Ординатура / Офтальмология / Английские материалы / The Art and the Science of Cataract Surgery_Boyd, Barraquer_2000

Overview

At present, there are four main avenues of development for new techniques in cataract surgery. Those who advocate them consider that they might be better than phacoemulsification. They are:

1) The Laser Techniques

Two groups of procedures are done with laser:

a)The Dodick Laser Photolysis System: This is the only one that has been approved by the FDA in the United States and is also clinically available in Europe. This system is manufactured by Laser Corp., based in Salt Lake City, Utah.

b)The Paradigm Nd:YAG Laser System, also known on the “Phantom”. This is under investigational development by Paradigm Medical Industries also of Salt Lake City.

2) The Catarex System, being developed by Richard Kratz et al.

3) The Phaco Tmesis System, of

Aziz Anis.

4) Warm Water Jet Technology.

DODICK’S PHOTOLYSIS SYSTEM

Dodick et al use a Q-switched Nd:YAG laser. The pulsed laser and a specially designed probe to use this energy are utilized for removal of the cataractous crystalline lens. The probe has a quartz-clad fiber. The proximal end of the quartz fiber is connected to the laser source. The fiber enters the probe through the probe’s infusion port and the distal end terminates in front of a titanium target inside the tip of the probe. This target is an essential element of the device (Fig. 252).

The titanium target acts as a transducer, causing optical breakdown and plasma formation to occur in the aspiration chamber, and sending out acoustic shock waves configured by the target’s shape to be maximized at the aspirating tip. At the aspirating tip nuclear material is shattered by the acoustic waves and evacuated out of the eye.

Surgical Technique

As described by Kanellopoulos et al a 1.4 mm clear-cornea incision is made for insertion of the Dodick photolysis laser-aspi- ration probe. A second, 0.9 mm corneal incision is made to provide irrigation or infusion through a second probe. The infusion and aspiration are done after a 6 mm CCC is performed. The laser delivers pulsing photic energy, which creates a shock wave that emanates from the probe tip in a focused

cone. These shock waves break down the substance of the cataract (Fig. 252). The fragmented particles of the cataract are then aspirated out of the eye.

The same probe is used to aspirate the cortex.

At present, the incision needs to be enlarged for insertion of a foldable IOL. Industry is working on making foldable lenses that can be introduced into the eye with incisions smaller than the 2.8 mm minimum used now.

Advantages

According to Dodick, photolysis has two primary advantages. One is that it will allow smaller incisions and two, it generates no heat. One of the disadvantages of classic phaco is that the wound may be damaged by heat. With laser photolysis, we will not have any wound burns.

Photolysis is felt to offer more protection of the corneal endothelium and presumably it is a somewhat simpler procedure than phaco.

THE CATAREX SYSTEM

This system is under investigational development under the leadership of Richard

P. Kratz, Shoeila Mirhashemi, Michael Mittelstein and John Sorensen. Through the years, Kratz has made several major contributions to improve the techniques of phacoemulsification.

Catarax is a different technology that may important advantages over phaco and ECCE.

Potential Advantages and Tech-

nique

Lindstrom is participating in the investigational work in animals. As he describes it, it only requires a 1.0 to 1.4 mm incision. The surgeon makes a one millimeter incision in the anterior capsule with diathermy, just inside the edge of the iris where he makes the wound. Then he puts in a device that looks somewhat like a blender blade into the eye that works through a vortex action. This basically breaks up the lens, allowing aspiration.

The potential advantage of Catarex seems to be that there should be no corneal

endothelial cell loss, in contrast to phaco, which even in good hands, may have a four percent endothelial cell loss or more. With Catarex, since all maneuvering is done inside the capsule with its tight seal, the endothelium should have no damage. The other potential advantage is that by working inside the capsule this procedure might decrease posterior capsular tears and eliminate iris damage. All these potential advantages should provide us a safer operation.

Another potential advantage is that it is hoped Catarex may be easier than phacoemulsification, which is a difficult operation. If so, this would be a very positive advance from the perspective of public health and the availability to many people that who cannot have phaco at present. Hopefully, the cost would be less.

Aziz PhacoTmesis

PhacoTmesis uses a spinning needle that also has ultrasound. It is a very powerful cutting tool.

Water Jet Technology

If you heat water to the right temperature, about 55 to 60 degrees centigrade, you can appear to melt the lens. There are several companies working on a water jet type technology to remove cataracts with basically heated balanced salt solution. It appears that this can be done without damaging the surrounding tissues from the heat either by using an endocapsular method or by having short pulses of the heated material directed at the cataract with cool material circulating in the anterior chamber.

The latter two methods mentioned above seem to be brilliant ideas but it is unclear whether they can be translated into practical reality.