Surgeon reports collagen cross-linking found safe, effective in the long term

BARCELONA – As the interest in collagen cross-linking for treating disorders such as keratoconus and post-LASIK ectasia grows in Europe, an increasing volume of long-term data from pioneers of the technique appears to support its safety and efficacy, according to a speaker here.

“Corneal topography shows that keratoconus progression was halted in every case so far treated. [Keratometry] readings decreased, and along with it, uncorrected vision increased in the majority of cases,” Theo Seiler, MD, said during Cornea Day here preceding the European Society of Cataract and Refractive Surgeons Winter Refractive Surgery Meeting.

“Quite unexpectedly, best corrected visual acuity also increased. We learned that this improvement, which surprised us at first, was due to the increased symmetry and regularization of the corneal surface that is produced by the treatment,” he said.

Prospective measurements in patients with bilateral keratoconus, in whom only one eye was treated, show that at 1 year the keratoconus index was significantly lower in the treated eye.

Adverse reactions were rare. Haze was relatively infrequent, while epithelial healing problems and scars were reported only in a small number of cases, he reported.

However, there are questions that need to be answered as surgeons gain more experience with the technique, Dr. Seiler noted.

These concerns include finding out at which stage of keratoconus the technique should be used to get the best results and at what age the technique should be used. Also, it is still unclear in which type of ectatic disorder — keratoconus, iatrogenic ectasia or pellucid marginal degeneration — the technique would work better, he said.

Another issue is the choice of optical rehabilitation: spectacles, contact lenses, intracorneal rings and PRK are possibilities, but the best solution has not yet been established, he said.

Surgeons have also been discussing whether the epithelium should be scraped off before treatment, he said. The corneal epithelium represents a barrier for riboflavin penetration, but some have suggested the use of tetracaine or similar substances as an alternative to mechanical abrasion to “digest” the tight junctions between the epithelial cells, he said.

From the beginning of his studies with the technique, Dr. Seiler said he always believed that collagen cross-linking would be safe because it is a physiological process that is well known in diabetes and aging.

As further evidence of the increased biochemical stability of collagen produced by the technique, Dr. Seiler showed an experiment involving two corneal buttons, one of which was previously cross-linked. After 3 days of immersion in trypsin and collagenase solution, the non-cross-linked corneal button was digested by the enzymes. In contrast, in the other corneal button, the cross-linked part of the cornea was not dissolved and the non-cross-linked deeper layer was, Dr. Seiler reported.

“This shows that cross-linking produces increased biochemical stability and therefore better resistance against collagenases in the cornea,” he said.

These items appeared originally as daily coverage from the meeting on OSNSuperSite.com. Look for more in-depth coverage of these and other topics in upcoming issues of Ocular Surgery News.

Surgeon: Needle and thread graft insertion technique makes DSAEK easier, safer

A graft insertion technique that involves using a needle and thread to pull the lamella into the recipient’s eye during Descemet’s stripping automated endothelial keratoplasty makes the surgery easier and safer to perform, according to a surgeon.

“I do automated preparation of the donor lamella, using a Refractive Technologies Horizon microkeratome, which, working under constant air pressure, allows a lower rate of endothelial cell loss and a more accurate cut diameter and depth,” Vincenzo Sarnicola, MD, said.

After preparing the donor graft and completing a descemetorrhexis, Dr. Sarnicola affixes a 10-0 polypropylene thread to the edge of the donor lamella using a single suture and a transscleral needle. Both the needle and thread are then used to pull the lamella through a corneal tunnel in the anterior chamber. Next, the donor lamella is unfolded with saline, and an air bubble is injected.

The method is better than forceps insertion, which causes significant endothelial cell damage in the area of forceps compression, he noted. Also, compared with glide insertion, it is easier and does not require any special instruments.

Dr. Sarnicola reported results for 16 consecutive patients treated with the needle and thread method of Descemet’s stripping automated endothelial keratoplasty (DSAEK).

At 1 year, nine patients were 20/40 or better and four were 20/50 or better.

Three patients had either macular scarring or glaucomatous optic nerve damage that precluded visual results better than 20/200, he said.

At 1 year follow-up, the endothelial cell count averaged 1,950 cells/mm².

Multifocal toric IOL shows promise for astigmatic patients undergoing refractive cataract surgery

Results obtained with the Acri.Lisa toric bifocal IOL show promise and are a step forward in phacorefractive surgery, according to two surgeons.

Detlev Breyer, MD, of Düsseldorf, presented results of microincision cataract surgery with implantation of the Acri.Lisa (Acri.Tec) multifocal toric IOL. Initial results are “promising, even in patients with high astigmatism and myopia or after keratoplasty,” he said.

Jorge L. Alió

OSN Europe/Asia-Pacific Edition Associate Editor, Jorge L. Alió, MD, PhD, of Alicante, Spain, also reported his results implanting the lens either alone (46 eyes) or in conjunction with a capsular tension ring (CTR; 32 eyes). In the study, Dr. Alió measured optical quality using the VOL-CT software (Saver and Associates) and evaluated differences in total aberrations, higher-order aberrations, spherical and coma aberrations, Strehl ratio and modular transfer function (MTF).

“Results were excellent in both groups, but the group implanted with both the Acri.Lisa and the [CTR] showed statistically significant reductions in intraocular aberrations compared with the group implanted without the CTR. A statistically significant increase in Strehl ratio and MTF was also observed,” Dr. Alió said.

These results, he said, show that the Acri.Lisa is an “excellent option” for astigmatic patients undergoing refractive cataract surgery, and that the use of a CTR can improve the results by enhancing lens stability.

Presbyopia correction procedure shows stable results over time

Long-term results with up to 4 years follow-up show that the LaserACE presbyopia correction procedure can restore accommodation in a safe, effective and stable manner, according to a surgeon.

“Patients regain 2 D to 3 D of accommodation and do not appear to lose [it] over time,” Dimitrii Dementiev, MD, said.

The procedure uses a 2.94 µm Er:YAG laser to create 600-µm microexcisions that lead to the decompression of connective tissue in three critical zones of the sclera. This simple and minimally invasive approach restores the physiological conditions necessary for the accommodative process, he said.

In an international, multicenter clinical trial, 64 eyes of 32 patients aged 42 to 69 years were treated with the LaserACE surgical procedure. Dr. Dementiev showed that 89% of the patients were able to read J3 or better, and 81% were J2 or better without reading spectacles. In addition, 95% were J5 and 85% were J3 for intermediate vision.

“On the whole, 78% of the patients were spectacle-independent for near and 98% were spectacle independent for intermediate,” he said.

All patients achieved some improvement in both quality and quantity of visual performance. Follow-up also showed a statistically significant suppression of presbyopia progression.

No major complications were reported, Dr. Dementiev noted.

Implantable device for cyclosporine release may be future of immunosuppression

An implantable device for the sustained delivery of cyclosporine over 1 year may be a valuable method of preventing graft failure, allowing for greater tissue drug levels and reduced side effects, according to a surgeon.

“Cyclosporine is the most commonly prescribed immunomodulator, with the longest clinical track record. It is a potent immunosuppressant, unique for its T-cell specificity and low myelotoxicity. Its topical use, however, has been complicated by poor solubility, lack of bioavailability and poor patient tolerance,” said Michael Belin, MD, of Albany Medical College in the United States.

A multicenter trial involving 25 U.S. sites and eight German sites is ongoing to test the safety and efficacy of implantable cyclosporine in a silicone matrix for preventing corneal graft rejection or graft failure in patients who have experienced one or more rejection episodes.

“This implant provides sustained release of the drug for at least 1 year. Concentration at the local level is at least 2 log units higher than that provided by either topical or systemic administration, while systemic levels are below the limits of detection. Silicone, on the other hand, is highly biocompatible, as proved by many trials,” Dr. Belin said.

The implant has an initial high release of the drug, followed by a slow delivery over 1 year.

“Implantable cyclosporine may be the future,” he said.

Excimer laser shows good results at 6 months, surgeon says

The Schwind Amaris excimer laser platform produces high-quality LASIK treatments in terms of visual outcomes, smooth surfaces, no induced high-order aberrations and high contrast sensitivity, according to the results of a multicenter study.

“Personally, I have performed more than 600 consecutive cases with the new-generation Schwind Amaris, and my results are more than amazing so far. Previously, our retreatment rate was 2%. Now I can see it is going to be far lower,” Maria Clara Arbelaez, MD, of the Muscat Laser Eye Center in Oman, said.

The Schwind Amaris is a laser with a 0.54-mm super-Gaussian profile, a 500-Hz repetition rate and automatic fluence adjustment. The 1,050-Hz turbo eye tracker is set for static and dynamic cyclotorsion and detection of both iris and limbus.

In the multicenter study, 500 eyes treated by different surgeons were analyzed. LASIK flaps were created using the Carriazo-Pendular microkeratome, Dr. Arbelaez said.

At 6 months, 95% of the eyes achieved 20/20 uncorrected visual acuity and 55% achieved 20/16. More than 75% of eyes were within ±0.25 D of intended correction and 92% were within ±0.5 D.

Spherical equivalent averaged —0.17 D and astigmatism averaged —0.16 D, with a small standard deviation in both cases, Dr. Arbelaez said.

Best corrected visual acuity improved in 44% of eyes, and a loss of one line of vision was seen in only 1% of eyes, she noted.

“This improvement in postoperative BCVA is due to the Schwind-Cam software, which produces ablation profiles with a minimum amount of induced spherical aberrations,” she said.

Contrast sensitivity was improved or maintained at all spatial frequencies, she added.

“To evaluate long-term stability, further follow-up is necessary. But after 6 months, we can say that results appear to be very promising,” Dr. Arbelaez said.

DALK, DSEK create different stromal cleavage planes, surgeon says

The cleavage plane created when separating Descemet’s membrane using the big bubble technique for deep anterior lamellar keratoplasty is different from the cleavage plane created during Descemet’s stripping endothelial keratoplasty, which involves the use of a blade, according to a surgeon speaking during Cornea Day.

“In recent years, we have differentiated the lamellar techniques that should be used when the endothelium is unaffected and the stroma is opaque and disorganized, and those where the stroma is unaffected and the primary defect is in the endothelial layer. The former pathologies are increasingly managed by DALK (deep anterior lamellar keratoplasty) and the latter by DSEK (Descemet’s stripping endothelial keratoplasty) or one of its variations,” Harminder Dua, MD, said.

These techniques have opened avenues for new research on the complex morphology of the endothelium-Descemet’s-posterior stromal interface, with the aim of better understanding the anatomical impact of surgical maneuvers in this area.

“To find the exact location of the cleavage plane in these two techniques, we simulated the DALK and DSEK separations in cadaver eyes. Intraoperatively and postoperatively by light and electron microscopy, we examined the donor endothelium removed from donor DALK buttons, the recipient deep stroma stripped of its endothelium by big bubble technique, the donor eyes’ endothelium and stroma mechanically separated, and the donor eyes’ endothelium and stroma separated by big bubble,” Dr. Dua said.

What appeared from these images was that a stroma separated with the big bubble technique appears different from the stroma separated with a crescent blade.

Dr. Dua proposed that, although variable, the Descemet’s separation obtained with a big bubble technique leaves behind a thin layer of deep posterior stroma – the posterior stromal layer – with a distinct architecture. The posterior stromal layer binds the Descemet’s to the stroma, is not populated with keratocytes and is attached to the more anterior stroma by fine strands of collagen.

“When we inject a big bubble, we separate behind the [posterior stromal layer] and not in front of it. But when we use a blade, we separate in front of it,” Dr. Dua said.

Proper alignment key to using toric IOLs in cataract surgery, surgeons report

With proper alignment, toric IOLs can provide sufficient correction of astigmatism to allow for spectacle independence after cataract surgery, according to a surgeon.

“We were very excited when we were offered toric IOLs in 2006 because we saw a possibility for correcting astigmatism at the same time of cataract surgery,” Margaret Kearns, MD, who runs a private practice in Sydney, said.

“We now use [such lenses] in about 50% of our cataract procedures, and it has given to us a real change in the quality of our results,” she said.

Dr. Kearns reported results for 144 consecutive eyes treated by two surgeons who implanted Alcon’s toric AcrySof T3, T4 or T5 IOLs or the Rayner toric IOL. The final refractive cylinder was 0.5 D or less in 88% of patients, she said.

“The performance of both these lenses is excellent,” Dr. Kearns said. “We now do very few laser enhancements, and patient satisfaction is high.”

However, Dr. Kearns emphasized the importance of correctly marking the toric axis on the cornea before implanting the lens.

“We sit the patient at the slit lamp and mark the axis with a 30-gauge needle,” she said.

Instrument measures accommodation in scleral implant-treated presbyopes

The iTrace visual function analyzer from Tracey is an effective tool for assessing the efficacy of procedures intended to restore accommodation, according to a surgeon.

Investigators used the device to measure accommodation in phakic and pseudophakic eyes that had undergone the scleral spacing procedure for presbyopia with Refocus Group’s PresView scleral implants.

“With this method, we can measure accommodation objectively by mapping the refractive power across the pupil during fixation at any distance through an open field of view,” Barrie Soloway, MD, said.

A preliminary study of 15 eyes of eight patients who underwent the spacing procedure was performed using the iTrace visual function analyzer. The power refraction wavefront map was obtained by viewing Snellen letters at a fixation distance of 20 feet and Sloan letters at 50 cm for near fixation.

Investigators then created a difference plot between these two measurements to assess the depth of field in near vision during fixation. This depth of field was then compared to near acuity in each eye, Dr. Soloway said.

“The eyes were found to have a depth of field in near vision of 1.2 D with a total range of 0.5 D to 2.5 D. There was a trend correlating depth of field in near vision with the ability to read smaller print,” he said.

Laser, CK combination a better option for hyperopic presbyopes

A combination of LaserACE and conductive keratoplasty may be a better option for treating hyperopic patients who also have presbyopia, according to results of a preliminary study.

Researchers in the United States treated 10 patients aged 47 years to 57 years with the LaserACE procedure to restore their dynamic accommodative abilities. They then performed CK using Light Touch CK (Refractec) 3 months later to treat low hyperopia and optimize the dynamic range of visual function. All treatments were performed bilaterally.

“The precision of accommodation changed significantly in response to the LaserACE procedure, especially for intermediate vision, with some patients achieving J1+ and a visual dynamic range up to 1.3 D,” Ann Marie Hipsley, PhD, said.

After bilateral CK, optimization of results was achieved, with restoration of the dynamic accommodation component up to 2 D or more, she said.

“In our opinion, CK might be a better option than LASIK or PRK for correcting hyperopia in combination with the presbyopic LaserACE procedure. It is a softer, safer, less invasive and reversible approach that preserves the cornea, and is a better choice also in view of future cataract interventions,” she said.

Tetracaine provides effective pain relief after PRK, without loss of contrast sensitivity

The use of tetracaine in the immediate post-PRK period gives immediate pain relief without negative effects on contrast sensitivity, as shown by a study.

“We all know that the main disadvantage of PRK is the pain that patients have to suffer in the first 6 to 72 hours after surgery, during which re-epithelialization occurs,” said Carole Liernur, MD.

But pain can be effectively relieved by tetracaine, without causing problems in the re-epithelialization process and in the final visual outcomes of the procedure, she said.

In a recent study, carried out by Cyrus Tabatabay, MD, and Dr. Liernur in Switzerland, it was demonstrated that the use of tetracaine in the immediate postoperative period does not delay re-epithelialization. The question was whether the use of this substance could have an impact on contrast sensitivity.

Between 2005 and 2007, tetracaine was used in 109 eyes of 55 patients undergoing PRK for spherical myopia ranging between –1 D and –9 D.

“At the end of the procedure, all patients were provided with one single use unit (0.4 mL) of tetracaine 1% to use in case of pain or discomfort. They were recommended to use as little as possible of this product, preferably in the evening to help them sleep better,” Dr. Liernur said.

Of the 55 patients included in the study, 36 (65% of the group) used the medication once or twice a day up to 3 days post PKP, while the remaining patients decided not to use the medication.

Preop and postop contrast sensitivity at three contrast levels (100%, 9% and 6%) was measured and compared in a period ranging from 6 months up to 2 years after surgery in all patients.

“At high luminosity (100%) no difference in contrast sensitivity was found between patients who had or had not used tetracaine. Only at the lowest contrast sensitivity levels (6%) results seemed better for non-users than for users: a contrast sensitivity loss was reported by 61% of users vs. 46% of non-users,” Dr. Liernur said.

However, since the two groups were not equal in size (72 vs. 37 eyes), this difference cannot be considered as statistically significant, she noted.

Faster re-epithelialization, less haze in PRK with sodium hyaluronate, surgeon says

Results of photorefractive keratectomy can be enhanced by the application of 0.25% sodium hyaluronate solution during the procedure, according to a study by researchers in Poland.

“The use of a small amount of sodium hyaluronate solution smoothens out the corneal surface during PRK, leading to faster re-epithelialization, less haze, better visual acuity and improved visual quality,” Ewa Mrukwa-Kominek, MD, said.

Dr. Mrukwa-Kominek and colleagues analyzed 40 eyes of 20 patients who underwent PRK for myopia or myopic astigmatism. Investigators applied the 0.25% sodium hyaluronate solution to one eye of each patient. They then compared outcomes between eyes treated with or without the solution at 36 months follow-up.

The researchers found that eyes treated with sodium hyaluronate healed faster and had less haze — grade 0 to 1 vs. grade 0.5 to 2 for non-sodium hyaluronate-treated eyes, Dr. Mrukwa-Kominek said.

“There was no significant difference in spherical equivalent between the two groups, although a loss of one line of best corrected visual acuity was observed in only one eye in the group where we used sodium hyaluronate and in two eyes in the other group,” she said.

LASEK and Epi-LASIK hold advantages, but to remain niche procedures, surgeon says

Both LASEK and Epi-LASIK provide a safe and effective surgical platform for surface treatment, but will never dominate the refractive practice, according to Vikentia Katsanevaki, MD.

Vikentia Katsanevaki

“Visual rehabilitation is an issue with both procedures as it is with PRK, and this is the reason why I think that surface treatments will never go beyond 10% to 15% of the total amount of laser refractive procedures,” she said.

The initial enthusiasm for these procedures, that she shared since they were introduced, decreased when several studies found that neither of them was really effective in preventing postoperative pain.

“In some case series, they were proven to be even more painful than conventional PRK. In our study carried out at the University of Crete, we had a good 10% of patients with significant pain in the first few hours, a percentage that is comparable to that of PRK,” Dr. Katsanevaki said.

On the other hand, one sure advantage of both these techniques is their ability to minimize corneal scarring and haze.

“This was also proved by several studies, including our own series where at 1 year and later at least 90% of the eyes had no haze or just clinically insignificant haze,” she noted.

“This is, in my opinion, the only potential benefit of these procedures. They minimize the risk of haze without the use of mitomycin, which is not such an innocent drug,” she said.

She emphasized that the use of mitomycin-C by refractive surgeons should be limited strictly to high-risk eyes. Cases of scleral melting were found, in her personal experience, 3 or 4 years following the use of this medication in pterygium surgery, and the need for dilution poses further and not negligible problems.

Dr. Katsanevaki said that her preference goes to thin-flap LASIK, which is the technique that now she most often uses in her practice.

Keratoplasty technique based on organ-cultured Descemet’s transplantation shows promise

Descemet’s membrane endothelial keratoplasty may have potential for becoming one of the best techniques for managing corneal endothelial disorders, according to a surgeon.

“The technique is based on the selective transplantation of an organ- cultured donor Descemet’s membrane,” Lisanne Ham, MD, said.

Dr. Ham reported preliminary clinical results for 10 patients with Fuchs’ endothelial dystrophy or pseudophakic bullous keratopathy treated with Descemet’s membrane endothelial keratoplasty.

The procedure involves creating a 3.5-mm clear corneal tunnel incision. Next, the anterior chamber is filled with air, and the Descemet’s membrane is stripped from the posterior stroma.

“We then inserted a 9-mm diameter Descemet’s membrane roll, harvested from an organ-cultured donor corneoscleral rim. The donor tissue was gently unfolded, positioned onto the posterior stroma and secured by filling the anterior chamber with air for 30 minutes,” Dr. Ham said.

Results were encouraging, she said. At 1 month, six eyes had a BCVA of 20/40 or better, and three eyes achieved 20/20. At 6 months follow-up, endothelial cell density averaged 2,030 cells/mm².

The transplantation was unsuccessful in three cases, she said.

“A complete detachment of the donor tissue occurred in the early postoperative period, but it was easy to remove the graft and perform a secondary Descemet’s stripping endothelial keratoplasty procedure,” Dr. Ham said.

She said she believes the technique holds great potential because it provides quick and nearly complete visual rehabilitation. In addition, because the donor membrane can be obtained from organ-cultured corneoscleral rims, the procedure may be readily accessible to most corneal surgeons, she noted.

LASIK best option for residual post-cataract surgery refractive errors

LASIK represents the best treatment option for correcting residual refractive errors after cataract surgery, according to Dr. Alió. However, results may be unpredictable and poor in eyes implanted with multifocal or accommodative IOLs, he noted.

“I recommend caution in these cases. Of all the factors that make the results of post-cataract LASIK still suboptimal, multifocal and accommodative IOLs are No. 1,” Dr. Alió said.

According to Dr. Alió, some degree of residual refractive error affects cataract surgery outcomes in most patients. The most common causes include clinically significant astigmatism, which is present in about 40% of patients, surgical complications, postoperative adverse events and errors in IOL power calculation. In addition, when either a multifocal or accommodative IOL is used, these factors have a greater impact, and patient satisfaction can be low in such cases.

Various options can be used to address residual refractive errors, although all have limitations, Dr. Alió said.

“LASIK is still the option that gives the highest degree of accuracy and allows us to address the astigmatic as well as the spherical components. However, results are still suboptimal, due to [several] potential hazards,” he said.

Dry eye, which occurs more frequently in elderly and middle-aged patients, goblet cell depletion related to suction ring time and possibly even post-cataract medications all may affect outcomes. Also, there are no proven preventive actions that can be taken, he said.

For best results, Dr. Alió prefers performing LASIK using a mechanical microkeratome and applying a customized aspheric treatment.

For cases involving accommodative or multifocal IOLs, he recommended waiting at least 3 months after cataract surgery to allow sufficient time for the lens to become stable and for neuroadaptation to occur.

Mixing and matching multifocal IOLs has advantages over using a single lens, surgeon says

Implanting a different multifocal IOL in each eye of patients after cataract surgery may be the better approach to using such lenses for correcting presbyopia, particularly in patients who desire good intermediate vision, according to a surgeon.

John S. Chang Jr.

John S. Chang Jr., MD, said that since the end of 2003 he has implanted 500 eyes with multifocal IOLs. Half were Tecnis IOLs (Advanced Medical Optics); the rest were about equally distributed between the Array (AMO), ReZoom (AMO) and ReSTOR (Alcon).

“As we know, all these lenses are good, but [they] also have limitations. With bilateral diffractive lenses, patients have good distance and near [vision] but poor intermediate vision. With bilateral refractive lenses, patients have fairly weak near vision,” Dr. Chang said.

“But by implanting a diffractive lens in one eye and a refractive lens in the other eye, the best of both worlds can be achieved,” he said.

Dr. Chang’s strategy for using multifocal IOLs involves a two-step approach, which begins with determining patients’ predominant activities in their day-to-day lives.

“In patients who read a lot, I implant a diffractive lens in the nondominant eye. If they are happy with their near vision, I offer a refractive IOL in the dominant eye to give them better distance and some intermediate vision for computer work,” he said.

“If they are not satisfied with their near vision, I implant a diffractive [IOL] in the dominant eye,” he said.

Conversely, in patients who predominantly drive and use computers but do not frequently read, Dr. Chang implants a refractive lens in the dominant eye.

“If they complain of poor near vision, I offer a diffractive lens in the other eye,” he said.

Dr. Chang has treated 27 patients so far with the mix-and-match approach. All patients tolerated the different lenses well and had a fairly high degree of satisfaction, with only minor complaints of night vision disturbances, he said.

No patients require spectacle correction for distance vision, 95% read and use computers without needing spectacles, and the remaining 5% use spectacles only occasionally, he noted.

Ex-vivo expansion of limbal cells a viable option for severe corneal conditions

Ex-vivo expansion of limbal stem cells may be an option to treat severe corneal conditions related to total limbal deficiency, as shown by F.E. Kruse, MD, of Erlagen-Nürnberg University, Germany.

This method is based on the culture of a small piece of limbal tissue, 1 mm × 2 mm, on a suitable carrier amniotic membrane or fibrin glue matrix. The tissue is left to grow into a 2 cm to 3 cm diameter transplantable cell sheet over a period of 2 to 3 weeks, trimmed down to the desired size and then transferred onto the ocular surface.

“We compared all carrier systems in vitro and found that the appearance of the cells on fibrin and amniotic membrane is similar. Also electron microscopy does not show any significant difference. The current stem cells markers are similarly expressed on fibrin and amniotic membrane,” Dr. Kruse said.

The most successful study on the use of autologous tissue-engineered limbal cell sheets was published by Paolo Rama and colleagues in Transplantation. Fibrin glue matrix was used as a carrier.

“Using this method, they treated corneas which were severely damaged, and in some cases had undergone one or more transplantation procedures, obtaining a high rate of success,” Dr. Kruse said. “It was after reading this paper that we chose to use fibrin instead of amniotic membrane, which has a considerable biological variability.”

Corneal inlay shows promise for presbyopic correction

The Invue corneal inlay from Biovision is an innovative and effective way of improving near vision in emmetropic presbyopes, according to some surgeons.

“It is a minimally invasive procedure, reversible, adjustable, which gives the ability to read without glasses,” Francisco Sánchez Leon, MD, of Mexico City, said.

The Invue corneal inlay is a small, 3-mm diameter, 15-µm to 20-µm thick hydrophilic acrylic lens, which is implanted approximately 200 µm into the cornea of the non-dominant eye to obtain monovision. In the center the lens has no power, but a pinhole for nutritional purposes, and near vision is corrected by the outer rim of the lens.

It has the advantage of being inserted into a small, self-sealing pocket.

“This means that there are no flap-related problems, and that the lens remains in a very stable position after implantation,” Dr. Leon said.

Prior to implantation, an intracorneal tunnel is created with a microkeratome or with a femtosecond laser and the lens is then placed into position with forceps or with a special lens-delivery system.

Dr. Leon has implanted more than 150 Invue lenses, with very satisfactory results.

“With some of the patients, we now have 5 years of follow-up, and the cornea is still crystal clear,” he said.

Over the years, the implant has undergone modifications. Dr. Leon told the audience that with the last model 100% of patients can read J3 or better and 80% J1 or better. Distance best corrected visual acuity is 20/25 or better in 100% of the patients and 20/20 or better in 80% of the patients.

“We have a potential for enhancement using a second procedure, such as PRK,” he suggested.

Also, Tobias Neuhann, MD, one of the European surgeons who have experience with the Invue implant in Europe, also spoke favorably of this option for correcting presbyopia, but he also pointed out some of its limitations.

“Visual rehabilitation can be quite slow in some of the patients,” he said.

In his experience, those who have the time and are willing to make an effort and practice reading without spectacles from the beginning, improve more quickly, and within 3 months are usually able to read newspapers without spectacles. However, most of the patients wear reading glasses straight after the procedure because they cannot do without them in their profession, and in these patients the recovery of near vision is of course delayed quite significantly.”

Also distance vision tends to be lower in the first months after implantation but improves over time. Distance vision also can be affected by tiny folds in the lens, which were observed in some cases, and may be related to the implantation.

Marking technique simplifies toric IOL alignment, improves accuracy

A new marking technique for the alignment of toric IOLs is “simple, accurate and reproducible,” according to one speaker.

Joseph Ma, MD, of Toronto University, said that currently, the gold standard technique for marking the eye is three steps: placing reference marks at the limbus, marking the axis at which the lens is going to be placed inside the eye and rotating the IOL precisely onto the intended axis of alignment.

Dr. Ma said it is known that alignment with the astigmatic axis is crucial with this type of lens, and that even the slightest error affects their functional results. A deviation of just 3° results in 10.5% residual cylinder, 15° in 51.8% and a 30° misalignment in complete failure of cylinder correction.

A good alignment technique, he said, should be a single step technique, to decrease the margin of error. In his procedure, the patient is placed in the same position in which the astigmatism was measured, normally the upright position, which is used for keratometers and topographers.

“Positioning is very important,” Dr. Ma said. “There is significant cyclotorsion when a person moves from a supine to an upright position. About 68% of the population has between 2° and 3° of rotation from this alone, which leads to a 10% loss of effective correction. Some patients have up to 17.5° of rotation, resulting in a 52% loss of effect.”

Centration should be on the visual axis rather than the cornea. The epithelium is marked with a 30-gauge needle at the slit lamp.

“I like using a Haag-Streit eyepiece, which has a built-in leveller and a reticle in the form of concentric circles, that allow the surgeon to position the marking exactly in the center of the visual axis.” Dr. Ma explained.

“These marks are easily visible, sharp and precise on the surgical microscope, and since you know exactly where the marks on your lens are going to be, you can superimpose epithelial markings on the lens markings,” he said.

He has been using this technique with both the STAAR Surgical toric ICL and the Alcon AcrySof toric IOL.

A note from the editors:

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