Education Committee Highlights WGC-2021 | part 6.2

Clinical Trial Summary

Have LiGHT, ZAP, MIGS trials changed my clinical practice?
In this talk, Dr. Kuldev Singh starts showing the results of the ZAP Trial, in which LPI is compared to observation in Chinese PACS patients. The risks and benefits of LPI should be considered since the occurrence of primary angle closure was very low, and some patients may prefer cataract extraction rather than LPI, especially if they have symptomatic cataracts.

Then Dr Singh presents the results of the LiGHT Trial, which primarily evaluated health-related quality of life at 3 years in newly-diagnosed OHT or POAG patients undergoing SLT or drops as first-line treatment. Since the good results reported with SLT, Dr Singh suggests that this could be used in newly diagnosed POAG patients. Care should be taken in OHT patients as many will not progress and in some glaucoma suspects than can be miscategorized as POAG and therefore do not need treatment. Compliance with visits is also a concern with SLT.

As regards MIGS Trials, many studies are available to assess safety and effectiveness but further prospective studies are needed, especially those addressing health-related quality of life and those comparing with the current standard of care. Despite this, Dr Singh believes that the decision of MIGS or trabeculectomy should be made in each individual patient and based on clinical experience.

Lessons from the UKGTS
Dr. Ted Garway-Heath begins explaining that the primary motivation for conducting this non-randomized placebo-controlled trial was the need to assess the benefit of treatment with prostaglandin monotherapy on visual field (VF) progression in glaucoma patients. Secondary objectives included identifying risk factors for progression, evaluating images as surrogates for progression and assessing quality of life measures among others. This trial also aimed to reduce observation periods in clinical studies.

The study mainly concluded that there was a significantly reduced risk of VF progression in the latanoprost arm after a two-year follow-up, that was also noticeable at the 12-month and 18-month time points, thus allowing shorter observation periods. The treatment also slowed the rate of VF deterioration.

Risks factors identified were bilateral disease, higher IOP and disc haemorrhages among others, while smoking was identified as a protective factor. The rate of RNFL thinning measured by OCT was also a strong predictor of the primary outcome, enabling the clinician to monitor for progression with OCT RNFL measurements.

Should SLT be the first line treatment?
In this presentation, Dr. Gus Gazzard explains some of the problems of medical treatment: poor adherence, reduced surgical success, cost and side effects of drops. Selective Laser Trabeculoplasty (SLT) avoids some of these issues and is less harmful for the trabecular meshwork.

The LiGHT trial was designed to assess the benefit of SLT vs drops as first-line treatment for newly diagnosed OHT or POAG patients in terms of quality of life, cost-effectiveness and pre-defined clinical outcomes.

The study concluded that after three years of follow-up, clinical outcomes such as visual acuity, IOP and visual field progression were similar between groups but a significant higher rate of trabeculectomies was found in the medication arm. Almost 80% of patients were at their target IOP in the SLT arm, most of them without drops or additional laser, suggesting a much better disease control when SLT is performed first. SLT showed to be safe, can be repeated reducing IOP in a consistent way and for a longer period, and appears to have a protective effect towards deterioration.
Finally, Dr Gazzard suggests in which patients SLT may be offered as a first or second option with different success rates.

Is PI necessary in angle closure suspects?
Dr. Benjamin Xu states that gonioscopy together with clinical findings allow us to define the three categories of angle closure disease: primary angle closure suspects (PACS), primary angle closure (PAC) and primary angle closure glaucoma (PACG), whose prevalence is increasing worldwide.

Laser peripheral iridotomy (LPI) can lower IOP in angle closure eyes with high IOP and can also break pupillary block. Therefore, it has been widely indicated in PAC and PACG patients. But since according to epidemiological studies, most patients are PAC suspects, the question that Dr Xu arises is if performing LPI in these patients may beneficial.

Although the ZAP Trial concluded that the risk of angle closure in PACS is reduced by half if an LPI is done, the very low risk even in untreated patients suggests that performing LPI extensively is not cost-effective. Dr Xu explains some of the limitations of the study and recommends LPI for fellow eyes of acute angle closure, patients who require frequent dilatation, patients over 70 years old and possibly in severe angle narrowing although this has not been confirmed.

The corruption of evidence-based medicine (EBM)
Dr. Vijaya Lingam starts explaining that even challenging, EBM has provided guidelines of diagnosis, treatment and prognosis of glaucoma. The corruption or bias of EBM refers to its own limitations: the generalizability of results, the fact that studies are funded, and the challenge of integrating study results with own expertise. Then Dr Lingam provides us with a few tips on how to deal with each one of these limitations.

She presents two examples of clinical trials in Glaucoma that may arise some concerns: the TVT Study and the EAGLE Study. She suggests, in agreement with other experts, that the TVT study should not change clinical practice since results are not widely generalizable, even though it was perfectly designed and conducted.

Dr Lingam affirms that results of the EAGLE Study should be interpreted carefully and suggests that lens extraction is probably best indicated in patients with significant cataracts and LPI should be offered in patients with clear lenses.

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