Lasers in Ophthalmology: Wavelengths, Settings and Safety
Last updated: October 2026
A quick reference to laser and light wavelengths used in ophthalmology, typical starting settings and key safety facts. For how lasers affect tissue and why the colour matters, see Lasers in Ophthalmology Made Easy.
Milestones
| Year | Milestone |
|---|---|
| 1917 | Albert Einstein describes stimulated emission |
| 1956 | Meyer-Schwickerath introduces xenon-arc photocoagulation (before lasers) |
| 1958 | Schawlow and Townes publish the theory of the optical maser (laser) |
| 1960 | Theodore Maiman builds the first working laser (ruby, 694 nm) |
| 1961–63 | First ruby laser retinal photocoagulation (Campbell, Zweng and colleagues) |
| 1968 | Argon laser photocoagulation (L'Esperance) |
| 1980 | Nd:YAG photodisruption for posterior capsulotomy (Aron-Rosa, Fankhauser) |
| 1983 | Trokel and Srinivasan: excimer ablation of the cornea |
| 1988–90 | First PRK (McDonald); LASIK (Pallikaris, Buratto) |
| 1995 | Selective laser trabeculoplasty (Latina) |
| 2001–2009 | Femtosecond laser LASIK flaps (IntraLase), then laser-assisted cataract surgery |
Wavelengths in diagnostic instruments
| Instrument | Light source | Wavelength (nm) |
|---|---|---|
| Short-wavelength automated perimetry (SWAP) | Blue stimulus on yellow background | 440 |
| Retinal thickness analyser | Green HeNe laser | 543 |
| Heidelberg Retina Tomograph (cSLO) | Diode laser | 670 |
| GDx (scanning laser polarimetry) | Diode laser | 780 |
| IOLMaster (partial coherence interferometry) | Diode laser | 780 |
| Lenstar (optical low-coherence reflectometry) | Superluminescent diode | 820 |
| Spectral-domain OCT (posterior segment) | Superluminescent diode | 840–880 |
| Swept-source OCT and biometry | Tunable laser | 1050 |
| Anterior segment OCT | Superluminescent diode | 1310 |
| Fundus autofluorescence (blue) | Excitation | 488 |
Therapeutic lasers
| Laser | Wavelength (nm) | Use |
|---|---|---|
| Excimer, argon fluoride | 193 | PRK, LASIK, PTK |
| Excimer, xenon chloride | 308 | Excimer laser trabeculostomy (ELT) |
| UVA (not a laser) | 365–370 | Corneal cross-linking |
| Argon blue-green | 488 / 514 | Retinal photocoagulation, ALT (largely replaced) |
| Frequency-doubled Nd:YAG (or Nd:YLF 527) | 532 | PRP, focal laser, retinopexy; Q-switched for SLT |
| Yellow (dye or solid-state) | 577 | Macular and micropulse laser |
| Krypton red | 647 | Through haemorrhage or cataract |
| Rostaporfin PDT | 664 | Photodynamic therapy (historical) |
| Diode (PDT) | 689 | Verteporfin photodynamic therapy |
| Ruby | 694 | The first laser (historical) |
| Diode, infrared | 810 | Transscleral cyclophotocoagulation, ROP, TTT, micropulse |
| Femtosecond (Nd:glass or Nd:YLF) | 1030–1053 | LASIK flaps, SMILE, FLACS |
| Nd:YAG, Q-switched | 1064 | Posterior capsulotomy, iridotomy, vitreolysis |
| Holmium:YAG | 2100 | Laser thermokeratoplasty |
| Erbium:YAG | 2940 | Laser phaco (historical), skin resurfacing |
| Carbon dioxide | 10 600 | Lid and skin surgery |
Typical starting settings
These are common starting points from standard texts. Always titrate to the tissue response, and follow your laser's manual and local protocols.
| Procedure | Laser | Starting settings |
|---|---|---|
| Nd:YAG peripheral iridotomy | Q-switched Nd:YAG | 2–8 mJ per pulse, 1–3 pulses per burst; Abraham lens; superior or temporal |
| Pre-treatment of thick brown irides | Argon or 532 nm | 50 µm, 0.02–0.05 s, 600–1000 mW, then YAG |
| Selective laser trabeculoplasty | Q-switched 532 nm | 400 µm (fixed), 3 ns, 0.6–1.2 mJ (just below bubble formation); about 100 spots over 360° |
| Argon laser trabeculoplasty | Argon | 50 µm, 0.1 s, 400–1200 mW; 50 spots per 180° |
| Peripheral iridoplasty | Argon or 532 nm | 200–500 µm, 0.3–0.5 s, 200–400 mW; contraction burns on the far periphery |
| Transscleral cyclophotocoagulation | Diode 810 nm (G-probe) | 1250–2000 mW, 2000 ms; probe edge at the limbus (fibre about 1.2 mm behind); spare 3 and 9 o'clock |
| Panretinal photocoagulation | 532 nm | 200–500 µm on the retina, 100–200 ms (20–30 ms with pattern lasers); power to a light grey-white burn |
| Focal / grid macular laser | 532 or 577 nm | 50–100 µm, 50–100 ms, mild burns (modified ETDRS) |
| Posterior capsulotomy | Q-switched Nd:YAG | 1–2 mJ per pulse; focus just behind the capsule |
| Phototherapeutic keratectomy | Excimer 193 nm | About 160 mJ/cm², 0.25 µm per pulse; keep at least 250 µm residual stroma |
Laser physics in brief
| Term | Meaning |
|---|---|
| Continuous wave | Constant output, measured in watts (photocoagulation) |
| Q-switched | Energy released in nanosecond pulses; high peak power (Nd:YAG capsulotomy, SLT) |
| Mode-locked | Even shorter (pico- or femtosecond) pulses with very high peak power, not more total energy |
| Solid-state lasers | Lasing ions in a crystal or glass: ruby, Nd:YAG, Nd:YLF, Er:YAG |
| Gas lasers | Argon, krypton, helium–neon (aiming beams), carbon dioxide |
| Excimer ("excited dimer") lasers | Noble gas plus halogen (ArF, XeCl) emitting ultraviolet |
| Dye lasers | Organic dyes in solution; tunable wavelength |
| Diode (semiconductor) lasers | Compact, efficient, usually red to infrared; usually grouped separately from crystal lasers |
Safety
Lasers are classified under IEC 60825-1 into classes 1, 1M, 2, 2M, 3R, 3B and 4. Aiming beams are class 2 or 3R; nearly all treatment lasers are class 4, so everyone in the room needs wavelength-specific eyewear. Full table: laser safety classes.
Where residents slip
- Thinking a mode-locked laser delivers more energy: it delivers shorter pulses with higher peak power.
- Forgetting that SLT energy is set just below the threshold for bubble formation.
- Using a laser's nominal spot size without allowing for the contact lens magnification.
Key sources
- American Academy of Ophthalmology. Basic and Clinical Science Course, Sections 3, 10 and 12 (current editions)
- Latina MA, Park C. Selective targeting of trabecular meshwork cells. Exp Eye Res. 1995;60:359-371
Related: Lasers made easy, Laser complications, SLT first line (LiGHT).
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📘 Want the exam-ready deep dive? This topic, and much more is covered in Ophthalmology Explorer (A High-Yield Clinical Reference for Ophthalmology Residents, Fellows & Board Exams) — available on Kindle. See all my books.
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