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News in Review
A Look at Today's Ideas and Trends
As the Academy Annual Meeting approaches, EyeNet brings you a preview of some papers to be presented there. Each paper was chosen by its session chairperson because it either constitutes important news in the field or is illustrative of a trend. Although only five subspecialties are represented below, there also will be paper sessions for intraocular inflammation/uveitis, neuro-ophthalmology, oculoplastics and pediatric ophthalmology. Look for a complete list of papers in the Final Program or Pocket Guide or at www.aao.org/programsearch11 .
New Combined Procedure for Keratoconus
With the odds stacked steeply against successful refractive correction, contact lens–intolerant keratoconus was previously treatable only with invasive procedures such as corneal transplantation or intracorneal ring segments. The introduction of corneal collagen crosslinking (CXL, which is not FDA approved) has slowed or stopped progression of keratoconus by stabilizing the cornea; but many patients, particularly if they are contact lens intolerant, remain visually incapacitated, with extremely high myopia and high astigmatism, said lead author David T. C. Lin, MD, clinical associate professor of ophthalmology at the University of British Columbia and medical director at the Pacific Laser Eye Centre in Vancouver, Canada.
Along with other small studies, however, a Canadian Health Protection Bureau (HPB) trial has obtained promising early results with this patient population. A case series of 12 eyes with six months’ follow-up found that 83 percent of eyes had UCVA of 20/40 or better, and 66 percent had improved BCVA following simultaneous topography-guided photo-refractive keratectomy (TG-PRK) and CXL using the iVIS laser. Mean astigmatism decreased from –3.25 D preoperatively to –0.95 D. There have been no signs of progression, said Dr. Lin, whose coauthor is Simon P. Holland, MD.
Making a case for the benefits of reducing central astigmatism and spherical aberration in keratoconus patients, Dr. Holland presented an earlier trial showing patients’ satisfaction with even a small central optical zone,1 said Dr. Lin. “So we brought this concept over to the iVIS by doing a tiny central ablation—regularizing the cornea with the iVIS—and then doing CXL afterward.”
A custom-driven platform, the iVIS suite has specific benefits for keratoconus, said Dr. Lin. Using corneal topography maps for every case, the iVIS Precisio is able to take up to 50 high-resolution images a second, making it possible to image difficult corneas, even those with extreme cones or keratometry greater than 60 D. In addition to a 1,000-Hz laser that shoots about twice as fast as those 500-Hz systems on the U.S. market, said Dr. Lin, the iVIS includes active cyclotorsion, allowing the laser to compensate during surgery and making it much more feasible to treat patients with keratoconus.
Using an all-surface laser, this TG-PRK can bring the central optical zone treatment area down to 1.5 mm to 2 mm, reducing the amount of corneal tissue removed and achieving results with a one-step treatment following epithelial calculations, said Dr. Lin. The iVIS can also perform a concurrent larger transepithelial all-laser debridement, which increases permeability for riboflavin—the first step in the CXL stage—and speeds re-epithelialization.
Dr. Lin said that although thin corneas may limit the depth of treatment, visual improvement is still sufficient to allow reasonable functioning without correction or with a soft contact lens, if necessary.
“In the past, our contact lens–intolerant keratoconus cases all went on to have corneal transplants,” said Dr. Lin, adding that now only one in 300 has needed to go this route.
1 Holland, S. P. and D. T. Lin. Collagen crosslinking for keratoconus with simultaneous topography-guided photorefractive keratectomy. Presented at the Annual Meeting of the American Society of Cataract and Refractive Surgery; March 27, 2011; San Diego, Calif.
Dr. Lin reports no financial interests.
Phaco With Femtosecond Takes Less Time, Energy
Dense cataracts required half as much total phacoemulsification energy for removal when the hardened nuclei were prefragmented with a femtosecond laser, Hungarian surgeons report.
A research group led by Zoltan Z. Nagy, MD, professor of ophthalmology at Semmelweis University, Budapest, Hungary, compared outcomes after they removed grade 4 nuclear cataracts from 40 eyes. At the Annual Meeting, the researchers will report results after 12 months of follow-up.
The study includes 20 surgeries using only conventional phaco techniques and 20 that were assisted by the LenSx laser.
“We use the laser to presegment the lens into quadrants, reaching no more than 90 percent of the lens thickness,” Dr. Nagy said. After this, the surgeon can go in with the phaco head, grasp the nucleus with the aspiration port (pressure: 250 to 300 mmHg) and use an ordinary chopper to finish dividing the nucleus along the lines precut by the laser, he said.
Dr. Nagy said that no phaco energy was required to complete the segmentation and that total phaco time was 48 percent lower in the laser-assisted procedures than in the conventional phaco surgeries.
He said that the surgeries used 51 percent less total ultrasound energy, expressed as cumulative dissipated energy (Alcon’s proprietary measure of phaco energy delivered to the eye).
Dr. Nagy also will report outcomes related to postoperative quality of vision, including IOL centration, higher-order aberrations, Strehl ratios and point-spread function.
“The femtosecond laser will never replace a good surgeon,” Dr. Nagy said. “Because even if the laser cuts the access incisions and the rhexis and prefragments the natural lens, you still need the surgical skill to divide the lens into four quadrants manually, to remove the cortex and then to implant the IOL.”
Dr. Nagy’s group has led investigations of the LenSx femtosecond laser since 2008. The group has used the laser, which Alcon recently announced its intention to acquire, in more than 600 cataract procedures.
Dr. Nagy is a consultant to Alcon and LenSx.
Rx for Corneal Ulcers: CXL
Corneal CXL has been widely reported to effectively treat keratoconus and post-LASIK ectasia. Now, doctors at the All India Institute of Medical Sciences (AIIMS), in New Delhi, report successfully treating six cases of infectious keratitis with the novel therapy.
Six eyes with nonresponsive corneal ulcer (four with hypopyon) were treated with CXL as an adjunct to topical antimicrobials and cycloplegics. Symptoms improved in all eyes within 48 to 72 hours, thus avoiding impending perforations. Hypopyon was completely resolved within two to four days. Re-epithelialization was noted in all eyes after 48 hours and was complete in 10 days. Ulcers completely resolved within three to five weeks, though all eyes showed either macular or leukomatous corneal opacity resulting from the ulcer.
CXL is simple to perform and inexpensive, making it an ideal treatment for potentially vision-threatening infections, which are especially prevalent in developing and underdeveloped countries, said Anita Panda, MD, the study’s lead author and professor of ophthalmology and head of cornea services, at Dr. Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS.
Explanations abound as to why CXL, which has been used to increase corneal rigidity, also heals wounds. Among the theories are inactivation of pathogens by direct damage to bacterial DNA, and increased stromal tensile strength and rigidity of corneal collagen, which may prevent melting.
“The immediate symptomatic relief in our study and the drastic decrease in the edema surrounding the ulcer can probably be explained by the anti-inflammatory and antinociceptive properties of riboflavin combined with the increased packing density of the collagen fibers and reduced stromal swelling rate after CXL,” said Dr. Panda.
She acknowledged the possible curative effect of the antimicrobials, which were continued with the CXL. But all eyes had received antimicrobial therapy four to 12 weeks prior to referral. “We considered that CXL acted as an adjunct.”
Dr. Panda reports no related financial interests.”
Study Sheds New Light on Implant Efficacy
In terms of overall measures of success—lower IOP, fewer glaucoma medications needed postoperatively and lower device failure rates—patients with refractory glaucoma fared better two years after implantation of the Baerveldt- 350 aqueous drainage device (AMO) than patients who received the Ahmed-FP7 valve (New World Medical), according to researchers conducting a seven-center international clinical study to compare the efficacy of the two devices over a five-year period.
Prior studies were retrospective and indicated similar success rates between these two most commonly used shunts, but inherent study design factors made it difficult to draw salient conclusions about the data, said Iqbal I. Ahmed, MD, assistant professor of ophthalmology and vision sciences at the University of Toronto. To resolve this issue, researchers recruited 238 refractory glaucoma patients and randomly assigned them to receive either the Ahmed-FP7 or Baerveldt- 350 implant.
Although outcome measures in this study have revealed a higher success rate in the Baerveldt group thus far, it is important to note that “a greater number of interventions and complications occurred in the Baerveldt group than the Ahmed group,” said Dr. Ahmed, the principal investigator.
“These are high-risk eyes, and the surgeries are considered relatively invasive, so it is not surprising that our patients experienced a number of postoperative complications that required intervention. In addition to device issues (e.g., malpositioning or the need for extension), shallow anterior chamber, choroidal effusion, iritis, corneal edema and bleb encapsulation were the most common complications. Interestingly, we found more corneal edema in the Baerveldt group and more bleb encapsulation in the Ahmed group,” Dr. Ahmed said.
Complications were directly correlated with the device configuration and implantation procedure, said Dr. Ahmed. For example, the Ahmed valve is flow restrictive and designed to reduce postoperative hypotony. This permits early postoperative flow, however, and tends to result in higher rates of encapsulation with associated elevated IOP. Conversely, the Baerveldt implant is not flow restrictive, so patients are at a greater risk for developing hypotony-related complications. Furthermore, as the device requires manual ligature of the tube during the early postoperative period, paracentesis, anterior chamber reformations and tube revisions were more common in the Baerveldt group, he said.
Dr. Ahmed receives speaker’s honoraria from Abbott Medical Optics and New World Medical.
Support for Bimonthly Injections for AMD
The possibility of bimonthly injections of antiangiogenic drugs for neovascular AMD, versus the standard protocol of monthly injections, continues to gain strength based on results with the drug aflibercept (also known as VEGF Trap-Eye).
Researchers report one-year results from the phase 3 VIEW 1 and VIEW 2 studies, which are the largest prospective, interventional studies of patients with wet AMD to date. “The VIEW studies were designed to demonstrate the efficacy and safety of intravitreal aflibercept in the treatment of exudative AMD compared with the current gold standard, monthly injections of 0.5 mg of ranibizumab,” said Jeffrey S. Heier, MD, partner at Ophthalmic Consultants of Boston and chairman of the steering committee for VIEW 1.
All told, 2,457 patients were randomized to intravitreal injections of 0.5 mg of ranibizumab monthly, 0.5 mg of aflibercept monthly, 2 mg of aflibercept monthly or 2 mg of aflibercept every two months after three initial monthly doses.
The results of the combined VIEW 1 and VIEW 2 analysis were consistent with earlier results from the separate studies and further support the concept of bimonthly dosing. In the pooled analysis, the percentages of patients losing fewer than 15 ETDRS letters were 96.1 percent of those receiving 0.5 mg aflibercept monthly, 95.4 percent of those receiving 2 mg aflibercept monthly and 95.3 of those receiving 2 mg aflibercept bimonthly. With ranibizumab monotherapy, 94.4 percent lost fewer than 15 ETDRS letters. All these findings were statistically significant. The most frequent side effects of treatment were those typical of intravitreal injections, said Dr. Heier.
The VIEW researchers initially released the study results separately. The rationale for the combined analysis was to further evaluate safety and efficacy.
Dr. Heier is a consultant to and receives grant support from Regeneron.