Imaging of the lamina cribrosa in glaucoma: perspectives of pathogenesis and clinical applications

Abstract

The lamina cribrosa (LC) is a sieve-like structure in the sclera where retinal ganglion cell axons exit from the eye. The LC has been known to play a critical role in the pathogenesis of glaucoma. With the advent of imaging technologies, such as enhanced depth imaging, spectral-domain optical coherence tomography (OCT) enables us to unveil the LC in vivo features. The application of adaptive optics technology and a compensatory image-processing algorithm has further improved the visualization of the beams and pores and neural pathways of the LC and the scleral insertion sites. Monitoring the changes of these structures in relation to acute and chronic elevation of intraocular pressure would be germane to decipher the relationship between the stress and strain response of the LC and optic nerve damage and improve our understanding of glaucoma pathophysiology. While the impact of investigating the integrity of LC is substantive, considerable challenges remain for imaging the LC. Nevertheless, with the rapid development of the OCT technology, it is expected that some of these limitations can be overcome and the potentials of LC imaging will be unraveled.

FIGURE 1

A series of coronal slices of the LC, extending from the anterior (upper left) to the posterior (lower right) was obtained in a healthy living subject by adaptive optics SD-OCT.

FIGURE 2

The clear visualization of the pore space demonstrated in Figure 1 permits 3D visualization of that space, allowing appreciation and measurement of the paths, volume, and tortuosity neural pathways through the LC. Pores appear as round elongated structures.

FIGURE 3

Improved visibility of the LC/sclera insertion sites (arrows) by the compensation algorithm. Note that the contrast of the anterior LC is improved and blood vessel shadows (asterisks) are corrected. Similarly, the visibility of the peripapillary sclera and the choroidal contrast are improved. (OCT image courtesy of Sean Sung Chul Park, MD, from the New York Eye and Ear Infirmary, New York, NY).

FIGURE 4

Visualization of poorly detected focal lamina defects (arrow) were enhanced by using compensation algorithms. Note the contrast of the anterior LC boundary is improved and blood vessel shadows (asterisks) are corrected. (OCT image courtesy of Sean Sung Chul Park, MD, from the New York Eye and Ear Infirmary, New York, NY).

FIGURE 5

The effect of chronic IOP elevation upon the rhesus macaque ONH as imaged by SD-OCT. The upper image was acquired at baseline, and the lower image was acquired 8 months after laser treatment to the trabecular meshwork. The structures delineated are the internal limiting membrane (green, first line), the posterior surface of the retinal nerve fiber layer (red, second line), Bruch’s membrane/retinal pigment epithelium and border tissue (dark blue, third line) and the anterior LC surface (light blue, bottom line). Note the profound posterior displacement of the internal limiting membrane and the surface of the lamina in the lower figure.