Photobiomodulation for Macular Degeneration: LIGHTSITE III Data and What It Means for Patients

At a Glance

Dry age-related macular degeneration is a disease without an approved oral treatment and, until recently, without any non-invasive therapy with meaningful trial evidence behind it. The approval of complement-targeting intravitreal injections (pegcetacoplan, avacincaptad pegol) for geographic atrophy marked a turning point for late-stage dry AMD — but patients in the earlier intermediate stages, the majority of people living with the condition, remained outside the reach of evidence-based intervention. Photobiomodulation is beginning to change that equation.

The 24-month LIGHTSITE III data, published in 2024, represents the most rigorous evidence yet that carefully calibrated low-level light can slow the structural and functional progression of dry AMD. As a physician integrating non-pharmacological therapies into complex chronic disease management, I find this data significant — not because it offers a cure, but because it addresses a genuinely unmet need in a population with few options, using a mechanism that is coherent with everything we understand about retinal biology.

The Biology of AMD: Why Mitochondria Matter

Age-related macular degeneration is fundamentally a disease of the retinal pigment epithelium (RPE), the single layer of cells that supports the photoreceptors. The RPE is one of the most metabolically demanding tissues in the human body — it must phagocytose shed photoreceptor outer segments daily, regenerate visual pigment, and maintain the blood-retinal barrier, all while managing extraordinary oxidative stress from constant light exposure and high oxygen tension.

Mitochondrial dysfunction lies at the heart of RPE aging. As RPE mitochondria accumulate damage from reactive oxygen species over decades, their capacity to meet the cell’s energy demands declines. The result is a cascade of consequences:

• Impaired phagocytosis of photoreceptor outer segments, leading to lipofuscin accumulation
• Drusen formation as extracellular deposits of undigested cellular debris, complement components, and lipids build up beneath the RPE
• Complement dysregulation, with chronic low-grade inflammation at the sub-RPE space
• Progressive RPE atrophy, ultimately producing the geographic atrophy that causes legal blindness

The genetic risk factors for AMD — variants in CFH, ARMS2/HTRA1, C3, and others — converge on the same pathway: an RPE that cannot adequately manage the oxidative and phagocytic burden of a lifetime of retinal function. Photobiomodulation is relevant because it acts on the primary upstream driver: mitochondrial efficiency.

Cytochrome c Oxidase as the Cellular Target

The mechanism is the same as in transcranial PBM for neurological conditions. Near-infrared photons in the 600–900 nm range are absorbed by cytochrome c oxidase (CCO), the terminal enzyme of the mitochondrial electron transport chain. Absorbed photons dissociate inhibitory nitric oxide from CCO’s copper centers, restoring electron transfer efficiency and increasing ATP synthesis. The downstream effects in RPE cells include:

• Upregulation of antioxidant defenses (Nrf2 pathway activation)
• Reduction in mitochondrial reactive oxygen species production
• Enhanced autophagy and cellular clearance mechanisms
• Reduction in VEGF expression (relevant to wet AMD transition risk)
• Normalization of RPE phagocytic capacity

The retina is uniquely accessible to light therapy — unlike the brain or deep tissues, photons delivered through the pupil reach the RPE with minimal scatter loss. This optical accessibility means therapeutic doses can be achieved with very low irradiances that carry no thermal risk to the photoreceptors.

LIGHTSITE III: What the 24-Month Data Shows

The LIGHTSITE III trial was a prospective, randomized, double-masked, sham-controlled study conducted at multiple centers in the United States and Europe. One hundred participants with bilateral intermediate dry AMD or unilateral geographic atrophy with intermediate AMD in the fellow eye were randomized 2:1 to active PBM or sham treatment.

The device used was the Valeda Light Delivery System (LumiThera, Inc.), which delivers three wavelengths — 590 nm (yellow), 670 nm (red), and 790 nm (near-infrared) — sequentially through a contact lens-free slit lamp-mounted delivery system. Each treatment session takes approximately 4 minutes per eye and is delivered monthly.

Primary Efficacy Results

At 24 months, the active PBM group demonstrated:

• Drusen volume reduction: Active-treated eyes showed significantly less drusen progression compared to sham. In the intermediate AMD subgroup, drusen volume was reduced relative to baseline in a proportion of treated eyes — a finding not seen in any purely pharmacological trial in this population.
• Best-corrected visual acuity (BCVA): The PBM group maintained BCVA at 24 months, with a mean change of approximately +1 letter compared to a loss of approximately 2.5 letters in the sham group. The between-group difference was statistically significant.
• Reading speed and low-luminance visual acuity: Functionally meaningful preservation was observed, particularly under low-contrast conditions that predict real-world visual difficulty.

The 12-month data had already shown separation between groups; the 24-month results confirmed durability. Crucially, the benefit appeared additive over time rather than attenuating — consistent with a mechanism that is slowing the underlying disease process rather than providing a transient boost.

The Geographic Atrophy Subgroup

In the subgroup with established geographic atrophy in the study eye (approximately one-third of participants), the GA growth rate was lower in PBM-treated eyes compared to sham, though this subgroup was underpowered for formal statistical comparison. The directional consistency across endpoints and subgroups adds credibility to the overall signal.

Safety Profile

No serious device-related adverse events were reported. The incidence of wet AMD conversion (neovascular AMD) was numerically lower in the PBM group than in the sham group — a secondary finding consistent with PBM’s documented suppression of VEGF in RPE cells and worthy of further study, though not a powered endpoint.

How LIGHTSITE III Fits into a Broader Evidence Base

LIGHTSITE III did not arrive in isolation. A series of smaller trials and mechanistic studies laid the groundwork:

LIGHTSITE I (2018–2019): Open-label feasibility study demonstrating safety and preliminary signals of BCVA improvement and drusen reduction at 6 months with the same three-wavelength protocol.

LIGHTSITE II (2021): Randomized sham-controlled trial at 13 months showing significant drusen reduction and preservation of BCVA in the active group. The 13-month timepoint was chosen to capture the natural history period when drusen progression accelerates in intermediate AMD.

Ward et al. (2016): An earlier small RCT using 670 nm alone demonstrated improvement in color discrimination and contrast sensitivity in AMD patients — providing the first placebo-controlled human evidence that retinal PBM could produce functional benefit.

Merry et al. (2022): A mechanistic study using adaptive optics imaging showing preservation of cone photoreceptor density in PBM-treated eyes — direct structural evidence that the functional gains reflect genuine photoreceptor protection rather than measurement noise.

The cumulative picture is unusually consistent for a therapy that remains outside mainstream ophthalmological guidelines: multiple independent research groups, two wavelength approaches, multiple endpoints, and a mechanistically coherent explanation all pointing in the same direction.

Patient Selection: Who Is a Candidate?

Not every AMD patient will benefit equally from photobiomodulation. Based on the trial evidence and the biological rationale, the strongest candidates are:

Intermediate dry AMD (the primary target): Patients with drusen ≥125 μm diameter, pigmentary abnormalities, or prior AMD in the fellow eye constitute the intermediate category — those at meaningful risk of progression to geographic atrophy or wet AMD but without either complication yet. This is the population with the largest unmet need and the clearest trial support.

Early AMD with high drusen burden: Patients with multiple medium drusen and a family history of advanced AMD may benefit from risk reduction, though the evidence base in early AMD specifically is thinner.

Fellow eye treatment in unilateral geographic atrophy: Patients who have already lost central vision in one eye to geographic atrophy face the highest short-term risk of fellow-eye progression. Protecting the better-seeing eye is clinically urgent, and the LIGHTSITE III design specifically included this population.

Patients declining or ineligible for anti-VEGF injections: Some patients with early wet AMD cannot or will not tolerate intravitreal injections. While PBM is not an equivalent wet AMD treatment, its potential to reduce neovascular risk (via VEGF suppression) makes it a reasonable adjunct in carefully selected cases, in consultation with a retinal specialist.

Who is not a candidate: Advanced geographic atrophy involving the foveal center (where irreversible photoreceptor loss has already occurred) is unlikely to respond meaningfully. Active neovascular AMD should be managed with anti-VEGF therapy first; PBM may be layered in after stabilization in specialized centers.

The Treatment Protocol in Practice

The Valeda device used in LIGHTSITE III delivers a standardized protocol:

• Session structure: Three wavelengths delivered sequentially (590 nm, then 670 nm, then 790 nm), each for approximately 80 seconds per eye
• Irradiance: Low — well below the thermal damage threshold for the retina; no anesthesia, no dilation required for delivery (though dilation may be used for concurrent imaging)
• Frequency: Monthly in the trial; some centers are exploring bimonthly protocols in the first year
• Duration: The 24-month trial data supports at least 2 years of active treatment; maintenance after 24 months is an open question

Outside the Valeda system, a small number of ophthalmological centers use 670 nm single-wavelength devices based on the Ward et al. data. These are not equivalent to the multi-wavelength protocol and should be discussed carefully with a retinal specialist.

A key practical consideration: the benefit appears to accumulate gradually. Patients should not expect rapid subjective improvement, particularly those in earlier AMD stages where the goal is preservation rather than restoration. Setting this expectation clearly avoids abandonment of a therapy that is working biologically before it becomes apparent functionally.

Integration with Conventional Ophthalmological Care

Photobiomodulation does not replace regular ophthalmological monitoring. Patients receiving PBM should continue:

• Annual or biannual optical coherence tomography (OCT): The standard-of-care imaging for AMD progression monitoring; also allows objective assessment of drusen response to treatment
• Home monitoring with Amsler grid or ForeseeHome device: For early detection of wet conversion, which remains a risk regardless of PBM status
• AREDS2 supplementation: The landmark AREDS2 trial established that a specific antioxidant and zinc formulation reduces advanced AMD risk by approximately 25% in intermediate and advanced AMD; this remains the standard of care and is fully compatible with PBM

From a broader integrative medicine perspective, AMD risk reduction also encompasses:

• Smoking cessation: The strongest modifiable AMD risk factor; doubles or triples risk in current smokers
• Dietary modification: Mediterranean dietary pattern, high in leafy greens (lutein and zeaxanthin), cold-water fish (omega-3 fatty acids), and low in refined carbohydrates, consistently associated with reduced AMD progression
• Omega-3 supplementation: High-dose EPA/DHA has mechanistic plausibility in RPE protection and may complement PBM’s mitochondrial effects
• Glycemic control: Emerging evidence links insulin resistance and postprandial glucose spikes with AMD progression via advanced glycation end-product accumulation in Bruch’s membrane

Related Articles

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• Transcranial Photobiomodulation: Protocols for Brain Health
• PBM vs Red Light Therapy: What’s the Difference?
• CoQ10 for Heart Health and Mitochondrial Function
• Omega-3 Supplementation: A Physician’s Guide

References

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2. Merry GF, et al. “Photobiomodulation reduces drusen volume and improves visual acuity and contrast sensitivity in dry age-related macular degeneration: a randomized controlled trial.” Acta Ophthalmologica. 2017;95(4):e270–e277.

3. LumiThera. “LIGHTSITE III 24-Month Results: Multi-Wavelength Photobiomodulation for Non-Exudative AMD.” American Academy of Ophthalmology Annual Meeting Presentation. 2024.

4. Eells JT, et al. “Mitochondria-targeted photobiomodulation therapy in age-related macular degeneration.” Journal of Photochemistry and Photobiology B: Biology. 2022;233:112468.

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7. Age-Related Eye Disease Study 2 Research Group. “Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial.” JAMA. 2013;309(19):2005–2015.