Trabeculectomy and optic nerve head topography

Abstract

The objective of the present study was to evaluate changes in optic nerve head parameters, measured by confocal laser tomography, before and after trabeculectomy in order to identify outcome measures for the management of glaucoma. The optic nerve head of 22 eyes (22 patients) was analyzed by confocal laser tomography with the Heidelberg retinal tomogram (HRT) before and after trabeculectomy. The median time between the first HRT and surgery was 4.6 months (mean: 7.7 ± 8.3) and the median time between surgery and the second HRT was 10.8 months (mean: 12.0 ± 6.8). The patients were divided into two groups, i.e., those with the highest (group A) and lowest (group B) intraocular pressure (IOP) change after surgery. Differences in the 12 standard topographic parameters before and after surgery for each group were evaluated by the Wilcoxon signed rank test and the differences in these parameters between the two groups were compared by the Mann-Whitney rank sum test. Multiple regression analysis was used to evaluate the influence of the change in IOP (∆IOP and ∆IOP%) and the changes in the other parameters. There were significant differences in the HRT measures before and after surgery in group A only for cup volume. In group B, no parameter was statistically different. The changes in group A were not significantly different than those in group B for any parameter (P > 0.004, Bonferroni correction for multiple comparisons). ∆IOP and ∆IOP% had a statistically significant effect on ∆ cup disk area, ∆ cup volume and ∆ mean cup depth. Changes in cup shape size were influenced significantly only by ∆IOP. Some optic disc parameters measured by HRT presented a significant improvement after filtering surgery, depending on the amount of IOP reduction. Long-term studies are needed to determine the usefulness of these findings as outcome measures in the management of glaucoma. CorrespondenceA. Paranhos Jr.

Effect of trabeculectomy on RNFL thickness and optic disc parameters using optical coherence tomography

“…There are studies investigating changes in optic disc topography demonstrated by the HRT, [11][12][13][14][15][16][17] and changes in the RNFL thickness by OCT [18][19][20] and GDx 21,22 following reduction in IOP, albeit with conflicting conclusions. The variable results of these studies may be due to other factors such as stage of the disease and age.…”

“…[11][12][13][14][15][16][17] This observation is likely owing to a simple shift in anatomic structures rather than recovery or reversal of damage. When the IOP is lowered, there is less stretch on the lamina cribrosa of the disc that probably causes the return of the laminar surface to its previous position before the raised IOP caused it to bow back.…”

“…16 Others have shown no significant change in optic disc topography. 17 The RNFL thickness after IOP reduction has been studied using optical coherence tomography (OCT) [18][19][20] and GDx. 21,22 These reports are conflicting as well.…”

Improved retinal function after trabeculectomy in glaucoma patients

“…Reversibility of optic nerve head cupping after IOP reduction has been reported in congenital glaucoma [4] and in adult patients with openangle glaucoma [5][6][7][8][9][10][11]. Significant improvements in optic disc topography parameters have been seen after both medical and surgical IOP reduction, which were dependent on the amount by which the IOP was reduced [5,[7][8][9][11][12][13].…”

The Acute Morphologic Changes That Occur at the Optic Nerve Head Induced by Medical Reduction of Intraocular Pressure

“…[4][5][6][7][8] Changes in optic disc topography identified by scanning laser ophthalmoscopy that represent a reversal of optic disc cupping after trabeculectomy have been documented. [9][10][11][12][13] However, although these studies have demonstrated that technology has reached a level of sensitivity where subtle changes in disc morphology can be reliably detected, the studies can be criticized by the relatively long interval between image acquisition before and after reduction in IOP, making an assessment of factors such as lamina compliance at any one time-point, inaccurate. Furthermore, images taken immediately after trabeculectomy may be influenced by altered globe morphology and a degree of postoperative optic disc edema, 14 potentially making comparison with preoperative images inaccurate.…”