eye examination and lasers

[meridannight]

i'm gonna go and get my eyes checked soon. i have no problems with vision currently, and never had any issues in the past. i just want to do a full check-up (my last one was 11 years ago). so i scheduled a complete full examination for my eyes (it includes getting a 3D image of my eyes, which i think is awesome).

my problem is, i think they use laser retina scan along with other things. which makes me kind of wary about it. doesn't that laser scan damage the eye? how is the medical laser safe, exactly? does anybody know?

every text i've been able to find on this topic says medical lasers are class III or IV, which is damaging to skin and eyes. and the doctors' answers just say it's safe, but don't explain how it's safe. it pisses me off. i need to know how exactly is laser retina scan safe. back when i was in flight school they wouldn't allow pilots to have laser surgery on the eye because the laser leaves some mark behind and that was not acceptable for pilot's visual standards. (i know laser surgery is not the same as laser scan, but still).

i know there are no ophthalmologists here and maybe i am overthinking it. i looked on the internet and i found no definitive answer to this question. have any of you actually had a laser retina scan done on your eyes? or what are your thoughts?

[Borg69]

Lasers have different power settings. I have a laser pointer that's essentially a cat toy. Then there's the ones that are planet destroyers like on the Death Star in Star Wars. I'm sure the ones they use to scan the inside of your eyes are very low powered and harmless - otherwise they wouldn't be using them.

I get that you're apprehensive, but let the doctor(s) do their work.
If it makes you feel any better, don't let them fly your planes or tell you how and you'll be even.

[ShiftyNJ]

i'm gonna go and get my eyes checked soon. i have no problems with vision currently, and never had any issues in the past. i just want to do a full check-up (my last one was 11 years ago). so i scheduled a complete full examination for my eyes (it includes getting a 3D image of my eyes, which i think is awesome).

my problem is, i think they use laser retina scan along with other things. which makes me kind of wary about it. doesn't that laser scan damage the eye? how is the medical laser safe, exactly? does anybody know?

every text i've been able to find on this topic says medical lasers are class III or IV, which is damaging to skin and eyes. and the doctors' answers just say it's safe, but don't explain how it's safe. it pisses me off. i need to know how exactly is laser retina scan safe. back when i was in flight school they wouldn't allow pilots to have laser surgery on the eye because the laser leaves some mark behind and that was not acceptable for pilot's visual standards. (i know laser surgery is not the same as laser scan, but still).

i know there are no ophthalmologists here and maybe i am overthinking it. i looked on the internet and i found no definitive answer to this question. have any of you actually had a laser retina scan done on your eyes? or what are your thoughts?

I had cataract surgery which involved lasers for more precision. My regular optometrist, who had no personal stake in what form of surgery I was to have, said the laser would be more precise. A year later I am very happy with the results. I'm not familiar with lasers for diagnostics though.

[Nanaki]

I'm not 100 percent sure, but I think I've had done what you're referring to about a year ago. If I am thinking of the right scan, it only took a second or two and I didn't feel a thing. I do know that I have had many comprehensive eye exams and laser surgeries over the years, and nothing they've done has ever hurt me.

The glaucoma test feels a little weird. And a dilated exam, where they dilate your pupils with drops and then shine a light into your eyes and look around, makes you super sensitive to light for a little while. Be sure to take along some sunglasses in case you need them.

Actually, I'm going to the opthalmologist in about a week. I'll try to remember to ask about this and see what I can find out.

[meridannight]

I'm not 100 percent sure, but I think I've had done what you're referring to about a year ago. If I am thinking of the right scan, it only took a second or two and I didn't feel a thing. I do know that I have had many comprehensive eye exams and laser surgeries over the years, and nothing they've done has ever hurt me.

Actually, I'm going to the opthalmologist in about a week. I'll try to remember to ask about this and see what I can find out.

that would be great man. if it's not too much trouble. i will ask my own doctor about it too (my appointment is two weeks away).

i'm not worried about pain or discomfort. i just want to know how exactly is the laser safe to be operated on the eyes. i'm sure there's a valid scientific explanation for it but i just don't know what it is.

[meridannight]

Lasers have different power settings. I have a laser pointer that's essentially a cat toy. Then there's the ones that are planet destroyers like on the Death Star in Star Wars. I'm sure the ones they use to scan the inside of your eyes are very low powered and harmless - otherwise they wouldn't be using them.

laser pointers, huh. they're generally 1 mW to 5 mW, depending on the country (in UK, for example, laser pointers above 1 mW are illegal; in US laser pointers range up to 5 mW).

Studies have found that even low-power laser beams of not more than 5 mW can cause permanent retinal damage if gazed at for several seconds; however, the eye's blink reflex makes this highly unlikely. Such laser pointers have reportedly caused afterimages, flashblindness and glare,[1] but not permanent damage, and are generally safe when used as intended.

The degree, character, and duration of vision impairment caused by eye exposure to laser light varies with the power of the laser, the wavelength(s), the collimation of the beam, the exact orientation of the beam, and the duration of exposure. Lasers of even a fraction of a watt in power can produce immediate, permanent vision loss under certain conditions, making such lasers potential non-lethal but incapacitating weapons.

you shouldn't point that into anybody's eyes either, even if it's just 1mW. it is generally safe, i agree. but permanent damage occurs when it's shined into the eye for several seconds. which means, there may be damage, albeit unnoticeable, already at a brief exposure. it also depends on the location of the exposure. fovea or optic nerve head damage will have a huge impact on vision.

retina is composed of rods and cones which are photoreceptors. it is imaginable that if permanent damage includes destruction of some of the light-sensitive receptors in the retina, then non-permanent damage might still mean some type of partial damage to those cells. in a sense that you're not gonna lose much function of your hand when you get your pinky cut off, but the damage is still there.

If it makes you feel any better, don't let them fly your planes or tell you how and you'll be even.

i know how planes are flown so i have so apprehension about flying.

[Nanaki]

that would be great man. if it's not too much trouble. i will ask my own doctor about it too (my appointment is two weeks away).

i'm not worried about pain or discomfort. i just want to know how exactly is the laser safe to be operated on the eyes. i'm sure there's a valid scientific explanation for it but i just don't know what it is.

No trouble at all, my appointment is 3 Feb. I realize now that's actually about a week and a half. But hopefully I get a technician who likes to talk and I can get some info before you go.

[Cuddly]

retina is composed of rods and cones which are photoreceptors. it is imaginable that if permanent damage includes destruction of some of the light-sensitive receptors in the retina, then non-permanent damage might still mean some type of partial damage to those cells. in a sense that you're not gonna lose much function of your hand when you get your pinky cut off, but the damage is still there.

i know how planes are flown so i have so apprehension about flying.

Fun fact, the cones are more prominent in the fovea, which is why our focussed vision is best in light and only in light, because they require the stimuli of 3 (or is it 4) photons to produce a signal. The rods are more prominent towards the corners of the retina (away from fovea) and these produce a signal on stimuli by a single photon. That is why our peripheral vision is best in low (dark) light.
I know nothing about lasers, but all such professional care is tested thoroughly before being used on humans, so you should be quite safe. Otherwise they would warn you in flightschool or before signing up for the test. Or both.

[meridannight]

[MENTION=20359]Cuddly[/MENTION], i am sure i'll be quite safe. lol. i just have this thing, as you probably can tell, i need to understand this thing. why it's safe. i'm not paranoid, and i'm sure doctors know what they're doing. but i need to know the physics behind this thing. it gets to me that i'm missing something here.

[Cuddly]

[MENTION=20359]Cuddly[/MENTION], i am sure i'll be quite safe. lol. i just have this thing, as you probably can tell, i need to understand this thing. why it's safe. i'm not paranoid, and i'm sure doctors know what they're doing. but i need to know the physics behind this thing. it gets to me that i'm missing something here.

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?