Intrastromal femtosecond method reduces presbyopia

The new minimally invasive treatment also can be used to correct refractive errors in thin corneas, study suggests.

ByMichela Cimberle

ALICANTE, Spain – A minimally invasive intrastromal treatment using a femtosecond laser is showing good results in reducing presbyopia without altering distance vision, according to a pilot study carried out in Bogotá.

The treatment reshapes the cornea by inducing a redistribution of biomechanical forces and is tailored to the individual patients by special software linked to the Femtec femtosecond laser (20/10 Perfect Vision).

“With the Femtec laser, a new model to predict the impact of intrastromal ablation on the biomechanics of the cornea has been developed,” Fritz Meisel, engineer at Perfect Vision, said on behalf of Luis Antonio Ruiz, MD, at the Alicante Refractiva International meeting here. “We do preliminary measurements with the Pentacam (Oculus) and transfer these data to our computer. The corneal finite-element modeling software uses a spatial 3-D grid adapted to the individual corneal curvature. Depending on the refractive properties as well as on the individual biomechanical and geometrical properties … a customized ablation pattern for each eye is calculated.”

To allow precise, 3-D positioning of the laser pulses, the cornea must be stress-free during the treatment. The Femtec fixation system has minimal biomechanical impact because there is no applanation and practically no pressure on the cornea, Mr. Meisel said.

Reshaping of the cornea in a multifocal pattern that re-establishes the patient’s ability to focus at all distances is obtained with little tissue evaporation, between 1 µm and 2 µm of corneal depth, which maintains the structural integrity of the cornea.

“A true revolution that makes laser treatment possible also for thin corneas” he said.

As a patient of Dr. Ruiz’s, Mr. Meisel showed how well he could read at near without any spectacle aid.

“I was able to do this from the moment I stood up after surgery,” he said. “The intrastromal ablation is minimally invasive, it is painless because it has no impact on the epithelium, has a low infection risk and no wound healing problems.”

Rewarding outcomes with all refractive problems

Unlike other treatments for presbyopia, the intrastromal Femtec procedure does not affect far vision. In most cases, a myopic shift of less than 0.5 D is produced, but patients do not lose, and in some cases, gain distance acuity. Mr. Meisel said visual quality is maintained, and only minor glare problems might be experienced for a short period of time by some patients.

“It is the ideal treatment also for patients who were implanted with a monofocal lens after cataract surgery or for post-LASIK patients as they grow older,” he said.

A clinical study is ongoing at the Centro Oftalmológico Colombiano in Bogotá to evaluate the potential of this new treatment modality for intrastromal correction of myopia, hyperopia, astigmatism and presbyopia. Since October, more than 100 patients have been treated.

Mr. Meisel showed several examples of the outcomes of this procedure in different situations.

One 66-year-old patient had both eyes treated that had previously received a monofocal IOL for cataract. Near vision improved from J9 and J10 to J2 in both eyes, and the patient retained 20/20 vision in one eye and improved from 20/25 to 20/15 in the other eye.

A second case was that of a 51-year-old patient. He had received LASIK in 1994. Some years later, he underwent cataract surgery and was implanted with a Rayner monofocal IOL.

Near vision was J9. After the treatment, this patient achieved 20/20 vision and near acuity improved from J9 to J1.

Another patient with previous radial keratotomy in both eyes had good vision at distance but J6 and J9 at near. After the Femtec intrastromal treatment the patient could read J2 and J1.

Presbyopia study results

Emmetropic presbyopic patients obtained good results.

Dr. Ruiz included 59 eyes in a study on intrastromal correction of presbyopia and disclosed the results at 1 month.

The age of the patients ranged between 41 and 66 years, with an average of 51 years.

Preoperative assessment included near visual acuity using Jaeger charts and distance visual acuity using Snellen charts, both under photopic conditions. Corneal measurements and biomechanical properties were evaluated with the Pentacam.

Before the treatment, mean near uncorrected visual acuity was 20/80. It increased to 20/28 within minutes to a few hours after the treatment and was stable at 1 month.

In Jaeger lines, the average reading before surgery was J8. One-day postop, the mean value increased to J2.5.

“In this study, an increase of near UCVA of up to 12 Jaeger lines was observed. The average gain at 1 month was 5.9 lines, but now that we have reached nearly 5 months of follow-up, we can see a further improvement, with an average gain of about seven lines,” Mr. Meisel said.

The average distance uncorrected vision even improved within the observation period of 1 month by 14% in comparison with preoperative data. Half of the patients gained visual acuity. In 29%, distance UCVA was not affected and only one case lost more than four Snellen lines because of decentration of the treatment.

“Centration is an aspect we should further improve,” Mr. Meisel said.

The average value of distance UCVA increased by 0.6 lines.

Before the treatment, 95% of the patients had a best corrected vision of 20/20. This value slightly decreased 1-day postop to 90%, but 1 month after the treatment, all patients had a distance BCVA of 20/20 or better. The number of patients with a distance BCVA of 20/15 or better even increased from 42% preop to 54% at 1 month.

“These preliminary results are extremely encouraging. This technique has a huge potential to improve near vision instantaneously, with no downsides so far,” Mr. Meisel said.

Further studies and a longer follow-up are necessary to evaluate the long-term stability of the treatment, he said.

For more information:

Luis Antonio Ruiz, MD, can be reached at Centro Oftalmologico Colombiano, Carrera 20 No. 85-11, Bogota, Colombia; +57-236-00-00; e-mail: lantonio@unete.com. Ocular Surgery News was unable to determine whether Dr. Ruiz has a direct financial interest in the products discussed in this article or if he is a paid consultant for any companies mentioned.

Fritz Meisel can be reached at 2010 Perfect Vision GmbH, Am Taubenfeld 21/1, 69123 Heidelberg, Germany; +49-6221-7502-0; e-mail: fritz.meisel@2010pv.com.

20/10 Perfect Vision AG, maker of the Femtec femtosecond laser can be reached at Am Taubenfeld 21/1, 69123 Heidelberg, Germany; +49-6221-7502-0; fax: +49-6221-7502-166; Web site: www.2010pv.com; e-mail: science@2010pv.com.

Michela Cimberle is an OSN Correspondent based in Treviso, Italy, who covers all aspects of ophthalmology. She focuses geographically on Europe.