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.