Relationship between the rate of change in lamina cribrosa depth and the rate of retinal nerve fiber layer thinning following glaucoma surgery

Early evaluation of optic nerve head morphology and choroidal thickness after PreserFlo MicroShunt implantation

PURPOSE

The aim of this study is to investigate changes in choroidal and optic nerve morphological parameters following MicroShunt PreserFlo implantation. The secondary aim is to investigate how the structural changes relate to the decrease in intraocular pressure (IOP).

METHODS

Prospective observational study on 15 eyes with glaucoma requiring MicroShunt implantation. Optical coherence tomography was used to measure macular choroidal thickness (MCT), peripapillary choroidal thickness (PCT), lamina cribrosa depth (LCD), cup depth and prelaminar tissue thickness (PLT), before and one day after surgery. Results were expressed in median and interquartile range (IQR) and correlated with IOP results.

RESULTS

The IOP decreased from a median of 25 (IQR = 11) mmHg to 8 (IQR = 2) mmHg the day after surgery. Median MCT increased after MicroShunt implantation from 252.1 (IQR = 156.4) µm to a postoperative value of 318.1 (IQR = 166.6) µm (p < 0.001), with a median increase of + 87.7 µm (+ 26.4%). PCT increased from 157.2 (IQR = 109.1) µm before surgery to 206.0 (IQR = 136.1) µm after surgery (p < 0.001). Moreover, we found a significant post-operative decrease in cup depth (median reduction of - 29.3 µm, p < 0.001) and an increase in PLT (median increase of 27.3 µm, p = 0.028). On the other side, LCD reduction 24 h after surgery didn't reach any statistical significance.

CONCLUSION

PreserFlo implantation determines retinal structural changes which appear similar to those caused by traditional filtering surgery, confirming the effectiveness of this device, meantime carrying a much smaller complications rate when compared to trabeculectomy.

One year structural and functional glaucoma progression after trabeculectomy

We evaluated the changes in visual field mean deviation (VF MD) and retinal nerve fibre layer (RNFL) thickness in glaucoma patients undergoing trabeculectomy. One hundred patients were examined with VF and spectral-domain optical coherence tomography (OCT) before trabeculectomy and 4 follow-up visits over one year. Linear mixed models were used to investigate factors associated with VF and RNFL. VF improved during the first 3 months of follow-up (2.55 ± 1.06 dB/year) and worsened at later visits (−1.14 ± 0.29 dB/year). RNFL thickness reduced by −4.21 ± 0.25 µm/year from 1st month of follow-up. Eyes with an absence of initial VF improvement (β = 0.64; 0.30–0.98), RNFL thinning (β = 0.15; 0.08–0.23), increasing intraocular pressure (IOP; β = −0.11; −0.18 to −0.03) and severe glaucoma (β = −10.82; −13.61 to −8.02) were associated with VF deterioration. Eyes with VF deterioration (β = 0.19; 0.08–0.29), increasing IOP (β = −0.09; −0.17 to −0.01), and moderate (β = −6.33; −12.17 to −0.49) or severe glaucoma (β = −19.58; −24.63 to −14.52) were associated with RNFL thinning. Changes in RNFL structure and function occur over a 1-year follow-up period after trabeculectomy. Early VF improvement is more likely to occur in patients with mild/moderate glaucoma, whereas those with severe glaucoma show greater decline over one year. Our findings indicate that progression is observable using OCT, even in late-stage glaucoma.