LSO 05: Bioeffects of Laser Exposure

Question 1

what is an eye?

Answer 1

organ of vision, detect light and convert to electrochemical impulses, transmitted to a brain by neurons

Question 2

Most Laser controls are designed for?

Answer 2

protect optical operators from laser radiation in workplace

Question 3

What are Cornea, Lens and Retina’s function?

Answer 3

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.

Question 4

What is Macula?

Answer 4

part of eye responsible for central high vision. Macular damage will result in obvious vision loss.

Question 5

What is an optic nerve?

Answer 5

collect different cellular and nervous cells and transmitting them to a brain for interpretation

Question 6

Which part of the eye is responsible for Visual accommodation?

Answer 6

Lens

Question 7

How is photoreceptor distributed?

Answer 7

high concentration of cones at the fovea whereas as you are at the fovea, it decreases

Question 8

Which cells are wavelength sensitive?

Answer 8

Cones cell are most sensitive to light with a wavelength of 550 nm

Question 9

What is skin?

Answer 9

serves as a protective barrier, loss of vision is more debilitating than damage to the skin

Question 10

What are three layers of skin

Answer 10

Epidermis, Dermis and Subcutis

Question 11

What is epidermis?

Answer 11

Outer layer of skin. Stratum Corneum provide much of the protection that skin offer to us

Question 12

What is dermis?

Answer 12

Nerves running through it and vascularized, tranmit pain, itch and heat sensation

Question 13

How does laser tissue interact?

Answer 13

Electromechanical and acoustic damage
Photoablation
Thermal damage
Photochemical damage

Question 14

What is electromechanical and acoustic damage?

Answer 14

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

Question 15

What is photoablation?

Answer 15

direct breaking of intramolecular bonds for eg: excimer lasers in the UV wavelengths with nanosecond pulses

Question 16

what is thermal damage?

Answer 16

laser energy is converted into heat. localized due to molecular target absorption characteristics, free water, hemoproteins, melanin

Question 17

What is photochemical damage?

Answer 17

Light triggers chemical reactions in tissue, can be accumulated over time
Usually due to short-wavelength ( blue and ultraviolet)

Question 18

315- 390nm damage would be in?

Answer 18

near ultraviolet ( 315-390)- primary site of tissue interaction : LENS ( excimer laser)

Question 19

400-1400nm damage would be in?

Answer 19

Retina ( RHS ; retinal hazard zone)

Question 20

1400-1mm, 180-315nm

Answer 20

Cornea ( Co2 laser potential for cornea damage)

Question 21

What part of the eye will be the target for energy absorption for a laser in the middle UV range?

Answer 21

Cornea ( 180-315)

Question 22

What are corneal injuries?

Answer 22

Mid UV: photo keratoconjunctivitis ( 270 nm)

Mid & Far IR: corneal thermal injuries

Question 23

what is lens injury?

Answer 23

Cataract, increased opacity of the lens, it’s a result of photochemical reaction ( 308 nm zenon laser responsible for cataract)

Question 24

What are retinal injuries

Answer 24

Thermal burns, photochemical and photo disruption

Question 25

what is scotoma?

Answer 25

A blind spot in the field of vision

Question 26

How is retinal injury determined?

Answer 26

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

Question 27

Points to remember

Answer 27

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

Question 28

A visible laser results in a corneal irradiance of 2W/cm2. What would be the potential resultant retinal irradiance of this laser?

Answer 28

100,000X 2W/cm2

Question 29

Important Card- Different eye effects

What wavelength cause photokeratitis?

Answer 29

100-315(UV C/B)

Question 30

What wavelength cause retinal burns?

Answer 30

380-1400 ( visible /IRA)

Question 31

What wavelength cause corneal burns?

Answer 31

1400-10^6 (IR B/C)

Question 32

What wavelength cause cataracts?

Answer 32

315-370 (UV-A) and 760-3000 ( IRA/B)

Question 33

What wavelength cause vision loss ( color and night)

Answer 33

400-780 ( visible, slight IR A)

Question 34

What are laser skin injuries

Answer 34

burns, carcinogenic effects

Question 35

What wavelength cause max skin damage

Answer 35

600-1200nm

Question 36

What is stratum corneum?

Answer 36

It’s a dead skin layer

Question 37

What are thermal laser skin injuries?

Answer 37

Typical burn, usually localized temperature increase serves as warning

Question 38

What is erythema?

Answer 38

1st degree burn : redning of skin

Question 39

What is blistering?

Answer 39

2nd degree burn: minimal scar from partial thickness burn ( epidermis and dermis damaged)

Question 40

What is Charring?

Answer 40

3rd degree burn ( all tissue layer destroyed), nerves and skin is damaged, not painful. laser areas will require grafting of parts of the body

Question 41

What is photochemical skin injuries?

Answer 41

UVB and UVC laser exposure

Question 42

What wavelength is responsible for Erythema and accelerated aging?

Answer 42

UBC ( 200-280nm)

Question 43

What wavelength is responsible for hyperpigmentation and skin cancer?

Answer 43

UVB ( 280-315)

Question 44

What is skin cancer?

Answer 44

maglinant melonoma, UV from sun is cause of skin cancer

Question 45

what wavelength is responsible for skin burn and pigment darkening?

Answer 45

315-400 (UV A) and 400- 700 ( visible)

Question 46

What wavelength is responsible for skin burn?

Answer 46

700-1400 ( near IR), 1400-3000 ( mid IR) and 3000-100,000 ( far IR)