After trabeculectomy, researchers had believed that the Schlemm canal constricts, and that subsequent laser treatment of the trabecular meshwork had no beneficial effect for patients who continue to have high intraocular pressure (IOP). Growing evidence, though, suggests that some regions of the trabecular meshwork may continue to function and, following selective laser trabeculoplasty (SLT), are still capable of improved drainage.

Approximately 54% of participants in a Journal of Glaucoma study who underwent SLT after having undergone prior incisional surgery (trabeculectomy) saw sufficient IOP reductions and reached their individual IOP targets — reporting lower peak-IOPs and less IOP-fluctuations after 1 year.

The research evaluated the medical records of 43 individuals who underwent trabeculectomy followed by SLT 3 to 11 years later to treat inadequately maintained mean diurnal IOP (mdIOP) or visual field loss. 

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The participants’ 1-day routine glaucoma workup prior to 360˚ SLT and approximately 12 months afterwards was performed at a tertiary university glaucoma service between May 2010 and October 2016. Six IOP measurements were taken: 5 with a Goldmann tonometer at 7 am, and 1, 4, 7, and 10 pm, as well as 1 supine reading with a handheld tonometer at midnight. During the 1-year follow-up, 10 of the 43 eyes needed medication change, re-SLT, or surgery to reduce mdIOP, leaving 33 eyes for inclusion in the final analysis.

Results demonstrated that with initially-prescribed therapy medication, at 12 months, median mdIOP decreased from 15.2 mm Hg (Q25 at 12.2 mm Hg, Q75 at 16.5 mm Hg), to 13.2 mm Hg (Q25 at 11.6 mm Hg, Q75 at 15.3 mm Hg), a statistically significant reduction (P =.027). Peak IOP also decreased considerably (P =.002). Fluctuations of diurnal IOP lessened as well, but not significantly (P =.094).

A reduction to achieve individual target IOP was successful for 54% of post-trabeculectomy eyes treated with SLT, indicating that in glaucomatous eyes there remain a number of trabecular meshwork regions able to be reactivated by SLT and better drain aqueous humor.

“Previous studies as well as the current study demonstrate that SLT efficacy is not correlated with the stage of disease, which can also be explained by the segmental variability and some unaffected regions of trabecular outflow,” the researchers explain.

Higher preprocedural IOP was not linked to greater IOP reduction, confirming prior analyses. However, linear regression showed that a higher preoperative peak IOP was an element predicting SLT’s success in reducing peak IOP (P =.006), and greater pre-surgery IOP fluctuations were associated with decreased 12-month diurnal fluctuations (P <.001). Factors such as age, lens status, sex, pachymetry assessment, number of medications, and severity or duration of disease did not impact reduction of mdIOP, peak IOP, or fluctuation. 

No patients in the current study experienced any serious adverse events such as spikes in IOP, uveitis, or peripheral anterior synechiae.

Limitations of the analysis included a retrospective design, and a sample composed of Caucasian patients only, as well as 1-day IOP readings taken twice; at baseline and 12-month visits. Conversely, a strength was adherence to original IOP-lowering meds during follow-up, precluding this from being a confounding factor. Also, investigators took 6 measurements, reading them at consistent times of day, and recorded a supine reading during the night.

Disclosures: Multiple study authors have declared affiliations with the biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 


Pillunat KR, Herber R, Wolfram S. Efficacy of selective laser trabeculoplasty on circadian intraocular pressure following trabeculectomy in advanced primary open-angle glaucoma. J Glaucoma. 2022;31(2):96-101. doi:10.1097/IJG.0000000000001971