Examining, Grading and Treating the Anterior Chamber Angle
Chat Highlights
December 4, 2002

Norma Devine, Editor

On Wednesday, December 4, 2002, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Examining, Grading and Treating the Anterior Chamber Angle."

Moderator:  Welcome, Dr. Wilson.  Tonight our topic is "Examining, Grading and Treating the Anterior Chamber Angle."  Can you first tell us what the  difference is between the anterior chamber and the posterior chamber?

Dr. Rick Wilson:  The anterior chamber of the eye is the part of the eye in front of the iris.  The posterior chamber is behind the iris, but in front of the lens.  The posterior segment is everything behind the lens.

Moderator:  Do you look at the posterior chamber when grading the anterior chamber?

Dr. Rick Wilson:  No.  The posterior chamber can't be seen, because it is behind the iris.

Moderator:  Where is the angle and what is its function?  

Dr. Rick Wilson:  The angle is the angle between the inside of the cornea and the front part of the iris.  The only function of the "angle" is to try to decide if the iris is too close to the drain (trabecular meshwork) and might get caught in it.  The trabecular meshwork is on the inside of the cornea, just in front of the iris.

Moderator:  How do you examine the anterior chamber angle?  Can you see with the naked eye if the angle is open or closed or do you need special equipment to see it?  

Dr. Rick Wilson:  Light from the angle gets internally reflected by the cornea and cannot be seen from outside the eye.  To see the angle, we use a lens on the eye with a mirror that changes the direction of light coming back from the angle. 

Moderator:  Does angle closure refer to the anterior chamber, the posterior chamber, or both? 

Dr. Rick Wilson:  Only to the anterior chamber

Moderator:  How do you grade the angle? 

Dr. Rick Wilson:  Most ophthalmologists grade the angle by the degrees between the plane of the iris and the plane of the inside of the cornea.  At Wills, we add the level of the inside of the eye that the iris inserts into, which is the A to E scale.

Moderator:  A is good?

Dr. Rick Wilson:  A is the worst, because it is the most anterior.  E is the deepest angle, although D is also normal, and, for many, also C. 

Moderator:  Would an open-angle glaucoma patient have grade E?

Dr. Rick Wilson:  Yes, but the patient could also have a D or C.  B means the iris inserts into the trabecular meshwork, and A means the iris inserts anterior to the trabecular meshwork.  Both B and A mean the angle is closed.

Moderator:  At what grade does treatment need to be started?

Dr. Rick Wilson:  Usually when the iris is in touch with the trabecular meshwork or comes quite close, especially when the pupil is dilated.

P:  How can a narrow angle be opened?

Dr. Rick Wilson:  Making a hole in the iris with a laser, or surgically, relieves the fluid pressure behind the iris and allows it to fall back, opening the angle.

Moderator:  What kind of treatment is the first option?  Are there different types of lasers to treat narrow or closed angles? 

Dr. Rick Wilson:  Almost everyone uses a Nd:YAG laser to make a hole in the iris to equalize the pressure behind the iris and in front of it, so the iris is not ballooned forward.

Moderator:  How does ALT (argon laser trabeculoplasy) differ from Nd:YAG laser?

Dr. Rick Wilson:  Argon laser trabeculoplasty is used for open-angle glaucoma.  In regard to making a hole in the iris or to keep the angle open, a laser works well.  As a rule, trying to lower IOP with an argon laser trabeculoplasty is not successful.

P:  I was told ALT (argon laser trabeculoplasty) may not work for me because my angle is somewhat narrow.  What does that mean?

Dr. Rick Wilson:  It might be very hard to thread the laser down the narrow angle onto the trabecular meshwork.

P:  Does pilocarpine open the angle?

Dr. Rick Wilson:  In most people, it narrows the angle slightly, but pulls the iris further away from the trabecular meshwork.

P:  What is a flat anterior chamber?

Dr. Rick Wilson:  A flat anterior chamber occurs when all the fluid in the anterior chamber is gone, and the iris and lens are pushed up against the cornea.

P:  Is a flat anterior chamber a common complication of glaucoma filtering surgery?

Dr. Rick Wilson:  Before the use of releasable sutures and laserable sutures, a semi-flat anterior chamber occurred about 3% of the time.  Now a flat chamber is unusual, but still occurs. 

P:  Does the appearance of the angle change after a trabeculotomy, and if so, in what way?  Can an ophthalmologist tell if a patient has had a trabeculotomy without knowing the patient's history?  

Dr. Rick Wilson:  There should be a hole in the wall of the eye with a little flap on top of it.  The hole is usually quite visible from the inside.

P:  How is the anterior chamber affected by aphakia (no lens)?  Also, does the vitreous tend to move forward, interfering with the functioning of the anterior chamber?

Dr. Rick Wilson:  The removal of the lens makes a lot of room in the front of the eye.  Removal of the lens is only a suspected cause of angle closure in children.  In adults, the iris usually falls back and opens the angle.  If the vitreous moves forward and blocks the pupil so that fluid made in the back of the eye cannot get into the front, the iris can still be pushed forward to block the angle and drain.

P:  Do peripheral anterior synechiae (PAS) cause closed-angle glaucoma? 

Dr. Rick Wilson:  Peripheral anterior synechiae are where the iris is scarred anteriorly over the drain.

P:  Can PAS be treated or is it permanent?

Dr. Rick Wilson:  Peripheral anterior synechiae can be mechanically lysed (disintegrated), but in most cases that is not done if medicines can adequately control the IOP.

Moderator:  Can peripheral anterior synechiae cause a blind spot?

Dr. Rick Wilson:  No, they are just a little spot where the iris is scarred to the trabecular meshwork.

P:  What does it mean that the iris is scarred to the trabecular meshwork? 

Dr. Rick Wilson:  The anterior surface of the iris is plastered to the inside of the trabecular meshwork and scarred there.

P:  In ICE (iridio-corneal) syndrome, is PAS the cause or the result of angle closure?

Dr. Rick Wilson:  PAS is the angle closure, so it is not really a chicken or egg sort of thing.

P:  Does aqueous misdirection play a role in the development of angle closure and flat anterior chamber?

Dr. Rick Wilson:  In aqueous misdirection, the fluid that the eye makes gets directed posteriorly, instead of anteriorly, into the anterior chamber.  The pressure builds up in the back of the eye, pushing everything forward, flattening the chamber.

Moderator:  In aqueous misdirection are both chambers closed?

Dr. Rick Wilson:  The front chamber is collapsed.  There may still be a little posterior chamber.

Moderator:  Can angle-closure glaucoma be cured?

Dr. Rick Wilson:  Yes, if caught early enough it can be cured and usually is.

Moderator:  What is the difference between acute angle-closure and chronic angle-closure?  Is the chronic form more difficult to treat?  Is the angle more likely to be scarred shut?  

Dr. Rick Wilson:  Acute angle-closure comes on suddenly, usually with the entire angle closed.  Chronic angle-closure usually comes on more slowly, and the entire angle may not be closed.  Acute-angle closure is more easily opened than chronic-angle closure.  Acute-angle closure will result in scarring of the iris to the drain if not treated.  

Moderator:  When does surgical intervention become necessary for someone with angle-closure glaucoma?

Dr. Rick Wilson:  When the pressures cannot be controlled with laser and medications.

P:  If the laser treatment making a hole in the iris only worked a little, can this be repeated or do I need surgery?

Dr. Rick Wilson:  If the hole is open, another laser treatment usually will not help.

P:  Is there any correlation between angle widths and IOPs, assuming the narrower angles remain open?

Dr. Rick Wilson:  No.

Moderator:  Does it make a difference when considering laser surgery if  the patient has uveitis? 

Dr. Rick Wilson:  Yes, the iris may be swollen and inflamed, with dilated vessels leading to more bleeding and inflammation afterward.

P:  How many degrees around the circumference of the iris is a peripheral iridectomy?

Dr. Rick Wilson:  A peripheral iridectomy is quite small, usually 50 to 100 microns and done from the 10:30 to 1:30 o'clock position under the upper lid.

Moderator:  The following question is from a patient who could not be here:  "I have acute angle-closure glaucoma in my right eye and have had two surgeries on that eye.  I have been told I probably will have more damage later to that eye from high intraocular pressure.  Are the chances high that I will completely lose my sight, as if I had primary open-angle glaucoma?"

Dr. Rick Wilson:  Clearly, anything I say in this case is total conjecture, since I can't examine the patient and am going on what the patient understood her or his doctor chose to tell her or him. There is usually not a definite reason for visual loss to be progressive unless the cataract progresses.  With good care, the loss of most of vision seems unlikely.

P:  How common is primary angle-closure glaucoma in the United States?

Dr. Rick Wilson:  It accounts for five to ten percent of the glaucoma cases in the U.S.  It is most prevalent in those over age 40.  Acute angle-closure glaucoma, which is most common between 55 and 65 years of age, can also occur in older people and children.  Acute angle-closure glaucoma is uncommon in blacks, but chronic-angle glaucoma is common.  The prevalence of primary angle-closure glaucoma may be similar for both races.

P:  Does acute angle-closure occur more often in men or in women?

Dr. Rick Wilson:  Women of all races develop acute-angle closure three to four times more often than men.  Women have shallower anterior chambers than men.  Two thirds present with no symptoms.

P:  I’ve heard angle-closure is more common in East Asians and Eskimos. Is that right?

Dr. Rick Wilson:  Yes. The prevalence is 1.4% in Chinese and 2.65% among the Inuit Eskimos. Open-angle glaucoma is relatively uncommon among the Inuit but somewhat more common among the Chinese.

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

End of highlights for December 4, 2002.

On December 11, Dr. Wilson discussed "Surgical Options in Glaucoma Care" in the Chat room. Click here for highlights of that meeting.

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