CORNEA 40 EWAP MARCH 2022 to the percentage of reinjection of air or gas among different surgeons,” he added, noting that his practice tends to reinject air more often because they’ve shown that one reinjection of air doesn’t affect cell count. “If we have someone bothered by edema, we reinject, and that’s about 20% of the time for virgin eyes,” Dr. Price said. When doing DSAEK, Dr. Lin said she will typically put in an air bubble at the end and that will resolve within 1–2 days after surgery. “If a graft detachment is going to happen, it will usually be noticed postop day 1 or postop week 1,” she said. Occasionally, the graft may be attached in the first week, but if there is severe edema present, it may be a sign that there is a low number of endothelial cells, and the graft could detach a few weeks later. When doing DMEK, Dr. Lin generally uses SF6 gas in the eye instead of air, which she said lasts longer. “Graft detachment may be more common with DMEK than DSAEK,” Dr. Lin said. “I put the SF6 gas in at 20% concentration, and it typically lasts at least a week, and I have the patient positioned on their back longer so the gas bubble can support the DMEK.” Once the gas bubble leaves, the DMEK should be in place, she said. With DMEK, you can either have a partial detachment or full detachment, Dr. Lin said. If there is a partial detachment, she recommended rebubbling to try to get the graft to reattach. If there is a full detachment, it’s usually scrolled up, she said, noting that she would either repeat DMEK or go with DSAEK rather than trying to rebubbble a detached DMEK graft. With a DSAEK detachment, whether partial or full, Dr. Lin said she will put in more air. Dr. Lin usually does rebubbling using topical anesthesia and trying to either get in through a prior paracentesis with a cannula or using a 27- or 30-gauge needle through the limbus to put in more air. She has done rebubbling at the slit lamp but said this tends to be a bit trickier. Special considerations Dr. Price noted that one group in which he’s more likely to reinject air, and the only group in which he uses long-acting gas routinely, are the eyes that have had previous PK because of the irregular surface that you get with the edge of the PK wound. A lot of these grafts don’t stick well, he said. “If you have large diameter PK, you can first make your DMEK donor smaller than the diameter of the PK, and you’ll probably be OK.” But if the DMEK graft is going to be larger than the PK diameter, there will be a higher likelihood of partial or increasing detachment. “What we’ve found is that with a larger diameter DMEK graft than the previous PK, you have to reinject air multiple times. We go to longacting gases and try to leave 80–90% gas fill to try to prevent them from detaching in the first place and to give it time to cover up irregular surfaces from PK,” Dr. Price said. Another patient group to consider carefully are those with soft eyes or hypotony. If the pressure is less than 8, Dr. Price said he will usually choose DSAEK. If the patient truly has hypotony, with pressure less than 5–6, he would recommend PK. The reason for this is if the eye is too soft, each time the patient blinks, they’re going to indent the cornea and that will make the graft come off. Patients with a large iris defect may also have problems. Dr. Price said it’s possible in these cases to lose the air because when the patient sits up, it could go to the back of the eye. In some of these patients, you might want to consider DSAEK, he said. Additionally, in patients with filters, especially tube shunts, there is an opening that the air can go up into. If it’s an inferior tube, this might not be a big deal, Dr. Price said, but if it’s a superior tube, you may have to either put in a reinjection of air once the air goes up in order to fill the anterior chamber or try long-acting gas. Another problem with filters, he said, is the air can block the filter and pressure can shoot up in the eye. He makes sure to tell patients not to rub or push on the eyes because that will cause a detachment. While detachments can occur during Permanent detachment in a young donor; the curl could not be reopened and pushed up against the recipient. Source: Francis Price, Jr., MD
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