Photobiomodulation (PBM) treatment for dry AMD with Valeda light therapy.
LIGHTSITE III study involves analysing its strengths, limitations, and areas for improvement. While the study presents promising results, it also has aspects that could be critiqued to provide a more balanced view-see below.

Strengths of the Study:
Randomised Controlled Design (RCT):
The randomised controlled trial (RCT) design is a major strength, as it minimises bias and allows for a more reliable comparison between the PBM and Sham groups. Randomisation ensures that other variables (e.g., patient demographics, disease severity) are evenly distributed between groups.
Statistically Significant Results:
The study reports statistically significant improvements in best-corrected visual acuity (BCVA) and a reduction in the development of geographic atrophy (GA) in the PBM group. These findings support the effectiveness of PBM therapy in treating dry AMD.
Clear Primary and Secondary Outcomes:
The study focuses on well-defined primary (BCVA) and secondary (GA) outcomes, which makes the results easy to interpret and compare with other studies.
Favourable Safety Profile:
The study highlights a favourable safety profile for PBM therapy, with no significant adverse events reported. This is an important factor for clinical acceptance of a new treatment, especially in the elderly AMD population.
Use of Multiwavelength PBM:
The use of multiwavelength PBM (590, 660, and 850 nm) is an innovative approach, targeting different depths and biological responses within the retina. This adds value to the therapeutic approach, as it broadens the potential mechanism of action.
Limitations and Criticisms:
Small Sample Size:
The study enrolled 100 subjects (148 eyes), which is relatively small for a clinical trial. Small sample sizes can lead to less robust conclusions and make it difficult to generalise findings to the broader AMD population. Larger, multicentre studies would be needed to confirm the results and validate the effectiveness of PBM therapy on a wider scale.
Short-Term Follow-Up:
Although the study’s final results will span 24 months, the current report is based on a 13-month analysis. AMD is a chronic, progressive disease, and 13 months may not be sufficient to assess long-term efficacy and safety. For example, the reduction in geographic atrophy is promising, but the long-term effects of PBM on disease progression and the potential for delayed adverse events are unknown.
Modest Improvement in Visual Acuity:
While the improvement in BCVA in the PBM group was statistically significant, the average increase was only 5.4 letters. Clinically, this represents a modest improvement in vision, and its practical impact on patients’ daily lives may be limited. Additionally, the Sham group improved by 3.0 letters, suggesting there may be natural variation or a placebo effect, further reducing the clinical significance of the PBM effect.
Potential Placebo Effect:
The Sham group also showed improvement in visual acuity (3.0 letters), which raises concerns about a potential placebo effect. Although PBM demonstrated a greater improvement, the difference between the groups (2.4 letters) was relatively small. This modest difference calls into question the clinical significance of the treatment compared to natural variation or psychological effects in both groups.
Lack of Details on Geographic Atrophy Mechanism:
The study reports a significant reduction in new-onset GA in the PBM group, but there is no clear explanation or in-depth exploration of the mechanism behind this effect. Understanding how PBM reduces the progression of GA would strengthen the study’s findings and help clinicians understand the therapeutic action of the treatment.
Selection Bias and Generalisability:
The study doesn’t provide extensive details on the inclusion and exclusion criteria, leaving open the question of how representative the sample is of the general AMD population. If the subjects had characteristics (e.g., disease stage, baseline visual acuity) that differ from the typical AMD patient, the findings may not apply universally.
No Discussion of Cost or Practicality:
The study does not address the cost or practicality of implementing PBM therapy in clinical practice. PBM requires specialized equipment (e.g., the LumiThera Valeda Light Delivery System), and its widespread adoption could be limited by financial or logistical barriers. Understanding the cost-benefit ratio would be important for healthcare providers and patients when considering this treatment option.
Repeated Treatments and Burden on Patients:
The treatment protocol involves multiple sessions (nine over 3 to 5 weeks, every four months for 24 months). This might be a significant burden for elderly patients with AMD, many of whom may have limited mobility or access to healthcare facilities. Additionally, the study does not discuss patient adherence or satisfaction with this intensive treatment regimen.
No Mention of Patient-Reported Outcomes:
The study focuses on objective clinical measures (e.g., BCVA, GA), but patient-reported outcomes such as quality of life, visual function in daily activities, or subjective improvement are not mentioned. These outcomes are critical in determining the real-world impact of the treatment and how patients perceive its benefits.
Unclear Long-Term Safety:
Although the study reports a favourable safety profile at 13 months, the long-term safety of repeated PBM sessions is still uncertain. Chronic exposure to PBM could potentially have cumulative effects, and the study would benefit from long-term safety monitoring beyond the 24-month period.
Additional Considerations:
Mechanism of Action of PBM:
While the multiwavelength PBM approach is innovative, the exact mechanism of action in treating dry AMD is not fully explained. PBM is believed to reduce inflammation and promote cellular repair, but further research is needed to elucidate how it specifically targets the retinal cells affected by AMD.
Combination with Other Therapies:
The study does not explore whether PBM therapy could be combined with other treatments for dry AMD, such as antioxidants (AREDS supplements) or emerging therapies. Understanding how PBM fits into the broader treatment landscape would be valuable.
Conclusion:
The LIGHTSITE III study is a well-designed RCT that provides promising evidence for the use of PBM therapy in treating intermediate dry AMD. The statistically significant improvements in visual acuity and reduction in geographic atrophy are important findings, but the study has several limitations. The small sample size, modest visual improvement, lack of long-term data, and limited patient-reported outcomes suggest that further research is necessary to fully assess the clinical utility of PBM. Additionally, practical considerations such as the burden of repeated treatments and cost are not addressed, which may impact the broader adoption of this therapy.

While PBM therapy shows potential, the uncertainties surrounding its long-term efficacy, safety, and cost-effectiveness mean that it is not yet ready to be considered a definitive treatment for dry AMD. Larger, longer-term trials with more diverse patient populations and a focus on real-world outcomes will be crucial to confirm its place in clinical practice. Would I offer PBM? Given that the visual improvement in the PBM group amounted to a modest 2.4-letter gain on a high-contrast, well-lit visual acuity chart, it is unclear whether this level of enhancement would have a meaningful impact on patients' real-world visual function, especially under lower contrast or suboptimal lighting conditions encountered in daily life. For the sake of 2.4 letters? Don't see the point!