Buyers Guide | What is OD (Optical Density) Laser Safety?
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Optical Density (OD) in laser safety is the amount of light attenuated[i] by the lens of the particular wavelength that is being measured. The required OD determined by the World Laser Safety in the USA found in ANSI Z136.1 are dependent upon several factors, including the wavelength of the laser. The standards were created through research based on how different wavelengths have different biological impacts.
Below is an example for how to read the shorthand notation for optical density and the attenuation of energy passing through a given filter.
Please note, each wavelength will have a different optical density. For simplicity, it is stated as a range of wavelengths.
Wavelength is the first parameter needed to begin assessing the type of laser safety protection needed.
There are typically two wavelengths associated with a laser:
The aiming beam is to aid the user in positioning the operating laser beam. Generally, the aiming beam will be low powered and typically red. Do not look directly at any laser including the aiming beam. A common use case for an aiming beam is a laser pointer. For more information on laser safety with an operating beam vs an aiming beam, click here.
If you are in doubt whether or not your aiming beam is eye-safe for diffused viewing, please check with your laser safety officer or call us before making any assumptions. Recently our team has come across wavelengths utilized for aiming beams that are inappropriate without proper laser safety protection.
Never look at any laser (including the aiming beam) directly. Stand behind the beam while viewing it, and do not bring your eyes near the axis during alignment or any other operation with lasers. All laser safety PPE is for unintentional direct and diffused viewing only. If you are hit with any laser in the eye, look away immediately.
If the alignment beam exceeds the MPE, use proper alignment eyewear (where the MPE threshold is not exceeded factoring appropriate exposure duration). Attenuating the laser to a point it cannot be seen is an issue. So, make sure to align the laser correctly. Laser safety alignment eyewear should be used at all times. Always be safe when dealing with lasers.
Having proper personnel with appropriate training and standard operating procedures during the alignment process are proper laser safety amongst several other laser safety controls.
Many lasers are within the range of the visible light spectrum of 380 nm (violet) and 740 nm (red). Individuals also need protection from lasers which emit Ultra-Violet light, (lower wavelength than visible light) and infrared light (higher wavelengths than visible light on the magnetic spectrum). It is important to know the wavelength of the laser you're working with - different lasers require different degrees of protection as outlined in ANSI.
[i] Outside of the context of laser safety, Optical Density more commonly refers to the refractive index, and the term 'Absorbance' is used in lieu of what we are referring to here as Optical Density.
Question and Answer Surrounding the Topic
Question: If my glasses have an optical density of 7+ between 190-385 nm, does that mean they provide that protection to wavelengths beneath 190, such as 110 nm?
Answer: No, this is not the correct way to view laser safety, protecting from a lower or higher wavelength outside the specified range for a laser safety product is not a safe way to shop.
Question: Can you provide me with laser safety glasses or goggles that protect from every laser?
Answer: No, by blocking the entire visible light spectrum, you would ensure that no visible light would be passing through the glasses and therefore would have no visibility. Although materials do block multiple wavelengths, blocking all wavelengths of visible light would defeat the purpose of having glasses - because you would not be able to see anything out of them.
However, some glasses offer protection from multiple wavelengths. Furthermore, another way to combat dealing with multiple lasers may be to wear multiple laser safety glasses.
Optometrists and ophthalmologists have several forms of retinal imaging at their disposal. Each plays a slightly different role in maintaining the health of your retina ' the thin layer of tissue in the back of your eye that is essential for good vision.
Some forms of retinal exams are better at detecting certain diseases than others. Your eye doctor will decide which test(s) to perform depending on any risk factors and/or symptoms you may have.
In addition to monitoring the overall health of your eyes, a retinal exam can be used to detect the early signs of some conditions, including:
Retinal detachment
Retinal tears
Diabetic retinopathy (a complication of diabetes)
For more information, please visit Laser Retinal Imaging.
Glaucoma
Age-related macular degeneration (AMD)
Hypertensive retinopathy (a complication of high blood pressure)
Retinitis pigmentosa
Cancers of the eye
If you've had an eye exam recently, there's a good chance you've seen a digital retinal scan machine. This quick and affordable form of retinal screening has become a staple in eye doctors' offices across the United States.
These retinal imaging devices use special technology to photograph an ultra-wide view of the inside of your eye in a single image. Included in the image is a detailed view of the retina, optic nerve and retinal blood vessels, all of which can show signs of underlying eye conditions. The process is quick and painless, and doesn't have any side effects.
While dilation is the best way for the doctor to see the whole retina and get an accurate view of the optic nerve, digital retinal imaging can be a very useful additional test.
Some eye care professionals bundle digital retinal imaging into the overall fee for a comprehensive eye exam, but it's more likely to be billed separately. In our nationwide eye exam cost survey, we found that eye doctors charged an average range of $25 to $50 for a digital retinal test.
There are many ways an eye doctor can examine your retinas ' and take their photos. These imaging tests and devices may include:
One of the most common retinal screening devices is Optos' optomap, which offers a 200-degree view of the retina. This type of digital imaging can be used for the everyday patient ' it's often offered with a comprehensive eye exam.
Other retinal tests are more specialized for diagnosing and monitoring specific eye conditions. They are usually performed by an ophthalmologist, or more specifically, a retinal specialist.
Also called OCT, optical coherence tomography is an imaging technique that uses light waves to take cross-sectional images of the retina. These images are then used to create a 3D map of the retina's layers and measure their varying levels of thickness. OCT can also help detect changes in the optic nerve.
Eye doctors may use OCT to detect, diagnose and/or monitor numerous conditions, including:
Problems with the macula
Glaucoma
Age-related macular degeneration
Multiple sclerosis
Ultrasounds use 'silent' sound waves to get a real-time view of the inside of your eye. They can be particularly useful when there is bleeding inside the eye, which can make it difficult for an eye doctor to spot the signs of retinal detachment, retinal tears or other retinal conditions.
Two different scans ' an 'A-scan' and 'B-scan' ' can be used to get different information about the retina and other tissues inside the eye.
Fundus photos are similar to digital retinal images, but they usually require pupil dilation beforehand. They also capture a smaller amount of surface area inside the eye. The images captured by fundus cameras are usually used to compare the progression of an eye disorder over time.
Fluorescein angiography is a test that involves injecting dye into the bloodstream and then taking pictures of the inner eye. It is usually used to monitor the retinal effects of diabetes, hypertension or macular degeneration.
Be careful not to confuse a fluorescein angiography with a fluorescein stain test, which is a way of detecting a scratched cornea or other issues on the front surface of the eye.
Having an eye doctor regularly examine your retinas, either with a digital imaging device or during a comprehensive eye exam with pupil dilation, ensures any retinal conditions are diagnosed and treated as early as possible.
Contact your eye doctor for more information about which retinal screening options are available for you.
Contact us to discuss your requirements of Indocyanine Green Angiography. Our experienced sales team can help you identify the options that best suit your needs.