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Endothelial keratoplasty makes it easier to follow patients with glaucoma and lowers the risk of ocular surface disease.
Take-home message: Endothelial keratoplasty makes it easier to follow patients with glaucoma and lowers the risk of ocular surface disease.
By Lynda Charters; Reviewed by Francis W. Price Jr., MD
Indianapolis-Glaucoma surgery can cause corneal decompensation and corneal transplant surgery can cause glaucoma, said Francis W. Price Jr., MD, who is in private practice in Indianapolis.
However, it is less well known that tissue-specific corneal transplants, such as endothelial keratoplasty (EK), provide a better understanding of how glaucoma surgery affects the cornea. Penetrating keratoplasty (PK) causes increases in IOP because of the use of topical steroids and changes in the angle.
EK takes substantially fewer tolls on patients with glaucoma and lowers the risk of ocular surface disease, since filters are highly detrimental to grafts, he noted.
Dr. Price and colleagues in a study of 10-year PK survival rates found that glaucoma present before surgery resulted in double the risk of rejection failures and of endothelial failure without rejections, and tripled the risk of ocular surface disease failures (Arch Ophthalmol. 2003;121:1087-1092).
The Cornea Donor Study (Ophthalmology. 2009;116:1023-1028) reported the presence of glaucoma significantly negatively affected the 5-year PK survival, with medically managed glaucoma associated with double the risk of failure, surgically managed glaucoma triple the risk of failure, and medical and surgical management seven times the risk of failure, he noted.
“We need to evaluate alternative grafting techniques whenever possible rather than PK to mitigate the risks associated with glaucoma and glaucoma surgery,” Dr. Price said. “We also need to adapt the data obtained from EK surgeries.”
Dr. Price explained the importance of these steps. When performing PK, factors such as IOP, visual field changes, and vision cannot be measured well with sutures in place during the first year and the glaucoma can worsen.
“EK allows a better understanding of glaucoma and grafts,” he said. “None of these are problematic with EK.”
In a study of patients who underwent Descemet stripping endothelial keratoplasty (DSEK) (Ophthalmology. 2009;116:1644-1650), Dr. Price and colleagues evaluated IOPs of 24 mm Hg or higher and those that increased over 10 mm Hg from the baseline value.
One year postoperatively, he reported, patients continued to have high IOPs despite instillation of a steroid drop once daily. One-third of the patients developed a high IOP by the end of 1 year. Investigators also found that with decreases in the steroid dose to lower the IOP, the risk of rejection doubled.
“It matters what we transplant, but the type of transplant, that is, full thickness, DSEK with stroma, or Descemet membrane endothelial keratoplasty (DMEK) also matters regarding rejection,” he said.
Dr. Price reported that there were significantly fewer rejections associated with DMEK than PK and DSEK (Anshu A, Price MO, Price FW. Risk of corneal transplant rejection significantly reduced with DMEK. Ophthalmology. 2012).
“DMEK was 20 times less likely to be associated with a rejection episode than PK and 15 times less than DSEK,” he said.
“In our practice, we performed 1,500 DMEK procedures in the past 6.5 years with only 18 documented rejection episodes,” Dr. Price said. “This is a huge change from what we saw with PK.”
New prospective studies of DMEK are under way. One is a comparison of the use of prednisolone acetate 1% with fluorometholone, and another a comparison of loteprednol 0.5% gel with prednisolone acetate 1%; 1 year after DMEK patients receive or do not receive steroid therapy.
“The goal is to determine how to decrease steroids safely to avoid increases in IOP without rejections,” Dr. Price said.
In the fluorometholone/prednisolone acetate study (Cornea. 2014;33:880-886), using fluorometholone reduced the percentage of IOP increases from 24% to 8% without a significant increase in the rejection rate, according to Dr. Price.
“This is changing the way we are treating our patients,” he said.
While medical management of glaucoma is a risk factor for PK failure, it is not so for DSEK because of the small incision created and the maintenance of corneal sensation, Dr. Price explained.
The 5-year survival rates were found to be worse when DSEK was compared with PK, i.e., in patients with pseudophakic and aphakic bullous keratopathy, 72% versus 90%, respectively. A closer look at the data showed in an earlier series of eyes that underwent PK only 3% of eyes had undergone a glaucoma surgery; however, in the DSEK series 33% of the eyes had had a glaucoma surgery.
“We are seeing that glaucoma surgery is becoming a more common reason to perform corneal transplants,” Dr. Price said.
He and his colleagues published a study (Ophthalmology. 2012;119:1982-1987) that put that finding into a better perspective. Eyes with no previous glaucoma surgery clearly had better survival rates after DSEK compared with those that had previous medically managed glaucoma, a previous trabeculectomy, and a previous shunt, with respective survival rates of 96%, 90%, 59%, and 25%.
When the investigators evaluated graft survival after DSEK under failed PK (Ophthalmology. 2011;118:2155-2160), the only significant risk factor 4 years postoperatively was a shunt surgery; 96% survival was seen in patients without a previous shunt procedure compared with 22% in those with a previous shunt procedure. Neovascularization of the cornea and previous failed PKs were not risk factors.
“Filters are bad for grafts,” Dr. Price emphasized.
He advises his patients that a filter is needed to avoid blindness and the cornea can be replaced, whereas the optic nerve cannot. He also tells patients that most corneal grafts fail by 5 years postoperatively with a tube, which will need replacement, and it is easier to replace an EK than PK.
Dr. Price and colleagues found that filters are detrimental to grafts because there are increased concentrations of proteins in the anterior chamber likely because of a disrupted blood-aqueous barrier (Molecular Vision. 2011;17:1891-1900).
A more recent analysis of the proteins in the anterior chamber showed that when control eyes undergoing cataract surgery and eyes with filters or those that underwent a trabeculectomy were compared, the last two had a 5% to 10% increase in protein concentrations.
“This may be why corneas are deteriorating,” he said.
Dr. Price likes the Alvarado technique because of its low-tube profile; there is no scleral elevation within 4 mm of the limbus. There also seems to be less trauma to the tube resulting from lid blinking, and no graft is needed.
In addition, the tube is short. Mitomycin C is used intraoperatively and postoperatively to control IOP. Alvarado et al. reported this procedure (Ophthalmology. 2008;146:276-284).
Dr. Price advised surgery in eyes in which IOP cannot be controlled medically and the optic nerve is in danger.
“I believe that the least-invasive technique should be performed. I prefer non-penetrating procedures,” he said. “If that is not an option, a trabeculectomy or express shunt followed by a tube procedure. We need to determine how to better manage these eyes that have high concentrations of protein in the anterior chamber.”
The take-home message is that filters are hard on grafts and EK surgery makes it easier to follow patients with glaucoma and minimizes the risk of ocular surface disease.
“Whenever possible an EK should be preferred rather than PK,” Dr. Price concluded.
Francis W. Price Jr., MD
This article was adapted from Dr. Price’s presentation during Cornea Subspecialty Day at the 2014 meeting of the American Academy of Ophthalmology, as well as the Asia Cornea Society meeting. Dr. Price does research for Bausch + Lomb.