Understanding the Risk of Glaucoma After Vitrectomy: The “Pseudophakic Penalty”

A recent large-scale meta-analysis published in Ophthalmology (2026) has provided definitive data on a long-suspected complication of vitreoretinal surgery: the significant increase in intraocular pressure (IOP) and glaucoma risk, particularly in eyes that have already undergone cataract surgery.

The Scope of the Study

Researchers analyzed 41 observational studies involving over 54,000 eyes to quantify the long-term effects of pars plana vitrectomy (PPV) on intraocular homeostasis. The study aimed to provide a “clinically interpretable framework” for risk stratification based on lens status—whether an eye is phakic (natural lens) or pseudophakic (intraocular lens).

Key Findings: Absolute and Relative Risks

The meta-analysis revealed that PPV is associated with a measurable and clinically meaningful risk of sustained IOP elevation.

• Overall Risk: The pooled absolute risk (AR) for developing post-vitrectomy ocular hypertension was 5.6%, while the risk for developing glaucoma was 3.9% over a mean follow-up of 26.5 months.
• The Pseudophakic Modifier: The most striking finding was the disparity in risk based on lens status. Pseudophakic eyes faced significantly higher odds of complications compared to phakic eyes:
  • Ocular Hypertension: 3.2-fold higher odds (OR 3.2).
  • Glaucoma: Nearly 12-fold higher odds (OR 11.8).

Clinical Metric: Number Needed to Treat for Harm (NNTH)

To make these findings more actionable for surgeons, the researchers calculated the Number Needed to Treat for Harm (NNTH):

• For OHT: For every 8 pseudophakic eyes undergoing vitrectomy, one additional case of OHT is expected compared to phakic eyes.
• For Glaucoma: For every 10 pseudophakic vitrectomies, one additional case of glaucoma is expected.

Why Does This Happen? The Biological Mechanism

The study highlights the “protective buffer” theory of the crystalline lens. In a healthy eye, the natural lens and vitreous body act as oxygen scavengers, protecting the delicate trabecular meshwork (TM) from oxidative stress.

When the vitreous is removed (vitrectomy) and the natural lens is absent (pseudophakia), this barrier is lost. The resulting increase in oxygen tension in the anterior segment leads to oxidative damage of the outflow pathway, compromising the TM’s ability to regulate pressure and potentially leading to chronic IOP elevation and glaucomatous neurodegeneration.

Other Contributing Factors

Beyond lens status, the study identified other variables that modified risk:

• Tamponade Type: The use of silicone oil (SO) was associated with markedly higher risks of OHT and glaucoma compared to gas or air tamponades.
• Surgical Indication: Higher rates of glaucoma were observed in surgeries for rhegmatogenous retinal detachment and retained lens fragments (up to 10.4%) compared to more routine macular surgeries like epiretinal membrane peeling.

Conclusion and Clinical Takeaways

This meta-analysis confirms that vitrectomy is not a pressure-neutral procedure. For the practicing retina surgeon, these findings support:

1. Tailored Surgical Planning: Recognizing that pseudophakia is a major risk modifier for postoperative glaucoma.
2. Enhanced Monitoring: Implementing more rigorous postoperative IOP surveillance for pseudophakic patients.
3. Proactive Counseling: Using the NNTH data to provide patients with realistic expectations regarding their long-term visual prognosis and the potential need for lifelong glaucoma management.

Source Note: All information is derived from Gallo Afflitto et al., “Ocular Hypertension and Glaucoma After Pars Plana Vitrectomy: A Systematic Review and Meta-Analysis,” Ophthalmology 2026.