Retinal Hazard Calculator
Retinal image size and irradiance of a laser beam viewed directly, from its wavelength, power, diameter and the pupil, compared with the ICNIRP 2013 retinal limits.
Educational only — not compliance-grade
These pages implement the published exposure limits for the cases each one states, but they are educational tools: no laser safety officer has signed them off.
- Do not use these results alone for PPE selection, NHZ / NOHD approval, controlled-area sign-off, enclosure/interlock approval, or formal classification.
- Always verify against ANSI Z136.1, IEC 60825-1, your local procedures, and the responsible laser safety officer / CLSO.
Power into the eye
10.0 mW
100 % through the pupil
Retinal image diameter
25.5 µm
no smaller than 25.5 µm
Retinal irradiance
1.96e+7 W/m²
1958 W/cm², before absorption
Corneal irradiance (7 mm)
260 W/m²
gain 75356× (75356× at a 7 mm pupil)
Max power within the eye limits
980 µW
Retina, thermal
Power / max power
10.2× (exceeds)
How much of the beam reaches the retina and how small the eye focuses it. The eye is a 17 mm lens that accommodates to the beam: a TEM₀₀ beam of 1/e² diameter d (capped by the pupil) focuses to 4λf/(πd), but aberrations and eye movements keep the image at 25.5 µm or more (α_min = 1.5 mrad × 17 mm), which ICNIRP 2013 (Health Phys. 105:271) assumes for every laser beam. A thin beam diverges more and makes a larger image. The retinal irradiance spreads the pupil power evenly over the image and ignores absorption in the eye, so it is an upper bound; ICNIRP puts the gain over the corneal irradiance at about 100 000. The limits are what to compare with: ICNIRP's retinal limits (thermal, and photochemical from 10 s at 400–600 nm) for a point source, as corneal exposure over 7 mm, and its anterior-segment limit, which ICNIRP has checked from 1150 nm and which binds from about 1300 nm, where the retinal limit has risen with C_C, or earlier for a beam under 1 mm, held to its peak. A smaller pupil lowers the retinal irradiance but not the limits: ICNIRP allows no credit for a pupil under 7 mm.
Retinal irradiance and image diameter against beam diameter for this power and pupil: thin beams diffract to a larger image, wide beams are cut by the pupil.
Model and references
Textbook approximation. A standard approximation from the literature (for example paraxial, plane-wave or Gaussian-beam), valid within the range the page states. About the tiers
A 17 mm eye focusing a TEM₀₀ beam to 4λf/(πd), at least 25.5 µm (α_min); retinal irradiance before absorption. Limits: ICNIRP 2013 retinal and anterior-segment, point source, 400–1400 nm.
- ICNIRP (2013). Guidelines on limits of exposure to laser radiation of wavelengths between 180 nm and 1,000 µm. Health Phys. 105(3), 271–295. Tables 2, 3, 5 and 8. doi:10.1097/HP.0b013e3182983fd4
- Sliney, D. H. & Wolbarsht, M. L. (1980). Safety with Lasers and Other Optical Sources. Plenum, New York. The 17 mm reduced eye. doi:10.1007/978-1-4899-3596-0