Diagnosing Glaucoma and Treatment Goals
Chat Highlights
November 28, 2001

Norma Devine, Editor

On Wednesday, November 28, 2001, Dr. George Spaeth, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Diagnosing Glaucoma and Treatment Goals."

Dr. George Spaeth:  Hi, all.

Moderator:  Welcome back,  Dr. Spaeth.  Can you tell us what diagnosing glaucoma involves?

Dr. George Spaeth:  Sure.  The most important thing is to determine if any damage has occurred.  You determine damage by looking at the anterior chamber angle or the optic nerve.  Which shall I discuss?

Moderator:  The anterior chamber first;  then the optic nerve.  How do you look at the anterior chamber angle?

Dr. George Spaeth:  You put a contact lens on the eye and use a microscope.  It is an essential part of any exam related to diagnosing glaucoma.  The angle determines how the pressure is controlled.  The aqueous (fluid) leaves via the angle.  If the meshwork gets blocked or is defective, the IOP (intraocular pressure) goes up.

P:  What is the function of the contact lens in checking the anterior angle?

Dr. George Spaeth:  It allows looking into the angle.  Without that, a doctor can't see the angle.  The most common cause of blindness in the world is angle-closure glaucoma, so it essential to be able to see the angle.  Different types of glaucoma can be diagnosed on the basis of the angle: neovascular glaucoma, exfoliation glaucoma, pigmentary glaucoma, Chandlers syndrome, and many more.  Since the treatment is different for the different types of glaucoma, the type of glaucoma needs to be determined.

Moderator:  Can the IOP be okay if the angle is closed?

Dr. George Spaeth:  Not usually.  Only in really, really sick eyes.  If the angle is closed, then the aqueous has to be getting out somewhere or the pressure can't be normal.  The angle controls the pressure, so being able to see the angles is essential to a correct diagnosis. 

P:  My angle is closed, my trabeculectomy is not working, my pressures are still okay, and my optic nerve looks good.  Could the fluid be backing up elsewhere in the eye, like in between layers?

Dr. George Spaeth:  No.  That would just make the pressure increase.  The fluid has to be getting out.  

P:  What is open-angle glaucoma?

Dr. George Spaeth:  In open-angle glaucoma, the trabecular meshwork is not blocked by the iris, blood or something else.  

P:  If the angle is open, and there is no obvious source of blockage (pigment, etc.), does it still appear differently in glaucomatous eyes?

Dr. George Spaeth:  Remember that "glaucomatous" can mean about 100 different things.

P:  I was examined by a doctor at Wills, but I do not remember a contact lens being inserted for an examination of the angles.

Dr. George Spaeth:  If the exam is not for glaucoma, then looking into the angle is not always done.

P:  What is the most important part of making a glaucoma diagnosis?

Dr. George Spaeth:  The most important thing is a careful history, a really careful history.  The second thing probably is looking into the angle and looking carefully at the nerve. 

P:  If there is a specific cause of blockage of the meshwork or the angle, is that treatable in a certain way?

Dr. George Spaeth:  That's the whole point!  You need to know what is causing the pressure elevation to determine how to treat.

P:  Isn't the contact lens different from the usual kind?  Is it a taller cylinder held on the eye?

Dr. George Spaeth:  The contact lens is small, and that part of the exam takes about one minute.  

P:  Is the contact lens inserted or merely held in front of the eye while the doctor looks through an instrument?

Dr. George Spaeth:  The contact lens touches the eye.

P:  If gonioscopy is performed with dilation, will that reverse the effects of a miotic the patient has used so the angle can be visualized in something close to its normal physiological state?

Dr. George Spaeth:  Yes and no.  Dilating the pupil pulls the lens back and deepens the angle.

P:  How about in an aphakic eye?

Dr. George Spaeth:  In an aphakic eye, the angle usually is not much affected by either miotics like pilocarpine or by dilating eye drops.  

Moderator:  Is gel put on the contact lens?

Dr. George Spaeth:  In the old-fashioned way, yes.  No gel is used with newer methods.  

Moderator:  Okay.  We know the angle is important to making a diagnosis.  How about the optic nerve?  

Dr. George Spaeth:  The angle tells you what type of glaucoma you have; the optic nerve tells you whether you have glaucoma.  

Moderator:  So you can have a closed angle and no visible optic nerve damage and NOT have glaucoma?

Dr. George Spaeth:  Yes, you can have a closed angle and not have glaucoma damage.  You can have an IOP of 10 mm Hg and have glaucoma.  You can have an IOP of 50 mm Hg and not have glaucoma.

P:  How important is the cup-to-disc ratio?

Dr. George Spaeth:  According to the new glaucoma terminology just published by the European Glaucoma Society, the cup-to-disc ratio is almost worthless.  The helpful signs are an acquired pit of the optic nerve (most helpful), a notch, or documented narrowing of the (neuroretinal) rim.  Asymmetry between the nerves is suggestive.

P:  Does ocular hypertensive mean the IOP is elevated?

Dr. George Spaeth:  Ocular hypertensive means IOP of over 21 mm Hg.  

P:  If the optic nerve is not damaged and the visual field is okay, is an IOP of 25 to 30 mm Hg okay or is it a risk?  

Dr. George Spaeth:  There are three things you need to know before you can even start thinking about treatment:  (1) the stage of the disease, (2) the rate at which the damage is worsening, and (3) how long the person will live.

P:  How do you make the decision when to treat if, for instance, the IOP is in the 30's, but there is no optic nerve damage?

Dr. George Spaeth:  Let's say, (1) early glaucoma, (2) getting worse rapidly, (3) a life expectancy of 50 years (the person may well need surgery).

P:  There are plenty of "glaucoma suspects" that are being treated with medicines and procedures.  I read in a chat highlight that you think if there's no optic nerve damage, there's no glaucoma.  How prevalent is that definition in the field of ophthalmology?  That is, do all ophthalmologists know that, and agree with it?

Dr. George Spaeth:  Wow!  Now we are really getting there.  The only reason to treat an ocular hypertensive is if the pressure is high enough (say 50 mm Hg or so) that it may cause rapid damage, or to prevent other damage, such as a retinal vein occlusion.  Otherwise, it usually makes sense to wait until you are sure there is some damage actually developing. 

P:  Do you always wait to treat until you have determined the rate of progression?

Dr. George Spaeth:  If the damage is advanced, then you don't wait for more damage.

P:  And if it is mild?

Dr. George Spaeth:  If the damage is very early and the person says, "I don't want any more damage," then you treat.  Now, let's say:  (1) early, with little damage; (2) rapidly getting worse; (3) but life expectancy of one month.   No treatment is warranted.  The goal of treatment is health.  If the optic nerve never becomes damaged to the point that the person loses enough vision that it causes problems, then the person is in good shape.

P:  Then the goal is not low pressure?

Dr. George Spaeth:  The goal is not low pressure.  The low pressure may be needed to keep the nerve from getting worse, but only when it would HURT the person if the nerve got worse.  I know I am hitting you with new thoughts about glaucoma, but they are worth pondering.

P:  In a visual field test, can it be easily determined whether the loss is from cataract or from glaucoma? 

Dr. George Spaeth:  Cataracts do affect the visual field.

P:  Isn't the pattern of visual field loss different for cataracts than for glaucoma?

Dr. George Spaeth:  Yes.  

P:  You list documented narrowing of the (neuroretinal) rim as a helpful diagnostic sign.  That requires observation over an extended period, does it not?

Dr. George Spaeth:  Yes.  That's why photos are important.

P:  Are there any circumstances, such as amblyopia or other profound visual acuity problems, that would alter your feelings about early treatment in ocular hypertension?

Dr. George Spaeth:  If there are other problems present that complicate the evaluation of the nerve or the field, then you have to use pressure as a guide.  Yes, then you need to treat more vigorously. 

P:  It has been said that 90% of ocular hypertensives never develop optic nerve damage.  Are the statistics the same for middle-aged and younger ocular hypertensives in generally good health?  Can 90% of this group expect to live the rest of their lives without significant damage to the optic nerve, or is it more like a 10% risk for every 10 years of ocular hypertension?

Dr. George Spaeth:  The issue is that doctors should not treat populations;  they treat individuals and every individual is unique and deserves unique care.

P:  I've had glaucoma for over 20 years.  Yesterday I saw a different doctor.  He said something I had never heard before.  He said my optic nerve shows substantial damage, my visual field is not bad (he has "seen worse"), and perhaps there is a genetic connection to the damage, not just glaucoma.

Dr. George Spaeth:  By and large, the disc and the visual field damage go together.  When they don't, the cause is usually not glaucoma. 

P:  Why isn't one of the treatment goals to try and figure out the root cause of glaucoma in someone young, with none of the risk factors?  And if blood pressure/flow may be a factor, why isn't it standard procedure to take blood pressure with each visit, along with IOP readings?

Dr. George Spaeth:  That's a good goal.  That's what genetic researchers are working on now.

P:  Would a pressure of 8 mm Hg be too low for a person using Pred Forte 18 months after a trabeculectomy?  I thought Pred Forte tended to raise the pressure.

Dr. George Spaeth:  "Too low" or "too high" depends on what was causing damage before.  If a person is not getting worse with an IOP of 30 mm Hg, that is not too high.  If a person is getting worse with an IOP of 19 mm Hg, then that is too high.

P:  Why does the old-style (1970s) cataract surgery lead to glaucoma? 

Dr. George Spaeth:  Old-style cataract surgery was not likely to lead to glaucoma unless there was a complication with the surgery,  In fact, the IOP is usually LOWER after cataract surgery.

P:  Dr. Wilson stated here that once the optic nerve becomes damaged, the amount of IOP reduction required to prevent further damage is greater than if the initial damage had been prevented.  Doesn't that argue for earlier preventive treatment (i.e., a more modest but earlier reduction in IOP) before the damage is detected?

Dr. George Spaeth:  Dr. Wilson is expressing the usual theory.  It makes sense to use caution when treating patients with damage, because they have already shown that they can get worse.  So treatment is important.  However, no evidence supports the idea that once damage has occurred it predisposes to more damage.

P:  Wouldn't the glutamate neurotoxicity theory support this?

Dr. George Spaeth:  It might.  But that is still speculative and, as you say, a theory.  What is not a theory is that most treatments have side effects and many of them are worse than the disease. 

P:  I'm being treated at Wills as a glaucoma suspect with pressures of 30-32 mm Hg but no significant optic nerve damage.

Dr. George Spaeth:  That is the usual way patients with IOPs of 30 mm Hg are handled.  It makes sense because 30 mm Hg probably predisposes you to a retinal vein occlusion.

P:  What is a retinal vein occlusion?

Dr. George Spaeth:  A retinal vein occlusion occurs when the vein that drains the blood from the eye gets blocked.

Moderator:  How is a retina vein occlusion detected?

Dr. George Spaeth:  The visual acuity usually gets worse, and the doctor sees that the vein is blocked when he or she looks in the eye. 

P:  Is there any way to prevent retinal vein occlusion?

Dr. George Spaeth:  Vein occlusions usually occur in people with bad blood vessels, so keeping the blood vessels healthy is the number one prevention.

P:  What is a secular iridectomy?  Would that have something to do with causing glaucoma?

Dr. George Spaeth:  A sector iridectomy is a wedge cut out of the iris.  It cannot cause glaucoma.  

P:  Is a sector iridectomy always done during a trabeculectomy?

Dr. George Spaeth:  No.  A peripheral iridectomy is usually performed during a trabeculectomy.  A piece, not the the entire sector, is removed from the iris.

P:  If a section of iris removed during a trabeculectomy is too large, could that precipitate hypotony?

Dr. George Spaeth:  No.  

P:  Why are sector iridectomies performed?  Were they done instead of the peripheral iridectomies before laser surgery became available?  

Dr. George Spaeth:  Sector iridectomies were done in the past because they could be done.  Peripheral iridectomies became possible when surgical techniques improved.  Also, sector iridectomies made it easier to see into the eye.  

Moderator:  Can you be certain that the optic nerve is damaged in a patient with nanophthalmic (dwarf) eyes?

Dr. George Spaeth:  It's thought that such a nerve is so small that it can be damaged without showing it. 

P:  I have a history of borderline to high IOPs (25 to 33 mm Hg) for four years.  Are visual field tests still indicated to complete the screening process?

Dr. George Spaeth:  By all means, in such circumstances, visual field tests are important.  

P:  The cataract implant in my good eye is becoming cloudy.  My specialist says that if we use the laser treatment, the pressure will probably rise.  My glaucoma has become very stable so I am concerned.

Dr. George Spaeth:  That is a real concern.  The simple laser treatment used to open a capsule can cause the IOP to rise.  IF such a rise is a danger, you want to be sure you really need the capsulotomy. 

P:  What is the significance of papillary atrophy?

Dr. George Spaeth:  Peripapillary atrophy is atrophy around or beside the nerve.  There are some correlations with peripapillary atrophy and the presence and severity of glaucoma.

P:  What is the significance of blood spots on the optic nerve?

Dr. George Spaeth:  It's a bad sign.  It usually means the glaucoma is getting worse.

P:  Do people who do not have glaucoma have disc hemorrhages?

Dr. George Spaeth:  Very rarely.  Disc hemorrhages occur with posterior vitreous detachment, too.

P:  In steroid-induced glaucoma, does the glaucoma continue after the use of steroids is stopped?

Dr. George Spaeth:  Steroid glaucoma never -- and I mean NEVER-- lasts after the steroids are stopped.  If your pressure is still up after the steroids, you had glaucoma before the steroids were used.  Steroid glaucoma is an interest of mine.  There is only one case reported (by Spiers) in which the IOP did not return to normal.  It was a messy case and probably was not steroid glaucoma. 

P:  I've noticed that the pharmaceutical industry in the past 15 years has put warnings on inhaled corticosteroids stating that systemic use might have glaucoma as a side effect.  

Dr. George Spaeth:  All kinds of steroids can cause temporary elevation of IOP.  

P:  I just had a GDx exam.  I wondered if the infrared laser can damage your eyes if the technicians are not as skilled as they should be.

Dr. George Spaeth:  The GDx is completely safe.  Not much help, but safe.  The Gdx has been carefully tested and the level of radiation is not damaging.  The laser light is like other light in that its ability to damage varies.  Some infrared lasers can cause huge explosions, while others cause no damage at all.

P:  Why is the GDx not useful?

Dr. George Spaeth:  Because it has low specificity.  An abnormal test does not mean you are abnormal;  a normal test does not mean you are normal.

Moderator:  Thank you for all the help, Dr. Spaeth.

Dr. George Spaeth:  You're welcome.  Good night, all.

Illustrations Copyright 2003 Tim Peters and Company, Inc. Peapack NJ 07977 USA. All Rights Reserved. www.timpetersandcompany.com

End of highlights for November 28, 2001.

On December 5, Dr. Werner joined the glaucoma chat support group in the Chat room to discuss "Cataracts and Glaucoma." Click here for highlights of that meeting.

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