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Meta-analysis finds contralateral IOP reduction after unilateral selective laser trabeculoplastyUnilateral SLT treatment linked to lower pressure in the other eye

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Key Takeaway
Consider possible contralateral IOP effect when planning unilateral SLT, but evidence is observational.

This systematic review and meta-analysis examined the effect of unilateral selective laser trabeculoplasty (SLT) on contralateral eye intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG) and ocular hypertension (OHT). The analysis included 9 studies comprising 478 eyes, with follow-up periods ranging from 3 to 6 months. The primary outcome was contralateral IOP reduction following unilateral SLT treatment.

The meta-analysis found a statistically significant mean contralateral IOP reduction of 1.85 mmHg (95% CI [1.23, 2.47]). When analyzed by SLT treatment extent, 360° SLT (264 eyes) showed a mean reduction of 2.21 mmHg (95% CI [1.06, 3.36]), while 180° SLT (55 eyes) showed a mean reduction of 2.29 mmHg (95% CI [1.30, 3.29]), with no significant difference between these two approaches (p = 0.91). A moderate positive correlation was observed between IOP reduction in SLT-treated eyes and contralateral eyes (Pearson's R = 0.65, 95% CI [0.54, 0.73]) based on 160 eyes.

Safety and tolerability data were not reported in the available evidence. The analysis has several limitations including the observational nature of the included studies, which precludes establishing causality, and the relatively short follow-up period of 3-6 months. The authors note these findings may have implications for future SLT studies and clinical practice, but clinicians should interpret the contralateral effect cautiously given the evidence limitations.

Researchers combined data from nine studies to look at how treating one eye with selective laser trabeculoplasty affects the other eye. The participants had primary open-angle glaucoma or ocular hypertension. The main goal was to see if the intraocular pressure dropped in the untreated eye after the laser procedure was done on the first eye.

The analysis showed a statistically significant average pressure reduction of 1.85 mmHg in the untreated eye. Results were similar whether the laser covered 180 or 360 degrees of the treated eye. There was also a moderate positive correlation between pressure changes in both eyes, meaning they tended to move together.

No safety concerns or adverse events were reported in the studies included in this review. However, because this is a meta-analysis of observational data, a direct cause-and-effect relationship cannot be confirmed. Readers should understand that while the link is clear, the exact mechanism for the pressure drop in the second eye remains uncertain.

These findings may influence future studies and clinical practice, but they do not change current treatment guidelines. Patients should discuss any concerns about their specific eye health with their doctor rather than relying on this single piece of evidence.

What this means for you:
Treating one eye with laser was linked to lower pressure in the other eye, but a direct cause is not proven.

Study Details

Study typeMeta analysis
EvidenceLevel 1
Follow-up3.0 mo
PublishedApr 2026
View Original Abstract ↓
This systematic review and meta-analysis assesses the effect of unilateral selective laser trabeculoplasty (SLT) in primary open-angle glaucoma (POAG) and ocular hypertension (OHT) eyes on contralateral eye intraocular pressure (IOP). A literature search was performed in PubMED, EMBASE, and Cochrane Library. We included all English randomised controlled trials, retrospective and prospective cohort studies, cross-sectional studies and case series published between 29 August 2004 and 29 August 2024 that performed unilateral SLT in POAG or OHT eyes with contralateral eye IOP reported at least 3 months after SLT. Risk of bias was assessed using the ROBINS-I tool. Meta-analysis was performed using the random-effects model and presented as forest plots. 9 studies (478 eyes) were included in the final pooled analysis, which demonstrated a mean contralateral IOP reduction of 1.85 mmHg (95% CI [1.23, 2.47]) 3-6 months after SLT. Subgroup analysis found a mean contralateral IOP reduction of 2.21 mmHg (95% CI [1.06, 3.36]) and 2.29 mmHg (95% CI [1.30, 3.29]) 3-6 months following 360° (4 studies, 264 eyes) and 180° SLT (2 studies, 55 eyes) respectively; there was no significant difference between both groups (p = 0.91). Meta-correlation analysis of 3 studies (160 eyes) found moderate positive correlation between IOP reduction in SLT-treated and contralateral eyes at 3-6 months (pooled Pearson's R = 0.65, 95% CI [0.54, 0.73]). Our meta-analysis suggests statistically significant contralateral IOP reduction 3-6 months following unilateral SLT, which was correlated with IOP reduction of SLT-treated eyes. These findings may have implications on future SLT studies and real-life clinical practice.Review Registration The protocol for this review was registered with PROSPERO (ID: CRD420251013653).
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