Purpose To evaluate photorefractive intrastromal cross‐linking (PiXL) treatment for low‐grade myopia, comparing three treatment protocols. Methods Healthy individuals, 25.6 ± 3.6 years of age, with low‐grade myopia underwent epi‐on PiXL with either: 4‐mm zone treated in high oxygen environment (4 mm‐HIGH; n = 15), 4‐mm/room air (4‐mm LOW; n = 6), or 6‐mm/high oxygen (6‐mm HIGH; n = 6). Efficacy was determined by change in uncorrected visual acuity (UCVA), manifest refractive spherical equivalent (MRSE) and corneal curvature (Kmean) over a 12‐month follow‐up. Safety was determined by best spectacle corrected visual acuity (BSCVA), corneal endothelial cell loss and registration of side‐effects. Results Twenty‐seven subjects were included. Due to insufficient effect with the 4‐mm LOW treatment and an unacceptable degree of initial light sensitivity/ocular irritation in the 6‐mm HIGH group, the inclusions to these treatments were stopped after inclusion of 6 patients in each group. The 4‐mm HIGH treatment showed a significantly larger improvement in UCVA (−0.45 ± 0.27 LogMAR) and MRSE (+0.99 ± 0.44 D) at 1, 6 and 12 months compared with the 4‐mm LOW treatment (p < 0.05). At 12 months posttreatment, endothelial cell count and BSCVA were unaltered. More initial side‐effects were noted with the 6‐mm HIGH treatment, compared with the 4‐mm HIGH treatment (p < 0.05). Conclusion Epi‐on PiXL may become a safe and effective non‐ablative treatment for low‐grade myopia. The effect is augmented by high oxygen environment and remains stable for 12 months. The initial ocular irritation is acceptable with a 4‐mm treatment zone. The present results justify further clinical studies on PiXL, including refinements of the technique and long‐term results.

Purpose To assess the effect of two high‐oxygen epi‐on PiXL treatments for low‐grade myopia. Methods This prospective, randomized, intra‐individually comparing, single‐masked study included 23 healthy volunteers (46 eyes) aged 18–35 years with mild myopia, −0.75 to −2.50 D manifest refractive spherical equivalent (MRSE). One eye was randomized to a 4.0‐mm homogenous treatment zone and the fellow eye to a 4.0‐mm annular zone (16:40 min at 30 mW/cm2, fluence 15 J/cm2). Uncorrected distance visual acuity (UDVA), MRSE, best spectacle‐corrected visual acuity (BSCVA), Scheimpflug light scattering depths, mean keratometry (Kmean) and endothelial cell count (ECC) were assessed through 24 months. Results Similar improvements in UDVA were seen for the homogeneous and annular protocols at 1 month: −0.52 (−0.59, −0.39) and −0.49 (−0.59, −0.39) logMAR, respectively (medians and interquartile ranges, IQR), p = 0.91, and MRSE: +1.0 D (0.94, 1.31) and +1.0 D (0.69, 1.25), p = 0.17. Light scattering depths were 496 (465, 527) and 349 (247, 378) µm, respectively, and the reduction in mean keratometry was −0.8 D (−1.1, −0.7) and 0 D (−0.1, 0.1), p < 0.001. The treatment effect remained stable throughout 24 months. At 1 week, the participants reported less ocular discomfort with the annular protocol. No reductions were seen in BSCVA or ECC. No adverse events were reported. Conclusion PiXL can reduce low‐grade myopia and improve uncorrected vision in healthy eyes. The initial ocular discomfort may be reduced with an annular treatment zone. Further studies are needed to optimize PiXL treatment parameters.

Forces acting on the skeleton could be divided into those originating from gravitational loading and those originating from muscle loading. Flat bones in a non-weight-baring segment of the skeleton probably experience forces mostly generated by muscle contractions. One purpose of muscle contractions is to generate blood flow within skeletal tissues. The present study aimed to investigate the pulsatile patellar bone blood flow after low and high intensity leg extension exercises. Forty-two healthy individuals volunteered for the study. Dynamic isotonic one leg extension/flexion exercises were performed in a leg extension machine. Randomly, the exercises were performed with the left or right leg with either 10 repetition maximum (10 RM) continuously without any resting periods (high intensity muscle work), or 20 RM with a 2 second rest between contractions (low intensity muscle work). The work load, expressed in kilograms totally lifted, was identical in both legs. The pulsatile patellar blood flow was recorded continuously using a photoplethysmographic technique. Blood pressure was measured continuously during muscle work by a non-invasive method (Finapress). The patellar pulsatile bone blood flow increased significantly more after high intensity muscle work (61%) compared to the same work load performed using a lower intensity (22%), p = 0.000073. Systolic blood pressure changed equally during and after both interventions. Post-exercise bone hyperaemia appears to be correlated to the intensity of muscle contractions in the muscle compartment attached to the bone

Purpose: To compare two annular epithelium-on (epi-on) high oxygen photorefractive intrastromal cross-linking (PiXL) illuminations protocols for treatment of low-grade myopia. Methods: In this randomized, single-masked, intra-individually comparative study, healthy individuals with bilateral low-grade myopia (manifest refractive spherical equivalent (MRSE) À0.75 diopters (D) to À2.50 D) were treated with high oxygen epi-on PiXL. One eye was randomized to receive pulsed accelerated 365-nm ultraviolet-A illumination in a central annular zone of 4.0 mm (1 second on, 1 second off; 30 mW/cm 2 ), and the fellow eye in a 3.5 mm annular zone (0.5 second on, 1 second off; 45 mW/cm 2 ). Uncorrected distance visual acuity (UDVA), MRSE, low-contrast visual acuity (LCVA), best spectacle corrected visual acuity (BSCVA), endothelial cell count (ECC) and Scheimpflug light scattering depths were assessed through 24-month follow-up. Results: Twenty-seven participants (54 eyes) were included. The 3.5 mm protocol rendered less subjective ocular discomfort posttreatment and a larger improvement than the 4.0 mm protocol in UDVA: À0.52 (À0.72, À0.32) logMAR (medians and interquartile ranges, IQR) and À0.38 (À0.50, À0.22), p = 0.003 and MRSE: +1.25 D (0.75, 1.50) and +1.0 (0.75, 1.0), p = 0.037. The transient reduction in LCVA was larger with the 3.5 mm protocol (p < 0.01). No adverse events, and no reductions in ECC or BSCVA were noted. Conclusion: Epi-on PiXL in high oxygen reduces myopia in healthy eyes. A larger reduction of myopia and less early posttreatment subjective ocular discomfort can be seen with a smaller treatment zone, but likely at the expense of a transient decrease in low-contrast visual acuity.