I'm Alan Sugar, Professor of Ophthalmology at the Kellogg Eye Center at the University of Michigan. And I'm going to be talking about hydrodissection and hydrodelineation, brief but very important steps in cataract surgery. Hydrodissection is the injection of fluid between the capsule and the cortex of the lens, and it's purpose is to mobilize the nucleus so that the nucleus can be rotated, and to enhance cortical cleanup by loosening the cortex from the capsule. It can also be done with viscoelastic. Viscoelastic, we'll talk about it a little bit later. In hydrodissection, there is a peripheral subcapsular injection that cleaves the capsule from the cortex or the cortex from the capsule and decreases the need for cortical cleanup later. A small syringe is used. If a large syringe is used, the pressure is excessive. So we don't want to create too much pressure, but we want to create enough pressure to separate the tissues. We also use medium gage cannula, rather than a fine cannula, so that a relatively wide stream without particularly high pressure is used. A flat cannula spreads the fluid wave a little bit better than a round cannula or small cannula, allowing a better wave of fluid. And a J cannula can be used to the subincisional cortex by bending the fluid back towards the surgeon. This is an example of some of the cannulas. The one I prefer is the one on the lower right. A flat broad cannula that creates a relatively wide wave of fluid. In hydrodissection, it's helpful to remove some of the viscoelastic in the anterior chamber. This is done by pressing on the posterior lip of the main incision. This allows for extra volume of fluid to be injected. The cannula tip is then placed across the anterior chamber and under the anterior capsule, lifting the capsule slightly to be sure that it's separated from the lens tissue. The fluid wave is then forced forward. This can be repeated at several sites as necessary to free the cortex. Hydrodeilineation, as we'll show later, can be done to show the edge of the nucleus, this is then spun to confirm that the nucleus has been separated from the cortex. This is an example of a J cannula being used to force fluid behind the lens. And you can see that the capsule bulges away from the lens tissue. This is an example showing the process in several sites, usually starting distal from the incision, and then moving towards the incision in the subincisional lens. Here you can see the edge of the fluid wave behind the nucleus moving away from the site of the injection. Cannula is placed across the chamber and beneath the capsule, capsule is lifted slightly and fluid's injected here at two sites. You can see the wave passing behind the lens. The nucleus was then pushed posteriorly, slightly, to allow fluid to pass forward. The nucleus is then spun, as you can see. Here the nucleus is engaged with cannula and it's moved clockwise to spin the nucleus. Hydrodissection can be repeated. It can be repeated at any stage of the nuclear sculpting. So, don't hesitate to rehydrodissect if you find that the lens can't be rotated well. Or after beginning sculpting, the nucleus is not mobile enough. Viscodissection, is a variation where viscoelastic is used as a cushion rather than balanced salt solution. The viscoelastic that's best used is a dispersive viscoelastic such as Viscoat. This is recommended in eyes with posterior polar cataracts where the posterior capsule is weak. With Zonular weakness, weakness where you want to decrease the stress on the Zonuls. When there's been trauma to the lens and possible disruption of the lens integrity at some point, that's not necessarily visible, and in subluxation lenses. One of the complications is capsule rupture. I mentioned that you don't want to use excessive pressure because it can rupture the capsule. Nuclear prolapse can be performed intentionally but it can occur unintentionally, when there's a large, hard lens nuclear prolapse into the anterior chamber, it can tear the posterior capsule. Capsular block syndrome is an important, although fortunately rare, complication, where the nucleus blocks the edge of the capsulorhexis, allowing the capsule to distend posteriorly, increasing the interocural and intracapsular pressure. And if injection is continued, the capsule can rupture posteriorly. This can be prevented by gently pushing on the nucleus after hydrodissection, pushing centrally to allow the fluid to come anteriorly. This is an example of hydrodissection, where you can see that the fluid behind the nucleus has pushed the nucleus against the edges of the capsulorhexis, if injections continued then the capsule can rupture, allowing the nucleus to go posteriorly. Hydrodelineation is the injection of fluid between the nucleus and the epinucleus or nucleus and various layers within the nucleus leaving the epinucleus to protect the capsule. Here you can see the cannula placed in the anterior chamber. And this is a young patient with a soft nucleus. So instead of hydrodissection, the hydrodelineation is performed separating the nucleus from the capsule. In this case, it's a nucleus that will not be cracked or chopped because it's too soft. This is an example of hydrodelineation. And you can see the edge of the hydrodelineationed nucleus as a bright light. And that's called the golden ring phenomena. So we've discussed hydrodissection and hydrodelineation. Brief steps in the cataract surgery process. Using all of these that we've talked about for a few minutes takes just a few seconds. It's important, however, and as you'll see throughout the course, the performance of each step in the cataract process, makes the following steps easier and safer. Thank you.
