Trabeculectomy is a traditional and common surgical intervention for IOP reduction in patients with open-angle glaucoma. CO2 laser-assisted sclerectomy (CLASS) procedures are less common but, according to a recent study, no less effective. Now, for the first time, researchers have compared trabeculectomy with CLASS (1). In an examination of 70 eyes – 37 in the trabeculectomy group and 33 in the CLASS group – the CLASS group reported a success rate of 97.2 percent, an increase on the 80 percent experienced by the NPDS group. We asked Juan Carlos Izquierdo, Chief of Glaucoma at the Oftalmosalud Eye Institute in Lima, Peru, and lead author of the study, to tell us more.
What inspired the CLASS study?
We were looking for a more controlled procedure, with a high rate of safety on one hand and with a similar efficacy to trabeculectomy on the other. That alternative was CLASS. Our experience with trabeculectomy showed good efficacy, but was associated with a relatively high rate of post-operative manipulations because of adverse events or complications, mostly associated with hyphotony or bleb-related complications. CLASS aims to solve both problems.
As a non-penetrating procedure, the aqueous outflow is based on the natural flow without the major resistance to the outflow, and it includes an alternative absorption pathway – the intra-scleral (or suprachoroidal) pathway –which reduces the dependency on the bleb and, therefore, far fewer bleb-related complications are observed. Performing laser assisted deep sclerectomy also adds the benefits of the laser itself: the laser is accurate, simple to control and operate, and it is very reproducible. This gives confidence to the user and in turn, the patient.
Any other benefits?
CLASS has a good safety profile and very good efficacy, which has already been proven in the long-term. The main benefit for the patient is the unique combination of safety and efficacy, as the CO2 laser is highly absorbed by fluid. So, once we have achieved percolation, the laser is no longer effective, and we have reached the desired outcome of the procedure in a controlled intrinsic manner. As for efficacy, IOP reduction is very similar to the standard trabeculectomy, but with significantly fewer complications and medications needed in the post-op.
The last point I will mention is that for me, as a surgeon, a huge benefit is that the procedure is reproducible, which is key in planning the post-op treatment.
Was there an effect on visual acuity?
The feedback on visual acuity is already totally different compared with trabeculectomy. CLASS is performed safely, as you don’t penetrate the anterior chamber, and in post-op the patient is in miosis, so the patient’s impression is that it is simply a cataract surgery. In contrast, trabeculectomy patients have blurred vision due to the use of atropine – required to help maintain the anterior chamber – for at least two weeks post-operation. With CLASS, there is no promotion of cataract development in the long-term as there is with trabeculectomy, and there is marginal improvement in BCVA.
If we compare results between trabeculectomy and CLASS (measured according to the Snellen chart converted into the LOGMAR chart), we can see that in the trabeculectomy group, BCVA increased from 0.196 ± 0.27 to 0.20 ± 0.32 at 1-year post-op, while in the CLASS group, BCVA declined from 0.20 ± 0.2 to 0.07 ± 0.1 at 1-year post-op. These results show a small deterioration in the trabeculectomy group, and significant improvement in CLASS group. This is a good indication of improvement in visual acuity.
In the study, the post-CLASS group required less medication to control IOP than the trabeculectomy group – why?
Because of the difference in the control mechanism of aqueous outflow. The trabeculectomy operation generates a new drainage channel for aqueous outflow, which is not natural, so the body suffers from many unexpected changes and fluctuations resulting from the natural adaptation of the eye to significant change. In the CLASS group, there is a use of the natural process of aqueous outflow, but with a reduction to major resistance of aqueous outflow in that natural route. These less radical changes in the surgical solution lead to less trauma to the eye and the patient, and therefore to shorter adaptation process of the eye to the surgical outcome. Not only that, the trabeculectomy group is more likely to experience adverse events, which require a greater number of medications to stabilize the outcome.
What would you say to clinicians who are reluctant to try something other than trabeculectomy?
As surgeons, we must seek the best practice for each patient and, as such, we must be open to new technologies. There are so many out there – especially for glaucoma surgery – which we should test and validate to make sure they provide accurate and reliable results with safe and effective operation. We must then decide on the right approach for each patient. Just because we didn’t learn about a certain procedure back in medical school doesn’t mean it isn’t good or shouldn’t be considered – it only means we are getting older! Laser-based solutions are already the running promise of many ophthalmic applications, so I think it makes sense to add laser for glaucoma surgery to this portfolio.
- JCI Villavicencio et al., “Comparative clinical results of phacoemulsification combined with CO2 laser-assisted sclerotomy vs. phacoemulsification combined with trabeculectomy in patients with open-angle glaucoma”, J Clin Exp Ophthalmol, 9, 5 (2018). DOI: 10.4172/2155-9570.1000749.
I’ve always loved telling stories. So much so, I decided to make a job of it. I finished a Masters in Magazine Journalism and spent three years working as a creative copywriter before itchy feet sent me (back)packing. It took seven months and 13 countries, but I’m now happily settled on The Ophthalmologist, where I’m busy getting stuck into all things eyeballs.
