LSO 05: Bioeffects of Laser Exposure Flashcards
what is an eye?
organ of vision, detect light and convert to electrochemical impulses, transmitted to a brain by neurons
Most Laser controls are designed for?
protect optical operators from laser radiation in workplace
What are Cornea, Lens and Retina’s function?
Cornea: transparent front part of eye that covers iris, serves to reflect light, contribute to optical power eyes. It contains aqueous humor.
Lens transparent biconvex structure that helps to focus the light to retina. focus at object at different distance. It changes shape to allow to see at a different distance.
Choroid: vascular layer that sits between the retina and sclera.
Retina: visual image at retina. its a layer structure. Rods and cones cells . Rod night light, cones for daylight and colors
Fovea : part of the eye in the center of a macular region in retina. Responsible for sharp vision.
What is Macula?
part of eye responsible for central high vision. Macular damage will result in obvious vision loss.
What is an optic nerve?
collect different cellular and nervous cells and transmitting them to a brain for interpretation
Which part of the eye is responsible for Visual accommodation?
Lens
How is photoreceptor distributed?
high concentration of cones at the fovea whereas as you are at the fovea, it decreases
Which cells are wavelength sensitive?
Cones cell are most sensitive to light with a wavelength of 550 nm
What is skin?
serves as a protective barrier, loss of vision is more debilitating than damage to the skin
What are three layers of skin
Epidermis, Dermis and Subcutis
What is epidermis?
Outer layer of skin. Stratum Corneum provide much of the protection that skin offer to us
What is dermis?
Nerves running through it and vascularized, tranmit pain, itch and heat sensation
How does laser tissue interact?
Electromechanical and acoustic damage
Photoablation
Thermal damage
Photochemical damage
What is electromechanical and acoustic damage?
required exposure to high power density laser in extremely very short pulses, the damage is permanent, can affect the larger area of the retina than thermal burns
What is photoablation?
direct breaking of intramolecular bonds for eg: excimer lasers in the UV wavelengths with nanosecond pulses
what is thermal damage?
laser energy is converted into heat. localized due to molecular target absorption characteristics, free water, hemoproteins, melanin
What is photochemical damage?
Light triggers chemical reactions in tissue, can be accumulated over time
Usually due to short-wavelength ( blue and ultraviolet)
315- 390nm damage would be in?
near ultraviolet ( 315-390)- primary site of tissue interaction : LENS ( excimer laser)
400-1400nm damage would be in?
Retina ( RHS ; retinal hazard zone)
1400-1mm, 180-315nm
Cornea ( Co2 laser potential for cornea damage)
What part of the eye will be the target for energy absorption for a laser in the middle UV range?
Cornea ( 180-315)
What are corneal injuries?
Mid UV: photo keratoconjunctivitis ( 270 nm)
Mid & Far IR: corneal thermal injuries
what is lens injury?
Cataract, increased opacity of the lens, it’s a result of photochemical reaction ( 308 nm zenon laser responsible for cataract)
What are retinal injuries
Thermal burns, photochemical and photo disruption
what is scotoma?
A blind spot in the field of vision
How is retinal injury determined?
The pupil limits the amt of light that enters the eye and ultimately is able to reach the retina. The size of the pupil and random eye movements
Points to remember
eye is designed to collect light and focus it on the retina. Energy is focused and concentrated on to the retina almost 100,000 times
A visible laser results in a corneal irradiance of 2W/cm2. What would be the potential resultant retinal irradiance of this laser?
100,000X 2W/cm2
Important Card- Different eye effects
What wavelength cause photokeratitis?
100-315(UV C/B)
What wavelength cause retinal burns?
380-1400 ( visible /IRA)
What wavelength cause corneal burns?
1400-10^6 (IR B/C)
What wavelength cause cataracts?
315-370 (UV-A) and 760-3000 ( IRA/B)
What wavelength cause vision loss ( color and night)
400-780 ( visible, slight IR A)
What are laser skin injuries
burns, carcinogenic effects
What wavelength cause max skin damage
600-1200nm
What is stratum corneum?
It’s a dead skin layer
What are thermal laser skin injuries?
Typical burn, usually localized temperature increase serves as warning
What is erythema?
1st degree burn : redning of skin
What is blistering?
2nd degree burn: minimal scar from partial thickness burn ( epidermis and dermis damaged)
What is Charring?
3rd degree burn ( all tissue layer destroyed), nerves and skin is damaged, not painful. laser areas will require grafting of parts of the body
What is photochemical skin injuries?
UVB and UVC laser exposure
What wavelength is responsible for Erythema and accelerated aging?
UBC ( 200-280nm)
What wavelength is responsible for hyperpigmentation and skin cancer?
UVB ( 280-315)
What is skin cancer?
maglinant melonoma, UV from sun is cause of skin cancer
what wavelength is responsible for skin burn and pigment darkening?
315-400 (UV A) and 400- 700 ( visible)
What wavelength is responsible for skin burn?
700-1400 ( near IR), 1400-3000 ( mid IR) and 3000-100,000 ( far IR)
