Variation of lamina cribrosa depth following trabeculectomy

To investigate the long-term changes in lamina cribrosa (LC) depth following trabeculectomy.

Serial horizontal B-scan images of the optic nerve head were obtained using spectral-domain optical coherence tomography from 28 primary open-angle glaucoma patients who underwent trabeculectomy and were followed up for at least 2 years. Approximately 65 B-scans covering the optic discs were obtained before surgery and at 6 months and ≥2 years postoperatively. The pre- and postoperative LC depth (the distance from the opening plane of Bruch's membrane to the level of the anterior LC surface) was determined on seven selected B-scan images from each eye and averaged (mean LC depth).

The intraocular pressure (IOP) decreased from 27.4 ± 9.0 (mean ± SD) to 9.7 ± 3.1 mm Hg at postoperative 6 months (P < 0.001) and subsequently increased to 12.7 ± 5.1 mm Hg at a mean final follow-up of 27.1 ± 3.3 months (P = 0.001). The mean LC depth was reduced from 625.6 ± 186.3 to 499.6 ± 140.6 μm at postoperative 6 months (P < 0.001). A subsequent slight, but nonsignificant, increase in the LC depth was noted at final follow-up. The degree of LC depth increase after 6 months was significantly associated with younger age, higher IOP at final follow-up, greater IOP fluctuation, and higher mean follow-up IOP from 6 months to final follow-up (all P < 0.05).

The postoperative reduction in the LC depth that was observed 6 months after surgery was not maintained in some eyes. The redisplacement of the LC after postoperative 6 months appeared more likely to occur in patients who were younger and who had higher IOP and IOP fluctuation during the postoperative follow-up.