In-vivo effects of intraocular and intracranial pressures on the lamina cribrosa microstructure

Abstract

There is increasing clinical evidence that the eye is not only affected by intraocular pressure (IOP), but also by intracranial pressure (ICP). Both pressures meet at the optic nerve head of the eye, specifically the lamina cribrosa (LC). The LC is a collagenous meshwork through which all retinal ganglion cell axons pass on their way to the brain. Distortion of the LC causes a biological cascade leading to neuropathy and impaired vision in situations such as glaucoma and idiopathic intracranial hypertension. While the effect of IOP on the LC has been studied extensively, the coupled effects of IOP and ICP on the LC remain poorly understood. We investigated in-vivo the effects of IOP and ICP, controlled via cannulation of the eye and lateral ventricle in the brain, on the LC microstructure of anesthetized rhesus monkeys eyes using the Bioptigen spectral-domain optical coherence tomography (OCT) device (Research Triangle, NC). The animals were imaged with their head upright and the rest of their body lying prone on a surgical table. The LC was imaged at a variety of IOP/ICP combinations, and microstructural parameters, such as the thickness of the LC collagenous beams and diameter of the pores were analyzed. LC microstructure was confirmed by histology. We determined that LC microstructure deformed in response to both IOP and ICP changes, with significant interaction between the two. These findings emphasize the importance of considering both IOP and ICP when assessing optic nerve health.

Thin Lamina Cribrosa Beams Have Different Collagen Microstructure Than Thick Beams

“…We are not aware of other studies characterizing LC beam microstructural properties and their relationship with the LC beam width. Several studies, for example in vivo imaging using optical coherence tomography, 18 , 19 , 46 – 49 and ex vivo studies using serial block face imaging, 50 second harmonic generated (SHG) imaging, 5 , 6 , 51 – 54 have quantified LC trabecular beam and pore morphology, including the diameters, but have reported no information on collagen microstructural characteristics, such as the crimp. Accurate measurement of collagen crimp requires high angular and spatial resolutions, otherwise the orientation information will encode both anisotropy and crimp.…”

Evaluation of Automated Segmentation Algorithms for Optic Nerve Head Structures in Optical Coherence Tomography Images

“…15 Quantitative measurement of nerve fiber layer thickness and ONH structure with OCT 16 now permits detailed examination of LC substructure and its positional movements with change in IOP and intracranial pressure. [17][18][19][20] For digital analysis to be useful in clinical practice and research, automated methods are needed that require minimal observer input.…”

Current concepts of cerebrospinal fluid dynamics and the translaminar cribrosa pressure gradient: a paradigm of optic disk disease

“…42 In addition to IOP, Wang and coworkers showed that CSF pressure affects the structure of the LC as measured by its thickness and fenestration pore size. 196 Changes in the pressure-gradient force at the LC (i.e., TLPD) are dependent on the IOP and orbital CSF pressure. While, in a conventional sense, elevated IOP and ICP are critical parameters in glaucoma and papilledema, respectively, alterations in TLPD may be particularly important in cases of NTG and ODE in the setting of normal ICP (Fig.…”