CATARACTS IN GLAUCOMA PATIENTS

Most of the problems associated with cataract surgery in glaucoma patients cease to be problems when recognised ahead of time and appropriate precautions are taken, said Khiun Tjia MD, Zwolle, The Netherlands.

It is not thinking about the problem and not identifying the problem which leads to the actual problem, Dr Tjia said at a Glaucoma Day session at the XXXI ESCRS Congress in Amsterdam.

The typical difficulties surgeons are likely to encounter include shallow anterior chambers, narrow pupils, posterior and anterior synechiae, cystic and very thin filtration blebs and weak zonules. Furthermore, eyes with advanced glaucoma risk losing what they have left of their visual field if they have extreme peaks of IOP postoperatively.

Surgical instruments

Injection of a viscoelastic prior to making the second incision will help establish a sufficiently deep anterior chamber for cataract surgery and greatly facilitate the entry of surgical instruments into the eye, Dr Tjia said. He recommended using dispersive viscoelastic for that purpose, because a small residual amount left in the eye is unlikely to induce high postoperative peaks of IOP.

When a patient’s pupil is smaller than the surgeon feels confident working through, a Malyugin ring is a very useful option, he noted. In some glaucomatous eyes the laxity of the zonule and the resulting folds in the capsule are such that a forced capsulotomy may cause sections of the zonule to be torn away from the ciliary body. For that reason, a sharp capsulotomy made with a knife is usually the best option.

Using a low fluidic strategy can be very advantageous in many glaucoma cases, Dr Tjia said. It minimises the iris movement and is therefore essential in eyes with floppy Iris syndrome. It also does not aspirate dispersive viscoelastic, which is best left in place during the procedure in order to protect the corneal endothelium and deepen the angle. The slower pace of surgery with a low-flow approach also gives the surgeon much more control overall.

“The lower the flow, the lower the opportunity for any inadvertent movement of the iris or capsule towards the tip. It will take a little bit more time to take the lens out with this very low flow strategy. But you're not in a hurry, so that is not a problem, and the extra time taken for the surgery will not have that much impact on the patient's outcome,” Dr Tjia added.

He noted that in the most severe cases he lowers the bottle 40cm, to provide an irrigation pressure of 47mm, and reduces aspiration pressure to the very minimum which is 12 mmHg.

Classic technique

When removing a cataract from a glaucoma patient, he prefers the classic divide-and-conquer technique. That is because it does not require reaching out to the periphery of the lens, where visibility is often very poor. He uses high vacuum in a special chop step to move the first quadrant to the middle to facilitate nucleus removal. He recommended use of a cohesive viscoelastic when implanting the IOL because it is the only type of viscoelastic that is easy to remove completely from the eye.

He added that a closed system is very important in some cases. It is therefore a good idea to create a very small side port through which to manipulate one’s second instrument. Bimanual irrigation and aspiration with very tight dedicated small incisions also creates more control in a closed anterior chamber system,
he said.

Stable IOP

A new technology that offers special advantages in glaucoma patients is the Centurion® Vision System phacoemulsification machine from Alcon. It allows surgeons to set a certain target IOP which it then maintains throughout surgery and at the same time also maintains an extremely stable IOP, Dr Tjia said.

He presented a video demonstrating how in a routine cataract case, even with very high 500 mmHg vacuum settings, neither the pupillary edge of the iris
nor the posterior capsule appeared to
be drawn to the phaco tip during occlusion break.

“This is truly groundbreaking technology. It gives us the opportunity do surgery in a very well-controlled manner with lower IOP than was possible previously. I have been extremely excited to be involved in the development of this system and I think it will help surgeons in the future,” Dr Tjia said.

Dr Tjia noted that Alcon also recently introduced disposable bimanual I/A handpieces with polymer tips. The tips have an extremely smooth surface and large aspiration opening (0.3mm) which reduces the risk of capsular damage when polishing the posterior capsule.

“It really gives you the option of doing bimanual irrigation and aspiration with very smooth aspiration control and without any risk of capsular tear of any sort. It really has improved safety a lot,” he said.

Khiun Tjia: kftjia@planet.nl