Eyeworld

143 October 2016 EW MEETING REPORTER the peripheral cornea help deter- mine the trephination depth. A Nd:YAG iridotomy preoperatively could prevent pupillary block if an air injection is needed. When it comes to using a big bubble, Dr. Nuijts said his person- al technique is trephine with the Hessburg-Barron vacuum trephine (8.0–8.5 mm) to 50% of the pe- ripheral thickness. He uses a bent 30-gauge needle, inserted into the peripheral stroma bevel down in the residual stroma to inject air. He noted that an alternative to air dissection is viscodissection. As for stromal removal, Dr. Nuijts injects viscoelastic with a 30-gauge needle into the big bubble to create space for the "quick knick." He recommends blunt scissors to excise four stromal quadrants. The stromal tissue should be lifted gently to avoid traction on deep stromal remnants, and one should avoid pressing too much on Descemet's membrane when removing the last stromal irregularities. While intraoperative OCT can be helpful in identifying residual stroma and detecting pseudo-cham- ber, he said it is limited in guiding the needle as it cannot detect metal instruments. Later, Dr. Holland offered encouragement to less experienced surgeons who might avoid DALK due to the learning curve. "There is a fear factor that if they don't get a big bubble that they've failed. All of the studies show there is a learning curve. … This panel is filled with experienced surgeons and our conversion rate is fairly low, but all of us have had per- forations and had to convert to PKs. I wouldn't let that [deter] you from at least trying," Dr. Holland said. Corneal translational research One session of the EuCornea meet- ing looked at corneal translational research, with topics including standardization of limbal stem cell culture for transplantation, ex vivo migration of corneal endothelial cells, clinical research on corneal endothelial cell injection therapy, nanofiber-based biomatrix for ocular surface reconstruction, and cell ther- apy with limbal MMSCs to prevent corneal graft rejection. Sophie Deng, MD, Los Angeles, highlighted the standardization of limbal stem cell culture for trans- plantation. She covered the defini- tion and hallmarks of limbal stem cell deficiency (LSCD). Dr. Deng also described treatment options for LSCD, which include cultivated oral mucosal epithelial transplantation (COMET), keratoprosthesis, and transplantation of LSCs. She went into detail on the concept of culti- vated LSCs and challenges. In conclusion, Dr. Deng said that transplantation of LSCs can reconstruct a corneal epithelial surface. LSCD and LSC function can be quantified by using in vivo confocal microscopy, she said. A standardized LSC therapy that incorporates the accurate grading of in vivo LSC function and potency of the cultivated LSCs is necessary to truly evaluate the efficacy of the LSC therapy. Additionally, different therapeutic approaches are likely necessary to treat different stages of LSCD, and controlled clinical trials comparing different therapies are necessary to investigate the efficacy of each approach. Unusual corneal infections, diagnosis, and novel treatment When it comes to unusual infec- tions, the key to the best opportu- nity of successful treatment is early diagnosis. That means remembering the 5% of corneal infections that are considered more unusual—Acan- thamoeba, fungi, microsporidia, atypical mycobacteria, and nocardia, for example—according to Matthew Burton, MD, London. Early diagno- sis is achievable with a good under- standing of epidemiology, taking a full patient history, making a careful examination, and keeping an open mind, he said. "Do not make a diagnosis of herpes simplex virus infection in a contact lens wearer until you have excluded the possibility that this is amoeba," Dr. Burton said, giving an example of how a patient history is helpful. A thorough investigation could include smear microscopy, culture, polymerase chain reaction, in vivo confocal microscopy, and biopsy. Dr. Burton said communication with the microbiologist in these cases is key, as well as using a variety of tests to achieve an accurate diagnosis. Crosslinking as a possible treat- ment for bacterial keratitis was also discussed during the symposium on corneal infections. Though not yet a clinically established method, Farhad Hafezi, MD, Zurich, Swit- zerland, described research that suggests it as a possible alternative, antibiotic-free treatment. "Antibiotic resistance is on the verge of becoming a global prob- lem," he said. The technique, known as PACK (photo-activated chromophore for infectious keratitis)-CXL, has been shown to be 99% effective against bacteria in vitro with the fluence used in clinical settings. It has been 60–70% effective against fungi. Dr. Hafezi said the fluence used in clinical settings has not been shown effective against Acanthamoeba or herpes simplex virus, but a higher fluence could be effective. "We have to find a way to increase the intensity … to kill the cysts without harming the stroma," he said. PACK-CXL works with three mechanisms, Dr. Hafezi said. It cre- ates oxidative stress on the surface; the photoactivity of the riboflavin integrates with the DNA of the pathogen and inhibits transcription; and it results in steric hindrance, which increases resistance to diges- tion. Dr. Hafezi said PACK-CXL should serve as a first line of treat- ment on early cases with later cases being unsuccessful. Currently in a Phase 3 trial for clinical validation, Dr. Hafezi warned that PACK-CXL should not be used routinely yet. EuCornea opening ceremony The opening ceremony of the EuCornea meeting included wel- come addresses, awards, and the EuCornea Medal Lecture. This year's EuCornea Medal Lec- ture was given by Paolo Rama, MD, Milan, Italy, on the topic of corneal stem cells. The ocular surface is a function- al and complex unit dedicated to the preservation of corneal transparen- cy, he said. Impairment to any part of the ocular surface can damage the cornea and the vision. A healthy ocular surface is absolutely neces- sary for preservation of the corneal transparency, Dr. Rama said. Tradi- tional corneal transplants cannot be successful when the ocular surface is impaired, he added. Dr. Rama highlighted therapies and procedures for patients pre- senting with these problems. For those with unilateral limbal stem cell deficiency (LSCD), he said that autologous limbal transplantation can be effective, referencing several studies. However, there are also limits of limbal autografts, including poten- tial risks for the healthy donor eye, they are not repeatable in case of failure, and only unilateral cases can be done. continued on page 144

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