The Science of Laser Vein Treatment: Selective Photothermolysis and Twenty Years of Chasing the Right Wavelength

Endovenous laser treatment is usually explained as "burning the vein closed." That is not wrong, but it skips the part that actually makes the procedure work — a principle borrowed from dermatology in 1983, and a two-decade argument about which wavelength best applies it.

This article follows that argument. It ends somewhere many people find surprising.

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Selective photothermolysis — the founding idea

Everything starts with a 1983 paper in Science by Anderson and Parrish at Harvard: "Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation." It reset what lasers could do in medicine.

The principle rests on three conditions holding at once.

A selective chromophore. Tissue contains molecules that absorb particular wavelengths far more strongly than their surroundings — melanin, oxyhaemoglobin, water. Match the laser's wavelength to the absorption peak of your target and the energy lands preferentially on that target.

Pulse duration shorter than the thermal relaxation time. Heated tissue sheds heat into its surroundings. Deliver the energy faster than the target can shed it, and the damage stays inside the target.

Sufficient fluence. Enough energy to actually destroy the target.

When all three align, a laser behaves less like a blowtorch and more like a marksman. That is the whole idea, and the history below is the story of trying to apply it to a vein.

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The birth of endovenous laser

Varicose veins were traditionally treated by stripping the saphenous vein under general anaesthesia — inpatient stay, extended recovery. From the late 1990s, work on endovenous alternatives accelerated, and endovenous laser ablation (EVLA) was one result.

The mechanics are simple: thread a thin optical fibre into the vein, deliver laser energy, damage the vein wall with heat. The vein fibroses and is reabsorbed. No incision, no general anaesthetic, same-day discharge.

What was not simple was choosing the wavelength.

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First generation — 810, 940, 980 nm: targeting haemoglobin

In 2001, Navarro, Min and Boné published the first clinical series of EVLA in Dermatologic Surgery, using an 810 nm diode laser. They reported 100% closure in 40 great saphenous veins with no significant complications. It is the starting point of the field.

Why 810 nm? Because the 800–1000 nm band coincides with a major absorption peak of oxyhaemoglobin. The reasoning followed selective photothermolysis directly: energy is absorbed by haemoglobin in the blood, the heated blood damages the vein wall, the vein closes. Blood acts as the intermediary.

940 nm and 980 nm diode lasers followed on the same logic, and clinically they performed similarly.

These lasers worked. They also hurt. Post-procedural pain, ecchymosis and vein wall perforation were common. The mechanism is not mysterious: concentrating energy in haemoglobin boils blood, forming steam bubbles that batter the vein wall. The energy was blunt and hard to control.

Van den Bos and colleagues set out these early mechanisms and limitations systematically in a 2008 technical review in the European Journal of Vascular and Endovascular Surgery, examining how wavelength, fluence, wattage and pullback speed shape the outcome.

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The turning point — wall, not blood

By the mid-2000s researchers were re-examining the mechanism. The question was direct: does the laser close the vein mainly by heating blood, or by heating the wall?

Wavelength sat at the centre of it. Water absorbs strongly above roughly 1300 nm — far from haemoglobin's peak. Since the vein wall is itself water-rich, shifting the wavelength toward water's absorption might heat the wall directly, without needing blood as a go-between.

That hypothesis produced the next two generations of device.

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Second generation — 1320 nm: the first move toward water

The 1320 nm Nd:YAG sits near the crossover where water absorption begins to exceed haemoglobin's.

Moul and colleagues reported a large retrospective series in the Journal of the American Academy of Dermatology in 2014: 1,171 procedures (1,066 great saphenous, 105 short saphenous veins), mean follow-up 11.4 months, 99.9% closure among patients not lost to follow-up, with no deep vein thrombosis, no permanent nerve injury and no pulmonary embolism attributed to the ablation.

Clinically convincing. Whether it worked for the reason its designers believed remained unsettled.

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Third generation — 1470 nm: the current standard

The most widely used wavelength today is 1470 nm, where water absorption is roughly forty times higher than at 810 nm. Energy is taken up by the water in the collagen and smooth muscle of the wall itself.

Almeida and colleagues tested this directly in 2009 in Vascular and Endovascular Surgery, under a title that states the claim outright: "Saphenous laser ablation at 1470 nm targets the vein wall, not blood." Treating 41 veins at 1470 nm with 30 J/cm at 5 watts, compared against a historical 980 nm control at 80 J/cm at 12 watts, they achieved closure at a dramatically reduced energy, with markedly less postoperative pain and ecchymosis — which they interpreted as evidence that vein wall perforations were minimised.

Less energy, same closure, fewer side effects. That is a real advance, and it is why 1470 nm became standard.

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Then the modelling studies complicated it

Here the story turns.

In 2014, Dutch and Belgian teams — Malskat, Poluektova and colleagues — published two papers in Lasers in Medical Science analysing EVLA with optical-thermal mathematical modelling.

Their argument was provocative. The dominant mechanism of vein wall heating, they concluded, is largely independent of wavelength and runs through two routes: heat conduction from a carbonised blood layer on the fibre tip reaching close to 1000 °C, and heat transferred from laser-heated blood surrounding it. Direct absorption of laser light by the wall plays a secondary role. Whether you aim at haemoglobin or at water, the underlying process looks much the same.

On this account, 1470 nm performs better clinically not because it heats the wall directly, but because higher water absorption distributes energy more evenly between blood and tissue, reducing the extreme local hot spots that cause perforation.

The empirical evidence supports the deflationary reading. A 2019 systematic review and meta-analysis by Malskat and colleagues pooled 28 randomised trials covering 2,829 great saphenous veins. Overall EVLA success was 92% — and there was no statistically significant difference between long and short wavelengths (95% vs 92%, p = .15) or between high and low delivered energy (93% vs 92%, p = .99). What did predict a higher reported success rate was study quality: trials at low risk of bias reported better results than those at unclear or high risk (93% vs 89%, p = .04).

That last detail deserves a moment. Across nearly three thousand veins, how well the study was conducted mattered more than which wavelength was used.

This is not merely academic. It means a clinic's choice of laser wavelength is a weaker predictor of your outcome than energy delivery, pullback technique and operator care — and that marketing built around a wavelength number is claiming more than the evidence supports. We have written separately about why the newest technique is not automatically the better one; this is the same lesson from a different direction.

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Fourth generation — 1940 nm and beyond

The frontier is above 1900 nm, where water absorption is many times higher again than at 1470 nm.

Whiteley and colleagues compared 1470 nm and 1940 nm in an in vitro porcine liver model, published in Lasers in Medical Science in 2022. The title is the finding: no significant difference between the two wavelengths in thermal spread — with more carbonisation at 1940 nm.

The theory says stronger absorption should confine energy nearer the surface and limit thermal spread. In practice, absorption that is too strong can produce local charring and less predictable heat distribution. A 2023 review of laser ablation mechanisms in vascular disease sets out the same tension between wavelength, fibre type and energy density. The optimal wavelength remains an open question.

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What actually improved outcomes — the fibre tip

Alongside wavelength, a quieter change mattered a great deal.

Early fibres were bare-tipped, emitting forward in one direction, striking the vein wall unevenly. Radial-emitting and jacket-tip fibres followed, distributing energy through 360 degrees around the vein's inner circumference.

Teter, Kabnick and Sadek's comprehensive review in Phlebology covers the clinical evidence that the combination of higher wavelength with radial fibres meaningfully reduces postoperative pain and bruising compared with lower wavelength and a bare tip.

It is worth noting how this sits against the modelling work: if wavelength alone does not explain the difference, then how the energy is distributed around the vein is a strong candidate for what does.

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What twenty years of wavelengths taught

• 810–980 nm targeted haemoglobin. Effective, but abrupt heating of blood caused pain and wall perforation.
• 1320 nm was the first shift toward water absorption.
• 1470 nm achieves closure at substantially lower energy with fewer side effects, and is the current standard.
• Mathematical modelling questions the premise that any of this works through direct wall absorption, and randomised evidence finds no significant efficacy difference across wavelengths.
• 1940 nm and above maximise water absorption but introduce carbonisation as a new problem.

The through-line is not that each generation beat the last. It is that selective photothermolysis is a discipline, not a device — define the target precisely, match the delivery to its properties, achieve the effect with the least collateral damage.

Which is also the practical takeaway for a patient. The wavelength number on a clinic's laser tells you less than you would think. What the operator does with it tells you more. At da Re-Fit we use 1470 nm with radial fibres for truncal ablation, alongside non-thermal options where they suit the vein better — our source vein treatment page sets out how the choice is made.

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References

• Anderson RR, Parrish JA. Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation. Science. 1983;220(4596):524-7. (PMID: 6836297)
• Navarro L, Min RJ, Boné C. Endovenous laser: a new minimally invasive method of treatment for varicose veins — preliminary observations using an 810 nm diode laser. Dermatol Surg. 2001;27(2):117-22. (PMID: 11207682)
• van den Bos RR, Kockaert MA, Neumann HA, Nijsten T. Technical review of endovenous laser therapy for varicose veins. Eur J Vasc Endovasc Surg. 2008;35(1):88-95. (PMID: 17920307)
• Almeida J, Mackay E, Javier J, Mauriello J, Raines J. Saphenous laser ablation at 1470 nm targets the vein wall, not blood. Vasc Endovascular Surg. 2009;43(5):467-72. (PMID: 19628516)
• Moul DK, Housman L, Romine S, Greenway H. Endovenous laser ablation of the great and short saphenous veins with a 1320-nm neodymium:yttrium-aluminum-garnet laser: retrospective case series of 1171 procedures. J Am Acad Dermatol. 2014;70(2):326-31. (PMID: 24314878)
• Malskat WSJ, Poluektova AA, van der Geld CWM, et al. Endovenous laser ablation (EVLA): a review of mechanisms, modeling outcomes, and issues for debate. Lasers Med Sci. 2014;29(2):393-403. (PMID: 24366291)
• Poluektova AA, Malskat WSJ, van Gemert MJC, et al. Some controversies in endovenous laser ablation of varicose veins addressed by optical-thermal mathematical modeling. Lasers Med Sci. 2014;29(2):441-52. (PMID: 24105396)
• Malskat WSJ, Engels LK, Hollestein LM, Nijsten T, van den Bos RR. Commonly Used Endovenous Laser Ablation (EVLA) Parameters Do Not Influence Efficacy: Results of a Systematic Review and Meta-Analysis. Eur J Vasc Endovasc Surg. 2019;58(2):230-242. (PMID: 31230868)
• Teter KA, Kabnick LS, Sadek M. Endovenous laser ablation: A comprehensive review. Phlebology. 2020;35(9):656-662. (PMID: 32631172)
• Whiteley MS, Cross AC, Whiteley VC. No significant difference between 1940 and 1470 nm in endovenous laser ablation using an in vitro porcine liver model. Lasers Med Sci. 2022;37(3):1899-1906. (PMID: 34687391)
• Zhang C, Lyu W, Qiu P, et al. Laser ablation on vascular diseases: mechanisms and influencing factors. Lasers Med Sci. 2023;39(1):18. (PMID: 38155274)