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100 Cards in this Set
- Front
- Back
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Which has higher energy, UV or IR?
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UV. E=hc/wavelength
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What is the visible spectrum that we use in class?
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380-760 nm i guess, im not sure
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UV-C = ?
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200-290, never reaches surface of earth
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What is the lowest wavelength that passes through the atmosphere?
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288nm, BUT other things on earth can create UVC
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UV-B?
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290-315 nm
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UV-A?
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315-380 nm
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IR-A?
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780-1400 nm
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IR-B?
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1400-3000 nm
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IR-C?
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3000-10,000 nm
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What is the only way radiation can damage tissue?
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It must be absorbed by the tissue.
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What wl is considered thermal?
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500 nm, green light + longer
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What is thermal energy?
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Causes rotational and vibrational changes in the molecules that absorb it, excess energy dissipates as heat.
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Hoe does thermal energy cause a burn?
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It denatures proteins. Must raise about 10-15 deg C. Hard to do since our vessels carry heat away.
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What wavelength is considered photochemical?
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shorter than 500 nm. Blue light and uv
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How do photochemical effects work?
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Photons create ions by removing electrons from atoms and molecules. The electrons and ions then damage other molecules like DNA, RNA, .
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When can photochemical effects damage?
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A photon can cause damage, low exposure over a long time, high exposure over a short time.
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What do we have to worry about with IR radiation?
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It can cause cortical cataracts. Also known as glassworker's or iron-puddler's cataract.
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Who has to worry about IR radiation?
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Rare in the industrialized world, mainly GLASSWORKERS who work with molten glass.
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Who are the only people who would be exposed to vacuum UV?
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Astronauts in Space
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What classification of UV will we see the most problems with in our patients?
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UV-B
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What is reciprocity?
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Photochemical damage done at low level exposure for a long period of time.
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What type of light does the cornea absorb?
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.IT absorbs everything from 300nm and down, so it absorbs UVC (200-290), and a tiny bit a b(the 290 - 200 part)
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T/F, the tiny bit of UV absorbed by the cornea (280-290) does not harm it.
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FALSO!
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Which light does the lens absorb?
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1.)Everything 400 and below. This means all the UV light not absorbed by the cornea is absorbed by the lens. The Lens TRANSMITS, everything above 400.
2.) The lens ALSO absorbed very high IR wls. |
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If IR-A passes through the lens, why do they say it can cause a cataract?
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They think that it may be absorbed by the iris.
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UV exposure as a child?
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At a young age, some UV may transmit through the lens. This is what is thought to cause ARMD. We worry about it until we are 20 years old.
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How much UV exposure does the retina receive before the age of 20.
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People think it's 40-50% of total UV in our entire lifetime.
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What are the main source of UVC we have to worry about?
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Welding arcs
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Characteristics of welder's flash, aka photokeratitis?
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Latent period, sun burn, foreign body sensation, photophobia, lacrimation, blepherosasm, pain.
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How long is the latent period of photokeratitis?
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30minutes-24hours, you can wake up in the middle of the night with crazy pain.
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How do you treat photokeratitis?
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usually heals on it's own
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T/F. We can build up a resistance to photokeratitis.
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You wish.
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What wl causes photokeracaca from the welding arc?
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290-300, the only uvB absorbed by the cornea. AND UVC from wielding arcs.
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When do we have to worry about only UVB causing photokeraputa (like, if you weren't using a welding arc)?
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Mostly in the SNOW. There isn't enough UVB collected in the eye otherwise. IT must be reflected and snow is awesome at doing this.
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How much of the UVB/light from the light that hits our head reaches the cornea?
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only about 5%, we have lots o stuff to protect us from it. Our gaze is usually downward when we walk.Typically higher in overcast days because we don't squint as much.
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How may sunglasses actually make our uv exposure worse, and what does this say about sunglasses we need?
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We decrease our natural protection like squinting and pupil constriction, so we need to get them more wrapped to make sure uv doesn't come in from the side
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Most important determinant of UV exposure that we will receive?
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The ground
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UVB snow reflectance.
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85%
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What kind of cataracts may be associated with UVB?
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Cortical
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What is the carnelo effect?
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Light coming in temporally is reflected and focused on the nasal part of the eye, causing pterygiums and stuff
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What part of the earth will you get the most UV?
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Equator
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Does UVA have an association with nuclear cataracts?
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NO,
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Problems with UV relating to Aphakia?
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Macular edema, decreased blue cone sensitivity, erythropsia
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T/F. There is no evidence that blue light CAUSES ARMD?
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TRUE, key word is causes. It MAY make it worse.
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What causes Solar retinopathy?
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Staring at the sun. Not caused by IR in our daily lives because retina dissipates heat with blood vessels.
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What is Retinitis pigmentosa?
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Slow regressive loss of rods, causes loos of night vision and visual field defects
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First symptom of RP?
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loss of night vision/poor dark adaptation
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First part of vf to go during RP?
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midperipheral
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Treatments for RP?
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Vitamin A may slow progression, but you must be careful because there may be health problems associated with vitamin A.
Lutein may prevent mid peripheral field loss. Vitamin E may make worse. |
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Why do we want to use tints for people with RP?
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1.)Protect the retina from blue light (bright yellow lens)
2.)Keeps them dark adapted, so it is easier when they go from outside to inside. |
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What is occlusion therapy for RP?
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Covering up one eye. Basically they protect one eye until the other one gets jacked up and then uncover it. They use an occluder contact lens for 6-8 hours a day.
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What is the research emphasis on for RP treatment nowadays?
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Gene therapy
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Do we hurt our patients with the lights we use?
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No, we don't have them exposed long enough to do any damage. Sick eyes may need less exposure. This is called SAFE TIME
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What is safe time exactly?
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How long you can shine green light on a given spot oo the retina.
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Why is it that we must be more careful with out lights during surgical procedures?
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If the patient is anesthetized, they will no be able to look away from the light.
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So why don't we just use blue blockers for everyone?
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1. gray 3 is a good sub 2.they alter color perception 3. issues with driving signals
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What are some suggestions as far as protection from all this crap in people with IOLs?
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use a yellow or brown tinted IOL.
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What are the problems with using blue blocking IOLs?
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1.)reduces scotopic vision since the pupil wont dilate 2.)may interefere with circadian rythms.
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What is an ipRGP?
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New type of light detecting cell that IS NOT a photoreceptor. It is sensitive to light and has melanopsin. They regulate circadian rhythms and maybe pupillary light reflex.
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What light are ipRGCs most sensitive to?
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BLUE LIGHT
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3 trade names for ARC?
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Crizal, Teflon, Color Free AR
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What are Transitions Vantage?
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Photochromics that become polarized when they darken.
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What decreases the effectiveness of photochromics?
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Heat
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Dielectic mirror coat?
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like a "reverse AR", you want proper thickness in order to get constructive interference. So it is 1/2 a wl
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Irlen lenses
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Colored lenses or filters used for people with reading problems. 1.) MEars-Irlen syndrome 2.) scotopic sensitivity syndrome 3.) pattern-related visual stress
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Do irlen lenses really work?
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Maybe, because the color may reduce the accomodative demand
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What are some of the criticisms of Irlen lenses?
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1.) Evidence is based on personal testimony only
2.)NOt introduced by a scholarly journal 3.)claims are exaggerated 4.)These promises hold false up and people become disappointed. |
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FL 41 lenses?
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Rose colored tinted lenses supposed to treat blephorospasms.
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Melanin lenses?
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Brown sunglasses that are supposed to have synthetic melanin. They block blue light. They absorb less than yellow lenses so they say it it effects color perception less.
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Do most contact lenses provide UV protection?
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NO
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Where is the cut off for UV light in contacts?
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Cuts off at 350, so you still block UVB.
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What are the government policies for UV protection?
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There aren't any. Only ANSI standards (Z80.3) which is just an agreed set criteria.
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What does "Prevents Blindness, America" recommend for UV protection?
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At least 1% transmission for UVA and UVB.
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How do you go about choosing non prescription sunglasses with uv protection?
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1.)Hard to predict by cost, but trivex and poly have the best. 2.)Also gray is probably the best option as far as tint.
3.) check for good optics with hand neutralization 4.) eyes should not be seen in mirror 5.) Make sure they fit right and don't let a lot of crap in from the side. Defeats the purpose of UV. |
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How useful are UV meters?
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Not really useful, they tend to OVERESTIMATE UV transmittance.
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IS UV protection a concern for computer screen?
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NO, the UV is like 10,000 times less then anything that will cause damage
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Some trade names of photochromic lenses?
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Transitions, sunsesors, *photogrey extra, photofusion.
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How are glass photochromics and sunsensors made?
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The material is suspended throughout the lens like a through and through tint. IN MASS
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What is surface imbibition, when would you use it?
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The photochromic material is behind the lens front surface. Use it on PLASTIC
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What is transbonding, when would you typically use it?
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Material layered on front surface. Use it on HIGH INDEX.
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What is the best photochromic and why?
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Transitions are, because their methods allow you to get photochromics in almost any material.
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What are instashades and how are they made?
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A new photochromic, where the material is in the mold.
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How good is the UV protection in photochromics for PLASTIC?
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With the exception of sun sensors, plastic is pretty good and has 100% UVA and UVB absorbed.
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Photogrey extra (glass photochromic) uv protection?
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100% UVB and 97% UVA laaame
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UV for sun sensors?
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100% UVB and 97% UVA booo
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UV for photofusion?
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100% below 400 damn
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What is on benefit of photogrey extra(glass photochromics) to plastic?
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They last forever. Plastics wears out after a couple of years.
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If you got a brand you pair of photogreyextra, you'd be a disappointing in how they darken for a few weeks because...
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They need time to break in. They will first be green then get darker and darker. LET PATIENT KNOW THIS.
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T/F, photochromics are perfect for the car because they get super dark!
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No, they are UV activated and not very much UV gets into the car.
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Cut off point for UV in for laminated front car windshield?
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Looks like about 370-380 from the graph. Everything below is absorbed,
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How may AR actually help the affects of Transition (maybe other photochromics?
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It helps because it increases trasnmittance of light to help increase activation of the lens.
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What is the main reason that Sun sensors suck?
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Besides having crappy UV absorption, they are only availble in 1.556 plastic, which is rare.
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If you are getting a photochromic lens in poly, what trade name are you most likely getting?
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LifeRX
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What is the color of sun sensors?
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gray with little green, tinted throught
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What is the color of transitions?
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gray with a little blue, edge is clear
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What is this new XtraActive photochromic everyone is talking about?!
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A photochromic that gets darker than normal.
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How much light do these xtra active photochromics transmit inside and out, and what does it mean?
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Outside = 10-20% which is good. Inside = 83%, which means they will be darker inside.
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What tiny advantage may the xtra active have beside getting darker outside?
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responds a little to visible light, so might be useful in the car.
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What is drivewear?
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ANOTHER damn photochromic but it becomes polarized and becomes a blue blocker. DO NOT use at night. used for outdoor only.
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drivewear light transmittance?
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low light = 37% gross, daylight = 25%, bright direct light = 10% nice!
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