TRANS-LAMINA CRIBROSA PRESSURE DIFFERENCE

 

The lamina cribrosa (LC) is a mechanical barrier between the intraocular compartment, having high pressure, and the intra-orbital space, which has comparatively lower pressure.

In the orbital part of the optic nerve sheath, the dynamics and composition of the cerebrospinal fluid (CSF) are different from the intracranial CSF.

The pressure difference between the intraocular pressure (IOP) and intracerebral pressure (ICP) at the level of the LC is called trans-lamina cribrosa pressure difference (TLCPD). This pressure difference has an important role in the development of cupping seen in glaucoma patients.

The difference between IOP and retrolaminar tissue pressure, divided by the thickness of the LC forms the translamina cribrosa pressure gradient.

The LC is apparently thinner in glaucoma patients compared to normal controls. In NTG patients the ICP is significantly lower than in normal individuals. These features contribute to the increase in the TLCPD and promote glaucomatous cupping.

It is also found that fluctuations in the IOP lead to repeated shear and strain at the level of the LC, increasing the cupping.

High TLCPD causes altered axonal transport, structural changes in the LC, and ischemia.

Therefore, it can be concluded that altered TLCPD plays an important role, singly or in combination with other factors, in the development and progression of glaucomatous optic nerve degeneration.