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Intracor femtosecond laser treatment shows good refractive stability two years on
By Linda Roach, Contributing WriterWith two years of follow-up, 92.6 percent of the presbyopic eyes treated with the Intracor femtosecond laser procedure have simultaneous distance UCVA of at least 20/25 and near acuity of J3 or better, according to the Colombian surgeon who pioneered this intrastromal procedure.
About 75 percent of the eyes had uncorrected near visual acuity (UCNVA) of J1 at the 24-month mark, 97 percent were at least J2 and 100 percent were at least J3. Before the procedure, three-quarters of the eyes had UCNVA of J6 or worse.
Even with distance correction (if needed), the treated eyes had a mean VA at near of 0.086 logMAR, or slightly better than J2, said Luis A. Ruiz, MD, of Centro Oftalmológico Colombiano, in Bogotá. Internal corneal incisions
The two-year results indicate that this incisionless refractive procedure has a good safety profile and produces stable refractive results, Dr. Ruiz reported at the 2010 ASCRS Annual Meeting in Boston.
“We have performed Intracor on patients out as far as 30 months now, and the results are really amazing,” Dr. Ruiz said in an interview. “The near vision improves a little bit, month by month, and the patients are very happy with the results.“
At two years post-op, the patients again said that the only time they needed reading glasses was in dim light (when the wider pupil would limit the benefit of the hyperprolate cornea that Intracor creates).
Twenty seconds of pulses
Intracor is a 20-second long procedure that delivers concentric rings of femtosecond-laser energy. The targeted tissue damage alters corneal biomechanics, steepening the anterior corneal surface. The cornea’s new multifocal, hyperprolate shape has greater negative asphericity and an increased depth of focus.
The basic pattern is a series of femto-disruptive cylindrical rings that begin within the posterior stroma at a variable distance from Descemet’s membrane. The rings spiral anteriorly through the mid-stroma until reaching a predetermined, fixed distance beneath Bowman’s layer. To treat low myopia or astigmatism, Dr. Ruiz has recently started adding radial patterns of intrastromal pulses.
Cavitation bubbles interfere with the patient’s vision for an hour and a half to two hours afterward, and most of the improvement in UCVA occurs during the first month after treatment, Dr. Ruiz reported.1
Three years of use
The data presented in Boston represents the longest follow-up on the stability and safety of Intracor since Dr. Ruiz performed the first such surgery in October 2007 with the Femtec laser (20/10 Perfect Vision, Heidelberg; now named the 520 FS laser and Technolas Perfect Vision).
About 80 percent of the treated eyes on which he reported had the same BSCVA after two years as they had preoperatively. Nineteen percent gained one line of Snellen BSCVA, and one eye lost oneline, he said.
This was an improvement from the previously reported six-month results, when two eyes (2.4 percent) eyes lost twolines of CDVA at six months.1 Between the six- and twelve-month exams, however, the previous VA losses were gradually neutralized.
Minimal refractive change among consistent cohort of 94 eyes in year two 94-eye cohort
During year two, spherical manifest refraction changed by ? 0.5 D in 93 of the eyes compared with 81 eyes with that level of change in the first postop year. One eye experienced greater refractive change, but the change was still ? 1.0 D, Dr. Ruiz reported in Boston.
The 94-eye study included presbyopic subjects who were within 2 D of emmetropia (mean: 0.54 D MRSph, 0.32 D MRSE), with minimal astigmatism, before Intracor treatment. Their average age was 54 years. At 24 months, the treated eyes had mean refractive error of -0.11 D (MRSph) and -0.39 D (MRSE).
Life after presbyLASIK
Prior to his first intrastromal procedure, Dr. Ruiz worked on correcting presbyopia with the excimer laser with presbyLASIK. But the results proved unsatisfactory. “The worst patient with the Intracor is better than the best patient with the presbyLASIK,” Dr. Ruiz said.
He has performed more than 1,000 Intracor corrections; 282 of them have been followed in a clinical study for at least six months and 214 for one year. (The firm has since joined with Bausch & Lomb to form Technolas Perfect Vision; this was when the Femtec was renamed the 520 FS.)
Intracor has received CE Mark approval in Europe for low presbyopic treatments ranging from +0.25 to +0.75 D with 0.5 D of cylinder. The CE approval prohibits surgeons from treating both eyes on the same day. Intracor is commercially available across Europe and Asia, with the system now installed in over 13 countries across these regions.
Quick consumer acceptance
Despite this restriction and the limited availability of the 520 FS laser, European ophthalmologists performed Intracor on more than 1,500 presbyopes during the first six months after the approval, Dr. Ruiz said.
Technolas Perfect Vision predicts that it will be at least five years before Intracor can win approval for use in the United States.
Dr. Ruiz said he was not surprised by the continued positive visual and safety outcomes in Intracor eyes beyond one year. Nevertheless, he wants to fine-tune the procedure’s predictability by studying the “outliers” in the data.
“Like with all surgery, there is variability in effect. Some patients improved from J10 to J1 after Intracor, and others only improved to J3. We are now carefully analyzing our data to try to determine what the factors are that influence this,” Dr Ruiz said.
Curvature changes count
These analyses so far suggest that the refractive results correlate with the relative curvature changes in the anterior and posterior cornea.
“We are finding a very interesting relationship between the asphericity of the anterior cornea and the change in its central thickness,” he said.
Despite looking for ways to improve the results, Dr. Ruiz regards using Intracor as a peak experience as a refractive surgeon, an ophthalmic “dream come true.” This 20-second procedure eventually might settle the debate over how accommodation works by making the issue clinically moot, he said.
“If you just change the cornea in a good way, if you can help it regain the negative asphericity that we know improves visual acuity, then you would not have to be very concerned about how the accommodative mechanism works at all,” he said.
Long-term analysis needed
Intracor is a promising procedure, with safe, effective, and favorable visual results that seem to improve during the first 12 months of follow-up. Further studies with a larger number of eyes and longer follow-up are recommended to more fully characterize this technology and support the positive outcomes observed thus far.
1. Ruiz LA, Cepeda LM, Fuentes VC. Intrastromal correction of presbyopia using a femtosecond laser system. J Refract Surg. 2009;25(10):847-854.
CONFLICT OF INTEREST
Dr. Ruiz continues to receive research funding and travel grants from the laser manufacturer now known as Technolas Perfect Vision (Heidelberg, Germany). He is listed as the inventor on two patents governing the intrastromal laser procedure for correcting presbyopia and will receive royalties from Intracor’s use.