Eyeworld

EW CORNEA 36 September 2011 Trekking continued from page 35 "In the 36 reports of fungal in- fection after the cornea transplant, of the ones that I reviewed there were 16 that involved lamellar pro- cedures that required cutting of the tissue," he said. "In nine of those re- ports there was documentation of removal from the storage container and precutting of the tissue at the eye bank." However, he stressed that this is not definitive evidence of whether or not contamination is being intro- duced during processing. "You can't draw definitive conclusions that all of these fungal infections came from the donor tissue," he said. "They could have been infections that were caused just by having the surgery." Independent investigation Meanwhile, a third presentation by Matthew P. Rauen, M.D., Rock Is- land, Ill., involved an independent study of microbiological cultures on tissue that was used for keratoplasty. In some cases this was cut by the eye bank technician prior to sending it to the surgeon and in others it was not. "Our main aim was with the newer cornea procedures we wanted to evaluate whether the additional handling that was introduced at the eye bank impacted donor coloniza- tion rates," Dr. Rauen. Investigators wanted to know especially for DSEK whether doing the additional step at the eye bank rather than in the op- erating room enhanced donor rim colonization. "We found that there was no increased rate in either bacteria col- onization or fungal colonization," Dr. Rauen said. He stressed that while most colonization events do not go on to infection, if an infec- tion does occur, oftentimes the donor rim culture is very predictive of the organism. Investigators also found that surprisingly, there was a trend to- ward less bacterial contamination with increased handling. This may be connected to the Optisol GS (Bausch & Lomb, Rochester, N.Y.) media that is being used. "The ac- tivity of the media is enhanced if that media is sitting at room tem- perature because antibiotics work on organisms that are trying to di- vide," Dr. Rauen said. Therefore, International point of view Madurai, India N. Venkatesh Prajna, M.D.(pictured), and Jeena Mascarenhas, M.D. Fungal keratitis is an important cause of ocular morbidity in the developing world. The advances in the field of antifungal therapy have not been commensurate with the magnitude of the dis- ease. A significant proportion of deep keratitis ul- timately requires a keratoplasty. The most common cause of recurrent fungal infection in the graft is often related to inadequate excision of the primary infected tissue. Lesions involving the limbal region have a higher risk of developing a reinfection. Sometimes a deeper stromal lesion with a peripheral deep satellite lesion or a deeper feathery infiltrate cannot be adequately assessed before excision. If possi- ble, it is better to excise at least 1 mm of completely uninvolved tissue to prevent reinfection. It is also important to remove as much exudates from the anterior chamber and the surface of the iris as possible to pre- vent reinfection. At our tertiary care institute, post-keratoplasty infections are com- monly bacterial, with Pseudomonas being the organism responsible in early cases and gram-positive cocci associated with suture-related infec- tions. Post-keratoplasty fungal infections, although rare except in circum- stances mentioned above, usually start at the graft-host interface and may happen any time following the graft. An immediate reinfection is usually due to inadequate clearance, while a late recurrence may be seen following topical steroid therapy. In our practice, even when we are con- fident that we have cleared the primary infection, we do not use topical steroids in the first fortnight. If we do use them later, we always use them under topical antifungal cover. In recent times, therapeutic deep anterior keratoplasty is being increasingly performed for fungal keratitis. In our experience, a suppurative lesion, even if it is present only up to the mid-stromal area, has a higher chance of reinfection than a dry ele- vated lesion. The more severe the pre-op status, the greater the likelihood of residual or recurrence of the infection. There are a few reports indicating an increase in the incidence of fungal infections following optical keratoplasty. The use of topical steroids can predispose to fungal infections, and in the event of trauma this risk increases markedly. An important source of infection that is often overlooked can be the donor tissue. Most eye banks in our region do not routinely culture the donor corneoscleral rim. There have been instances of cluster infection due to tissues from the same eye bank; this has to be kept in mind, and constant surveillance has to be carried out, especially in eye collection centers. Post-keratoplasty fungal infection can be devastating. The manage- ment is challenging and treatment can be prolonged with a high risk of graft failure. Elimination of infection should be a top priority rather than trying to maintain a clear graft. Oral ketoconazole should be supple- mented after assessing liver function. A high index of suspicion and timely appropriate therapy may help in improving outcomes. EW Editors' note: Dr. Mascarenhas is a medical consultant at Aravind Eye Hospital, Madurai, India. Dr. Prajna is the chief of the department of medical education at Aravind Eye Hospital. Contact information Mascarenhas: doctorjeena@rediffmail.com Prajna: prajnja@aravind.org perhaps raising the tissue to room temperature to make further cuts had some impact. Dr. Glasser thinks that this is a reasonable hypothesis. "We know that warming the cornea and the media that contains antibiotics al- lows the antibiotics to function more effectively in killing the bacte- ria," he said. The fact that no differ- ence was found in the number of fungal cultures here was not surpris- ing since this isn't targeted by Optisol. "There aren't any antifun- gals in the storage media, so there wasn't any reason for it to go down," Dr. Glasser said. Potentially adding an antifun- gal to the media is under considera- tion. "There have been some published reports on adding flu- conazole to Optisol GS, and it looks to be effective but for a limited time frame," Dr. Glasser said. Since flu- conazole only suppresses fungal growth for a limited time, however, this is not something that could be effectively added by the manufac- turer and then left to sit on the shelf. "It would have to be put in shortly before use, perhaps in the eye bank," Dr. Glasser said. Prelimi- nary studies seem to suggest that it can be tolerated at concentrations that are high enough to kill organ- isms but not high enough to kill en- dothelial cells, he pointed out. Overall, Dr. Glasser was encour- aged by the findings presented. "I think that there's more work to be done, but it's reassuring to see that there's no evidence that the corneas are becoming contaminated during the processing of the tissue," he said. "It appears more likely that the organisms are coming from the donor originally, from the recipient, or the environment, and the eye bank is not introducing them." EW Editors' note: Drs. Aldave, Barone, Glasser, and Rauen have no financial interests related to their comments. Contact information Aldave: aldave@jsei.ucla.edu Barone: 301-827-6040, samuel.barone@fda.hhs.gov Glasser: dbg@comcast.net Rauen: mprauen@gmail.com

• Cover