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07-03-2019 | Ophthalmology | News | Article

Cataract surgery adjuncts studied in diabetic macular oedema

medwireNews: Both triamcinolone acetonide and bevacizumab improve visual acuity when given as an adjunct to cataract surgery in patients with diabetic macular oedema, but only triamcinolone acetonide results in a sustained anatomical improvement, researchers report.

The prospective Diabetic Macular Edema at the time of Cataract Surgery Trial (DIMECAT) was conducted at a single centre in Australia and included 58 patients with visually significant cataract and centre-involving current (79%) or prior (21%) diabetic macular oedema.

At 6 months post-treatment, the 28 eyes randomly assigned to receive intravitreous bevacizumab 1.25 mg during cataract surgery recorded a mean 17.3-letter improvement in best-corrected visual acuity (BCVA), from a baseline of 55.1 letters.

This did not significantly differ from the mean 21.4-letter improvement, from a baseline of 50.5 letters, observed among the 33 eyes randomly assigned to receive triamcinolone acetonide 4 mg as an adjunct to surgery.

However, there was no improvement in central macular thickness (CMT) among eyes in the bevacizumab group. Indeed, in this group, CMT increased by a mean 15.6 µm overall, from a baseline median of 307.5 µm.

By contrast, CMT was 51.4 µm thinner at 6 months than at baseline (316.0 µm) in the triamcinolone acetonide group and, after adjusting for longitudinal effects, nesting, baseline CMT and diabetic macular oedema status, the difference in CMT between the groups was statistically significant, the investigators report.

There was also a significant difference between the two groups in the proportion of eyes requiring retreatment during the first 6 months of the study, at 57% with bevacizumab versus 24% with triamcinolone acetonide, and a mean number of retreatments of 1.43 versus 0.24.

Regarding adverse events, the rate of intraocular pressure elevations above 21 mmHg was 11% in the bevacizumab group and 12% in the triamcinolone acetonide group, and there were no cases of endophthalmitis or any other serious treatment-related adverse event in either group.

Writing in the British Journal of Ophthalmology, Lyndell Lym (University of Melbourne, Victoria, Australia) and co-authors say: “The differences in morphological outcomes between the two drugs may be explained by their differing effects on intraocular cytokines.”

They note that triamcinolone acetonide inhibits both inflammatory and angiogenic cytokines, whereas bevacizumab only reduces vascular endothelial growth factor (VEGF), and suggest that their data therefore “provide further evidence in favour of the pathogenesis of [diabetic macular oedema] being due to a combination of inflammatory cytokines and not purely VEGF levels, a conclusion that is echoed in results from other groups.”

Lym et al conclude: “Although we could not show statistically significant differences in visual function between the groups, a better understanding of the reason behind these differences may be elucidated by detailed analysis of [optical coherence tomography] morphology variations between the groups, which we plan to report in a future paper.”

By Laura Cowen

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