**2. Anatomy of the trabecular meshwork**

As we know, there are three ways of draining the aqueous humor [3]:

1.The conjunctival pathway.

2.The trabecular pathway.

3.The suprachoroidal pathway.

All three routes can be surgically approached both ab interno and ab externo. The trabecular pathway is the physiological drainage pathway and it is where most of the keys of the pathophysiology of many types of glaucoma lie.

The trabecular pathway allows the aqueous humor to pass from the anterior chamber to the systemic circulation and we should see it like a dynamic mechanism instead of like a static mechanism.

	- a.The uveal TM (**Figure 1**): it is located adjacent to the anterior chamber and is arranged in bands that extend from the root of the iris and the ciliary body to the peripheral cornea.
	- b.The corneo-scleral TM (**Figure 1**): it consists of trabecular sheets that extend from the scleral spur to the lateral wall of the scleral groove.
	- c.The juxtacanalicular TM (**Figure 1**): it forms the inner wall of the canal of Schlemm and the aqueous humor moves through and between the endothelial cells that line the inner wall of the canal of Schlemm. As we advance in these areas, the difficulty of the aqueous humor outflow increases, so it is believed that the juxtacanalicular TM is the main site of resistance to the outflow of the aqueous humor.

The TM is a pressure sensitive drainage site and acts as a one-way valve, regardless of the energy. Furthermore, its cells are phagocytic and can exhibit this function in the presence of inflammation and after laser trabeculoplasty [3].

**25**

**Figure 1.**

*Cataract Surgery Combined with Trabecular MIGS (Minimally Invasive Glaucoma Surgery)*

We should not understand this system as a succession of static networks. We should understand it as a tissue embedded in an extracellular matrix in which there is a continuous intra and extracellular filtration towards the Schlemm's canal (SC), in which there is a progressive deterioration in the case of eyes with glaucoma. Thus, in eyes with glaucoma, there are some alterations that will produce rigidity of this

2.The SC (**Figure 1**) is a single canal that surrounds the anterior chamber 360° and has a diameter of 200–300 μm [3]. SC is lined with an endothelial layer that rests on a discontinuous basement membrane [3]. It is not a homogeneous or rigid conduit. Microscopically it is a complex structure, as it is crossed by tubules and has partitions and duplications and has some structures such as cylindrical anchoring structures that communicate the trabecular face with the mouth of the collecting tubules that perform a valve-like function [3]. The outer wall of the Schlemm's canal is made up of single-layered cells of endothelium without pores [3]. With OCT we can also appreciate how the canal and

3.Finally we have the complex formed by the collectors, venous plexuses and the aqueous veins [3]. It is a complex system of vessels with abundant arteriovenous anastomoses, in which the transmission of the heartbeat is essential, and whose function is to carry the aqueous humor from SC to the systemic

the trabecular meshwork modifies with changes in IOP [4].

tissue difficulting the drainage of the aqueous humor.

*Trabecular meshwork (uveal, corneo-scleral and juxtacanalicular); Schlemm's canal.*

*DOI: http://dx.doi.org/10.5772/intechopen.95416*

*Cataract Surgery Combined with Trabecular MIGS (Minimally Invasive Glaucoma Surgery) DOI: http://dx.doi.org/10.5772/intechopen.95416*

#### **Figure 1.**

*Current Cataract Surgical Techniques*

surgery.

or nonpenetrating glaucoma surgery, as they present the highest hypotensive efficacy

As an intermediate step, in mild or moderate glaucomas that do not require a high tensional decrease but in which an additional decrease in IOP than that obtained with isolated cataract surgery is needed, we can associate MIGS techniques with cataract surgery, since they offer good tensional responses (although smaller than those obtained with classical glaucoma surgeries) with a lower complication rate (both in number and severity) than with classical surgical techniques. All MIGS have in common a better postoperative recovery compared to other more invasive filtering procedures, the absence of complications associated with the bleb, the respect of the conjunctiva that will allow future techniques if required and the

(but also a higher rate of complications than other less invasive techniques).

possibility of being performed easily in combination with cataract surgery.

As we know, there are three ways of draining the aqueous humor [3]:

**2. Anatomy of the trabecular meshwork**

1.The conjunctival pathway.

3.The suprachoroidal pathway.

instead of like a static mechanism.

to the peripheral cornea.

outflow of the aqueous humor.

2.The trabecular pathway.

In the following chapter, we are going to talk about the role of the trabecular approach and the MIGS techniques that use this approach associated with cataract

All three routes can be surgically approached both ab interno and ab externo. The trabecular pathway is the physiological drainage pathway and it is where

The trabecular pathway allows the aqueous humor to pass from the anterior chamber to the systemic circulation and we should see it like a dynamic mechanism

1.The first structure in contact with the aqueous humor is the trabecular

a.The uveal TM (**Figure 1**): it is located adjacent to the anterior chamber and is arranged in bands that extend from the root of the iris and the ciliary body

b.The corneo-scleral TM (**Figure 1**): it consists of trabecular sheets that extend

c.The juxtacanalicular TM (**Figure 1**): it forms the inner wall of the canal of Schlemm and the aqueous humor moves through and between the endothelial cells that line the inner wall of the canal of Schlemm. As we advance in these areas, the difficulty of the aqueous humor outflow increases, so it is believed that the juxtacanalicular TM is the main site of resistance to the

The TM is a pressure sensitive drainage site and acts as a one-way valve, regardless of the energy. Furthermore, its cells are phagocytic and can exhibit this function

most of the keys of the pathophysiology of many types of glaucoma lie.

meshwork (TM). In the TM we differentiate three zones [3]:

from the scleral spur to the lateral wall of the scleral groove.

in the presence of inflammation and after laser trabeculoplasty [3].

**24**

*Trabecular meshwork (uveal, corneo-scleral and juxtacanalicular); Schlemm's canal.*

We should not understand this system as a succession of static networks. We should understand it as a tissue embedded in an extracellular matrix in which there is a continuous intra and extracellular filtration towards the Schlemm's canal (SC), in which there is a progressive deterioration in the case of eyes with glaucoma. Thus, in eyes with glaucoma, there are some alterations that will produce rigidity of this tissue difficulting the drainage of the aqueous humor.


circulation (it connects SC with the episcleral veins, that drain into the anterior and superior ciliary ophthalmic veins, which drain into the cavernous sinus) [3]. The organization of the collectors is not homogeneous, since they are mainly found in the lower nasal area.

In summary:

