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Reduced displacement of lamina cribrosa observed after trabeculectomy
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Enhanced depth imaging of the optic nerve head showed significantly reduced displacement and increased thickness of the lamina cribrosa in eyes with glaucoma that underwent trabeculectomy, a study found.
“Our data show that the previously known reversal of the optic disc cupping is likely to mainly result from the anterior movement of the [lamina cribrosa]. It seems that the decompression of the [lamina cribrosa] and restoration of the prelaminar tissue also contribute to the cupping reversal,” the study authors said.
The study included 35 patients with primary open-angle glaucoma who underwent trabeculectomy. Spectral domain optical coherence tomography was used to image the optic disc preoperatively and at 1 week and 1, 3 and 6 months postoperatively.
B-scans were used to determine preoperative and postoperative magnitude of lamina cribrosa displacement, defined as the distance from the Bruch’s membrane opening plane to the level of the anterior lamina cribrosa surface. Thickness of the lamina cribrosa and prelaminar tissue were also measured.
Study results showed that IOP decreased from 27.2 mm Hg preoperatively to 10.5 mm Hg 6 months postoperatively. Mean posterior displacement of the lamina cribrosa decreased from 614.58 µm preoperatively to 503.90 µm at 6 months; the decrease was statistically significant (P < .001).
Lamina cribrosa thickness increased from 169.39 µm preoperatively to 204.75 µm at 6 months. The increase was statistically significant (P < .001). Prelaminar tissue thickness increased from 95.77 µm preoperatively to 101.71 µm at 6 months; this increase was also significant (P = .048).
Diameter of the Bruch’s membrane opening was significantly reduced at all follow-up points (P < .05).
Perspective
Back to TopGeorge L. Spaeth, MD
Lee and colleagues have provided important information regarding the nature of changes in the optic nerve in patients with glaucoma. Added to other exciting studies from other centers, such as Burgoyne’s and Ritch’s, it is becoming apparent that such changes are real. In 1869, von Jaeger’s disc drawings showed improvement in the optic nerve of a patient whose intraocular pressure fell rapidly. Because these alterations are often subtle and go against the belief that glaucoma only moves in one direction — deterioration — most ophthalmologists have been skeptical, do not look for such “improvements,” and therefore do not see them. What is still not clear is the clinical implications of these changes. Does a forward displacement of the lamina indicate that intraocular pressure has been lowered enough to be clinically beneficial? Do patients with such a change have a better course than those not showing such a change? My studies suggest that the change may be a better indicator of future course than pressure. What is clear is that discs change in different ways, and understanding the clinical implications of these alterations will result in better outcomes for patients.
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Ophthalmology. 2012;119(7):1359-1366.
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