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The use of epi-on photorefractive intrastromal cross linking reduced myopia by about 0.25 D in a small study; In a high-oxygen group, the effect averaged 1.25 D.
Reviewed by Anders Behndig, MD
Take-home: The use of epi-on photorefractive intrastromal cross linking reduced myopia by about 0.25 D in a small study; In a high-oxygen group, the effect averaged 1.25 D.
Photorefractive intrastromal crosslinking-or PiXL for short-may be a potential new treatment for low-grade myopia, according to Anders Behndig, MD, Department of Clinical Sciences/Ophthalmology, Umea University Hospital, Umeå, Sweden.
Dr. Behndig presented information about his ongoing study, which included healthy volunteers with myopia in the range of -0.5 and -2.6 D (mean, -1.5 D).
All volunteers had epithelium-on (epi-on) PiXL treatment. This treatment included the use of topical anesthesia, isotonic riboflavin that was applied every 90 seconds for 10 minutes, and pulsed crosslinking. A circular central 4-mm cornea zone was irradiated with 30 mW/cm2 for 16:40 minutes.
“Thirty-nine eyes of 20 patients were treated, of which 12 eyes were treated in room air (20% O2) and 27 eyes in 94.3% O2, which was the high-oxygen group,” Dr. Behndig said.
The groups represented 6 patients and 14 patients, respectively.
Dr. Behndig collected information on uncorrected visual acuity (UCVA), subjective refraction, spherical equivalent, and corneal endothelial cell count.
A minor increase in spherical equivalent was seen in the room air group at 1 month (+0.33 D). However, there was a more pronounced effect in the group in the high-oxygen group (+1.18 D).
“The UCVA increased by 0.13 and 0.60 logMAR, respectively,” Dr. Behndig said. “In the high-oxygen group, the UCVA at 1 month was 0.11 logMAR.”
He did not observe any reduction in endothelial cell count or other adverse effects.
“Based on the preliminary results of this ongoing study, a reduction of myopia of about 1 D can be achieved with a 4-mm epi-on PiXL treatment of 15 J/cm2 in a high-oxygen environment,” Dr. Behndig concluded.
Although the approach is safe, he added that it requires fine-tuning both to boost the effect of the treatment and to reduce variability.
Anders Behndig, MD
This article was adapted from Dr. Behndig’s presentation at the European Society of Cataract and Refractive Surgeons’ Winter Meeting in Maastricht, The Netherlands. Dr. Behndig is a consultant for Avedro.