What is diplopia, and why is it a concern after glaucoma surgery?

Diplopia, commonly known as double vision, arises when the eyes fail to align correctly, leading the brain to receive two separate images. After procedures like Baerveldt glaucoma implant (BGI) surgery and trabeculectomy (TE), the oculomotor system's ability to adjust can be exceeded, leading to misalignment and diplopia. It is concerning because it can severely impact a patient's vision, depth perception, and overall quality of life, making everyday tasks challenging.

Why does BGI implantation lead to diplopia more often than TE?

Research shows that the Baerveldt glaucoma implant (BGI) surgery leads to diplopia more frequently than trabeculectomy (TE). The study found that 28% of BGI patients experienced diplopia, while only 2% of TE patients reported this complication. This is primarily because BGI surgery has a more pronounced effect on ocular motility and alignment. BGI patients showed more frequent duction changes and shifts in near horizontal ocular alignment, especially towards exodirection, alongside a significant reduction in their fusion range.

What specific eye movement difficulties are associated with diplopia after BGI surgery?

Following Baerveldt glaucoma implant (BGI) surgery, several specific eye movement difficulties can lead to diplopia. These include challenges in elevation (looking upward, with 13% of BGI patients), abduction (moving the eye outward, with 13% of BGI patients), elevation in adduction (looking up and inward, also 13%), and elevation in abduction (looking up and outward, with 25% of BGI patients). These issues reflect the impact of the surgery on the muscles controlling eye movement.

How can changes in ocular alignment and fusion range affect vision after BGI implantation?

After Baerveldt glaucoma implant (BGI) surgery, a shift in ocular alignment, particularly towards exodirection (outward deviation), and a decreased fusion range can significantly affect vision. The fusion range is essential for maintaining single vision; its reduction means the eyes struggle to work together, leading to diplopia. These changes disrupt the brain's ability to merge the images from both eyes into one coherent view, impairing depth perception and making it difficult to perform visually demanding tasks.

What steps are being taken to minimize the risk and impact of diplopia after glaucoma surgery?

Researchers are studying diplopia prospectively using comprehensive orthoptic measurements and questionnaires to better understand its occurrence after glaucoma surgery. This includes detailed analysis of eye movements, alignment, and fusion. This research aims to develop strategies to reduce the risk of diplopia. Patients undergoing glaucoma surgery should be informed about the potential risk of diplopia and the available management options. Further research is needed to explore techniques that can reduce the risk of diplopia and improve visual outcomes.

Illustration representing double vision after glaucoma surgery.

Double Vision After Glaucoma Surgery? What You Need to Know

Mira Elwood in Health & Wellness December 2025 • 4 min read.

"Understanding the Risks and Management of Diplopia Following Glaucoma Treatments"

Glaucoma, a condition characterized by damage to the optic nerve, often requires surgical intervention to lower intraocular pressure (IOP) and prevent further vision loss. While procedures like trabeculectomy (TE) and glaucoma drainage device (GDD) implantation are effective in managing glaucoma, they can sometimes lead to unexpected side effects, including diplopia, or double vision.

Diplopia occurs when the eyes fail to align correctly, causing the brain to receive two different images. This misalignment can arise from various factors, including disturbances in eye motility. While the oculomotor system is remarkably adaptable, surgical procedures around the eye can sometimes exceed its capacity to adjust, leading to motility issues and, consequently, diplopia.

A recent study investigated the incidence and characteristics of diplopia following Baerveldt glaucoma implant (BGI) surgery and trabeculectomy (TE). The research aimed to quantify any changes in ocular motility and the occurrence of diplopia after these procedures, shedding light on the potential risks and underlying mechanisms.

Why Does Diplopia Occur More Often After BGI Implantation?

Illustration representing double vision after glaucoma surgery.

The study, published in Translational Vision Science & Technology, analyzed 51 patients who underwent BGI implantation and 52 patients who underwent TE. Researchers assessed the presence of diplopia one year after surgery and measured ductions (eye movements in different directions), ocular alignment, and fusion range (the ability to maintain single vision despite misalignment) before and after the procedures.

The results revealed a significantly higher incidence of diplopia in the BGI group compared to the TE group. Specifically, 28% of BGI patients experienced diplopia, while only 2% of TE patients reported this complication. Furthermore, duction changes were more common in the BGI group (35%) than in the TE group (19%), indicating a greater impact on eye motility.

Elevation: Difficulty looking upward (13% of BGI patients)
Abduction: Difficulty moving the eye outward (13% of BGI patients)
Elevation in Adduction: Difficulty looking up and inward (13% of BGI patients when the eye was turned 25 degrees inward)
Elevation in Abduction: Difficulty looking up and outward (25% of BGI patients when the eye was turned 25 degrees outward)

Additionally, the study found that 32% of BGI patients experienced a shift in their near horizontal ocular alignment, primarily towards exodirection (outward deviation). The fusion range, which is crucial for maintaining single vision, also decreased significantly in the horizontal direction among BGI patients. These findings suggest that BGI surgery has a more pronounced effect on ocular motility and alignment compared to TE, thereby increasing the risk of diplopia.

What Can Be Done to Minimize the Risk of Diplopia?

While the study highlights the increased risk of diplopia following BGI surgery, it also emphasizes the importance of understanding the factors that contribute to this complication. By studying diplopia prospectively with comprehensive orthoptic measurements and questionnaires, researchers can gain better insight into its occurrence and develop strategies to minimize its impact. Patients undergoing glaucoma surgery should be informed about the potential risk of diplopia and the available management options. Further research is needed to explore techniques that reduce the risk of diplopia and improve the visual outcomes for patients undergoing glaucoma surgery.