This article is more than 5 years old. Information may no longer be current.
Keratectasia may not be a long-term problem
At the European Society of Cataract and Refractive Surgeons meeting, improved techniques and reduced complications were prominent topics.
Click Here to Manage Email Alerts
![OSN at ESCRS [logo]](/~/media/images/shared-images/osn-at-escrs-logo.gif){kind=logo}
LISBON — A discrepancy between the expected rate of keratectasia after LASIK and the actual number of reported cases suggests that “there is probably not an epidemic of ectasia after LASIK,” said Patrick Condon, MCh, FRCS(Irl), FRCOphth.
Dr. Condon delivered the Ridley Medal Lecture here at the European Society of Cataract and Refractive Surgeons meeting, with the title “Will keratectasia be a long-term complication of LASIK?”
“Why does ectasia occur?” Dr. Condon asked. “Because the cornea is a membrane, we must remember the membrane theory of elasticity.” Changing the shape and structure of the cornea during refractive surgery may lead to the complication, he said.
| Marie-José Tassignon, MD, (left) presented Patrick Condon, MCh, FRCS(Irl), FRCOphth, with the Ridley Medal. Images: Mullin DW, OSN |
“A steepening in the back of the cornea, not the front, may be a reason,” he said.
Mid-peripheral steepening of the cornea results in an immediate reaction and swelling, he said.
Reviewing published reports of keratectasia after refractive surgery, Dr. Condon noted that Daniel Z. Reinstein, MD, reported a 0.12% incidence in 5,212 eyes, and Ioannis Pallikaris, MD, reported a 0.66% incidence in 2,873 eyes. According to Market Scope, more than 17 million people worldwide have undergone LASIK.
Based on published incidence rates and the number of patients who have undergone LASIK, Dr. Condon noted, there could potentially be 52,800 cases of keratectasia worldwide. His literature review, however, found only 85 cases reported.
“So what is preventing more cases of ectasia from being reported?” Dr. Condon asked. “Maybe it’s not a short-term problem after all,” he said.
The published literature suggests that biomechanical shifts, topographic changes, higher-order aberrations and flap diameters may all play a role, he said.
“The thickness of the residual stromal bed is a major factor of ectasia,” Dr. Condon said, noting that the current “rule” of leaving a residual stromal bed of 250 µm is actually an evolving principle.
Looking ahead, Dr. Condon said he believes that corneal biometry will help to screen for patients with keratoconus, a generally accepted risk factor for ectasia after refractive surgery.
Presenting data from his own practice, Dr. Condon reviewed 137 eyes that underwent LASIK between 1994 and 2000. The mean patient age was 40 years, mean refractive error was –14.76 D, and mean pupil size was 5.25 mm. Average optical treatment zone was 6 mm.
In planning the LASIK surgery, he said, ideally 30% of total corneal thickness was left as a residual corneal bed. Lasers used to perform LASIK in these patients included the Summit Autonomous, Meditec and Technolas.
Postoperatively among these eyes, eight had macular degeneration, 13 had cataracts, eight had decreased night contrast, eight had glare that was not present preoperatively and one had keratoconus.
Twenty percent of the eyes were followed for 8 years, Dr. Condon said.
“Despite our intended undercorrections, at 8 years, 38% were still within 1 D,” he said. The refractive stability over the period was good, he said.
Dr. Condon urged any surgeon who experiences or treats a case of keratectasia following refractive surgery to report it so that a truer incidence and occurrence rate can be calculated.
Other highlights from the ESCRS meeting follow. Look for in-depth coverage of these topics and others from this meeting in upcoming issues of Ocular Surgery News.
Funding for multinational trials
The ESCRS will promote the undertaking of multinational European clinical studies by providing funds for research at an international group of clinical centers, an organization official announced.
José Cunha-Vaz, MD, past president of the ESCRS, outlined progress in this effort at this year’s annual meeting.
“We need to have more joint projects within the European Union,” he said.
Currently, a conglomerate of 15 clinical sites in Belgium, France, Germany, Greece, Italy, the Netherlands, Portugal, Spain and the United Kingdom have agreed to share information about ongoing clinical trials, all of which will be funded by the ESCRS, he said. Trials will be concentrated in four major clinical research areas: optics, surgical healing and inflammation, imaging and biomaterials, tissue engineering and drug delivery.
The goal of the joint undertaking, he said, is to “create an active area of research” in the European Union.
American, European practice styles similar, survey finds
Ophthalmologists on both sides of the North Atlantic seem to have more similarities than differences in cataract and refractive surgical practice styles, a survey suggests.
The results of the survey, which assessed the practice choices of members of the American Society of Cataract and Refractive Surgery and the ESCRS, were presented by David V. Leaming, MD.
|
|
Respondents from the two ophthalmic groups showed similarity in their choices for anesthesia in cataract surgery, type and location of incision, and IOL choice, as well as similarities in refractive surgery practices, Dr. Leaming said. There were also differences between and within the groups, he said.
Topical administration was the most popular choice for anesthesia in cataract surgery among respondents from both ESCRS and ASCRS. A temporal incision site for cataract surgery was the No. 1 choice among members of both societies, but it was more commonly favored by ASCRS respondents (65%). Clear corneal incision was the predominant choice among both societies, but ASCRS members tended to favor a totally avascular location, while more ESCRS members favored a near-clear-corneal incision, “perhaps due to fear of endophthalmitis,” Dr. Leaming said.
Performance of cataract surgery in an outpatient facility was the predominant choice for respondents in both groups. In one example of a difference in preferences, 6% of ESCRS respondents reported performing bilateral same-day cataract surgery, while almost no ASCRS respondents reported that practice. Bimanual microincision phaco was more commonly used by ESCRS respondents.
Hydrophobic acrylic was the No. 1 preferred IOL optic material in both groups. Among ESCRS members, hydrophilic acrylic was the second most preferred IOL optic material, while among American respondents silicone was No. 2.
Regarding refractive surgery, the most common procedure performed by ESCRS respondents was LASIK, accounting for 35% to 40% of cases, followed by refractive lens exchange and phakic IOL implantation. ASCRS members reported performing LASIK in a higher percentage of cases (53%), followed by a lower percentage of refractive lens exchange and only a small percentage of phakic IOL surgeries.
“The use of phakic IOLs is just gaining acceptance in the United States,” Dr. Leaming said.
He also noted that more variability of choices and practices was seen between ESCRS members in the individual countries of Europe than was seen from region to region among U.S. respondents.
Databases for cataract, refractive surgery outcomes
Two new databases designed to allow surgeons to record, audit and confidentially compare their cataract and refractive surgery outcomes were announced by ESCRS officials.
|
![I. Howard Fine, MD [photo]](/~/media/images/shared-images/i-howard-fine-md-photo.jpg)
“The purpose of this project is to reflect the outcome in routine care and form a basis for improvement and benchmarking,” said Mats Lundström, MD. The analysis of these data will also provide “useful information for patients, authorities and media,” he said.
Emanuel Rosen, FRCOphth, added that this new effort by ESCRS will promote the standardization of protocols, methods and evaluation systems.
“If we want to achieve reliable conclusions and improve our results, we need to standardize the data and compare like with like, and not apples with oranges,” Mr. Rosen said.
I. Howard Fine, MD, advocated the involvement of U.S. ophthalmologists in the project.
“Ophthalmology is global, the ASCRS and ESCRS are sister societies, and we should therefore share the same data,” Dr. Fine said. “By combining our studies, we can also share some of the costs involved. We should remember that the world is never going to be better than we are willing to work to make it, and only through our joint efforts and cooperation can we make the best for our patients.”
Details about the program can be obtained from the ESCRS.
![[bar]](/images/commonart/gradient.gif)
Cataract Surgery
‘Marked improvement’ in U.K. cataract surgery outcomes
A nationwide survey of cataract surgery outcomes in the United Kingdom found a “marked improvement” compared with 1997 data, according to a physician involved with the study.
“A continuous prospective collection of data from National Health Service departments is being carried out throughout the country,” said Robert Johnston, MD. “We have so far analyzed the outcomes of 16,541 operations for age-related cataract. While the first stage of the survey was focused on preoperative data, the second part is dealing with outcomes, namely anesthetic complications, intraoperative and postoperative complications and postoperative visual acuity.”
A preliminary analysis of the data showed that phacoemulsification is currently performed in 99% of cases, compared with only 77% in 1997 and just over 5% in 1991.
The frequency of the five most commonly occurring intraoperative complications (posterior capsular rupture with or without vitreous loss, dropped nucleus, incomplete cortical cleanup and hyphema) fell from 7.5% in 1997 to 5.08% in 2002-2003. According to Dr. Johnston, a dramatic decrease in posterior capsular rupture from 4.4% to 1.35% is probably due to surgeons becoming more familiar with phaco techniques over the past decade.
Visual acuity results have slightly improved over the years, he said.
“A significant trend towards better outcomes when cataract surgery is performed at a relatively younger age could be an indication for lowering the threshold for cataract surgery,” Dr. Johnston noted.
While the overall frequency of postoperative complications dropped from 23% to 2.4%, the rate of endophthalmitis was substantially unchanged, with a slight decrease from 0.1% in 1997 to 0.03% in 2002 and 2003.
The survey was carried out across hospital eye departments in the United Kingdom using specialty-specific electronic clinical systems.
“This survey is the first collaborative study using electronic records through out the U.K.,” Dr. Johnston said. “The number of participants is constantly growing, and now we can probably rely on 60,000 to 70,000 cases per year, which will build a huge database with detailed records of every single cataract patient.”
Prevent epithelial cells from transforming
To effectively combat the formation of posterior capsular opacification, lens epithelial cells should not be “killed,” but rather prevented from transforming and differentiating, according to Marie-José Tassignon, MD.
Promising results in this direction have been obtained with her “lens in the bag” technique of IOL implantation, Dr. Tassignon said. In this technique, both an anterior and a posterior capsulorrhexis are performed, and a lens with a special 360° grooved haptic design is used to enclose the edges of the anterior and posterior capsules.
“With this technique we have had a 0% complication rate needing YAG capsulotomy over a period of 5 years,” she said.
She showed images of patients with 4 years of follow-up with a perfectly clear optic. A close look showed some lens epithelial cell proliferation in the periphery, but attendees could see that no cells penetrated into the center of the posterior capsule.
In order to exclude the influence of the lens material on these results, an experimental study was carried out using two IOLs produced by the same manufacturer with the same biomaterial but different designs, one for standard in-the-bag implantation and one for Dr. Tassignon’s bag-in-the-lens procedure. An additional group of patients with no lens implanted was also evaluated as a control.
“While in the other groups there was a high rate of cell proliferation within the capsule, the same complication occurred only in two cases with the lens-in-the-bag technique. In both cases this was due to the capsule not being properly captured between the lens haptics,” Dr. Tassignon said.
She concluded that the key to PCO prevention is in keeping the lens epithelial cells out of any contact that can stimulate their transformation, such as the capsular bag itself and the biomaterial of the lens, as well as creating a closed system in which there is no influence from factors released by the stress of surgery or in the postoperative period.
PCO reduced with distilled water
Sealed capsule irrigation (SCI) with sterile distilled water, and possibly with more aggressive agents, may reduce PCO formation, according to Gerd U. Auffarth, MD.
|
Seventeen patients who underwent SCI following standard phacoemulsification showed an observable tendency for less fibrotic reaction after 1 to 2 years compared with controls, with no adverse effect related to the treatment, Dr. Auffarth said.
The procedure is performed with the PerfectCapsule device from Milvella, which provides a vacuum seal inside the capsular bag after cataract removal.
“After lens removal, the device is placed on the capsulorrhexis opening and firmly plugged onto the capsular bag by creating a vacuum. Two holes allow for in-and-out irrigation. In this safe, enclosed compartment you can apply any kind of substance for cleaning the capsular bag without damaging the surrounding tissues,” Dr. Auffarth said.
No reduction of endothelial cell density was produced by the device, and both pachymetry and visual acuity outcomes were identical to those of the control group, Dr. Auffarth said. This is so far the safest procedure for PCO prevention, he said.
“We need longer follow-ups to evaluate the results in the long term, and we are also considering the use of other agents, such as hyperosmolar solutions or cytostatic drugs,” he said.
Panel debates ‘best choice’ for MICS
After designing numerous irrigating choppers and having used many others, Alessandro Franchini, MD, said the best choice for microincision cataract surgery (MICS) is a front-opening chopper with a 19-gauge diameter.
“As a straightforward consequence of the Poseuille law, the 19-gauge open ended chopper guarantees the best irrigation of 77.2 mm/min with the bottle placed at 140 cm,” he said during a panel discussion on the topic. “In comparison, both the 20 gauge and all the choppers with lateral openings are far less efficient.”
Recent advances in phaco technology have helped to overcome the problem of increased turbulence created when irrigation flow is concentrated at just one point, he said.
“Turbulences are insignificant in contrast with the followability and holdability of the new software,” Dr. Franchini said. For insertion and maneuvering, the chopper blade should be angled at 110°, he said.
Peter De Lint, MD, agreed, and added that a further advantage of front-opening choppers is the capability of converting to a divide-and-conquer technique in the course of surgery.
“Most surgeons are used to divide-and-conquer, and when they start using MICS they are likely to prefer an instrument that will allow them to get back to their old habits if the procedure is not coming out successfully,” he said.
An oval-shaped 20-gauge irrigating chopper with 70° angulation was introduced during the session by Fernando Arraujo Gomez, MD.
“When a circular instrument is inserted through an incision, it creates an oval opening with too much empty space for leakage on both sides of the circular device. This forces you to place the bottle in a very high position or to set high flow of about 75 mm. Some leakage is necessary, but not too much,” he said.
New sleeve aids MICS
A new ultrasound sleeve called the Ultra Sleeve provides the benefits of bimanual MICS with the safety of coaxial cataract surgery, according to Robert Osher, MD.
|
![Robert Osher, MD [photo]](/~/media/images/shared-images/robert-osher-md-photo.jpg)
The Ultra Sleeve, from Alcon, permits coaxial phacoemulsification surgery through a 2.2-mm incision “with superb chamber stability and efficient coaxial emulsification of any grade nucleus,” Dr. Osher said.
Dr. Osher said the Ultra Sleeve, used in conjunction with the Alcon Infiniti phaco system, permits 60% more flow than a 20-gauge irrigating chopper and is superior in flow to 19-, 20- and 21-gauge irrigating choppers.
A 6-mm one-piece foldable IOL can be inserted with an injector through the unenlarged 2.2-mm incision, he said.
“This innovative sleeve design allows the surgeon to perform coaxial phacoemulsification and enjoy all of the benefits of bimanual microphacoemulsification without the associated drawbacks,” Dr. Osher concluded.
Ring for pupil dilation effective in bimanual cataract surgery
A new device can be used for pupil dilation in complicated cases of bimanual cataract surgery, said Khristo Takhchidi, MD. The pupil ring is made of PMMA and has a special design with a small loop that captures and stretches the iris during phacoemulsification maneuvers. The ring is inserted through a paracentesis and positioned with a hook.
“Thanks to this ring we obtain a stable 5.5-mm to 6-mm pupil dilation, which is sufficient to safely carry out our surgical maneuvers,” Dr. Takhchidi said.
Dr. Takhchidi reported on 57 cases of cataract complicated by glaucoma, pseudoexfoliation syndrome, diabetes or uveitis that were operated on using a bimanual microincision technique at the Fyodorov Eye Microsurgery center in Moscow. In 25 eyes the pupil expander device was used, while a conventional iris retractor was used in the other 32 eyes.
“Surgery-related complications were fewer in the group of patients where the new expander was used. The ring holds the iris well in place, making surgical maneuvers safe and easy,” he said.
Postoperative endothelial cell counts suggested that the ring provides better endothelial cell protection than conventional retractors. The ring was also associated with less hyphema, fewer fibrinoid reactions and less IOP increase.
The device is not yet commercially available, Dr. Takhchidi said.
Electrosurgical device performs capsulorrhexis in difficult cases
A plasma knife appears to be a useful tool for performing capsulorrhexis in eyes with congenital, post-traumatic or mature cataracts and in pseudoexfoliation syndrome, said Siegfried Priglinger, MD.
He described the use of the Pulsed Electron Avalanche Knife fine-cutting (PEAK-fc) for capsulorrhexis in difficult cases.
“The device allows precise ‘cold’ and traction-free dissection of tissue in a liquid medium,” Dr. Priglinger said. “The probe performs a precise, selective cut, gently moving on the surface of the lens at a speed of 1 mm per second. There is absolutely no pressure on the lens, no stress on the zonules or damage to the surrounding tissue,” he said.
The device was clinically investigated in five children with congenital cataract, six patients with mature cataracts, three post-traumatic eyes with zonulolysis and three patients with uveitis and posterior iris synechiae.
“In one case the iris was completely attached to the lens capsule, and in spite of several attempts we had been unable to loosen it with conventional instruments. With PEAK-fc, we were able to release it with no collateral damage,” he said.
Dr. Priglinger added that the same device was used to remove heavy anterior capsular opacification in two patients.
“The opacification was thoroughly removed with the help of forceps, with easy, gentle maneuvers,” he said.
Refractive Surgery
Custom ablation algorithms should consider corneal optics
Algorithms for custom ablation must be modified to resolve regional differences in the cornea and to create optical symmetry between patients’ eyes, said Marco Lombardo, MD. Compensating for these differences by modifying the algorithm could improve the quality of the optical system of the whole eye, he said.
Dr. Lombardo presented the results of a study that examined differences in the biomechanical and optical responses of the peripheral regions of the cornea after PRK.
In the study, 60 eyes were measured using corneal topography preoperatively and at 1, 3, 6 and 12 months after PRK performed with a scanning-spot excimer laser. The eyes were divided into four groups based on preop spherical equivalent refraction. The data were imported into custom mapping software that analyzed regional corneal response and higher-order aberrations.
Preoperatively, the corneas were flatter in nasal periphery than the temporal periphery, and this difference was reflected in a mirror symmetry of higher-order aberrations in both eyes, he said. In contrast, postoperatively, there was a greater curvature of the nasal periphery as compared with the temporal periphery. The interocular symmetry of higher-order aberrations was also altered, he said.
In the future, custom ablation algorithms should better consider the optical response of the cornea and seek to minimize the asymmetry between the two eyes, Dr. Lombardo said.
Address pupil distortion early in patients with phakic IOLs
Surgeons should not wait to try to rectify pupil distortion in patients who have been implanted with phakic IOLs, according to Antonio Marinho, MD, PhD. He said “doing nothing” is not an option for most of these patients.
Dr. Marinho, a member of the OSN Europe/Asia-Pacific Edition Editorial Board, spoke on the topic at the Luso-Brazilian Joint Surgical Symposium, held during the ESCRS meeting.
“If treated in a timely fashion, the distortion can be partially reversed,” Dr. Marinho said. “If we use angle-support lenses and we see ovalization, we shouldn’t wait until we have to do an iridectomy.”
Dr. Marinho said three options for remedial action are rotation, explantation and replacement of the IOL.
|
|
He said rotating the IOL is often not a good remedy because it simply creates stress at another point on the iris. Explanting the lens is a viable option, but he cautioned that “the patients won’t be happy” because they will not want to go back to wearing contact lenses or other external correction.
In older patients, explantation of the lens followed by clear lens extraction is a reasonable alternative, because these patients could have an incipient cataract. Performing phacoemulsification in these patients could be complicated, though, because a large incision is needed to remove the IOL, he added.
“Phacoaspiration may compensate, but extra care is in order,” he said.
In younger patients, simply replacing the lens could be the most feasible approach. He described a case in which he explanted the angle-supported IOL and implanted an Ophtec/Advanced Medical Optics Artisan/Verisyse lens. He said he was careful to avoid the atrophic areas of the iris.
“We were able to achieve partial reversal of the distortion,” he said.
LASIK may affect optic nerve head structure
LASIK surgery may induce transient changes in the optic nerve head, said Jose Miguel Roman Guindo, MD.
He told attendees that changes in the optic nerve head could be caused by mechanical stretching of the vitreous base after increases in IOP during the application of the microkeratome suction ring.
Dr. Roman Guindo presented data from a prospective, single-masked study of optic nerve head changes in 54 eyes that underwent LASIK for less than 6 D of myopia and less than 2 D of astigmatism. Measurement of the optic nerve head was taken with the Carl Zeiss Meditec OCT 3 preoperatively and at 1 and 3 months postoperatively. He found a statistically significant increase in the optic disc area at 1 month, rising from 2.18 mm2 to 2.24 mm2. He also said there was a statistically significant increase in cup area from 0.4 mm2 to 0.44 mm2.
Dr. Roman Guindo said these measurements returned to baseline at the 3-month follow-up point.
“LASIK seems to induce a transient change in the optic nerve head structure,” he said.
Improvements made to dual-optic accommodating IOL
A second generation of a dual-optic accommodating IOL has led to increased safety, better predictability and improved functionality of the lens, according to H. Burkhard Dick, MD, PhD.
He said Visiogen’s Synchrony IOL has been modified with design changes to address concerns noted with the first generation.
Dr. Dick said the posterior stabilizers have been improved to “ensure proper position, to compensate for size variations and to prevent decentration of the lens.”
The IOL now includes fluid channels in the anterior portion to facilitate fluid exchange from the anterior chamber to the interface between the two optics, as well as to help support the anterior capsule, he said. In addition, the haptic design has been improved upon, and the spring force has been optimized. Dr. Dick said the new design incorporates displacement limiters to prevent direct contact between the two optics.
To ease implantation, Dr. Dick said, the new version of the Synchrony can be loaded into a specially designed injector system that was not available for the earlier version.
“The implantation is made easier, and there is a controlled release of both IOLs. Once [the lens] is upside down it is easy to rotate in the bag,” he said.
Dr. Dick said a prospective, multicenter trail of the new design of the Synchrony is under way. So far, he said, his center has 29 eyes implanted with the lens with 3 months of follow-up. Overall, the postoperative spherical equivalent in these eyes is much closer to what investigators wanted to attain than with the earlier version of the lens, he said.
He stressed the importance of careful biometry preoperatively, as well as careful intraoperative cleanup. Capsular fibrosis seems to be less a problem with this second generation of the lens, as does PCO, he said.
“There were no additional surgical interventions. I see a clear improvement over previous lens refractive modalities,” Dr. Dick said, adding that longer follow-up data are needed.
Conjunctival goblet cell changes possible cause of post-LASIK dry eye
A transient decrease in the population of conjunctival goblet cells after LASIK may be associated with post-LASIK dry eye syndrome, one speaker said.
Ahmed Galal, MD, conducted a prospective, controlled noncomparative study to evaluate this hypothesis in 20 eyes of 10 patients undergoing LASIK for the correction of myopia. Dr. Galal performed conjunctival impression cytology at the superior bulbar conjunctiva and the inferotemporal conjunctiva before LASIK and then 1 week and 1 and 3 months postoperatively.
The samples were stained and examined using optical microscopy with 100× and 200× magnification in order to analyze the cellular density, epithelial morphology and nuclear chromatin matter.
His results showed that the mean preoperative goblet cell density was 485 cells/mm2. Postoperative samples showed a statistically significant goblet cell count decrease to a mean 312 cells/mm2.
By the third month, he said, the cell counts returned to normal in all patients.
“The changes are limited to damage by the suction ring,” he said.
Relying on eye tracking systems alone not advised
Monitoring the patient and ensuring proper light fixation during refractive surgery are still important for proper centration, despite advances in eye tracking systems, said Ahmed Osman, MD.
“Perfect stabilization is impossible,” he said.
Dr. Osman studied the results of tracker-assisted and manual ablation zone centration in 180 eyes undergoing LASIK for myopia and myopic astigmatism. In group 1, including 120 eyes of 60 patients, LASIK was performed using tracker-assisted ablation with the Carl Zeiss Meditec MEL-70 G-scan flying-spot excimer laser or the Visx Star S4 IR laser. In group 2, 60 eyes of 30 myopic patients underwent LASIK with the Nidek EC-5000 laser without an eye tracker.
The mean decentration was similar in the two groups: In group 1 it was 0.57 mm; in group 2, 0.52 mm. Decentration was found to be more common in patients with high myopia, he said.
“Eye tracking systems are important for centration, but we should not rely on them alone,” Dr. Osman said.
CK for presbyopia complements previous refractive procedures
Conductive keratoplasty can improve near vision in presbyopic patients who have undergone previous refractive surgical treatments, Daniel S. Durrie, MD, told attendees.
|
![Daniel S. Durrie, MD [photo]](/images/commonart/durrie.jpg)
“Conductive keratoplasty complements our LASIK and refractive IOL practice,” Dr. Durrie said.
He presented data on 27 patients who underwent CK for presbyopia after LASIK or PRK. The mean patient age was 53, and the mean uncorrected distance vision before CK was 20/40.
Patients were treated in one eye with eight spots at a 7.5-mm-diameter optical zone. Follow-up visits at 1 day and 1 and 3 months included measurement of near and distance acuity and wavefront analysis.
At the 3-month follow-up point, the mean near UCVA was 20/39, with 7.4% of patients seeing 20/20 or better, 40.7% seeing 20/30 or better and 70.4% seeing 20/40 or better.
The mean distance UCVA was 20/41, the mean sphere was –0.75 D, and the mean cylinder was –0.51 D, he said.
Dr. Durrie added that 52% of the patients wore glasses for reading preoperatively; this fell to 10% after CK.
“There is high patient satisfaction with functional vision and little or no compromise in uncorrected binocular distance acuity,” he said.
Biometry issues turn from ‘should we’ to ‘which one’
The latest debate anterior segment surgeons must face is not whether biometry is useful preoperatively, but rather which of numerous methods is the best for the surgeon and the procedure at hand, Daniel Z. Reinstein, MD, said.
|
|
“Would an orthopedic surgeon operate on a broken bone without an X-ray? No. But until recently, ophthalmologists were content to operate on an unknown,” he said.
Dr. Reinstein said biometry can help surgeons to monitor lens position – something that he deems of utmost importance as more surgeons are implanting lenses for presbyopia.
“These lenses will be in patients’ eyes for 40 to 50 years,” and biometry is the key to success, he said.
Biometry can also help surgeons identify which candidates should undergo surgery and which should not. In LASIK cases that require enhancement, the surgeon can use biometry to diagnose the cause of the undercorrection before proceeding to further surgery, he said.
Dr. Reinstein said he uses the Ultralink Artemis II to measure preoperative pachymetry, flap composition, irregular astigmatism and mechanical complications. He said that in cases in which the Artemis is used for keratoconus screening, the device can identify corneal changes easily.
“You’ll see back surface changes before you see front surface changes,” he said.
He added that in both hyperopes and myopes, white-to-white and sulcus-to-sulcus distances have no correlation to one another, and the Artemis can be used to measure the intraocular distance objectively.
Stromal bed thickness most important in post-LASIK keratectasia
The thickness of the residual stromal bed after LASIK is the primary factor in the development of keratectasia, according to a study by Teresa Pacheco, MD, and colleagues.
Dr. Pacheco said that in reviewing data on 2,500 eyes that had undergone LASIK, she and co-workers identified six eyes with postoperative keratectasia. The researchers evaluated the thickness of the residual stromal bed in the six eyes and compared those with three post-LASIK eyes that had a residual stromal bed thickness of less than 350 µm but no ectasia.
In three of the eyes with keratectasia, the corneal flap had to be removed because of complications, she said. In all the eyes with keratectasia, the preoperative myopia was higher than 8 D, and the calculated residual stromal bed was less than 250 µm in thickness.
In the three eyes with no ectasia, refraction remained stable as long as 6 to 9 years after surgery, she said.
“Our conclusion is the flap is not important to corneal stability after LASIK,” Dr. Pacheco said. “The stromal bed is the decisive factor, although this does not preclude the development of keratectasia after LASIK.”
Presby-LASIK holds promise for young presbyopes
A LASIK procedure that results in a multifocal cornea shows promise as a future method for correction of presbyopia in relatively young patients, Jose Ruiz Colecha, MD, said.
Dr. Colecha presented a study comparing results with the technique, called presby-LASIK, to results with pseudoaccommodating and accommodating IOLs.
“Presby-LASIK has got a great potential, and with more development in the software, this method will be the future for the young presbyope,” he said.
In the study, uncorrected distance and near visual acuities were recorded preoperatively and postoperatively, and best corrected distance and near visual acuities were recorded preoperatively. The data for both UCVA and BCVA were plotted together on a graph designed by the Vissum Institute in Alicante, Spain.
The study he presented included 56 eyes, of which 14 underwent presby-LASIK, 28 were implanted with a pseudoaccommodating IOL and 14 were implanted with an accommodating IOL.
According to Dr. Colecha, the presby-LASIK eyes showed improvement in distance visual acuity and what he called a “variable improvement” for near vision.
The pseudoaccommodating lenses showed varying results, he said, sometimes showing stability for near vision but not for distance, and sometimes the opposite.
“The results so far for the pseudoaccommodative lenses are not encouraging because of great variability in the outcome,” Dr. Colecha told the audience.
He concluded that accommodating IOLs held promise for patients with presbyopia due to their stable performance for both distance and near vision.
Biometry tells story of accommodative IOLs, surgeon says
Measuring the movement of the IOL optic is the only reliable method of assessing whether an accommodating IOL actually works, according to Oliver Findl, MD.
|
Studies that rely on psychophysical measures, such as distance-corrected near visual acuity, to show that accommodating lenses work can be influenced by other variables that can affect the outcome, Dr. Findl said.
Variables including the patient’s pupil size, astigmatism and corneal multifocality, as well as the motivation of patient and examiner, can influence the depth of field and therefore might give the impression that the lens is moving back and forward in the capsular bag.
“If you want to see the optic shifting, why not measure the shift itself so you know if it’s the IOL that’s working, or other factors?” Dr. Findl asked.
Dr. Findl and his colleagues evaluated the optic movement of accommodative IOLs using the Carl Zeiss Meditec IOLMaster, which uses noncontact partial coherence interferometry (PCI) to measure structures in the anterior chamber.
Dr. Findl said that PCI allows measurements inside the anterior segment with precision within a range of a few microns.
Using PCI, they found no or little forward movement of the lenses. In addition, the amount of movement they found varied substantially between patients, he said.
“There is a tradeoff between questionable accommodation vs. a definite compromise in bag performance,” Dr. Findl said. “The future might be found in dual optic lenses, which could be promising because they operate under a different principle.”
Debate format highlights ISRS/AAO symposium
A debate format led to sometimes heated, sometimes humorous exchanges between presenters at a session jointly sponsored by the International Society of Refractive Surgeons of the American Academy of Ophthalmology here. Color-coded programs allowed the audience of 550 attendees to judge the winners of the pro-con presentations.
|
|
In the symposium, entitled Refractive Surgery on the Cutting Edge, Jack T. Holladay, MD, MSEE, FACS, sparred with Scott MacRae, MD, about whether or not wavefront-guided refractive surgery is for everyone. Dr. Holladay took the con side, and Dr. MacRae was on the pro side.
Marguerite B. McDonald, MD, and Matteo Piovella, MD, engaged in a more sporting debate about the future of surface ablation, with Dr. McDonald speaking for and Dr. Piovella against. Guy M. Kezirian, MD, argued in favor of laser microkeratomes, while Richard L. Lindstrom, MD, used personal experience from his practice to argue that the laser will not replace conventional microkeratomes for the time being.
Other presenters and panel members included, Jorge A. Alió, MD, PhD; Roberto Bellucci, MD; Francesco Carones, MD; Cesar Carriazo, MD; Dr. Condon; José Güell, MD; W. Bruce Jackson, MD; Robert Kaufer, MD; Michael C. Knorz, MD; Thomas Kohnen, MD; Ronald R. Krueger, MD; Emanuel Rosen, MD; Steven C. Schallhorn, MD; Theo Seiler, MD; Gustavo Tamayo, MD; Carlos Verges, MD; and Roberto Zaldivar, MD.
Cornea
Fibrin glue aids adherence in lamellar keratoplasty
Fibrin glue can be used to create a uniform adherence of host Descemet’s membrane to donor stroma during total anterior lamellar keratoplasty (TALK), according to Thomas John, MD.
Dr. John presented results on 10 patients who underwent the TALK procedure with fibrin glue used for adherence.
He defined the TALK procedure as “complete exposure of Descemet’s membrane within the area of host corneal trephination combined with transplantation of donor cornea that is devoid of membrane and endothelium.”
Patients in his series ranged in age from 33 to 67 years, with a mean age of 48 years. Indications for the procedure were keratoconus in seven patients and corneal scarring in three. The average follow-up was 6 months.
Surgeons “cannot use an automated technique in TALK,” he said, so manual corneal lamellar dissection was used in all cases. During TALK, Descemet’s is “fully exposed up to the trephination mark,” he said.
The fibrin glue has two components, thrombin and fibrinogen, Dr. John said.
“It’s bioabsorbable and biocompatible,” he added.
Because it helps create tissue adhesion in a wet environment, the fibrin glue can result in an even, smooth adherence of host Descemet’s membrane to donor stroma.
“No Descemet’s membrane folds or interface pocket was seen in any of the eyes,” he said. “Postoperative healing was uniform, without any inflammation or interface scarring of the cornea.”
Lastly, he said, the glue dissolves and disappears within 24 hours after TALK surgery.
Tissue engineering makes autografts for acute corneal damage possible
Radical surgery at the acute phase of ocular surface disorders can be accomplished with ocular tissue engineering, Shigeru Kinoshita, MD, PhD, told attendees.
“Most doctors think that radical surgery at the acute phase is a contraindication, but if we could use this kind of cultivated epithelial cell sheet, maybe we could make some sort of paradigm shift,” Dr. Kinoshita said
He said a good-quality epithelial cell sheet must have proliferative activity in the basal cells and must maintain tight adhesion to the most superficial cell layers.
Dr. Kinoshita presented cases in which corneas scarred as a result of chemical injuries were treated with the application of epithelial cell sheets. In one case, surgeons took limbal tissue from the contralateral eye and created a cell sheet, which was then applied to the scarred eye, resulting in a clear cornea 2 years later.
“We are confident in the autograft of a cultivated epithelial cell sheet,” he said.
He also presented cases in which surgeons cultivated autografts from cell sheets created from buccal epithelial cells. He said the clinical success rate in these cases was 87%.
Deep lamellar keratoplasty with air dissection useful for keratoconus
Deep lamellar keratoplasty with air bubble dissection allows the surgeon to treat keratoconus while preserving the patient’s endothelium, Mohammed Alaa El-Danasoury, MD, said.
“Endothelial rejection is the main disadvantage of penetrating keratoplasty,” he said.
To test the efficacy of the technique, Dr. Alaa treated 50 patients with keratoconus using the deep lamellar keratoplasty technique with air bubble injection in the pre-Descemet’s plane.
“This is a planned exposure of Descemet’s membrane,” he said.
At 1 year postoperative, of 46 eyes examined, 80% reached 20/40 or better BCVA, Dr. Alaa said. Complications included fixed dilated pupil, irregular astigmatism and temporary Descemet’s membrane detachment, but no endothelial rejection occurred.
“Overall, inserting the air bubble makes deep lamellar keratoplasty safer in higher risk patients, and there’s an easy conversion to penetrating keratoplasty if you need it,” he said. “The disadvantage is, it’s a time consuming procedure.”
Metal corneal ring may reduce immune rejection after PK
A type of intrastromal corneal ring may decrease immune rejection in corneal graft patients, said Jorg H. Krumeich, MD, presenting 2-year results with the ring.
In his study, 268 patients had an 8-mm cobalt-titanium-molybdenum alloy ring (HumanOptics) sutured into their PK wounds. Postoperative results were compared with 285 patients who did not have the ring inserted during PK.
Keratoconus was seen in a similar number of patients in both groups, he said. About 10% of the patients who had the rings implanted presented with keratoconus, compared with 17.6% of those in the control group without the ring.
Postoperative BCVA was similar between the groups, he said. After 5 years, the eyes with the ring may be more stable than those without a ring, but the difference was not statistically significant, he said.
“So why should we continue to use the ring if there does not seem to be any inherent advantages?” he asked.
The rings may have been responsible for a reduction of immune rejection by about 25% in the ring group compared with the control group, he said.
“The ring seems to offer three outright advantages: protection against deformation, inhibition of ingrowing vessels and postop astigmatic control,” he said.
Potential applications for biodegradable biomaterials
Biodegradable biomaterials can potentially be beneficial in a number of applications in ophthalmology, according to Hannu Uusitalo, MD, PhD. Their possible uses include acting as a space maintainer in deep sclerectomy, as a vehicle for drug delivery, and in such complex applications as gene therapy and tissue repair.
Biodegradable copolymers are easy and inexpensive to produce, he said.
“The main difference [between the types of copolymers] at the moment is the degradation time,” Dr. Uusitalo said.
Dr. Uusitalo said three biomaterials have been shown to date to interact well with several types of human cell lines, including corneal epithelial cells and retinal cells.
“All three synthetic biomaterials are accepting those cells well,” he said.
In an experimental study, deep sclerectomies were performed on rabbits, and copolymers were used to maintain intrascleral space. Dr. Uusitalo said one of the copolymers was shown to have the fastest degradation rate, breaking down at 4 weeks.
“There was some activation of extracellular matrix, which means there is a minor wound-healing process happening,” he said.
He told the audience that drug delivery is one of the newest possible applications of the materials being investigated, with a focus on promoting better wound healing.
“It could be very beneficial to combine the drugs with the implant,” he said.
He explained that the environment surrounding the biomaterials has a significant effect on how the drug is released.
Potential applications for the biomaterials include using external energy such as a laser to make a solid gel out of the liquid biomaterial after intraocular injection. This would allow the material to be injected into the posterior segment.
He said another “simple application” might be to create artificial corneal tissue using these materials.
Glaucoma
Indications for sequential surgery
Phaco-trabeculectomy is not appropriate for all patients with concomitant cataract and glaucoma, so surgeons must understand the appropriate conditions for a sequential approach to surgery, according to Philippe Sourdille, MD.
|
Dr. Sourdille said it is crucial to understand the conditions that determine when to avoid a combined procedure, as well as how to decide upon the best approach for sequential surgery.
“Since more and more phaco-[trabeculectomies] are routinely performed with the application of mitomycin-C (MMC) to enhance filtration, and since this is prone to complications such as hypotony, bleb leak, blebitis and even endophthalmitis with a final loss in visual acuity ... should we consider a more selective approach of a combined surgery and the use of MMC?” Dr. Sourdille asked.
He said sequential surgery should be considered in patients with coexisting open-angle glaucoma and incipient cataract, with the glaucoma surgery performed first.
In special anatomic conditions, such as closed- or narrow-angle glaucoma, phacoemulsification alone can resolve both the cataract and glaucoma at once, Dr. Sourdille said.
“We know this is more frequent in Asia than in Europe. Cataract surgery can open the angle and deepen the anterior chamber, which are both important for aqueous outflow and circulation,” he said.
In cases where both surgeries are needed, cataract surgery can be performed first when the patient has angle-closure glaucoma that has been successfully treated, or a previous iridectomy or iridotomy.
Other factors to be weighed include the condition of the optic nerve, whether the target IOP has changed since an earlier glaucoma surgery, whether medical therapy has been effective, and the presence of surface inflammation or a vascular condition. The condition of an existing filtering bleb should also be evaluated.
“When considering glaucoma surgery and cataract extraction, we must also deal with the incidence of cataract and compare between penetrating and nonpenetrating surgeries,” Dr. Sourdille said.
|