The authors investigated the relationships between the lamina cribosa depth and lamina cribosa depth rate of change over time, and the RNFL thickness change over time, during the first years following a filtering surgery in 29 subjects with glaucoma (16 underwent trabeculectomy and 13 deep sclerectomy). RNFL thickness and lamina cribosa depth were estimated from Spectralis OCT scans of the optic nerve head. The patients were followed 12-29 months after the surgery. A significant IOP decrease was achieved after the surgery (from 24.0 ± 8.9 mmHg preoperatively to 12.7 ± 4.4 mmHg at the last follow-up). A significant decrease of the lamina cribosa depth was found (from 465.3 ± 136.4 µm preoperatively to 342.8 ± 90.3 µm at the last follow-up).
They did not find a lot of RNFL thickness change over time. The average RNFL thickness was 59.3 ± 15.8 µm pre-operatively, 64.9 ± 19.8 µm at one month, 58.9±19.0 µm at three months, 56.4 ± 15.6 µm at six months and 55.0 ± 14.0 µm at the last follow-up. The RNFL thickness and lamina cribosa depth were not significantly correlated at the last follow-up.
They did not find a unique relationship between the rate of change in lamina cribrosa depth and the rate of retinal nerve fiber layer thinning during the different periods of the follow-up.
This study confirms the significant and sustained reduction of the lamina cribosa depth after a filtering surgery
I think that this study confirms the significant and sustained reduction of the lamina cribosa depth after a filtering surgery. It also confirms the significant increase of the RNFL thickness (swelling?) one month after surgery and a return to the initial value after three to six months.
Regarding the relationship between the lamina cribosa and RNFL thickness rate of change over time, it is likely that the results are influenced by the study period. During the first months after the surgery the RNFL increases. After three to six months the RNFL gradually decreases. Further studies could evaluate the long-term change of RNFL thickness and lamina cribosa depth (e.g., over a three to five years period excluding the first six months of follow-up). Also, this study includes patients that underwent both penetrating and non-penetrating filtering surgeries. The magnitude of the IOP reduction could differ, and thus impact the results.