Not all randomly assigned controlled trials (RCTs) are equal.

Depending on the scientific question asked and the robustness of methodology, some can substantially affect clinical practice and are therefore considered landmark studies. Although it is now well established that IOP reduction is the cornerstone in the management of glaucoma, it was not until the late 1990s that the evidence to support this notion became available. Several landmark RCTs published in the late 1990s and early 2000s provided solid evidence that lowering IOP reduces the risk of progression of open-angle glaucoma (OAG) and the risk of conversion of ocular hypertension to OAG. Two additional landmark RCTs independently identified the same risk factors for the conversion of ocular hypertension to OAG.

These data enabled the development of a risk prediction equation with predictive utility (risk calculator).Although these early landmark studies were hugely important for the management of ocular hypertension and OAG, questions remained unanswered regarding the medical and surgical management of glaucoma. Some of these questions have been answered by more recent landmark RCTs, which I will discuss here.

The TVT study
Whereas aqueous shunts were already commonly used for the management of complex/refractory glaucoma and were starting to become popular as an alternative to trabeculectomy in those at high risk of filtration failure, it remained unknown which was the best approach for patients with prior ocular surgery. The Tube Versus Trabeculectomy (TVT) study (NCT00306852) was designed to investigate the safety and efficacy of tube shunt surgery versus trabeculectomy with mitomycin C (MMC) in eyes with prior cataract and/or filtration surgery.The study enrolled 212 patients who had had prior cataract and/or failed filtration surgery and uncontrolled glaucoma on the maximum number of medications.Outcome measures were: IOP, visual acuity, visual field, surgical complications, glaucoma medications, and treatment failure. The follow-up period was 5 years. The cumulative probability of failure was higher for trabeculectomy versus tube shunt surgery. No difference in mean IOP was observed, but IOP control in the first 2 years was better with trabeculectomy.

Early complications were more frequent with trabeculectomy but there was no difference in late postoperative complications.There was no significant difference between groups in the number of medications needed, although the trabeculectomy group required fewer in the first 2 years. Thus, the TVT study provided evidence that both tube surgery and trabeculectomy with MMC are appropriate in those with previous cataract and/or failed filtration surgery.However, the study’s results need to be interpreted with caution because the subgroup of patients with previous failed trabeculectomy may have introduced bias in favor of the tube group. For the same reason, tube surgery may be more appropriate in those with failed filtration surgery. The TVT study challenged the traditional paradigm that tube shunts should be reserved for patients with refractory glaucoma.

Journal of Clinical and Experimental Ophthalmology is now accepting submissions on this topic. A standard EDITORIAL TRACKING SYSTEM is utilized for manuscript submission, review, editorial processing and tracking which can be securely accessed by the authors, reviewers and editors for monitoring and tracking the article processing. Manuscripts can be uploaded online at Editorial Tracking System (https://www.longdom.org/clinical-experimental-ophthalmology.html) or forwarded to the Editorial Office at manuscripts@longdom.org

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Regards,

Lina Gilbert