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Surgeon: Anterior chamber iris-fixated IOL preferred design for phakic implantation
PARIS – An anterior chamber iris-fixated lens is the best location and the design of choice for phakic IOL implantation, according to Lucio Buratto, MD.
Dr. Buratto, of Milan, delivered this assessment in a review of the development of phakic IOLs in his Binkhorst Medal Lecture here at the European Society of Cataract and Refractive Surgeons (ESCRS) meeting.
“My personal view is that because of their location and the fact that they don’t need precise measurements, [iris-fixated] lenses can stay in the eye for a longer term with fewer side effects [than other types of anterior and posterior chamber phakic IOLs],” Dr. Buratto said.
He noted that the one model of iris-fixated lens available is made of a familiar material with a long track record. The only iris-fixated phakic IOL currently in widespread use is the Artisan/Verisyse IOL from Ophtec/Advanced Medical Optics.
Dr. Buratto, a founding medical editor of Ocular Surgery News Europe/Asia-Pacific Edition, said he is skeptical of other anterior chamber and posterior chamber phakic IOLs. He reviewed a number of published studies of other phakic lens designs in his presentation.
![Lucio Buratto, MD [photo]](/~/media/images/news/print/ocular-surgery-news-europe-asia-edition/2004/01_january/burrato_125_206_6748.jpg) Lucio Buratto, MD, displays his Binkhorst Medal at the ESCRS meeting. |
“Considering that myopic eyes are prone to cataract and glaucoma, and that any surgery increases these risks, my personal view is, because of its location, a posterior chamber phakic IOL cannot be tolerated long-term without secondary effects, especially in young patients with an active life. My personal view on posterior chamber IOLs is that they can cause cataracts over a long term due to frequent contact with crystalline lens,” he said.
Currently, Dr. Buratto said, the two phakic IOLs with the widest clinical experience are the Artisan/Verisyse and the STAAR Surgical Visian ICL, a posterior chamber lens. The Ophtec/AMO lens recently received Food and Drug Administration approval. The STAAR lens is still awaiting FDA approval.
“A number of [other] anterior chamber IOLs with different designs have appeared on the market, but none of them have stayed on the market for more than 3 years, and none of them have been submitted for FDA approval,” Dr. Buratto said. “The studies presented for FDA approval are probably the most complete, and the results for both IOLs are excellent from the refractive and visual point of view and without many complications.”
Dr. Buratto cautioned, however, that “these results are the best a surgeon can hope for because when a company wants to have its lens approved, it will select the best surgical facilities, the best surgeons who select ideal patients, and the best operation.”
Regarding which lens he would recommend to another surgeon, Dr. Buratto said, “I would choose the lens that gives the lowest incidence of complications. According to the published literature, the Artisan has the lowest incidence of complications, followed by the ICL. Today, I would not implant any other lenses.”
Dr. Buratto said that “a proactive responsibility” lies in the hands of the surgeon, who has a responsibility to add to the learning process.
“Doctors must follow every single patient for as long as possible, collecting and reporting as much comprehensive data as they can,” he said. “Surgeons must be actively involved in reducing intraoperative complications.”
Dr. Buratto concluded by giving surgeons some tips for improving the quality of phakic IOL implantation.
“First, carefully choose the patients, and carefully test the eye; second, only use a lens with a long follow-up and FDA approval; third, perform the highest quality surgery you can. We have the opportunity to improve the quality of life of millions of people. We must not waste it,” he urged the audience.
Following are some of the other highlights of the ESCRS meeting:
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Cataract/IOL
PCO low with AcrySof
Results regarding the posterior capsular opacification performance of the one-piece and three-piece Alcon AcrySof IOLs were presented by Oliver Findl, MD. According to Dr. Findl, both models performed equally well at 2-year follow-up. He compared the two designs of the Alcon hydrophobic acrylic IOL along with colleagues at the Medical University of Vienna.
The researchers designed a bilateral, randomized, masked study to compare PCO formation with the two IOL designs. The same surgeon performed all surgeries in 104 eyes of 52 patients in the study. Each patient received a one-piece AcrySof in one eye and a three-piece AcrySof in the other. Thirty-four patients completed 2-year follow-up. PCO was graded both by slit-lamp evaluation and with the AQUA automated image analysis system for evaluating PCO.
At 1 year postop, Dr. Findl said, the amount of regeneratory PCO based on the AQUA score was statistically significantly higher in the eyes with the one-piece lens. By 2 years postop, however, there was no statistically significant difference in AQUA scores between the two IOL designs, he said. The same was true with the subjective slit-lamp grading, he said, with a slight but significant difference at 1 year but no significant difference at 2 years.
Tension ring effect on PCO
The effect of capsular tension ring implantation on the formation of PCO is incompletely understood and may vary depending upon the design of the IOL implanted with the ring, a study suggests.
Khiun Tjia, MD, of Zwolle, Netherlands, discussed the study at a session on PCO.
The study compared the effect on PCO of capsular tension rings (CTRs) implanted with two types of hydrophobic acrylic IOL, the AcrySof three-piece MA-60 with a squared posterior optic edge and the AMO Sensar AR40 with a rounded edge. The IOLs were implanted bilaterally in 15 patients each, with a CTR implanted simultaneously in one eye of each patient and no CTR in the contralateral eye.
According to Dr. Tjia, in the 13 patients with the squared-edge IOL who completed 3-year follow-up, five YAG capsulotomies were needed in the eyes with a CTR and two were needed in the eyes with no CTR. In the 11 patients with the rounded-edge IOL who completed 3-year follow-up, there were no YAGs in the eyes with CTR and four in the eyes with no CTR.
“Our study suggests that the influence of tension rings on PCO is not clear, and that the effect may be different for rounded than for squared-edge IOLs,” Dr. Tjia said.
IOL formula sans fudge factor
A new formula based on precise measurements of the eye allows IOL power calculation without a surgeon “fudge factor,” according to a presentation here. The formula is accurate even for eyes that have undergone refractive surgery, one of the presenters said.
Paul-Rolf Preussner, of the University of Mainz, Germany, where the Okulix power calculation method was developed, described the rationale for the technique and preliminary results with it. He said that “calibration of measurement equipment and application of transparent, exact calculation procedures make ‘individualizations’ obsolete.”
Dr. Preussner said calculations with the Okulix formula employ several precise measurements: ray tracing of the pseudophakic eye; objective IOL data including radii, thickness and refractive index of the material, rather than the manufacturer’s “power” labeling; laser interferometry to measure axial length; and three-dimensional corneal topography to extract corneal radii. Anterior chamber depth is calculated by “a simple approach … previously calibrated in cooperation with the Vienna Eye Hospital,” he said.
According to Dr. Preussner, the mean prediction error with the Okulix formula, calculated in 65 eyes at the Mainz Eye Hospital, was “practically zero,” without any bias for long or short eyes.
Tanja M. Rabsilber, MD, of Heidelberg, described use of the Okulix formula in 12 eyes of eight patients undergoing cataract surgery after previous excimer laser refractive surgery. Corneal topography was performed with the Technomed C-Scan, and axial length was measured using the Zeiss IOLMaster.
Accuracy of prediction was calculated by comparing attempted to achieved spherical equivalent. In the 12 eyes, the mean postoperative error was less than 0.8 D, she said.
Dr. Rabsilber said the Okulix formula is suitable and reliable to calculate IOL power for patients after excimer laser refractive surgery.
AquaLase and cell counts
Endothelial cell loss was the same in cataract surgery with AquaLase and standard ultrasound phacoemulsification, according to a study comparing the two modalities by Helga P. Sandoval, MD, and colleagues.
One eye of each of 30 patients was randomly assigned to undergo lens removal using the Alcon AquaLase modality, Dr. Sandoval said. The fellow eye of each patient was treated using standard ultrasound.
There was no statistically significant difference between the patients’ two eyes in preop visual acuity, pachymetry measurements or endothelial cell counts, Dr. Sandoval said.
A significant increase in pachymetry was noted only at 1 day postop and only among AquaLase eyes. This subsequently decreased, and both groups had similar pachymetries at all other follow-up points, Dr. Sandoval said.
Both groups also experienced similar decreases in mean endothelial cell counts, she noted.
Near vision better with multifocal
Following cataract surgery, multifocal IOLs can provide significantly better near vision than monofocal IOLs, and distance vision is comparable between the two, according to a poster by A. Burak Bilgin, MD, and colleagues.
They reported results in 46 eyes implanted with either a multifocal or monofocal IOL after cataract surgery using phacoemulsification. The AMO Array SA40N multifocal IOL was implanted in 23 eyes, and the AMO Sensar AR40N monofocal IOL in 23 eyes.
No significant difference in uncorrected distance vision was seen between the two groups after a mean follow-up of 4.3 months. Patients in the monofocal IOL group had a mean uncorrected visual acuity (UCVA) of 0.73. Patients in the multifocal IOL group had a mean UCVA of 0.8.
All eyes achieved a BCVA of at least 0.6. Both groups had similar amounts of surgically inducted astigmatism, averaging 0.56 D. Both near UCVA and near BCVA were significantly better postoperatively for patients in the multifocal group, the study authors said.
Nine eyes in the multifocal group and one eye in the monofocal group had postoperative glare. There were no decreases in BCVA in either group, and no eyes required capsulotomy, according to the poster.
OCT study of capsule
The anterior and posterior lens capsules completely enclose the optic of an implanted IOL within 1 day following cataract surgery, according to a study performed using ocular coherence tomography. Formation of the capsular bend may require up to 2 weeks, said Stefan Sacu, MD.
Dr. Sacu presented the results of a prospective, randomized study evaluating the use of optical coherence tomography to document capsular bend formation.
The study included 33 eyes of 33 patients with age-related cataracts. Phacoemulsification was used for lens removal in all eyes. Eyes were randomly assigned to receive one of three types of IOL: the one-piece acrylic Alcon AcrySof, the three-piece AcrySof or the three-piece silicone Pfizer 911A.
The mean distance between the anterior capsule and the IOL was 197 µm at day 1 postop in the one-piece acrylic IOL group, 161 µm in the three-piece acrylic IOL group, and 220 µm in the three-piece silicone IOL group, according to the study.
In 28 of the 33 eyes (85%), the posterior capsule contacted the IOL within 1 day following completion of surgery, Dr. Sacu said. Capsular bend formation was noted after a mean follow-up of 10 days in patients implanted with the one-piece acrylic, 13 days with the three-piece acrylic and 15 days with the silicone IOL, Dr. Sacu said.
‘Bag-in-lens’ technique
A novel technique for congenital cataract surgery that uses an anterior and posterior capsulorrhexis of the same size results in a rate of zero PCO after 4 years, said Marie-Jose Tassignon, MD. She discussed the results of a preliminary study of the procedure.
In her technique, an anterior and a posterior continuous curvilinear capsulorrhexis (PCCC), both of the same size, are created and then glided into a peripheral groove around the 5-mm optic of a specifically designed IOL, she said.
Dr. Tassignon said the lens epithelial cells (LECs) are trapped between the anterior and posterior leaves of the capsule. No vitrectomy is performed.
In an initial study in 15 eyes of 10 children who ranged in age from 7 months to 11 years, “we saw extremely interesting and extremely encouraging results” with the bag-in-lens technique, Dr. Tassignon said.
Because of the lens design, the remaining capsular bag is closed, preventing the LECs from coming in contact with anterior chamber fluid, posterior chamber fluid or anterior vitreous, Dr. Tassignon said.
“No PCO could be detected at all,” she said. “This result has never been achieved by any other type of lens implanted according to the lens-in-the-bag way of implantation.” The longest follow-up to date is 4.5 years.
The lens, made for Dr. Tassignon by Morcher, has optic sizes of 4.5 to 5.5 mm, she said.
Sealed capsular irrigation
A device that irrigates the capsular bag with sterile water following cataract removal reduced the development of capsular opacification when compared to control eyes at 1 year, according to Anthony Maloof, MD.
Dr. Maloof and colleagues in Sydney, Australia, conducted a study evaluating the Milvella PerfectCapsule sealed capsular irrigation (SCI) system in 25 cataract patients. Dr. Maloof presented the results at a satellite symposium before the ESCRS meeting.
The study compared rates of both anterior capsular opacification (ACO) and PCO at 12 months in 14 study patients and 11 control patients. The capsular chambers of patients in the study group were selectively sealed using the SCI system and then irrigated with 10 mL of sterile water to eliminate any lens epithelial cells remaining following cataract extraction.
At 12 months, patients in the study group had significantly lower ACO scores compared to the control patients (P = .03), he said. There were no cases of capsular phimosis in the study group and three cases in the control patients, Dr. Maloof said.
Nonphaco sutureless surgery
A nonphaco sutureless technique can be more practical than phacoemulsification for removal of white cataracts, according to S.K. Basak, MD.
Phaco of mature, white cataracts is challenging, costly and time consuming, while nonphaco sutureless cataract surgery is simple, safe, fast and far less expensive, Dr. Basak said.
He said white cataract is a significant burden in many developing countries, including India. White cataracts comprise 8% to 11.6% of cataracts operated in some published series from developing countries, he said.
Dr. Basak described a study he performed with colleagues in Barrackpore, India, comparing phaco with a foldable IOL to nonphaco sutureless surgery with a one-piece 6-mm or 6.5-mm PMMA IOL. In the study, 250 eyes with white cataracts were randomized to one of the procedures.
In the phaco procedure a stop-and-chop technique was used, followed by implantation of a foldable IOL. In the nonphaco sutureless procedure, which Dr. Basak showed in an unedited real-time video during his presentation, a 6-mm to 6.5-mm scleral tunnel incision was created, followed by creation of a modified envelope capsulotomy and delivery of the nucleus using an irrigating vectis. A rigid one-piece IOL was implanted in these eyes.
Outcomes at 1 month were compared. Dr. Basak said average operative time was two-thirds less with the nonphaco than the phaco technique, about 4 minutes vs. 12 minutes. BCVA was similar between the two groups of eyes. Mean astigmatism at 1 month was greater in the nonphaco group, but endothelial loss was similar between the groups.
Notably, the cost of surgery was US$190 in the phaco group and US$10 in the nonphaco group. A large part of this difference was due to the much lower price of the one-piece PMMA IOL, about one-twentieth of the price of the foldable IOL, Dr. Basak said.
Refractive
Corneal nerves after PRK, LASIK
Corneal innervation recovers more quickly after PRK than LASIK, according to a confocal microscopy study presented in a poster here. Jay C. Erie, MD, and William N. Bourne, MD, found that neural recovery after LASIK was prolonged compared to PRK, and the number of sub-basal nerves was still reduced by 40% at 3 years after LASIK.
The study authors used custom software with a tandem scanning microscope to measure the nerve density in sub-basal nerve fibers.
In their study, PRK was performed in 24 eyes of 14 patients using the Visx Star S2 excimer laser. Mean patient age was 40 years, with a range of 22 to 53 years. The mean refractive error was –3.7 D, with a range of –1.25 D to –5.75 D.
LASIK was performed on 17 eyes of 11 patients using the same laser. A planned 180 µm flap with a superior hinge was created using a Bausch & Lomb Hansatome microkeratome. Mean patient age was 32 years, with a range of 21 to 49 years. Mean refractive error was –6.6 D, with a range of –2 D to –11 D.
The authors found that the mean number of sub-basal nerves was reduced by more than 90% at 1 month after both LASIK and PRK and was still less than 50% of preoperative levels at 1 year after both procedures. By 2 and 3 years after PRK, the number of sub-basal nerves was not significantly different from before PRK. In contrast, the number of sub-basal nerves 3 years after LASIK was still significantly lower than before LASIK.
Corneal response after LASIK
The biomechanical response of the cornea to tissue ablation affects the refractive outcome of LASIK perhaps more than most surgeons realize, according to a physicist speaking here. Cynthia Roberts, PhD, said nomograms that take into account the cornea’s biomechanical changes after ablation may help to achieve more satisfying results from LASIK.
“We think we are removing a lenticule from the cornea during laser ablation, but actually we are changing the structure of the cornea, and its shape changes as a result of that,” Dr. Roberts said.
Speaking during a clinical research symposium on night vision problems after refractive surgery, Dr. Roberts noted that excimer lasers are not programmed to achieve a certain visual acuity result; they are programmed to change the shape of the cornea. Correcting the shape of the central cornea to correct spherical and cylindrical error is relatively straightforward, she said, but when correction of higher-order aberrations is the target, the critical area becomes larger.
“Problems arise when the pupil expands,” Dr. Roberts said. She said with myopic corrections, spherical aberration increases toward the periphery of the cornea.
“With increasing amounts of correction, there is increasing corneal steepening outside the central optical zone, leading to spherical aberration,” she said.
The biomechanical response of the cornea to excimer laser ablation modifies the clinical result, she said, but it is possible to use “biomechanical-friendly” algorithms to take this change into account.
Foldable phakic iris-fixated IOL
A foldable version of the Artisan iris-fixated phakic IOL is showing a “clear improvement” over the PMMA version in early clinical experience, according to H. Burkhard Dick, MD.
Dr. Dick reviewed preliminary results with the Ophtec Artiflex silicone-PMMA IOL, the foldable version of the familiar Artisan phakic IOL. He said that, although the number of cases to date is small, the lens appears to be safe and effective, predictable and stable with 3 months of follow-up.
The Artiflex, which has a 6-mm diameter silicone optic and an overall length of 8.5 mm, can be implanted through an incision of 3.1 mm, Dr. Dick said. The lens is currently available in powers from –2 D to –12 D, he said. It is inserted into the anterior chamber using a special instrument that grasps both of the PMMA haptics.
Eyes that are candidates for the lens should have more than 2,000 cells/mm2and deep anterior chambers, Dr. Dick said. He discussed 19 eyes that have reached 3-month follow-up.
The eyes in the study had a mean preop refractive error of –9.4 D. Dr. Dick said the mean UCVA achieved postoperatively was better than the patients’ mean preoperative BCVA, with a ratio of preop BCVA to postop UCVA of 1.09. Induced astigmatism with the 3.1-mm incision was “extremely low,” he said.
“I see a clinically clear improvement with this lens over the PMMA version,” Dr. Dick said. He said despite the low number of cases to date, the overall European results with the lens are “very promising.”
Amadeus II initial study
A second-generation microkeratome is producing results comparable to its predecessor in a trial that commenced earlier this month, according to Eric D. Donnenfeld, MD.
In a preliminary review of 100 eyes of 52 patients who underwent LASIK with the AMO Amadeus II microkeratome, Dr. Donnenfeld said there were two small epithelial abrasions, but no buttonholes, no irregular flaps, free flaps or striae were observed.
In the study, 56 eyes were randomized to the 140 µm head and 36 to the 160 µm head, Dr. Donnenfeld said.
“The advantages to this system are that it dramatically decreases the learning curve, freeing up your second hand to perform the ablation,” he said. The Amadeus II has a smaller handpiece and all its components are internalized, he added. Additionally, the system gives voice confirmation at every step.
An initial analysis of the patient data indicated a relatively even flap depth for both the 140 µm and the 160 µm head on the AMO device, Dr. Donnenfeld said. The 140 µm head had a mean flap cut of 133.89 µm, and the 160 µm had a 143.16 µm mean cut depth.
“What we saw was some nice bunching with the 140 head, and the 160 head also had a nice cluster,” he said.
New biometry device
A novel biometry device is showing efficacy for determining the size of even small intraocular distances within the anterior chamber in both phakic and pseudophakic eyes, according to Wolfgang Haigis, MD. Dr. Haigis presented the 12-month results of a study evaluating the new ACMaster from Carl Zeiss Meditec.
The ACMaster uses partial coherence interferometry to make segmental measurements of the anterior chamber, cornea and lens along the eye’s optical axis, according to Dr. Haigis.
Phakic and pseudophakic patients, as well as patients implanted with phakic IOLs, were included in the study. Unlike ultrasound devices, the ACMaster was able to image the central thickness of the stroma and PMMA IOLs with a high degree of precision, Dr. Haigis said. The retrolenticular space in pseudophakic eyes could also be measured, he noted.
Mean reproducibility was within 1.9 µm for measurements of corneal thickness, 4.8 µm for anterior chamber depth, and 2.5 µm for the position of the posterior lens vertex, Dr. Haigis said.
New algorithm preserves tissue
A new customized ablation program for the MEL 80 excimer laser can remove less corneal tissue in some patients than the conventional software while providing comparable visual results, according to Frank Goes, MD.
Dr. Goes presented the results of a study comparing the efficacy of the new Aberration Smart Ablation (ASA) Profile from Carl Zeiss Meditec at a company-sponsored symposium held during the ESCRS meeting.
The ASA uses a significantly more shallow ablation depth than the standard algorithm, Dr. Goes said. For instance, in a patient treated for –1.5 D to –2 D using a typical 7-mm treatment zone, a standard algorithm would produce an ablation depth of about 110 µm. In that same patient treated with the ASA algorithm, the ablation depth would be 67 µm, Dr. Goes said.
He said he believes this algorithm will be beneficial in patients needing re-treatments or patients with thin corneas.
The study included 62 eyes of 31 patients with myopia ranging from –1 D to –8.25 D, with or without astigmatism. One eye of each patient was randomly selected to undergo LASIK using the ASA software. The fellow eye of each patient was treated using the standard algorithm.
Because the ASA software removes less tissue, differences in contrast sensitivity were expected, particularly in mesopic conditions, Dr. Goes said. However, no significant difference was found, he said.
Predictability of the treatments was also equal.
“Of course, when you look at the whole group, there were some differences, but the differences were not important,” he said.
Among a subgroup of patients treated for refractive errors from –3 D to –7 D, Dr. Goes said, eyes treated with the standard algorithm performed slightly better than eyes treated with the ASA. Also, more eyes in the higher ranges of the trial treated with the ASA had complaints of slight visual phenomena, such as glare and halos.
“But predictability was the same. And I would like to mention that not one of these patients has complaints or shows differences clinically between both eyes,” he said. “The key issue here is the ability to save tissue and save ablation depth.”
Beginning with errors above –6 D, the new algorithm removes more tissue compared to the standard algorithm, he said.
Topography-based PRK in keratoconus
Using vector planning to create surface ablation treatment parameters produced predictable outcomes in patients with mild keratoconus undergoing refractive surgery, according to Noel A. Alpins, MD.
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![Noel A. Alpins, MD [photo]](/~/media/images/news/print/ocular-surgery-news-europe-asia-edition/2004/01_january/alpins_70_90_6748.jpg)
Vector planning uses corneal topography measurements, not wavefront measurements, to calculate ablation parameters. The axes of corneal astigmatism and refractive astigmatism are plotted on a double-angle vector diagram, and the vectorial difference between the refractive and corneal astigmatism is calculated, Dr. Alpins explained.
“The magnitudes are the same, but the angles are doubled. So when you are drawing these two together, you have a progeny called the ocular residual astigmatism, or ORA,” he said. This is also known as lenticular astigmatism or noncorneal astigmatism, he said.
The applied treatment is intended to reduce both corneal astigmatism and refractive astigmatism by about 50%, rather than eliminating the corneal astigmatism altogether, Dr. Alpins said.
“It is a dioptric value,” Dr. Alpins noted, “and in this group it was about 50% higher than usual due to the great irregularity in shape of the keratoconic corneas.”
The study included 44 eyes with a minimum BCVA of 20/40. All eyes had stable keratoconus with corneal steepening of about 1.5 D.
Eleven eyes were excluded from the study because they received spherical correction only, Dr. Alpins said. Thirty-three eyes underwent astigmatic treatments using PRK for an average of 1.92 D of corneal astigmatism and –1.65 D of refractive astigmatism. Mean ORA was 1.22 D, ranging from about 0.19 D to about 3.55 D, Dr. Alpins said.
Treatments were targeted to correct about 40% of the corneal astigmatism, based on corneal topography, and 60% of the refractive astigmatism. At 3 months follow-up, mean corneal astigmatism was reduced to 1.11 D, and mean refractive astigmatism was reduced to 0.51 D, Dr. Alpins said.
“But if we had treated 100%, we in fact would have expected 1.85 D of corneal astigmatism, which is effectively 40% extra, over and above the 1.11 D. We essentially saved this patient from 0.75 D of astigmatism,” Dr. Alpins said. He noted that there was no progression of keratoconus following treatment.
“Using vector planning will result in less corneal astigmatism than treatment by refractive values alone. And refractive astigmatism values are not compromised,” he said. “Vector planning really has potential to reduce aberrations and improve spectacle corrected visual acuity. At the end of the day, the patient has less corneal astigmatism, which at the end of the day is also going to reduce any aberrations of the second order (spherical and cylinder) and third order (trefoil and coma).”
Epi-LASIK procedure
Chris P. Lohmann, MD, discussed his experience with the epi-LASIK procedure in a presentation here at the meeting He has performed more than 300 cases of epi-LASIK using the Gebauer Epitome, the device now called the EpiLift and distributed worldwide by Visijet. (See Business Briefs sidebar.)
Dr. Lohmann said he switched to epi-LASIK more than a year ago not because his results were better with than PRK, LASIK or LASEK, or because the procedure was cheaper, but because epi-LASIK gives him consistent results without the risk of the stromal flap inherent in LASIK or the pain associated with LASEK. Dr. Lohmann said EpiLift gives him an epithelial sheet of consistent thickness in every procedure.
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“I know that the results I have here, everyone else will also get with a little training,” he said.
The procedure has a short learning curve, especially for surgeons who have already been performing LASIK, he said. He cautioned, however, that when learning the technique, surgeons should view it differently from LASIK. For instance, the epithelial sheet should not be treated like a LASIK flap. Dr. Lohmann removes the epithelial sheet with the specially designed epikeratome with an angled edge that slides along the surface of the eye, but he replaces the sheet using two sponges to help dry the surface before applying a bandage contact lens.
The bandage lens can be removed at 1, 2 or 3 days postoperatively, according to Dr. Lohmann.
He said the surgeon must ensure that there is no movement of the epithelial sheet before removing the bandage lens, but if the lens is kept in the eye too long it will result in edema.
“Remove the lens as soon as you are certain the epithelium will not move,” he advised.
Dr. Lohmann said in 309 cases he performed he has seen no flap problems, and no patients complained of intraoperative pain. He prescribes topical antibiotics and non-preserved topical steroids to be used four times a day for 2 weeks and then two times a day for 2 weeks. He also prescribes non-preserved artificial tears for use four times a day for 4 weeks. He noted that he has had no complaints of dry eye from patients following the procedure.
Dr. Lohmann reported patients had an average BCVA better than 20/40. At 1-day follow-up, patients averaged 20/30, after 3 days 20/40 and at day 6, 20/20. Dr. Lohmann said he has had no complaints of haze.
Temporal hinge for hyperopic LASIK
A temporal hinge gives surgeons a larger working area than a superior hinge when performing LASIK on patients with hyperopia, according to Cesar Carriazo, MD.
“The best treatment for hyperopic eyes is the temporal cut,” Dr. Carriazo said. “When you use a superior hinge, you can just work in a 5-mm space. Using a temporal cut can give you a 7-mm work space.”
Dr. Carriazo also advised surgeons to use an oblique hinge to avoid astigmatism problems when treating patients with myopia.
Cornea
Microkeratome-assisted keratoplasty
A modified lamellar keratoplasty technique that uses the same microkeratome to create the recipient corneal bed and the donor corneal cap may be successful for cases of corneal ectasia, suggested Lawrence Pe, MD. He described results with the technique of microkeratome-assisted lamellar allograft keratoplasty (MALK) in 10 patients with iatrogenic or idiopathic corneal ectasia.
With the eye under peribulbar anesthesia, a Moria LSK microkeratome was used to remove a 200-µm-thick, 9-mm-diameter section from the recipient’s cornea, Dr. Pe said. A donor cap approximately 350 µm thick and 8 mm in diameter was then created from a donor eye and sutured onto the recipient’s corneal bed.
“Having the graft 1 mm smaller than the recipient’s bed creates a mechanical effect on the bed when it is sutured in place,” Dr. Pe said.
After 6 months of follow-up, UCVA improved from a preoperative mean of 20/400 to a postoperative mean of 20/60. Mean BCVA improved from 20/80 preop to 20/30 postop, Dr. Pe said.
Spherical equivalent also improved from a mean of –5.77 D preop to –2.93 D postop, Dr. Pe said.
Two eyes developed some subepithelial haze, he said, but he attributed the haze to the age of the donor cornea at the time of transplant. In cases in which haze developed, the corneas were older than 4 weeks, he said.
Deep lamellar keratectomy
In cases at high risk for graft failure or rejection, deep anterior lamellar keratoplasty (DALK) can be a viable alternative to penetrating keratoplasty, said Alberto Villarrubia, MD.
Dr. Villarrubia reported on five cases in which he performed the DALK technique (originally described by Gerrit Melles, MD) instead of PK. He said the five cases had a high risk of PK failure. Four eyes had vascularized herpetic disease, which carries a high risk of recurrence and stromal thinning. One eye that suffered caustic injury presented with a partial limbal insufficiency.
Following DALK, all patients had a good anatomic result with no signs of failure or rejection, Dr. Villarrubia said. Complications included two microperforations and one episode of necrotizing stromal keratitus. Both resolved with a second DALK, he said.
“In all cases except one with a deep amblyopia, functional results were acceptable,” Dr. Villarrubia said.
‘Pachy-link’ for transplant
A pachymetry-guided nonpenetrating transplant procedure can help corneal surgeons achieve greater safety and faster recovery than with traditional lamellar procedures, according to Dr. Carriazo. He called the procedure “pachy-link,” or pachymetry-associated laser keratoplasty (PALK).
The PALK procedure uses a series of pachymetry measurements taken in a multitude of positions on the cornea, along with computer software analysis, to give the surgeon a better idea of the shape and depth of the cornea. The surgeon can then choose the correct depth, on the order of microns, for the stromal bed in a nonpenetrating corneal transplant.
Dr. Carriazo said PALK involves creating a laser-assisted lamellar keratectomy in the recipient eye by linking the pachymetric data to an excimer laser.
With the new system, Dr. Carriazo said surgeons can remove corneal damage to a depth of 100 µm in the stroma.
The method involves several steps, Dr. Carriazo said. First, the surgeon maps the anterior and posterior surfaces of the patient’s cornea with topography. Corneal pachymetry is then used to define the desired depth for the corneal bed. Once the ideal is determined, he said, the surgeon can guide the surgical laser in the ablation in the anterior surface of the patient’s cornea to produce the desired corneal bed depth.
In a preliminary study of the technique, 15 eyes underwent the procedure. In all 15 cases a smooth stromal bed was attained, with an average thickness of 130 µm.
Dr. Carriazo described some of the advantages of the new procedure: “There’s no endothelial rejection, fewer complications, less risk of future keratoplasty, faster recovery, and the donor cornea does not need to be fresh and does not need to contain a high number of active endothelial cells,” he said.
‘Big bubble’ technique
The “big bubble” technique for lamellar keratoplasty offers surgeons a safe and consistent alternative to PK in selected cases, said Mohamed Anwar, MD.
Endothelial and stromal rejection are rarely seen with the technique, and graft survival is long-term, Dr. Anwar said.
“Rejection of the bubble is virtually nil,” he said. “There is no immune rejection because the host endothelium is retained.”
To execute the technique, the surgeon places an air bubble at the posterior edge of the stroma to separate the stroma from Descemet’s membrane. The surgeon should use a 27-gauge to 30-gauge needle to insert the air bubble, he said.
The surgeon must be aware the air bubble will raise IOP to around 50 mm Hg or 55 mm Hg, he said, “so you don’t want it there for long.”
The time the air bubble remains in place should be limited to 15 or 20 minutes.
Dr. Anwar reported results of the bubble technique in 547 eyes of 409 patients; 316 of the eyes had keratoconus, 93 had superficial scars, 87 had climatic keratopathy, 45 had corneal dystrophy, 24 had pellucid marginal degeneration and 22 had post-LASIK ectasia. Follow-up ranged from 6 months to 17 years.
Dr. Anwar said visual acuity and recovery time following the big bubble procedure were similar to results reported with PK.
Postop detachment of Descemet’s membrane occurred in 39 cases, requiring a tamponade with air into the anterior chamber, Dr. Anwar said. None of the patients experienced infection.
Contraindications for the technique include a fragile Descemet’s membrane, macular dystrophy, keratoconus and failure to form the big bubble.
Surgeons should be prepared for a lengthy learning curve when adopting the procedure, he added.
Donor corneal cell survival
Donor-derived corneal stromal and endothelial cells can survive on a graft recipient’s eye for up to 30 years after PK, according to Ulf Stenevi, MD. Dr. Stenevi prospectively analyzed the donor-derived corneal epithelial and stromal cells of corneal buttons removed at reoperation from 75 sex-mismatched PK patients — graft recipients whose sex was different from the donor of the original cornea.
Using fluorescent in situ hybridization, X and Y chromosomes in samples of the patients’ corneal tissues were stained in order to identify those cells carrying the sex chromosomes of the person of origin, Dr. Stenevi said.
Donor-derived corneal epithelial cells were shown to remain for at least 2 years after transplantation, he said. Stromal cells, which Dr. Stenevi said were what mainly interested him, were shown to remain in the graft 30 years after being transplanted.
“It is obvious that cells from the graft remain alive for a long time after surgery in these patients, which probably should have us look at the way we treat our patients,” he said.
“It also imposes the question of what happens to these cells. Are they multiplying? Or are they just staying there? What happens when the endothelium is gone?” he said. “That is something we have to look at.” Regardless of the reason for the surgery, “there are still cells surviving in the graft from the donor,” he said.