevated intraocular pressure (IOP). The anatomical relationship between the lens and the eye’s drainage system means that cataract surgery can play a role in managing glaucoma.
Understanding Cataracts and Glaucoma
A cataract forms when proteins in the lens lose transparency, causing blurry vision and glare. Over time, the lens often thickens and expands in volume within the eye. This physical enlargement can crowd the front part of the eye, known as the anterior chamber.
Glaucoma is characterized by damage to the optic nerve, often stemming from an imbalance in the production and drainage of aqueous humor. This fluid is continuously produced behind the iris and must drain through the trabecular meshwork, located in the angle between the iris and the cornea. When the lens thickens, it pushes the iris forward, narrowing the drainage angle. This impedes the flow of aqueous humor, causing IOP to rise.
How Lens Removal Impacts Intraocular Pressure
Cataract surgery involves removing the cloudy, thickened natural lens and replacing it with a thinner, artificial intraocular lens (IOL). This procedure, called phacoemulsification, immediately creates more space in the anterior chamber. The increased space pulls the iris back, widening the drainage angle and allowing aqueous humor to exit the eye more freely through the trabecular meshwork.
The effectiveness of this pressure reduction varies significantly depending on the type of glaucoma. For those with angle-closure glaucoma, where the drainage angle is physically blocked by the iris, cataract surgery is highly effective. Removing the lens relieves the physical crowding, often resulting in a significant and sustained drop in IOP, which can reduce or eliminate the need for glaucoma medication. For the more common open-angle glaucoma, where the blockage is within the trabecular meshwork itself, the effect is more modest. While a beneficial pressure drop is often observed, the surgery alone does not resolve the underlying drainage problem.
When Combined Glaucoma Procedures Are Necessary
For patients with moderate to advanced glaucoma, cataract surgery alone is often not sufficient to achieve the target intraocular pressure required to prevent further optic nerve damage. Dedicated glaucoma procedures are frequently performed simultaneously with cataract removal to enhance pressure control. This combined approach avoids a second surgery and leverages the single incision used for cataract removal.
Minimally Invasive Glaucoma Surgery (MIGS) procedures are common additions for those with mild to moderate open-angle glaucoma. These techniques involve placing microscopic stents or creating tiny bypasses to improve the flow of aqueous humor through or around the trabecular meshwork. For patients with severe or poorly controlled glaucoma, more traditional filtration surgeries, such as trabeculectomy, may be combined with cataract surgery. This major surgery creates a new drainage pathway from the eye’s interior to a filtering bleb under the conjunctiva, which provides a much greater reduction in IOP than MIGS or cataract surgery alone. The decision to combine procedures is based on the severity of the glaucoma and the patient’s need to reduce their reliance on daily eye drops.