A study published in the British Journal of Ophthalmology compared the effects of repeated low-level red light (RLRL) treatment on axial length (AL) growth and spherical equivalent refractive error (SE) changes in myopic and pre-myopic children.
Give me some background.
As a growing global public health concern, myopia is estimated to impact a total of 49.8% of the world population by 2050.
Previous studies have demonstrated that RLRL treatment with 3-minute sessions twice daily can prevent and control myopia in children.
However, recent studies have also shown that there can be a slight rebound effect after cessation of treatment.
Plus: There is currently a dearth of data on the long-term effects of RLRL therapy on myopic children.
Now, what exactly is RLRL therapy?
Currently, the only instrument used for RLRL therapy is the Eyerising (Eyerising International) device, which is approved in Australia, New Zealand, the United Kingdom, the European Union, and China.
The device is comprised of a semiconductor laser diode that emits a 650 nm wavelength with 2.0±-0.5 mW output and is used twice a day for 3 minutes, 5 days per week.
Now talk about the study.
In this prospective, randomized, parallel-control study, 144 subjects (mean age at baseline: 9.19±1.23 years) were included in the analysis and were assigned randomly to four subgroups:
- Myopia-RLRL group (M-RL)
- 32 participants
- Myopia-control group (M-C)
- 36 participants
- Pre-myopia-RLRL (PM-RL)
- 40 participants
- Pre-myopia-control (PM-C)
- 36 participants
Subjects in the RLRL group completed a 12-month treatment comprised of a 3-minute RLRL treatment session twice daily, with an interval of at least 4 hours, for 7 days per week.
Tell me more.
Investigators scheduled follow-up visits at 1, 3, 6, 9, and 12 months after the treatment.
Participants in the study were able to take a RLRL device home and the instrument was designed to send the date and time of treatment automatically to a server to guarantee the patients were compliant with treatments.
Findings?
After 12 months of RLRL treatment, the changes in SE and AL were as follows:
- M-RL group
- SE: −0.078±0.375 D
- AL: 0.033±0.123 mm
- M-C group
- SE: −0.861±0.556 D
- AL: 0.415±0.171 mm
- PM-RL group
- SE: −0.181±0.417 D
- AL: 0.145±0.175 mm
- PM-C
- SE: −0.521±0.436 D
- AL: 0.292±0.128 mm
Anything else?
Subjects in the PM-RL group had a lower incidence of myopia than the PM-C group (2.5% vs. 19.4%).
Further, the percentage of AL shortening in the M-RL was higher than that in the PM-RL before the 9-month follow-up.
Expert opinion?
Previous studies have shown that the choroid thickens after RLRL treatment and that these changes at 3 months could predict 12-month myopia control efficacy.
Further, past studies have shown that choroidal thickness in myopic children was thinner than in non-myopic children, and as myopia progressed, choroidal thickness also decreased.
And tieing things back to this study…
The study authors suggested that “myopic children may have a higher degree of improvement in choroidal thickness compared to non-myopic children, which might also be a reason for the lower AL and SE changes in the myopic subgroup.”
Limitations?
In addition to no appropriate sham equipment available for the control groups, this study did not include choroid-related data, which may have a role in understanding the differences in treatment effects between the myopic and pre-myopic subgroups.
Additionally, the investigators did not assess the time course of a short-term rebound in AL after treatment discontinuation.
Take home.
These findings suggest that RLRL can effectively delay myopia progression in myopic children and reduce the incidence of myopia in pre-myopic children.
Further research is warranted to elucidate why the effect of using RLRL in myopic children is higher than in pre-myopic patients.