also, as we're getting onto the topic of the physiology of the eye, cones are responsible for color vision. rods can't detect color but they detect intensity of light, which is why they function better in low light conditions (you need more light to be able to distinguish the colors, or actually you can't distinguish colors in low light very well because cones are not as sensitive then).
humans have three types of cones called red cone, blue cone and green cone (they peak at different wavelengths near red, blue, and green respectively). relative activation of these three cone types simultaneously is responsible for exactly what color we perceive.
Cuddly Wrote:In order to damage the cells the light needs to carry alot of energy. They only need a reflection to create an image.
It's like being afraid you'll blow your roof off by turning on the tablefan. Are you reassured?
is that what they're doing? reflecting the laser off of some surface that absorbs most of its energy before directing it into your eyes?
i am gonna get these tests done (it's an amazing technology), it's not about that. i just want to know the physics behind it. how they modified the laser so as for it to be safe to be used on the eyes.
meridannight Wrote:is that what they're doing? reflecting the laser off of some surface that absorbs most of its energy before directing it into your eyes?
i am gonna get these tests done (it's an amazing technology), it's not about that. i just want to know the physics behind it. how they modified the laser so as for it to be safe to be used on the eyes.
Honestly, I have no idea. I'm just guessing.
I've tried to quickly find something, but the whole Iris-identification thing dilutes the science. So it's pretty hard to find. I'm preping for an exam tomorrow, so I can't go into it now.
Try youtubing around a bit, you know more details than I do, so maybe you have more luck.
Best I found, but it has none of the lazer-technical stuff in it, just a resume of the information you can get from looking at the retina.
01-24-2015, 02:44 AM (Edited 01-24-2015, 02:53 AM by meridannight.)
okay. this thing was really bugging me and i did some digging on the internet, and i think i found my answer.
i found information on two types of laser technology used on the eyes (there may be more, but i discovered these two for now). the two are Optical Coherence Tomography (OCT) and Scanning Laser Ophthalmoscopy (SLO), and a variant of this, confocal SLO (cSLO).
i found out that OCT uses near-infrared laser which is said to be safe for the eyes and damage is unlikely.
cSLO uses incident power of 580 μW, which is about half the power of 1mW, and this is said to be below the maximum permissilble radiant power for SLOs at the wavelength of 840 nm.
it is in the fact that they use low illumination levels that safe retinal exposure is maintained. this however produces a low signal strength for the image, a problem that is overcome by taking multiple frames, and by removing image distortions due to eye movements.
i know the clinic i'm going to has technological capacity of both OCT and cSLO. if they'll even use it on me, but i assume they will, since this is how 3D images of the eye are produced.
No the laser they use is set real low in intensity. While it is coherent light (focused into a thin stream of light) its not anywhere as strong as a laser pointer or any type of laser we can see that does do damage.
Those medical lasers that you are getting information about are most likely the cutting/surgical kind which can do damage. They are of a much higher intensity and are designed to cut through tissues.
Spectrum also plays a role. Most lasers we think of are visual parts of the spectrum like red or green.
At your age you need to get your eyes checked at least every two years. When you hit 40 don't be surprised to find out that suddenly all fonts have gotten smaller. Nearly everyone when they hit 40 discover that their eye muscles are losing their ability to focus for close up work, so reading glasses may be in your future.
Astigmatism is another one that is 'tricky' It can come and go depending on various situations. Age can cause it. Astigmatism is basically when the eyeball stops being spherical and becomes more like an egg or American football in shape.
Bowyn Aerrow Wrote:Those medical lasers that you are getting information about are most likely the cutting/surgical kind which can do damage. They are of a much higher intensity and are designed to cut through tissues.
no, OCT and SLO are medical imaging techniques, not surgical cutting lasers.
I've had a retina scan photograph taken every time I visit the optometrist (which is once every one or two years). Never had a problem. They use it to look inside your eye more clearly, and it's a medical record for your eyes. Since I have a family history of glaucoma, I don't want that happening to me and want it, if it happens, to be caught early.
In this, as in any situation where you are receiving medical treatment, you have a right to know what is going on. You should simply talk to the doctor before the exam. If the exam is to be conducted by a technician, ask to talk to the doctor first. One of the questions I would ask is why this particular exam and technology is necessary. There is no reason to do something just because it can be done. What information are you and the doctors seeking?
LJay Wrote:What information are you and the doctors seeking?
it's a full thorough examination of the eyes. i'm not looking for anything, other than getting a clear that all parts of my eyes are the way they're supposed to be and doing what they should be doing.
vision-related disease is often asymptomatic, and by the time you start noticing deterioration, it's already too late to do anything significant about it. but it is possible to catch it in time, before any symptoms, and the earlier it's caught the better. thus eye examination should really be a regular practice, as [MENTION=12444]Bowyn Aerrow[/MENTION] pointed it out too. seeing as i haven't had my eyes checked for 11 years, i'm long overdue on it.
and i'm kind of a nerd for this type of information. initially i was just gonna go see an optometrist, but then i found out there's a clinic that does 3D imaging of the eyes (covering the examination of all parts of the eye in the process), and i was sold right there. i wanna see what my eyes look like inside. i am that much of a junkie for this. they'll study the retina, optic nerve head, blood vessels, all of it. in addition to standard pupil dilation, and visual acuity tests.
eye examination and lasers
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