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Facundo Gregorio Sanchez, David Sebastian Sanders, Brad Fortune, Stuart Keith Gardiner, Juan Reynaud, Eugene Lowry, Steven L Mansberger; Lamina cribrosa depth and mean cup depth changes in the setting of trabeculectomy in patients with open angle glaucoma. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5612.
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© ARVO (1962-2015); The Authors (2016-present)
This study used optical coherence tomography (OCT) to examine the effect of trabeculectomy on optic nerve head (ONH) anatomy, and on diagnostic parameters used in clinical glaucoma management.
We obtained OCT scans (24 radial B-scans centered on the ONH, each spanning 15 degrees, containing 768 A-lines and averaged 25 times; and 6° radius circle scans, Spectralis, Heidelberg Engineering, GmbH) in 21 eyes of 17 subjects with primary open-angle glaucoma that underwent trabeculectomy. We computed mean anterior lamina cribrosa surface depth [(ALCSD), relative to the 3D reference plane fit to Bruch’s membrane opening (BMO)], mean cup depth [(MCD), defined as the average depth of the internal limiting membrane (ILM) within the ONH below a plane fit to the ring of ILM points on or just inside BMO], minimum rim width (MRW), minimum rim area (MRA), and retinal nerve fiber layer thickness (RNFLT). We calculated the rates of change over an approximate 6-month interval from the visit before the trabeculectomy to the visit after the surgery. We compared these rates against two 6-month control intervals in the same eye that did not contain a trabeculectomy, using a generalized linear model with compound symmetry correlation structure to account for the correlation between time intervals for the same eye and between eyes.
The trabeculectomy interval demonstrated decreased intraocular pressure (-9.1mmHg, p<.01), decreased ALCSD (-20.3mm, p=.06), decreased MCD (-12.9mm, p=.06), and increased MRW (+5.8µm, p=.06). The control intervals showed a decrease in MRW (-4.4µm, p=.006). When comparing the trabeculectomy interval to the control intervals, trabeculectomy created significant differences in IOP, ALCSD, MCD, MRW, and MRA (all p<.03, Fig. 1). RNFLT and perimetric mean deviation both decreased slightly in both groups, but changes were similar between trabeculectomy and control intervals.
Glaucoma surgery was associated with a decrease of ALCSD and MCD, and an increase of rim thickness and area (MRW and MRA), which correspond to a clinical impression of reduced “cupping” (glaucomatous ONH deformation). These changes may represent an improved anatomic profile for stabilization of glaucoma. This discontinuity should be considered when using these measurements to assess disease progression.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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