It’s not long before an anticipated 24,000 Annual Meeting attendees from all over the world will converge on New Orleans to learn what’s hot in ophthalmology. This month, News in Review asked the chairmen and chairwomen in charge of the Cornea, Glaucoma, Refractive Surgery and Retina papers to select one abstract that is illustrative of either trends or important news in the field. For a comprehensive listing of papers and posters—including times and locations—see the insert in this issue.
Acute Angle Closure: Phaco or LPI
Patients with acute primary angle-closure glaucoma who are also cataractous are much less likely to suffer another rise in intraocular pressure if they have early cataract surgery than if they undergo laser peripheral iridotomy, according to the results of a randomized trial that is being presented at Sunday’s session of Glaucoma papers.
At the end of 18 months, 3.2 percent of the phacoemulsification patients and 46.7 percent of the iridotomy patients in the 62-subject study had experienced another rise in IOP requiring chronic medication (P < 0.0001). The researchers calculated the risk of a subsequent IOP rise in the iridotomy group at 14.9 times that of the phaco group (hazard ratio = 14.9; 95 percent confidence interval = 1.9 to 114.2). Subjects whose acute spike in IOP had a maximum of more than 55 mmHg were four times more likely to have another IOP rise in the postoperative period.
“Phacoemulsification, we believe, looks very promising as a long-term solution for preventing high IOP,” said Dennis S. C. Lam, MD, principal investigator of the study and professor and chairman of ophthalmology at The Chinese University of Hong Kong.
Over the last several years, published reports have proposed phaco as an effective therapy for acute primary angle-closure glaucoma, even in cases of mild cataract. Most of these studies were small and nonrandomized, and they did not directly compare iridotomy and phaco, but they have sparked more ophthalmologists to consider using phaco to widen the angle of some patients.
“We believe that our study may increase this trend,” Dr. Lam said. He noted that, in addition to averting visual loss, phaco might greatly limit the need for pressure-lowering medications later. “The mean number of glaucoma medications the laser iridotomy group was using at 18 months postop was 0.90 vs. 0.03 in the phacoemulsification group,” he said. “Therein lies a much better quality of life for the phacoemulsification group because of the much lower need to use glaucoma medications in the long run.”
The gain in visual acuity, combined with the IOP-lowering effect, make phaco and intraocular lens implantation a “very attractive option,” said coauthor Dexter Yu-lung Leung, MBBS, FRCS, honorary clinical assistant professor of ophthalmology and visual sciences at the university. More data will be necessary in order to determine whether phaco also would be preferable to laser iridotomy in patients who have clear lenses, he said.
“When there is a clear lens to start off with, the benefits in terms of vision gain may be less immediately obvious,” Dr. Leung said. “We believe that we may need a proper cost-effective analysis, utilizing measures such as quality-adjusted life years, before we may know which strategies will ultimately serve our patients best.”
Randomized Trial on Early Phaco vs. Laser Peripheral Iridotomy to Prevent IOP Rise After Acute Primary Angle Closure: 18-Month Results. Sunday, Nov. 11, 10:15 a.m., Room 244.
Refractive Surgery Paper
Ten-Year Follow-Up of PRK for High Myopia
Ten years of follow-up have revealed that photorefractive keratectomy for extreme myopia is not associated with the excess of late complications that, during the earliest days of refractive surgery, some in the ophthalmic community feared might follow laser refractive surgery, according to a study being presented during Tuesday’s Refractive Surgery paper session.
The results represent one of the first analyses of patient subsets drawn from a 3,000-case prospective study by a University of Alicante, Spain, group whose senior member is Jorge L. Alio, MD, PhD. The study’s two-year results for the 3,000 subjects were published in 1998.1
Researchers collected their 10-year data from 70 eyes of 54 patients who had PRK to correct a preoperative spherical equivalent (SE) ranging between –10 D and –17.75 D. At 10 years postop, 28 eyes (40 percent) were within ± 1 D of their original postop correction. The mean SE regressed toward myopia at a mean rate of –0.23 ± 0.3 D per year; leaving patients with –7 D to +2 D of refractive error. However, most of the regression occurred in the first five years after surgery, after which it slowed to less than 0.05 D per year. Re-treatments were done in 28 eyes.
Concern about the safety of PRK for high refractive corrections has been so great that the FDA has approved excimer lasers for PRK of no more than 7 D of myopic correction, said Orkun Muftuoglu, MD, a former fellow at Alicante who will present the results. He currently is a fellow in cornea and refractive surgery at the University of Texas Southwestern Medical School in Dallas.
The results of the study were both reassuring and a little surprising, Dr. Muftuoglu said. “In the beginning, we thought we might see ectasia because so much tissue was removed from the cornea.” But he said, “There were no patients with ectasia. That’s important to know as these patients had a mean treatment for myopia of 12 D, and none were under 10 D.”
|LONG-TERM SAFETY. As is the case with PRK on eyes with moderate myopia, PRK on eyes with high myopia appears to be relatively safe. |
PRK ablates through Bowman’s layer, so another complication the researchers unsuccessfully looked for was ocular infection. Corneal haze—a common problem in early PRK—mostly disappeared between the 1998 study and the 10-year exam.
“A lot of surgeons were concerned about this, and we saw that most of the haze in these patients went away over the long term. In the end, they have a reasonable amount of haze,” he said.
Using a formula proposed by George O. Waring III, MD (postop BCVA divided by preop BCVA), the group calculated a safety index for PRK in these high myopes at 1.12, reflecting an overall gain in visual acuity. They found an efficacy index (postop UCVA divided by preop BCVA) of 0.78, which is probably a reflection of regression in eyes that were not re-treated, Dr. Muftuoglu said.
“Millions of people worldwide have undergone this surgery. And, although PRK h9:54 PM 10/30/2007as lost some of its early popularity, it is rebounding because of the use of MMC, LASEK and epi-LASIK,” Dr. Muftuoglu said. “That’s why long-term data for these patients are much more important than they might otherwise be.”
1 Alio, J. et al. J Cataract Refract Surg
Ten-Year Follow-Up of PRK for High Myopia. Tuesday, Nov. 13, 11:39 a.m., Hall D Session Room.
Seprafilm Promising for Retinal Breaks, Tears
Could repairing a torn retina one day be as easy as putting a high-tech Band-Aid on it? Probably not—but fanciful imaginings seem inevitable when considering the research by a group at the Schepens Eye Research Institute.
The study found that a sticky layer of sodium hyaluronate/carboxymethylcellulose/modified anionic polysaccharides placed on retinas of four eyes with rhegmatogenous detachments sealed retinal breaks after vitrectomy and then melted away a month later—without the need for persistent gas bubbles or face-down positioning.
After mean follow-up of one year, none of the four patients had developed a retinal redetachment. The procedure’s only complication was transient ocular hypertension.
This repair procedure is in contrast to previous attempts at covering retinal breaks with other materials, such as fibrin glue (it melts too quickly), mussel protein (it provokes inflammation) and even cyanoacrylate “superglue” (it dries stiff so can’t be used for large tears).
The Schepens study may be the first to describe the ophthalmic use in humans of this patching material called Seprafilm II Adhesion Barrier (Genzyme). Seprafilm was developed more than a decade ago to prevent adhesions after abdominal surgery.
Sodium hyaluronate, usually in its viscoelastic form, has been tested in animals for prevention of adhesions and fibrosis in strabismus and glaucoma filtration surgeries since the 1980s. The results have been mixed, and the literature contains no reports on research progressing beyond the preclinical stage.
Seprafilm is known for adhering strongly to moist tissue and for persisting long enough to block unwanted tissue interactions after surgery. In the first 48 hours after application, it forms a transparent, impermeable, hydrophilic protective gel at the site where it was placed.
In the case of a retinal tear, this long-lasting gel bandage prevents contact between the retinal pigment epithelium and vitreous, thus reducing the risk of proliferative retinopathy and redetachment, the Schepens researchers explain in a 2006 article.1
“The exposure of a large area of RPE can give the RPE cells a chance to migrate to the vitreous and initiate the cascade of events leading to the development of PVR,” they write. “In fact, no procedure used today to reattach the retina closes the retinal break; all current procedures simply put the edge of the retinal tear in contact with the RPE. Unless edge-to-edge closure of the retinal tear is accomplished, the break remains open to the vitreous cavity.”
1 Sueda, J. et al. Invest Ophthalmol Vis Sci
The authors report no related financial interests.
Seprafilm Is a New Sealant for Patching Retinal Breaks. Tuesday, Nov. 13, 9:40 a.m., Room 244.
Device to Ease DSAEK
As an alternative to corneal transplantation, the success of DSAEK (Descemet stripping automated endothelial keratoplasty) depends greatly on the surgeon’s skill at several tasks:
- gently folding an 8- to 9-mm disc of donor endothelium and coaxing it through a 4- to 5-mm incision,
- navigating the tissue into the anterior chamber without damaging either the chamber or the lenticule,
- unfolding the transplant tissue with the correct side toward the cornea, and
- positioning the transplant against the stroma.
Mechanical trauma during this process can damage the endothelium, with a theoretical risk that the number of cells per mm2 might fall low enough to compromise the graft’s ability to keep the recipient’s cornea clear.
With that in mind, a trio of Singaporean ophthalmologists will inform attendees at the Cornea papers session on Monday about their device for inserting a DSAEK graft into the eye with minimal danger to the endothelium.
Normally, the donor lenticule is coated on the endothelium side with viscoelastic and then folded into an asymmetric “taco” shape, stromal side out, for insertion. Rarely, it unfolds upside down in the chamber, raising the risk of further cell damage as the surgeon turns the tissue over.
After laboratory trials that quantified endothelial damage from folding, the researchers devised an alternative. Their device is a modified standard anterior chamber sheet glide made of flexible clear plastic, onto which the viscoprotected sheet of corneal tissue is placed. After inserting the glide through the scleral wound, the surgeon pulls the lenticule into the chamber with an intraocular forceps.
Donald Tan, MD, head of the cornea service at the Singapore National Eye Center, will present the details of these investigations, which the authors say resulted in minimal endothelial damage during 23 DSAEK cases.
The group also compared primary graft failure rates against 20 cases of the conventional folding technique. “With the folding technique, we encountered a primary graft failure rate of 25 percent [five out of 20 cases], while with our glide technique we only had one primary failure out of 23 consecutive glide cases [4.3 percent primary failure rate],” said Dr. Tan. “The only failure we encountered with our glide technique was the first time we tried the procedure. The cause of graft failure was Descemet’s detachment from the donor because the donor was too thick (400 µm) and should not have been inserted in the first place,” he said.
A New Glide Insertion Technique for Descemet Stripping Automated Endothelial Keratoplasty. Monday, Nov. 12, 10:24 a.m., Room 244.
The Academy announces a new designation, “Best Papers,” for this year’s Annual Meeting. The expert panel for each session will name one paper as best of that group. The Best Papers will be announced in the Academy Live e-newsletter, which is sent out each night from the Annual Meeting, and in the Academy Notebook section of January’s EyeNet.