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Editors Selection IGR 17-4

Surgical treatment: Trabectome surgery

Comment by Sameh Mosaed on:

67223 Impact of a Glaucoma Severity Index on Results of Trabectome Surgery: Larger Pressure Reduction in More Severe Glaucoma, Loewen RT; Roy P; Parikh HA et al., PLoS ONE, 2016; 11: e0151926

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This retrospective review by Loewen et al. found that patients with higher glaucoma severity scores experienced a more profound IOP reduction with trabectome surgery as compared to those in lower severity groups. Glaucoma severity was defined with a Glaucoma Index, which was created on a scale between one to four and was based on visual field damage, number of preoperative glaucoma medications, and preoperative IOP. All groups showed similar one-year postoperative IOP of about 16 mmHg, hence the patients with the higher preoperative IOP showed a more profound IOP reduction.

These results mirror several prior published data that confirm the finding that in successful trabecular ablation patients, typical postoperative IOP is the mid-teens, regardless of preoperative IOP. This is because following trabecular ablation, IOP is dictated by the pressure in the collector channels and episcleral venous system.

Following trabecular ablation, IOP is dictated by the pressure in the collector channels and episcleral venous system

However, this study differs from prior similar studies such that in addition to IOP alone, other glaucoma severity indicators were evaluated such as visual field and glaucoma medication burden. While the group with the highest Glaucoma Index had the greatest IOP reduction, it also had the lowest overall success rate at the 12-month follow up (71% as compared to 90% in the lowest glaucoma index group). This once again underscores the difficulty historically seen in controlling IOP in the sickest eyes with the most severe, refractory glaucoma.

This study has several strengths. Firstly, a very large study population of 842 subjects was included in the analysis. Secondly, the numbers in each of the four Glaucoma Index groups were balanced and robust for meaningful analysis. Only subjects undergoing trabectome were included in the study, and any simultaneous cataract extraction or other procedure were excluded from analysis. This differs significantly with other published data on angle-based surgeries where simultaneous cataract extraction confounds the results. Also, varied POAG subsets were included, and only subjects reaching a minimum postop period of one year were analyzed.

With this paper, the authors provide more evidence that the trabectome procedure can be employed for treatment of early to refractory glaucoma with excellent results throughout the spectrum of disease, and that typical IOP of mid-teens can be expected regardless of preoperative IOP or disease severity.

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