Intrastromal lenticule rotation shows promise in treatment of high astigmatism
The lenticule is created with the SMILE software and rotated by 90° inside the stromal pocket.
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A novel technique of intrastromal lenticule rotation effectively treats high astigmatism up to 10 D in a minimally invasive manner, according to two specialists.
“Managing high astigmatism (> 5 D) is difficult. The current approaches through arcuate keratotomy or intracorneal ring segments have relatively low predictability and a large variability of outcomes,” Jesper Hjortdal, MD, PhD, said.
At Aarhus University Hospital, Denmark, small incision lenticule extraction has been performed for many years, but the laser is not CE marked for the treatment of mixed astigmatism nor for an astigmatic correction of more than 5 D in eyes with myopic astigmatism.
“We had this idea of creating an intrastromal lenticule using the SMILE software (Carl Zeiss Meditec) with half the intended astigmatic correction and then freeing the lenticule under the cap and rotating it by 90°. In this way, you redistribute the stromal tissue, subtracting tissue thickness from the flat meridian and adding it to the steep meridian. As a result, the astigmatic correction will be twice the magnitude of the programmed cylinder referenced to the corneal plane,” Hjortdal said.
This concept was first applied to human donor corneas deemed unsuitable for patient treatment due to low endothelial cell count. Using lenticules of various thickness, cylinder correction was set to either 2.5 D or 5 D, aiming at final cylinder correction of 5 D and 10 D, respectively, after rotation.
“The lenticule was then rotated and repositioned within the pocket. Pentacam (Oculus) images showed a high correlation coefficient between surgically induced astigmatism and target astigmatism, with a minimal angle of error. Central corneal thickness did not change after the procedure, but there was a little steepening of the total corneal refractive power, with consequent myopic shift,” Hjortdal said.
This first study provides useful information for further research and clinical trials, he said.
From bench to bedside
Pavel Stodulka, MD, PhD, performed the first 10 intrastromal lenticule rotation surgeries in patients and is satisfied with his results.
“I got very enthusiastic about the idea because we have limited options for astigmatic correction with surgery, and also because I am a fan of SMILE surgery, do quite a lot of myopic SMILE and was one of the investigators of hyperopic SMILE for Zeiss. As soon as I heard about this potential method for correcting astigmatism as well, I thought, ‘Well, that’s really a very bright idea,’” he said.
Stodulka’s Gemini Eye Clinic is a high-volume surgical center, and it was possible to find a suitable patient for the first surgery, a woman with 5 D astigmatism in an amblyopic eye.
“It was the right choice to prove the concept, and it worked out very well because subjectively we ended up with 0 D astigmatism, and keratometric astigmatism decreased from 5 D to 0.5 D. We had a myopic shift, as anticipated, but this first experience was positive,” Stodulka said.
The following patients achieved an astigmatic correction close to 0 D cylinder; all of the patients had a myopic shift, and 6-month outcomes will be available soon. The follow-up visits so far showed refractive stability.
“I think this is a very promising new way of correcting high astigmatism, mainly mixed astigmatism and hyperopic astigmatism because of the myopic shift,” Stodulka said.
High astigmatism is not so frequent in the population, but it is a highly debilitating refractive error. A procedure that helps eliminate or at least decrease it without subtracting tissue is, according to Stodulka, a welcome opportunity. Because all the tissue is left inside the pocket, corneal stability is only minimally affected by the femtosecond laser cut.
“That’s a great advantage and creates the basis for potentially fine-tuning the refraction by PRK because the corneal thickness is not decreased,” he said.
Rotating and repositioning the tissue inside the pocket may be challenging at first. If not properly spread until flat, the stromal lenticule may create some amount of corneal irregularity after surgery, resulting in higher-order aberration, and a learning curve is required to confidently perform these maneuvers.
“However, our results are so far very nice, and we had no complications. We presented our first data at the ESCRS meeting in Marrakech, where they raised a lot of interest, and we are planning to present more in October at the ESCRS meeting in Amsterdam,” Stodulka said.
He is currently the only surgeon performing this procedure but expects that other colleagues will experience it soon.
“The problem is that patients with such a high astigmatism are a small minority, and only high-volume practices have the numbers to integrate this procedure into their offer,” he said. – by Michela Cimberle
- For more information:
- Jesper Hjortdal, MD, PhD, director of corneal and refractive surgery in the Department of Ophthalmology, Aarhus University Hospital, Denmark, can be reached at email: jesper.hjortdal@dadlnet.dk.
- Pavel Stodulka, MD, PhD, the head surgeon and CEO at Gemini Eye Clinic in Zlin and Prague, Czech Republic, and Vienna, Austria, can be reached at email: stodulka@lasik.cz.
Disclosures: Hjortdal and Stodulka report no relevant financial disclosures.
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