read through your almost-closed fist.

My Father-in-Law did this recently, but I’d like to know how it works.

Speedy said:

read through your almost-closed fist.

My Father-in-Law did this recently, but I’d like to know how it works.

Same as a pin-hole camera.

Speedy said:

read through your almost-closed fist.

My Father-in-Law did this recently, but I’d like to know how it works.

Hehe I just tried that, it does work.

Speedy said:

read through your almost-closed fist.

My Father-in-Law did this recently, but I’d like to know how it works.

Smaller aperture gives increased depth of field, like a camera.

Michael V said:

Speedy said:

read through your almost-closed fist.

My Father-in-Law did this recently, but I’d like to know how it works.

Smaller aperture gives increased depth of field, like a camera.

Okay. Makes little sense to me though.

With my own eyes (with keratoconus), my vision is almost perfect outside on a sunny day. This is because the pupil contracts, minimising distortion.

How can looking through a dark tunnel, I assume with a pupil dilating, increasing distortion, also improve vision?

Speedy said:

Michael V said:

Speedy said:

read through your almost-closed fist.

My Father-in-Law did this recently, but I’d like to know how it works.

Smaller aperture gives increased depth of field, like a camera.

Okay. Makes little sense to me though.

With my own eyes (with keratoconus), my vision is almost perfect outside on a sunny day. This is because the pupil contracts, minimising distortion.

How can looking through a dark tunnel, I assume with a pupil dilating, increasing distortion, also improve vision?

The central rays of light are focussed. The more peripheral ones are defocussed (if you are over a certain age and trying to look at something close up). A pinhole cuts out the peripheral unfocussed light and gives you a clear, but darker image. It’s not to do with the pupil dilating.

buffy said:

Speedy said:

Michael V said:

Smaller aperture gives increased depth of field, like a camera.

Okay. Makes little sense to me though.

With my own eyes (with keratoconus), my vision is almost perfect outside on a sunny day. This is because the pupil contracts, minimising distortion.

How can looking through a dark tunnel, I assume with a pupil dilating, increasing distortion, also improve vision?

The central rays of light are focussed. The more peripheral ones are defocussed (if you are over a certain age and trying to look at something close up). A pinhole cuts out the peripheral unfocussed light and gives you a clear, but darker image. It’s not to do with the pupil dilating.

I might alter that…the central light rays are essentially parallel, so appear focussed. But it’s a minor detail.

buffy said:

buffy said:

Speedy said:

Okay. Makes little sense to me though.

With my own eyes (with keratoconus), my vision is almost perfect outside on a sunny day. This is because the pupil contracts, minimising distortion.

How can looking through a dark tunnel, I assume with a pupil dilating, increasing distortion, also improve vision?

The central rays of light are focussed. The more peripheral ones are defocussed (if you are over a certain age and trying to look at something close up). A pinhole cuts out the peripheral unfocussed light and gives you a clear, but darker image. It’s not to do with the pupil dilating.

I might alter that…the central light rays are essentially parallel, so appear focussed. But it’s a minor detail.

Thanks buffy. Is the theory about my own vision in sunlight still correct?

Speedy said:

buffy said:

buffy said:

The central rays of light are focussed. The more peripheral ones are defocussed (if you are over a certain age and trying to look at something close up). A pinhole cuts out the peripheral unfocussed light and gives you a clear, but darker image. It’s not to do with the pupil dilating.

I might alter that…the central light rays are essentially parallel, so appear focussed. But it’s a minor detail.

Thanks buffy. Is the theory about my own vision in sunlight still correct?

Yes, you are observing pinhole pupil effects doing the same thing as a pinhole – allowing the parallel central rays to go through to the retina and blocking at least some of the dodgy keratoconussed rays. Some keratoconics can get good vision in certain eye/head positions too. Sometimes it’s with chin down, which I suspect is a top lid effect of some sort, again cutting out some of the dodgy peripheral stuff.

:)

A recognized fast triage method for “I can’t see clearly!” is to get the person to look through a pinhole. If that clears up the vision, it’s refractive – they need their glasses, or updated glasses or whatever. If the pinhole makes no difference you start looking for disease/damage etc to the bits of the eye. Generally starting with the cornea at the front and working back through the anterior chamber, lens, vitreous and then retina.

For example, when I had the horseshoe tears that busted little blood vessels inside my eye, the blood was in my line of sight, so obscuring vision. Pinhole didn’t make a difference. But at the same time, if I moved my eye, I could “swish” the blood out of the way and get momentary good central vision – so I knew my macula was still intact and I didn’t have a macula-off retinal detachment. A little knowledge can be a good thing. And nearly 40 years of optometry meant I also knew that pit of the stomach fear of knowing what could go wrong.

buffy said:

Speedy said:

buffy said:

I might alter that…the central light rays are essentially parallel, so appear focussed. But it’s a minor detail.

Thanks buffy. Is the theory about my own vision in sunlight still correct?

Yes, you are observing pinhole pupil effects doing the same thing as a pinhole – allowing the parallel central rays to go through to the retina and blocking at least some of the dodgy keratoconussed rays. Some keratoconics can get good vision in certain eye/head positions too. Sometimes it’s with chin down, which I suspect is a top lid effect of some sort, again cutting out some of the dodgy peripheral stuff.

:)

So with age-related vision loss requiring reading glasses, the pin-hole camera system works as only those parts of the image not requiring much work to focus are allowed in?

buffy said:

A recognized fast triage method for “I can’t see clearly!” is to get the person to look through a pinhole. If that clears up the vision, it’s refractive – they need their glasses, or updated glasses or whatever. If the pinhole makes no difference you start looking for disease/damage etc to the bits of the eye. Generally starting with the cornea at the front and working back through the anterior chamber, lens, vitreous and then retina.

For example, when I had the horseshoe tears that busted little blood vessels inside my eye, the blood was in my line of sight, so obscuring vision. Pinhole didn’t make a difference. But at the same time, if I moved my eye, I could “swish” the blood out of the way and get momentary good central vision – so I knew my macula was still intact and I didn’t have a macula-off retinal detachment. A little knowledge can be a good thing. And nearly 40 years of optometry meant I also knew that pit of the stomach fear of knowing what could go wrong.

I remember you has laser, was it, just before Christmas. Has that all settled for now?

Speedy said:

buffy said:

A recognized fast triage method for “I can’t see clearly!” is to get the person to look through a pinhole. If that clears up the vision, it’s refractive – they need their glasses, or updated glasses or whatever. If the pinhole makes no difference you start looking for disease/damage etc to the bits of the eye. Generally starting with the cornea at the front and working back through the anterior chamber, lens, vitreous and then retina.

For example, when I had the horseshoe tears that busted little blood vessels inside my eye, the blood was in my line of sight, so obscuring vision. Pinhole didn’t make a difference. But at the same time, if I moved my eye, I could “swish” the blood out of the way and get momentary good central vision – so I knew my macula was still intact and I didn’t have a macula-off retinal detachment. A little knowledge can be a good thing. And nearly 40 years of optometry meant I also knew that pit of the stomach fear of knowing what could go wrong.

I remember you has laser, was it, just before Christmas. Has that all settled for now?

Yes, I had green laser surgery to repair tears in my retina. If it wasn’t done there was a risk of the retina pulling away and me needing considerably more involved surgery to stick it back on. I’ve still got floaters, the blood takes months to resorb. The retinal surgeon has looked at my other eye, and it’s fine at present. I see him again in March (3 months from the last visit) and I expect it to be 6 months after that for the next check. I will keep an active referral going in case the other eye behaves the same – if I phoned I expect to go straight down, same day. As we discussed, they are the same age and it’s an ageing thing. You are just supposed for only the jelly to come adrift, it isn’t supposed to take a bit of retina with it. I saw the jelly bit go, then I recognized the complications a week or so later. I’m hoping the other eye just does the normal thing.

Speedy said:

buffy said:

Speedy said:

Thanks buffy. Is the theory about my own vision in sunlight still correct?

Yes, you are observing pinhole pupil effects doing the same thing as a pinhole – allowing the parallel central rays to go through to the retina and blocking at least some of the dodgy keratoconussed rays. Some keratoconics can get good vision in certain eye/head positions too. Sometimes it’s with chin down, which I suspect is a top lid effect of some sort, again cutting out some of the dodgy peripheral stuff.

:)

So with age-related vision loss requiring reading glasses, the pin-hole camera system works as only those parts of the image not requiring much work to focus are allowed in?

Yes, that’s pretty much it.

at least now we can run around in circles of confusion

buffy said:

Speedy said:

buffy said:

A recognized fast triage method for “I can’t see clearly!” is to get the person to look through a pinhole. If that clears up the vision, it’s refractive – they need their glasses, or updated glasses or whatever. If the pinhole makes no difference you start looking for disease/damage etc to the bits of the eye. Generally starting with the cornea at the front and working back through the anterior chamber, lens, vitreous and then retina.

For example, when I had the horseshoe tears that busted little blood vessels inside my eye, the blood was in my line of sight, so obscuring vision. Pinhole didn’t make a difference. But at the same time, if I moved my eye, I could “swish” the blood out of the way and get momentary good central vision – so I knew my macula was still intact and I didn’t have a macula-off retinal detachment. A little knowledge can be a good thing. And nearly 40 years of optometry meant I also knew that pit of the stomach fear of knowing what could go wrong.

I remember you has laser, was it, just before Christmas. Has that all settled for now?

Yes, I had green laser surgery to repair tears in my retina. If it wasn’t done there was a risk of the retina pulling away and me needing considerably more involved surgery to stick it back on. I’ve still got floaters, the blood takes months to resorb. The retinal surgeon has looked at my other eye, and it’s fine at present. I see him again in March (3 months from the last visit) and I expect it to be 6 months after that for the next check. I will keep an active referral going in case the other eye behaves the same – if I phoned I expect to go straight down, same day. As we discussed, they are the same age and it’s an ageing thing. You are just supposed for only the jelly to come adrift, it isn’t supposed to take a bit of retina with it. I saw the jelly bit go, then I recognized the complications a week or so later. I’m hoping the other eye just does the normal thing.

Glad that it’s stable :)

SCIENCE said:

at least now we can run around in circles of confusion

You would be a lot better off in the circle of least confusion really.

That’s a neat trick. It could have been useful in town today.

‘70 more coronavirus cases confirmed on Diamond Princess cruise ship
By North Asia Correspondent Jake Sturmer and Yumi Asada in Yokohama with wires

Posted about 4 hours ago | Updated about an hour ago

Nearly 10 per cent of the people on board the Diamond Princess cruise ship are now known to have coronavirus, with the total now sitting at 355.’

I bet someone makes a movie out of this.

Probably won’t bear any resemblance to the facts, but that’d hardly be a first.

captain_spalding said:

’70 more coronavirus cases confirmed on Diamond Princess cruise ship
By North Asia Correspondent Jake Sturmer and Yumi Asada in Yokohama with wires

Posted about 4 hours ago | Updated about an hour ago

Nearly 10 per cent of the people on board the Diamond Princess cruise ship are now known to have coronavirus, with the total now sitting at 355.’

I bet someone makes a movie out of this.

Probably won’t bear any resemblance to the facts, but that’d hardly be a first.

Wrong thread. (sigh)

buffy said:

A recognized fast triage method for “I can’t see clearly!” is to get the person to look through a pinhole. If that clears up the vision, it’s refractive – they need their glasses, or updated glasses or whatever. If the pinhole makes no difference you start looking for disease/damage etc to the bits of the eye. Generally starting with the cornea at the front and working back through the anterior chamber, lens, vitreous and then retina.

For example, when I had the horseshoe tears that busted little blood vessels inside my eye, the blood was in my line of sight, so obscuring vision. Pinhole didn’t make a difference. But at the same time, if I moved my eye, I could “swish” the blood out of the way and get momentary good central vision – so I knew my macula was still intact and I didn’t have a macula-off retinal detachment. A little knowledge can be a good thing. And nearly 40 years of optometry meant I also knew that pit of the stomach fear of knowing what could go wrong.

Thanks for that. Yes, pinhole for refractive problems only. And I just checked, closed fist works for left eye (refractive) but not for right eye (macular).