Robert J. Landry

Adjustment of guidelines for exposure of the eye to optical radiation from ocular instruments : statement from a task group of the International Commission on Non-Ionizing Radiation Protection (ICNIRP)

A variety of optical and electro-optical instruments are used for both diagnostic and therapeutic applications to the human eye. These generally expose ocular structures to either coherent or incoherent optical radiation (ultraviolet, visible, or infrared radiation) under unique conditions. We convert both laser and incoherent exposure guidelines derived for normal exposure conditions to the application of ophthalmic sources.

Endoilluminators: evaluation of potential retinal hazards.

The potential for retinal photic injury from exposure to endoilluminators was evaluated. The spectral irradiance for each endoilluminator configuration was weighted with the American Conference of Government Industrial Hygienists (ACGIH) aphakic action spectrum. The result was compared with the threshold limit value (TLV) published by the ACGIH and a time to TLV (timeTLV) was calculated for each configuration. The calculated timeTLV ranged from 0.27 to 3.5 min, times that are significantly shorter than typical operating times. The effects of incorporating short-wavelength cutoff filters were evaluated and found to significantly increase the timeTLV. Exposure reduction techniques for use during surgery are discussed.

Retinal phototoxicity: a review of standard methodology for evaluating retinal optical radiation hazards.

Optical radiation (light) safety standards can be difficult to use for the evaluation of light hazards to the retina, even for persons experienced in radiometry and photometry. This paper reviews terminology and methodology for evaluating optical radiation hazards to the retina in accordance with international standard ISO 15004-2 Ophthalmic instruments—Fundamental requirements and test methods, Part 2: Light hazard protection (2007). All optical radiation safety standards use similar methods. Specifically, this paper illustrates how to evaluate the retinal hazards from various ophthalmic instruments including the following: diffuse illumination of the cornea; incident light diverging at the cornea (direct ophthalmoscope, operation microscope, fixation lamp); and incident light converging at the cornea (indirect ophthalmoscope, fundus camera, slit lamp biomicroscope). A brief review of radiometry and the use of certified optical components by manufacturers as specified by the ISO standard is also provided. Finally, the authors provide examples of the use of photometric measurements in hazard evaluation.

Temperature dependent response of optical radiation measurement instrumentation

An experimental arrangement to study the temperature dependence of the response of instrumentation used for the measurement of cw or chopped laser radiation is described. Preliminary measurements of the temperature dependent responses for five instruments are presented. The results indicate that the temperature dependent response for certain instruments is significant.

Study of the effect of involuntary user movement on the potential light hazards from some ophthalmic instruments.

A study was undertaken to determine whether involuntary user movement provides a basis for relaxing the measurement conditions for evaluating the potential optical radiation hazards to the eye from slit lamps and indirect ophthalmoscopes. This was accomplished by assessment of the extent to which light from these devices can be maintained in focus on a 1-mm-diameter fiber-optic cable for 45 s. The results suggest that, although involuntary user movements can be significant, they do not provide a basis for relaxing the measurement conditions for evaluating the potential optical radiation hazards to the cornea and lens from slit lamps and indirect ophthalmoscopes.

Electron paramagnetic resonance spectroscopy of free radicals in corneal tissue following excimer laser irradiation

Electron paramagnetic resonance spectroscopy (EPR) has been used to examine free radical formation during corneal tissue photoablation. Bovine corneal strips were frozen in liquid nitrogen, irradiated with excimer laser pulses, and assayed by EPR. Exposure conditions were varied to study radical formation dependence on laser intensity and repetition rate. Results were measured against a quantifiable standard to calculate radical quantum yield. EPR measurements indicate that corneal radical formation is largely a photochemical process driven by the 193 nm laser radiation. Reactive radical species are produced in substantial numbers, and likely have a significant clinical role.

Evaluation of the Potential Optical Radiation Hazards with Led Lamps Intended for Home Use.

Abstract The authors evaluated the potential for ocular damage from optical radiation emitted by Light Emitting Diode (LED) based lamps used for general illumination. Ten LED lamps were randomly selected off the shelf from a local home improvement store. The LEDs were behind diffusers in half of these lamps, while in the other half, the LEDs were clearly visible. In addition, a battery powered LED lantern having a LED source behind a diffuser was measured. The optical radiation emissions from two common incandescent lamps were also measured to compare the relative hazards of LED and incandescent lamps. All lamp samples were evaluated in accordance with procedures specified in the American National Standards Institute/Illuminating Engineering Society of North America (ANSI/IESNA) Standard RP‐27.3. For comparison purposes, the lantern and 100 W incandescent lamps were also evaluated according to ANSI RP‐27.1. These measurements indicate that no lamp evaluated poses any photobiological hazard, and therefore, all lamps fall in the RP‐27.3 category of Exempt Group. However, when evaluated in accordance with RP‐27.1, the 100 W incandescent lamp would be classified in Risk Group 1 (low risk), while the LED lantern would be classified in Risk Group 2 (moderate risk).