**3. Combined cataract–glaucoma surgery**

#### Indications

**2. Glaucoma surgery overview**

474 Glaucoma - Basic and Clinical Aspects

**•** the glaucoma drainage devices **◦** with valve (Ahmed, Krupin)

**◦** mini shunt (Ex-PRESS)

endophotocoagulation)

**2.1. Classification of MIGS**

**• Ab externo** (canaloplasty)

Gold microshunt)

Aqueous dynamics

shunt)

**• Bleb related** (Deep sclerectomy)

Surgical technique

shunt)

Bleb formation

**◦** without valve (Molteno, Baerveldt)

Surgical techniques of the glaucoma surgery include:

**•** the penetrating techniques (trabeculectomy and its variations)

**•** The trabecular aspiration in pseudoexfoliation glaucoma

the formation of a filtering bleb and the aqueous dynamics

**•** Increasing outflow through the trabeculum (canaloplasty)

**•** the non-penetrating techniques (deep sclerectomy, viscocanalostomy, canaloplasty)

**•** newer devices (Glaukos iStent, Eyepass, Trabektome, CyPass, Solx gold shunt, Aquashunt,

The concept of minimally invasive glaucoma surgery (MIGS) has gained a lot of interest in the recent years. The aim of these procedures is to minimize the side affects of the classic trabe‐ culectomy by avoiding the formation of a large filtering bleb. The primary indication for MIGS is early to moderate open-angle glaucoma as they tend not to lower the IOP as much as trabeculectomy. The classification of MIGS can vary according to the surgical technique used,

**• Ab interno** (Glaukos iStent, Trabektome, Cypass, Eyepass, Aquashunt, Solx Gold micro‐

**• Blebless** (canaloplasty, Glaukos iStent, Trabektome, CyPass, Eyepass, Aquashunt, Solx

**•** Increasing outflow through collector channels (trabectome, Glaukos iStent, Eyepass)

All the above techniques can be combined with simultaneous cataract extraction.

**•** Increasing outflow through suprachoroidal space (CyPass, Solx Gold microshunt, Aqua‐

The main indications for combined surgery are:


#### Pros


#### Cons


The procedure that the surgeon will undertake first largely depends on the level of the IOP and the severity of the glaucomatous damage. It is known that phacoemulsification has a small hypotensive effect [15,16, 17]. Phacoemulsification can be considered first when the there is mild glaucomatous damage which progresses very slowly (as assessed by fundoscopy and standard automated perimetry), the IOP is in the mid twenties and the patient's main concern is poor vision due to cataract. Furthermore cataract extraction can take place first if there is a bulky cataractous crystalline lens that is the most likely cause of an elevated IOP.

Trabeculectomy should be considered first if the glaucomatous damage is extensive and/or the IOP is very high and when the cataract operation is likely to intervene with the success of the glaucoma filtering procedure (e.g.: zonular instability due to pseudoexfoliation). The surgeon should be aware of the fact that phacoemulsification following trabeculectomy has a adverse effect on the survival of the antiglaucoma procedure [18]

The combined procedure should be considered when there is significant cataract in the presence of significant glaucomatous damage in a patient whose cataract operation is likely to be uneventful or when the patient would not like to have two separate procedures done or the surgeon feels that it is risky for a particular patient to be taken to theatre twice.

#### **3.1. Anaesthetic considerations**

The combined surgery can be done under general anaesthesia, retro/peribulbar or sub-Tenon's block or with topical anaesthesia. All topical blocks are carried out with the patient lying on the operating bed. We use a mixture of 1:1 lidocaine 2% and bupivacaine 0.5%.

**4. Combined phacoemulsification–trabeculectomy**

There is evidence that the two-site surgery offers slightly lower IOP (1-3 mmHg) than the onesite surgery [19-21]. The authors favor the two-site technique as it causes less damage to the area of filtration and subsequently less fibrosis with better chances for the survival of the

Combined Cataract-Glaucoma Surgery http://dx.doi.org/10.5772/54808 477

In the one-site technique the main incision of the phacoemulsification is done under the sclera flap and the cormeoscleral block excision is done at the site of the main incision. In the twosite approach the main incision of the phacoemulsification is done 90° away from the trabe‐

In the surgeons' experience there was no significant difference in the IOP control between the

The limbus and fornix based conjunctival flaps are equally effective in lowering IOP [22-24]. However there is evidence that limbus based flaps are more prone to late hypotony and bleb infection [22,25]. Early bleb leaks were more common in the fornix based flaps [23,24].

The aim of the trabeculectomy is to bypass the conventional outflow pathway through the trabeculum and Schlemm's canal. The aqueous humor flows through an internal ostium at the level of the trabeculum under the scleral flap in the subconjunctiva/sub-Tenon's space with the formation of a filtering bleb. The scleral flap reduces the unrestricted flow of aqueous and can be secured to the sclera with fixed, releasable or adjustable sutures. A peripheral iridec‐ tomy at the site of the operation prevents the peripheral iris from obstructing the internal ostium. In some cases such as pseudophakic or myopic eyes where the peripheral iris rests well away from the ostium the peripheral iridectomy can be avoided. In this way the chances

**•** *Black race*. The AGIS study showed weak evidence that Afro-Caribbean origin is a risk factor for failed trabeculectomy [26]. The results by Scott et al [27] agree with AGIS outcomes. However two studies by Sturmer et al [28] and Broadway et al [29] did not show statistically significant differences. The latter publication although it reports higher success rate in white patients it concludes that this difference was not statistically different. The authors speculate that trabeculectomy generally is considered to be less successful in black patients and the reason for that being their younger age during surgery and the fact that Tenon's capsule is capable of producing more intense inflammatory and subsequently fibrotic response.

**4.1. One–site versus two–site combined surgery**

culectomy site and towards the temporal side of the eye.

**4.2. Limbus versus fornix conjunctival incision**

**4.3. Aqueous humor dynamics in trabeculectomy**

**4.4. Risk factors in trabeculectomy**

of hyphaema and significant postoperative inflammation are reduced.

The long term success of the trabeculectomy depends on several risk factors:

trabeculectomy over time.

two approaches.

We perform retrobulbar anaesthesia with a 23G needle. The inferior orbital rim is palpated through the skin at the junction of its middle and lateral thirds and the needle is inserted through the skin just above the rim with the patient looking straight ahead. It is then advanced parallel to the orbital floor and when the 4/5 of the length of the needle have been advanced it is slightly retracted and then redirected upwards and slightly nasally to enter the muscle cone. The plunge is retracted to check for blood reflux (blood reflux indicates that the needle may have entered a vessel and the mixture may be injected in the blood circulation). Five to 7 ml of the mixture are injected. Immediate drooping of the upper eyelid is an indication that the anaesthetic is being injected in the muscle cone. Retro/peribulbar block offers excellent anaesthesia and akinesia. The main complications are: globe perforation, retrobulbar haemor‐ rhage, central retinal artery occlusion (due to severe and untreated retrobulbar haemorrhage), and inadvertent brain stem brainstem anaesthesia due to puncture of the meningeal sheaths of the optic nerve and injection of the anaesthetic agents in the cerebrospinal fluid circulation. As the risk of globe rupture increases with the axial length of the eye it should be avoided in big eyes as well as in patients who receive anticoagulants.

The subtenon's block is done as follows: after topical anaesthesia with tetracaine drops, a speculum is inserted and the conjunctiva and Tenon's capsule are grasped with serrated forceps 5-7 mm from the limbus in the inferonasal or inferotemporal quadrant. A fold of conjunctiva is raised with the forceps and a small incision is made with Westcott scissors. A subtenon's canula is inserted through the incision and in closed contact with the globe it is advanced around and behind the eye. Three to 5 ml of the anaesthetic mixture are injected. If the canula is in the subtenon's space then there should not be any conjunctival chemosis. Presence of significant chemosis indicates that the canula lies in the subconjunctival rather than the subtenon's space. The surgeon should make a deeper incision through both conjunc‐ tiva and Tenon's capsule and guide the canula behind the globe in close contact with the globe. Subtenon's block also offers adequate anaesthesia but less good akinesia. The most common complications are: subconjunctival haemorrhage and conjunctival chemosis. The risk of globe perforation is minimized as the subtenon's canula is blunt.

Topical anaesthesia is provided with tetracaine drops and Visthesia ampoules containing 2% lidocaine. It is the least invasive procedure but it does not offer akinesia. As the iris is not anaesthetized the patient may be more uncomfortable during the operation compared to the above techniques especially during the iridectomy.

General anaesthesia is seldom done and it is more suitable for claustrophobic patients or those who cannot lie flat and still for lengthy periods of time. In the case of general anaesthesia, retro/ peribulbal and subtenon's block the eye needs to be rotated downwards with the use of a traction suture (described later) in order to expose the superior bulbar conjunctiva.
