Glaucoma questions

[rppa]

I've just had rather a scary eye exam. This isn't precisely news, as potential problems with my optic nerve were first picked up a year ago and that's why I was scheduled for this imaging in the first place.

Nevertheless, it wasn't very reassuring for the opthalmologist yesterday to tell me my images were "alarming", even after she told me there was nothing to do about it at this point and I shouldn't worry.

So here's the question: the problem is with "cup to disk ratio" on the optic nerve. I tried to get her to explain anatomically what I was looking at, what a large cup meant, what the "cup" was in terms of the optic nerve. But all she could say was that a large cup meant glaucoma.

She also told me that some people are just born this way, and that's why she needed to follow me for 4-5 years to see whether there's any changes going on. Also, I am severely myopic and I read something on the web last night that said that a large cup can be associated with myopia and be otherwise harmless.

So can somebody explain it to me? What is the cup in terms of the functioning of the optic nerve? Does that indicate detached nerve ends, and the only functional part of the nerve is at the edges of the disk? Does that mean I've already lost 80% of my visual field or so (my own estimate of the relative areas; she didn't give me a number)? But if so, then how can a large cup be benign? My visual field doesn't look like 80% of it is missing.

By the way, all other tests including pressure are normal, and I'm 48, early for glaucoma.

 

[Jyera]

Hi rppa,

I have recently been concern with vision as well.

And found this link
http://www.visionsimulator.com/default.asp
Click on Glaucoma and see the simulation.

I thought it would be useful to share it.

Have you seen it?

Any useful link on Glaucoma ?

 

[Iamme]

rppa---Why didn't you ask the opthamologist? She knew all the terminology. Why wouldn't she know enough to answer your questions? She would know best because SHE is the one who examined you. Call her up. Tell her your concerns, and then talk technical.

 

[John Bentley]

rppa

Just to make sure we're talking about the same thing:
1: When you say you are severely myopic, do you mean you can see things close to your face well, but everything further than basically the length of your arm is a hopeless blur? Just making sure that you're using the terminology correctly before speculating.

2. Have you been myopic all your life, or was this something that developed after you were an adult?

 

[Jyera]

rppa---Why didn't you ask the opthamologist? She knew all the terminology. Why wouldn't she know enough to answer your questions? She would know best because SHE is the one who examined you. Call her up. Tell her your concerns, and then talk technical.

Your presumption here is that the opthamologist is competent.
But not ALL opthamologist are equal. It is good to have the answers and then ask the question to see if the opthamologist knows her stuff.

If she find that the patient is knowledgable, she'll likely ensure she is more knowledgable. When the patient demostrate knowledge, the opthamologist might also be a little more willing to discuss more, as she'll trust that her "technical" discussion will be short sweet. Otherwise, technical explanation and jargon might only serves to worry you.

 

[Jyera]

...snipe...
Nevertheless, it wasn't very reassuring for the opthalmologist yesterday to tell me my images were "alarming", even after she told me there was nothing to do about it at this point and I shouldn't worry.
... snipe...

I'd find this uncomfortable as well.
However if we allow the doctor or opthamologist to give such advise, I seems to justify people like homeopath or Naturopath ti do the same.

 

[rppa]

Your presumption here is that the opthamologist is competent.

She is. I trust her. My wife is under treatment from her for a long-standing problem that no other doctor had been able to help her with.

But not ALL opthamologist are equal. It is good to have the answers and then ask the question to see if the opthamologist knows her stuff.

This is the second opinion. The condition was first picked up by another opthalmologist a couple of years ago. I came to this practice because I didn't trust the competence of the first practice.

If she find that the patient is knowledgable, she'll likely ensure she is more knowledgable. When the patient demostrate knowledge, the opthamologist might also be a little more willing to discuss more, as she'll trust that her "technical" discussion will be short sweet. Otherwise, technical explanation and jargon might only serves to worry you.

This is a chronic problem I have in discussions with all doctors. They don't seem to be equipped to have technical discussions with patients.

I've also validated what she told me on health sites on the internet. But those too, talk down to the patient. Nobody is addressing the technical, anatomical questions I want to know.

Frustratingly, so far nobody here on this site is doing so either. Is there another forum I might look at? I don't want to talk about doctor-patient relationships, I want to talk anatomy. I know we have considerable biological and medical expertise on this board. Doesn't anybody want to discuss the PHYSIOLOGICAL issues with me?

 

[rppa]

rppa

Just to make sure we're talking about the same thing:
1: When you say you are severely myopic, do you mean you can see things close to your face well, but everything further than basically the length of your arm is a hopeless blur?

Considerably shorter than "the length of my arm". On my 14" monitor without glasses, I need to be about 18" from the screen before the large letters "JREF Forum" at the top of this page are recognizably letters, and perhaps 12" from the screen before I can read them.

2. Have you been myopic all your life, or was this something that developed after you were an adult?

Not all my life. Just since the age of six or so.

It stopped progressing for awhile when I was a teenager, but seems to be accelerating a little now. In the last couple of years I changed prescriptions more times than my vision coverage plan was willing to pay for. Plus I'm getting the normal aging effects on visioin. I've been wearing graduated lenses now for three or four years.

 

[rppa]

rppa---Why didn't you ask the opthamologist?

Perhaps you missed the part where I said I asked the opthalmologist.

 

[rppa]

Re: Re: Glaucoma questions

I'd find this uncomfortable as well.
However if we allow the doctor or opthamologist to give such advise, I seems to justify people like homeopath or Naturopath ti do the same.

No it doesn't. Non sequitur.

The reasons for this giving this particular advice on this particular condition is that, medically, it is the correct advice to give.

I have no problem with the advice. It lines up fine with the wealth of information out there from many sources. I just want some physiological information, which are lacking in those sources. I want to find the stuff aimed at the doctors and the researchers, perhaps.

 

[John Bentley]

Not all my life. Just since the age of six or so.

It stopped progressing for awhile when I was a teenager, but seems to be accelerating a little now. In the last couple of years I changed prescriptions more times than my vision coverage plan was willing to pay for. Plus I'm getting the normal aging effects on visioin. I've been wearing graduated lenses now for three or four years.

OK, so we're talking about a problem you were essentially born with. During the years when this condition was progressing, did anyone explain why it was progressing rather than remaining static? Was it considered normal aging of the lens, or was something else going on?

Generally speaking, congenital myopia is caused by the length of the eyeball (from front to back), not matching the focal length of the lens in your eye. The lens is attached by fibers to the iris. When the iris muscle is relaxed, the lens is allowed to "bulge" or become more convex. This allows light rays that are essentially parallel (coming from a distance) to be focused on the surface of the retina. If the length of your eyeball is incorrect, the image will be focused either behind or in front of the retina, causing it to be blurred. As you age, the lens becomes less pliable, and the ability to adjust the focus of the lens becomes impaired. So older people are both near sighted and far sighted at the same time. The lens focus essentially becomes "fixed" and only able to focus clearly at one focal distance.

Next topic:
The retina of mammals is wierd in its embryological development. It is essentially backwards. The cells sensitive to light are on the bottom, with the nerves that carry signals placed on the surface. Light has to pass through the nerves, and the cell bodies of the cones and rods before ever hitting the light sensitive portion of the cell. (Intelligent design? I don't think so.) Anyway, as a consequence of this arrangement, the nerves all pass across the surface of the retina, then gather at one spot on the back of the retina, pass through the retina and out the back of the eye as the optic nerve. Because the nerve fibers pass all the way from the front to the back of the retina, there are no light sensitive cells in that spot. Everyone is essentially blind in that spot, but the brain makes up for it by making you move your eye slightly when you are looking at something and then interpreting the serial images to "paint" the missing spot in with an image. Sometimes the brain is wrong and lots of semi-amusing optical illusions are based on this physiological quirk of the mammalian eye.

Finally:
The optic cup in adults is simply an invagination in the center of the optic disc. It can be benign, and most people have a small optic cup in their disc. It can be a sign of increased pressure in the eye (glaucoma). It does not necessarily mean that the nerves in the cup portion are dead or no longer functioning. It is purely statistically significant that a large cup to disc ratio means problems.

If your eye pressure is normal, then you can assume that you don't have acute glaucoma. As to whether you have visual field loss, you can have your visual fields tested to see if you have blind spots. You would not be able to tell subjectively, because the brain would simply "paint" in the missing image. The more the brain has to guess, the more likely it is to be wrong. So if you have a lot of spots on your retina that aren't working, you are much more likely to have a hard time reading, driving, etc.

 

[rppa]

Thank you for this writeup. Exactly what I was hoping for.

OK, so we're talking about a problem you were essentially born with. During the years when this condition was progressing, did anyone explain why it was progressing rather than remaining static? Was it considered normal aging of the lens, or was something else going on?

I always had the impression from knowing other near-sighted people that everybody's prescription gradually gets stronger as they age. In fact the optometrist was very surprised when it stopped progressing during my teen years. Isn't that why they want to measure you every year or so?

Next topic:
The retina of mammals is wierd in its embryological development. It is essentially backwards. The cells sensitive to light are on the bottom, with the nerves that carry signals placed on the surface. Light has to pass through the nerves, and the cell bodies of the cones and rods before ever hitting the light sensitive portion of the cell. (Intelligent design? I don't think so.) Anyway, as a consequence of this arrangement, the nerves all pass across the surface of the retina, then gather at one spot on the back of the retina, pass through the retina and out the back of the eye as the optic nerve.

OK, so where in all this arrangment is the disk and cup of the optic nerve. Obviously it's inside the eye somewhere right?

The optic cup in adults is simply an invagination in the center of the optic disc. It can be benign, and most people have a small optic cup in their disc. It can be a sign of increased pressure in the eye (glaucoma). It does not necessarily mean that the nerves in the cup portion are dead or no longer functioning. It is purely statistically significant that a large cup to disc ratio means problems.

Yet if it is changing, that is an indicator of problems. Is that just because the growth of the cup is correlated statistically with nerve damage, or is a growing cup actually something being damaged?

I've seen my pictures and compared them with pictures on the web. The size of the cup is indeed kind of alarming. It looks like the patients who are pretty advanced cases.

As to whether you have visual field loss, you can have your visual fields tested to see if you have blind spots.

Yes, I've had that test (normal) and I'm scheduled for another next week. One more thing they want to track over time.

Vision fascinates me, and at one point I studied visual processing in the brain (I once gave a talk proposing that the cortex be used as a model for computing, a year or so before people started actually building "artificial neural networks"). Yet I never got a clear picture of how things are laid out in the eye. I've seen lots of diagrams showing rods and cones, but never one relating it to the optic nerve and the blind spot as your verbal description did. I'd love to see a picture with all of that.

 

[John Bentley]

I always had the impression from knowing other near-sighted people that everybody's prescription gradually gets stronger as they age. In fact the optometrist was very surprised when it stopped progressing during my teen years. Isn't that why they want to measure you every year or so?

Yeah, that's the normal age changes I was talking about, but they are usually pretty slow during young age, and accelerate during old age.

OK, so where in all this arrangment is the disk and cup of the optic nerve. Obviously it's inside the eye somewhere right?

I really need to figure out how to scan a picture and post it here. If you know how to do that, tell me on the PM and I can show you some good pictures.

Yet if it is changing, that is an indicator of problems. Is that just because the growth of the cup is correlated statistically with nerve damage, or is a growing cup actually something being damaged?

Alas, here we pass out of my realm of expertise, and we are left with speculation. I know scads about the normal physiology of the eye, but would have to do some research about human diseases to give you a meaningful answer. (I'm a veterinarian). I'll see what I can dig up in my optho texts.

Vision fascinates me, and at one point I studied visual processing in the brain (I once gave a talk proposing that the cortex be used as a model for computing, a year or so before people started actually building "artificial neural networks"). Yet I never got a clear picture of how things are laid out in the eye. I've seen lots of diagrams showing rods and cones, but never one relating it to the optic nerve and the blind spot as your verbal description did. I'd love to see a picture with all of that.

Like I said, tell me how and I can get you some good pics.

I, too, used to do some hobby work on VLSI chips replicating the human retina. Carver Mead at Cal Tech pioneered the idea with CMOS designs. Was incredibly successful, as was his work with a "hearing chip" replicating the human cochlea. I've got his original textbooks on the subject. Too cool. I've often wondered if his work is what is used as a basis for the cochlear implants and retinal implants in people. I know his retinal designs were used in robot vision systems, but haven't seen anything on that for a long time. (No pun intended). I know at one time he was starting a project to replicate the brain one system at a time. Haven't heard from him since.