CHICAGO – LASIK and corneal surface ablation approaches to refractive surgery are “complementary procedures,” each with their own set of advantages and disadvantages, said Scott M. MacRae, MD. He spoke on the topic “Surface vs. lamellar: Which is best” during the Refractive Surgery Subspecialty Day here at the American Academy of Ophthalmology meeting.

Surface ablation allows the surgeon to treat patients with thin corneas who might be contraindicated for LASIK, Dr. MacRae said. A surface approach also “causes less tendency toward dry eye in patients with borderline tear film,” he said. In addition, the newer surface procedures such as epi-LASIK offer faster recovery from neurotrophic dry eye, there is less risk of ectasia, no risk of flap complications, and the techniques are simpler and easier to teach than LASIK, he said.

The disadvantage of surface ablation compared with LASIK is the longer recovery period, Dr. MacRae said. In his experience, on average, patients need 3 to 5 days after surface ablation before returning to work, driving or recreational activities. “The biggest obstacle is really the slower recovery period,” he said. “It usually takes 1 to 8 weeks for full visual recovery.”

Scott M. MacRae, MD [photo]
Scott M. MacRae

In his practice, Dr. MacRae said, the incidence of postoperative corneal haze has become minimal after PRK with the use of mitomycin and scanning-spot lasers.

Regarding the advantages of LASIK, Dr. MacRae noted that new microkeratomes now allow thinner flap creation. “We’ve found that flaps under 100 µm have a better postop visual acuity compared with thicker flaps,” he said.

With customized LASIK, Dr. MacRae said, the postoperative induction of higher-order aberrations has been reduced. In a study in 48 eyes of 24 patients in whom one eye underwent conventional LASIK and one underwent customized LASIK, the mean induction of higher-order aberrations was 35% in the conventional LASIK eyes and 18% in the custom-treated eyes, he said.

Dr. MacRae said he still performs LASIK in about 85% of patients in his practice, and surface ablation procedures are reserved primarily for patients with dry eye or anterior basement membrane disease, patients with thin corneas and patients with higher myopia.

Wavefront-optimized equals wavefront-guided for patients

Wavefront-guided and wavefront-optimized LASIK with the WaveLight Allegretto Wave laser achieved nearly identical visual outcomes at 3 and 6 months postop, and neither treatment induced higher-order aberrations, according to information from WaveLight.

In an instructional course, Bill Bond, MD, presented 3- and 6-month results of a randomized study comparing the two techniques, according to a WaveLight press release. Patients with myopia of up to 7 D and astigmatism of up to 3 D were eligible for participation in the multicenter study.

In the 81% of participants with less than 0.3 µm of preoperative higher-order aberrations, equivalent outcomes were achieved with either laser platform, according to WaveLight. For those with preop higher-order aberrations greater than 0.3 µm, aberrations were reduced slightly more with wavefront-guided treatment than with wavefront-optimized treatment on the Allegretto Wave laser. Neither platform induced aberrations after treatment.

“Approximately 82% of all patients reported postoperative visual acuity better or equal to preoperative BCVA, and 55% of patients gained one or more lines of vision. No loss of contrast sensitivity was observed with either platform,” the press release stated.

Wavefront-optimized treatment is the standard treatment on the Allegretto Wave laser. Dr. Bond noted in the press release that “wavefront-optimized LASIK provides considerable benefits to all patients without inducing spherical aberrations. Only a small proportion of patients benefit from wavefront-guided treatments, and it is still unclear how much benefit is achieved.”

Perceptual training sharpens contrast sensitivity

A vision-training regimen based on visual stimulation and repetition may help sharpen contrast sensitivity and visual acuity in low myopes and patients with residual refractive error after refractive surgery, said Donald T.H. Tan, FRCS.

Prof. Tan described his experience with the NeuroVision NVC vision correction technology here during Refractive Subspecialty Day. The technology is a noninvasive, patient-specific treatment based on visual stimulation and facilitation of the neural connections responsible for vision, Prof. Tan said. The system uses an Internet-based, computer-generated visual training exercise regimen of patient-specific stimuli to sharpen contrast sensitivity and visual acuity, he said.

Patients undergo treatment three times a week “until there is no more visual improvement,” Prof. Tan said during his podium lecture. The average treatment lasts 2 to 3 months.

“How we see involves a complex interaction of optics and image processing pathways in the visual system from the cornea to the cortex,” Prof. Tan told attendees.

The system can be used “to enhance contrast sensitivity and hence improve visual acuity in mild to moderate states of visual blur, such as amblyopia, myopia or residual refractive error,” Prof. Tan said.

“The whole concept is now called perceptual learning,” Prof. Tan said during his interview. “You do the same thing when you learn how to ride a bike or train for a marathon … you do repetition and you get better at it. The brain remembers how to ride faster and balance better, and this is the same thing.”

At his clinic, 20 patients with an average refractive error of –1.5 D underwent treatment; 15 patients have been followed for at least 6 months. “Their mean unaided contrast sensitivity function improved to within the normal range,” he said during his lecture.

More than 300 patients have completed treatment with the NeuroVision system at sites in Brazil, China, Korea, Japan, Malaysia, Singapore and the United Kingdom, Prof. Tan said. Some patients had mild myopia at baseline while others had residual refractive error after LASIK, he said. “The post-LASIK group showed worse contrast sensitivity function in comparison to the low myopia subgroup, although their refraction and visual acuity were similar,” he said.

Of those with low myopia, (mean –1.34 D), after undergoing the Neuro-Vision treatment, a 2.7-line improvement on a visual acuity chart was noted. The average residual refractive error in the LASIK group was –1.14 D, and those patients had a mean improvement of 2.6 lines after the treatment, Prof. Tan said.

“On average, 92% of the eyes had one logMAR line or more improvement after treatment, 72% had two lines, 42% had three lines. The mean manifest refractive error remains unchanged,” he said.

LASIK still most common refractive procedure

An annual survey indicates that LASIK is performed by about 90% of refractive surgeons, said Richard J. Duffey, MD, during Refractive Surgery Subspecialty Day.

After LASIK, the most common refractive surgical procedure is PRK, performed by 68% of respondents, followed by limbal relaxing incisions/IOL (57%), refractive lens exchange (39%) and limbal-relaxing incisions alone (26%). Other refractive procedures were performed by less than 25% of respondents.

The survey was sent to the 2,000 members of the International Society of Refractive Surgeons; 246 responses were received, a response rate of 16.4%.

The survey asked respondents what their preferred surgical approach would be for several hypothetical refractive surgery candidates. “For a 30-year-old, –10 D [patient], LASIK is preferred by 40% of surgeons, with phakic IOLs a close second, at 35%” Dr. Duffey said. “For a 45-year-old, +3 D [patient], LASIK is the preferred choice, but for a +5 D [patient], refractive lens exchange is the preferred method.”

The Bausch & Lomb Hansatome was preferred by the largest percentage (40%) of respondents, and 22% reported using the IntraLase FS femtosecond laser. The Visx Star S4 laser was preferred 2-to-1 over other laser systems, Dr. Duffey said.

Among the IOLs now available for presbyopia correction, “the (Alcon) ReStor lens has already surpassed the (eyeonics) crystalens,” he said.

Monovision is still the most common mode for refractive surgical correction of presbyopia, preferred by 53%. Modified monovision was the second most preferred technique at 23%.

Almost three-fourths of respondents (72%) said they require a minimum central corneal pachymetry between 480 µm and 500 µm for performing LASIK.

Comanagement of refractive surgery patients has increased, from 40% of respondents in 2004 to 60% in 2005, he said.

Results of this year’s survey will be available on www.duffeylaser.com, Dr. Duffey said.

Study pits mechanical, laser microkeratomes

LASIK flaps created with a mechanical microkeratome achieved more consistent and accurate intended flap thickness with a lower total surgery time than flaps created with a femtosecond laser, a study presented here found. But the manufacturer of the laser microkeratome pointed out in response to the study that the standard deviation of the flap thickness was greater with the mechanical device.

Hung Ming Lee, MD, of Tan Tock Seng Hospital in Singapore, discussed the prospective, randomized, contralateral trial of corneal flaps for LASIK using the Zyoptix XP microkeratome (Bausch & Lomb) and the IntraLase FS 15 kHz femtosecond laser during a press event hosted by Bausch & Lomb.

Dr. Lee performed bilateral surgery in 50 patients using the Zyoptix XP to create the flap in one eye and the IntraLase FS in the other.

Users of the Zyoptix XP “can expect to achieve the same level of precision, predictability and outcomes that have been ascribed to the latest generation laser flap-creation technology,” Dr. Lee said.

For the study, Dr. Lee used an intended flap thickness of 120 microns. The Zyoptix flaps were a mean 4 microns thinner than the IntraLase flaps, according to ultrasound pachymetry, and 11 microns thinner according to optical coherence pachymetry (OCP), he said.

The study found similar standard deviations in flap thickness with the two devices, Dr. Lee said. The Zyoptix XP flaps had a standard deviation of 16.1 microns as measured with ultrasound and 14.4 microns as measured with OCP, while the IntraLase flaps had a standard deviations of 16.2 microns with ultrasound and 15.9 microns with OCP.

Dr. Lee said he still uses both the IntraLase and the Zyoptix microkeratomes in his current practice, and he estimated that he uses them in an equal number of procedures.

“The results of this contralateral study have demonstrated that both technologies deliver excellent performance and precision,” Dr. Lee said, “but more importantly to me, the visual outcomes are equivalent in both high and low contrast conditions.”

During the AAO meeting, officials at IntraLase commented on the findings of Dr. Lee’s study. They said the femtosecond laser keratome flaps had a smaller standard deviation than those produced by the mechanical keratome. IntraLase also noted in a press release that its newest laser, with a speed of 30 kHz, was not used in the study.

Ronald Kurtz, MD, IntraLase vice president and medical director, noted in an interview that Dr. Lee measured the achieved flap thickness with both ultrasonic pachymetry and OCP. He said OCP is “consistently more accurate” than ultrasonic pachymetry, and he went on to discuss the flap thickness achieved results as measured by OCP.

Using the data reported by Dr. Lee — that the Zyoptix XP flaps had a standard deviation on OCP of 14.4 µm and the IntraLase flaps had a standard deviation of 15.9 µm — Dr. Kurtz calculated these standard deviations into percentages. The Zyoptix XP flap SD was 13.2%, and the IntraLase flap SD was 11.5%, he said.

Public perception matters in ophthalmic political issues

The public is the newest ally in ophthalmologists’ battle to limit optometric scope of practice, according to H. Dunbar Hoskins, MD.

Susan H. Day, MD [photo]
Susan H. Day

Dr. Hoskins said a recent survey by the National Consumers League showed that “people are confused about who is doing eye care.”

“(The survey showed) that people want to know who is doing (surgery), and they do care who does what to them,” he said during the AAO meeting’s opening session. “The battle continues.”

In her address during the opening session, outgoing AAO President Susan H. Day, MD, said that the issue of maintaining patients’ trust is perhaps the most important facing ophthalmologists today.

“We are in an age of increasing accountability” as the public begins to question and notice ophthalmologists’ relationships with industry, she said.

Randolph L. Johnston, MD, OCS, the AAO’s senior secretary for advocacy, agreed that the public is starting to take notice of the AAO’s national Surgery by Surgeons campaign, which seeks to bar optometrists from performing laser surgery and prescribing certain drugs, both of which are viewed by the AAO as the domain of ophthalmologists only.

This article also appears in Ocular Surgery News, a SLACK publication.