New findings from a study published in Ophthalmology compared the efficacy and safety of low-intensity red light (LRL) for controlling myopia progression across different powers.
Give me some background first.
Prior research has indicated that LRL exposure induces hyperopia and slows myopia progression.
LRL has also been shown to increase choroidal thickness by increasing choroidal blood flow—increasing oxygen supply to the myopic fundus, and inhibiting the rapid growth of the axial length (AL).
Go on…
As such, LRL may help reduce the potential consequences of reduced choroidal perfusion
To note, however, the exact molecular pathways underlying the mechanism of action of LRL and its influence on choroidal and scleral responses and myopia are not yet fully understood.
Now talk about the study.
This 6-month, single-center, randomized controlled trial enrolled 200 pediatric patients (ages 6 to 15) with myopia >-0.50D and astigmatism <-2.5D.
Investigators performed cycloplegic refraction testing and refractive examinations were completed on each eye using an autorefractor three times and then averaged.
Tell me more.
Participants were randomized into four groups: three intervention and one control; the control cohort only wore single-vision spectacles (SVS) throughout the day.
Comparatively, the intervention groups wore SVS and were randomly assigned to receive LRL therapy at either:
- 0.37 mW
- 0.60 mW
- 1.20 mW
Therapy was administered twice daily for 3 minutes each session, with at least a 4-hour interval in between.
What were the main outcome measures?
The primary outcomes of the study were assessed via:
- Spherical equivalent (SE)
- AL
- Subfoveal choroidal thickness (SFCT)
Findings?
The researchers observed a statistically significant reduction in AL elongation in the LRL groups (P<0.001):
- Control group
- 0.27 mm (95% confidence interval [CI]: 0.22, 0.33)
- 0.37 mW group
- 0.04 mm (95% CI: -0.01, 0.08)
- 0.60 mW group
- 0.00 mm (95% CI: -0.05, 0.55)
- 1.20 mW group
- -0.04 mm (95% CI: -0.08, 0.01)
What about choroidal thickness?
Similarly, statistically significant increases in SFCT were observed in all three LRL power groups (P<0.001):
- Control group
- -5.07 μm (95% C: -10.32, -0.13)
- 0.37 mW group
- 22.63 μm (95% CI: 12.13, 33.34)
- 0.60 mW group
- 36.17 μm (95% CI: 24.37, 48.25)
- 1.20 mW group
- 42.59 μm (95% CI: 23.43, 66.24)
And spherical equivalent?
The effect of LRL on SE was not consistently significant across all follow-up times (P<0.001):
- Control group
- -0.22D (95% confidence interval [CI]: -0.50, 0.30)
- 0.37 mW group
- 0.01D (95% CI: -0.12, 0.15)
- 0.60 mW group
- -0.05D (95% CI: -0.18, 0.07)
- 1.20 mW group
- 0.16D (95% CI: 0.03, 0.30)
This could be potentially explained by the study’s short duration and measurement error by the autorefractor, according to the study authors.
Any adverse events?
Nope!
There were also no statistically significant differences noted in myopia control efficacy between the three powers of LRL.
Although … the authors noted that this data could indicate a potential trend indicating that higher power LRL is linked with improved effectiveness.
Expert opinion?
The authors noted: “It would be valuable to investigate whether there is a rebound effect similar to atropine drops once LRL treatment is stopped, and whether higher LRL power may lead to a more significant rebound effect.”
Take home.
While LRL therapy effectively controlled myopia progression at varying levels (0.37 mW, 0.60 mW, and 1.20 mW), the authors concluded that further studies with more extensive samples and longer follow-up periods are needed to identify the optimal LRL power determination.