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Editors Selection IGR 23-3

Basic Research - Sclera: Visualization lamina cribrosa

Comment by Eytan Blumenthal on:

46459 Visualization of the lamina cribrosa using enhanced depth imaging spectral-domain optical coherence tomography, Lee EJ; Kim T-W; Weinreb RN et al., American Journal of Ophthalmology, 2011; 152: 87-95

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The lamina cribrosa is assumed by many to be the anatomical site where glaucomatous damage meets the ganglion cell axon, by way of blocking axoplasmic flow. Having said that, little do we know about the shape and function of the lamina cribrosa in health and disease. Why might an ophthalmologist want to image the lamina cribrosa of his/her patient in the first place? Perhaps because instability and deformation of this structure might prove to be an early diagnostic sign of glaucoma, or because its pre-existing shape might prove to be a risk factor for future development of this chronic, lifelong disease.

Instability and deformation of the lamina cribrosa might prove to be an early diagnostic sign of glaucoma

In this paper, Lee et al. (1348) apply enhanced depth imaging spectral domain OCT (EDI-SD-OCT) to better visualize this important structure (the lamina cribrosa). What is EDI? One can think of it as shifting the focal plane deep into the tissue, such that an EDI image scans poorly the retina layers, while 'focusing' deep into the tissue, thus providing a much higher resolution image of the lamina cribrosa. While standard SD-OCT can image the anterior surface of the lamina cribrosa reasonably well, it cannot penetrate deep enough to clearly image the posterior surface. Exchanging SD-OCT with EDI-SD-OCT led, in this study, to a doubling in depth penetration from 369 ± 75 to 728 ± 124 micron, leading the authors to conclude that the lamina cribrosa can now be visualized in its entirety. Of interest, EDI was originally developed to image the full thickness of the choroid. Lamina cribrosa thickness data was collected on three groups of subjects: normals, suspects and glaucoma patients, with thinner values found in the glaucoma group. The authors state that it is not clear whether this thinning might be a risk factor or perhaps a consequence of glaucomatous optic neurapathy. Lamina pores were seen smaller and less variable in size in normals as compared to glaucomatous eyes, and in two patients who underwent glaucoma surgery, with a significant drop in IOP, an anterior shift of the lamina was documented.

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