Femtosecond laser-associated LASIK complications manageable, surgeon says

ALICANTE, Spain — The introduction of femtosecond laser technology has greatly benefited LASIK, but femtosecond laser-related complications exist and can occur in some cases, according to a surgeon.

Fortunately, if managed appropriately, none of the potential intraoperative or postoperative complications would jeopardize surgical success, J. Vicente Rodriguez, MD, said at the Alicante Refractiva International meeting.

Dr. Rodriguez said he uses an IntraLase femtosecond laser (Advanced Medical Optics) and thus focused on possible complications associated with this device. In particular, suction loss may occur during surgery when creating the raster pattern, he said.

“You can continue with the treatment, using the same cone and a new ring. [But] if suction loss occurs when you are on the visual axis, it is better to wait about 1 month and then go about 40 µm deeper,” he said. “If suction loss occurs during the side cut, repeat the side cut only, reducing the flap diameter with a new, smaller ring.”

Vertical gas breakthrough represents another common complication and may occur when creating thin flaps of 100 µm or less or if there is a focal break or a scar in the Bowman’s layer, he said.

“If this happens, you should never try to lift the flap because you are likely to end up with a buttonhole,” Dr. Rodriguez said.

On the other hand, a horizontal gas breakthrough may occur when the gas is vented in quick bursts.

Another potential complication is opaque bubble layer (OBL), which is a collection of gas bubbles in the intralamellar space, above and below the resection plane. Early OBL tends to spread ahead of the raster pattern, whereas late OBL appears as opaque patches in areas of the raster pattern, he said.

“OBL is an excess of gas and water and may be due to several reasons. It is more common in brown eyes and may occur when energy power levels are too high or when the pocket is near the limbus, not deep enough or too narrow,” Dr. Rodriguez said.

OBL occurs in about 20% of patients and disappears after 15 to 45 minutes. It does not affect surgical results, although it may create problems with using the eye tracker and when lifting the flap, he said.

Occasionally, gas bubbles can also diffuse into the anterior chamber via Schlemm’s canal.

Dr. Rodriguez said such a complication is not severe, but it can disrupt the excimer laser tracking system and may require several hours to fully dissipate.

Postoperative complications, namely diffuse lamellar keratitis and transient light sensitivity syndrome, were more common with the previous generations of IntraLase and are rarely reported with the latest 60 kHz model, he said.

“In femto-LASIK, [diffuse lamellar keratitis] might be related to energy levels since the latest generation of IntraLase is associated with very few of these cases,” Dr. Rodriguez said.

Transient light sensitivity syndrome is a rare phenomenon strictly related to femto-LASIK and generally appears 2 to 6 weeks postoperatively. It might be caused by keratocyte activation or gas migration to the corneal periphery or to the episclera.

Patients can present with moderate to extreme light sensitivity, although they maintain good visual acuity. Transient light sensitivity syndrome disappears spontaneously between 1 and 3 months postop, and it can be treated with corticosteroids, Dr. Rodriguez said.

“Again, this problem seems to have been overcome by the latest generation of IntraLase,” 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.

Presbyopia correction the ‘Holy Grail’ of refractive surgery

Presbyopia correction is still “the Holy Grail of refractive surgery,” according to Ioannis Pallikaris, MD.

Ioannis Pallikaris

“Compared to other refractive procedures, we have the highest variety of possible treatments, but none of them offers the solution for complete restoration or substitution of the accommodative mechanism,” he said.

Multifocal IOLs allow pseudophakic patients to visualize images at different focal distances without relying on capsular mechanics or ciliary body function. However, they have drawbacks such as glare and halos that often overcome the advantages of spectacle independence, Dr. Pallikaris said.

Accommodative IOLs mimic the properties of the natural crystalline lens.

“They are based on a good principle and even show better visual results at intermediate distances than multifocal IOLs, but accommodative amplitude is limited and definitely not enough for complete spectacle independence,” he said.

There are surgical options that address the sclera with the aim of restoring accommodation, such as scleral implants, scleral incisions or LaserACE ablations. There are corneal techniques that create monovision, such as conductive keratoplasty, corneal inlays and one-eye laser procedures. Finally, there are excimer laser profiles that are aimed at creating a bifocal or multifocal cornea, but results are unpredictable and the procedure is not reversible, Dr. Pallikaris said.

“This plethora of techniques means that we have not achieved the final solution for the correction of presbyopia,” he said.

The aging baby boomer generation represents a growing population that the pharmaceutical and medical industry recognizes as a potentially new market for presbyopia correction. Today’s society is orientated toward all of the products and interventions that improve appearance, psychological well-being, everyday life and overall quality of life, Dr. Pallikaris said

“So we have a goal,” he said. “But the fact that we have made a step on the moon does not mean that we have already conquered the universe.”

Surgeons must be aware of glaucoma risk after refractive surgery

The risk of glaucoma after refractive surgery procedures should not be underestimated, according to one surgeon.

“I have to play the part of devil’s advocate by speaking about this topic in a refractive surgery meeting,” said José Belda, MD, of Vissum Institute in Alicante. “Still, we have to consider that what we see is only the tip of the iceberg. And below it, we may have a large quantity of patients presenting this problem in the future.”

The volume of refractive surgery is constantly increasing. Figures are difficult to estimate in Europe, but in the United States, about 1.4 million refractive procedures are performed per year, according to Dr. Belda.

“We must take into account that the largest part of refractive surgery procedures are done in myopic patients, amongst which the prevalence of glaucoma is three to four times higher than normal, even without any surgical procedure,” he said.

For glaucoma related to refractive surgery, surgeons must look at the causes, and these vary according to the technique used, Dr. Belda said.

One problem all techniques have in common is that true IOP levels are difficult to assess after surgery. IOP can be underestimated, and glaucoma can go undiagnosed for a long time, he said.

Surface techniques hold some advantages because no suction is applied during the procedure. But more corticosteroids are used to prevent haze, which may lead to corticosteroid-induced glaucoma, particularly in patients with high myopia, Dr. Belda said.

Meantime, suction can be a problem with LASIK. The vacuum phase is short, but pressure values are high — between 60 mm Hg and 90 mm Hg — and can reach as high as 200 mm Hg as the blade presses against the cornea, he said.

“Time is also surgeon-dependent. Inexperienced surgeons might prolong this stage and cause damage to the optic nerve,” Dr. Belda said.

There is no evidence to prove that this risk applies to normal eyes, but nobody has yet proved that this pressure increase is safe in eyes with underlying glaucoma or ocular hypertension, he said, adding that even less is known when femtosecond lasers are used for LASIK.

“We know that suction is lower, pressure is lower, but since the procedure is longer, we are going to flatten the cornea for a longer time than with mechanical microkeratomes, and so some damage can still be caused to the optic nerve,” Dr. Belda said.

He said he believes, however, that most cases of glaucoma after refractive surgery are related to the increase in IOP induced by the use of corticosteroids.

Corneal inlay showing positive results in multicenter European study

Preliminary data from a multicenter European clinical trial suggest that the AcuFocus ACI 7000 corneal inlay has potential to become a new, minimally invasive option for treating patients who have presbyopia, according to a surgeon.

Jorge L. Alió

To date, 70 patients have been implanted with the device as part of the study, and 23 have reached 12 months follow-up, Günther Grabner, MD, said.

At 1 year, uncorrected near vision averaged J1, and intermediate and distance vision averaged 20/20, Dr. Grabner said.

However, “some time is needed for adaptation, but vision at all distances improves steadily over time,” he said.

Preoperatively, near vision averaged between J7 and J8 and improved to average J2 at 1 month and J1 at 9 months, Dr. Grabner said.

Potential problems are mainly related to implant positioning, as the device must be well-centered, he said. In implanting the ACI 7000 corneal inlay in 45 patients, Dr. Grabner has had to re-center the implant in three cases.

OSN Associate Editor Jorge L. Alió, MD, PhD, also stressed the importance of good centration on the line of sight. In addition to restricting light penetration, which is characteristic of the implant, decentration can lead to optical aberrations, he said.

“We mark the line of sight on the cornea, with the aid of a special device, and this definitely helps centration,” Dr. Grabner said.

In addition, the inlay does not seem to interfere with surgeons’ abilities to perform ophthalmic examinations or surgical procedures at the corneal, anterior chamber, lens or retinal levels, he noted.

“If you need to perform macular surgery, you can easily remove the implant, carry out the procedure and put the implant back in place,” Dr. Grabner said.

Epithelium integral in refractive surgery outcomes, surgeon says

The corneal epithelium plays a critical role in modulating healing after refractive surgical procedures, and taking steps to address epithelial ingrowth is important to preventing poor visual outcomes, according to a surgeon.

“When you make large abrasions in the corneal epithelium, you get three to six sheets of cells moving from the periphery to the center,” said Harminder S. Dua, MD, of Nottingham University, England. “When they meet, the lines of contact between [the cells], which [when] stained with fluorescein look like dendritic figures, affect vision.”

Such irregularities will eventually disappear, and only then will patients recover their full potential visual function, he said.

LASEK represents a good example of this process because the short-term outcomes vary according to the conditions of the epithelial flap, Dr. Dua said.

“If you have a damaged epithelial flap, which is no longer viable, and you put it back into place, there will be a new epithelial layer growing underneath it. The two layers of epithelium will compete with each other, and until the new healthy epithelium takes over and the damaged, more superficial layer falls off, vision will remain poor,” he said.

Conversely, if the flap is healthy, recovery is faster because the healthy flap prevents keratocyte activation. There is little haze and the patient’s vision improves within 3 days after surgery, Dr. Dua said.

Epithelial ingrowth may also develop under a LASIK flap when there is a discrepancy between the flap and the underlying stromal bed. In particular, the risk is highest after LASIK re-treatments, he said.

“This happens particularly when, to re-lift the flap, the surgeon makes a small opening and peels it off,” Dr. Dua said. Such maneuvers often lead to epithelial tearing and abrasion, which triggers a chain of healing processes and consequent epithelial ingrowth.

To avoid this, he suggested cutting along the previous LASIK flap edge using a fine needle before lifting the flap.

By doing this, I have a zero rate of epithelial ingrowth following LASIK enhancement,” Dr. Dua said.

Multifocal IOLs specifically designed for mix-and-match technique warranted

Although the mix-and-match technique of implanting multifocal IOLs provides patients with a high degree of spectacle independence, using the approach involves a do-it-yourself element, which some ophthalmologists do not like, according to a surgeon.

“I do mix-and-match with Tecnis and ReZoom [IOLs] (Advanced Medical Optics), and 93% of my patients don’t use spectacles. Particularly for intermediate tasks, like computer work or daily activities like shopping, it works very well,” Werner W. Hütz, MD, said in an interview with Ocular Surgery News. “But personally, I find that implanting two lenses with two different types of ocular principles is not as professional and scientifically correct as we would like it to be.”

In Dr. Hütz’s opinion, manufacturers should produce the same lens with complementary design and light distribution for the dominant and nondominant eye.

“There should be, for instance, a diffractive Tecnis for near and a diffractive Tecnis for far, so we wouldn’t have to mix two different principles and implant two different lenses, one diffractive and the other one refractive, in some cases produced by two different companies,” he said. “The diffractive principle, in my opinion, works well, and we should have a diffractive in both eyes, one dominant for far and one for near.”

Aspheric IOLs compensate similar to a young, natural lens, study shows

Aspheric IOLs have the ability to reduce spherical aberration and to compensate for coma in a similar way as a young phakic eye, according to a study carried out in Germany.

“A previous study by Tabernero et al demonstrated that in the young eye, we have a natural compensation for corneal coma at [the] lens’ level. The so-called angle K, which is the difference between the line of sight and the pupillary axis, is reversed and therefore compensated at the lens level,” Hakan Kaymak, MD, said.

In their study, Dr. Kaymak and colleagues used a new device called a Purkinje meter, which was developed by Franck Schaeffel of Tübingen, Germany. The researchers found that aspheric IOLs not only significantly reduce spherical aberration and increase contrast sensitivity compared with spherical lenses, but they also compensate for coma aberration in cases of slight tilt or decentration.

“We tested this ability with the AcrySof IQ lens (Alcon), with the new Tecnis one-piece (Advanced Medical Optics), with the aspherical Hoya and Acri.Tec 35A and found no significant difference between these models,” Dr. Kaymak said.

Experts debate cataract surgery rates in developed countries

Two surgeons squared off over whether unnecessary cataract surgeries are being performed in the developed world.

Except for the most developed countries, cataract remains the leading cause of blindness in all regions of the world, accounting for 48% of world blindness, according to Dr. Dua. Associated with aging, it is even more significant as a cause of low vision in developing and underdeveloped countries, where 90% of the world’s visually impaired live.

“However, it is in these regions of the world, where it is mostly needed, that we have the lowest cataract surgical rates (CSR, cataract operations per million population per year), while the vast majority of cataract operations are performed in the industrialized countries,” Dr. Dua said during the debate.

About 2.5 million cataract surgeries are performed annually in the United States and 250,000 in the United Kingdom. The CSR in the U.K. is between 4,000 and 4,500. In Australia, where the rate is the highest in the world, it is 6,500, and in the U.S., the number falls somewhere in between. However, seldom do surgeons in developed countries see and operate on patients with cataract at the most advanced stages, Dr. Dua said.

Whether a percentage of such a high volume of cataract operations may be due to surgeons’ interests rather than patients’ needs is perhaps a legitimate question, and Dr. Dua raised the question: “Are we doing much unnecessary cataract surgery?”

Taking the other side of the argument, Bal Dhillon, MD, said visual acuity, cataract morphology and grading are no longer the leading criteria for cataract surgery indications.

“Quality of life and the patient’s subjective perception of a disturbed vision are the criteria. Whenever benefits outweigh risks and whenever symptoms impair life quality, cataract surgery should be done,” he said.

A note from the editors:

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