October 2010




Viable option for TASS patients

by Matt Young EyeWorld Contributing Editor


Post-op DSEK; DSAEK may provide effective rehab post TASS Source: Mark Gorovoy, M.D.

Descemet's stripping automated endothelial keratoplasty (DSAEK) may be an excellent method for visually rehabilitating patients suffering from toxic anterior segment syndrome (TASS). A new study, published in the June issue of the Journal of Cataract & Refractive Surgery, is the "first to evaluate primarily the surgical and visual outcomes of DSAEK in eyes with corneal edema due to TASS," according to study co-author Mustafa nal, M.D., Akdeniz University Medical Faculty, Department of Ophthalmology, Antalya, Turkey.

Although the researchers considered DSAEK the "preferred type of endothelial keratoplasty," pointing to the procedure's established success for treating conditions like Fuchs' endothelial dystrophy and aphakic bullous keratopathy, they found its success for TASS patients to be particularly notable. "All grafts were clear at the 12-month postoperative visit," Dr. nal reported. "All eyes had better visual acuity 6 months postoperatively than preoperatively."

Ten good results

Dr. nal analyzed 10 eyes of 10 patients that underwent DSAEK after TASS. "The potential causes of TASS were inadvertent use of an undiluted intracameral anesthetic agent containing lidocaine 10% in 1 eye, surgeon inexperience with a new hydrophilic intraocular lens in 1 eye, intraocular use of surgical instruments that were sterilized with glutaraldehyde solution and not adequately cleaned before autoclaving in 2 eyes, and intracameral antibiotic (gentamicin) mixing errors in 4 eyes," Dr. nal reported. "The cause of TASS was unknown in 2 cases."

There were no primary graft failures or rejections. "Two eyes (patients 1 and 5) had an initial graft rejection episode between 7 months and 10 months after grafting," Dr. nal wrote. "Both rejections were resolved with topical steroid therapy."

Meanwhile, visual acuity vastly improved from a mean 20/260 uncorrected distance visual acuity pre-op to 20/46 by 6 months post-op. Corrected distance visual acuity (CDVA)measurable in five eyes pre-opwas 20/160, improving to a mean 20/33 post-op. CDVA did not improve in all eyes, however, as two were affected by macular pathology. Endothelial cell count (ECC) was reduced at 12 months (1,683 cells/mm2) compared to both baseline (2,740 cells/mm2) and 6 months (1,690 cells/mm2). "The mean reduction in ECD from preoperatively was 38.2% at 6 months and 38.5% at 12 months," Dr. nal reported. "The decrease was 0.4% from 6 months to 12 months."

Although endothelial cell loss after DSAEK was considerable, it was within the expected range of loss. "The reported rate of endothelial cell loss after endothelial keratoplasty ranges from 25% to 54% at 6 months and from 24% to 61% at 1 year," Dr. nal reported. "Our rate of 38% is acceptable and comparable to the incidence in other studies of DSAEK in patients with corneal edema caused by etiologies other than TASS."

Why it works

Dr. nal explained that when TASS occurs, concomitant localized endothelial damage can be severe. "Anterior segment tissues, including the corneal endothelium, which is extremely sensitive to preservatives, are severely damaged in TASS cases," Dr. nal reported. "Descemet-stripping automated endothelial keratoplasty, which involves stripping Descemet membrane off the posterior stroma of the recipient and replacing it with donor tissue comprising posterior stroma and endothelium allows selective replacement of the diseased host endothelium with a healthy donor posterior lamella."

Prior experience with DSAEK may be helpful for successful surgery. "We have been performing DSAEK for 3 years in eyes with corneal edema due to endothelial disease," Dr. nal noted.

Overall, Dr. nal believes DSAEK is a promising alternative to PK in eyes with severely compromised vision due to TASS. "DSAEK was a safe and effective procedure with encouraging surgical and visual outcomes in eyes with TASS-associated corneal edema," Dr. nal reported. John D. Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Virginia Medical School, Norfolk, Va., agreed that those with severe TASS-related corneal decompensation may require a corneal transplant, and options other than PK exist. "Endothelial keratoplasty is an ideal solution for patients who lose corneal detergence as a result of TASS," Dr. Sheppard said. Meanwhile, Dr. Sheppard said TASS continues to be a real problem. "TASS patients are ubiquitous," Dr. Sheppard said. "Half of TASS outbreaks go undiagnosed."

They can result from a variety of factors, some of which are as subtle as an upset in a clinic's air conditioning system, he said. A disturbance in a clinic's autoclave is another possible cause. "Most surgery centers have had TASS cases," Dr. Sheppard said. Fortunately, he said, most TASS cases are resolved and patients don't require corneal transplants. Another group of patients that do particularly well with corneal transplants is uveitis patients who undergo DSAEK, Dr. Sheppard said. Some uveitis patients experience a "barrage of inflammatory disturbance to the endothelium and decompensate," he said. He intends to report a dozen such cases undergoing DSAEK in the near future.

Editors' note: Dr. nal has no financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.

Contact information

Sheppard: 757-622-2200, docshep@hotmail.com
nal: mustafaunalmd@gmail.com

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