Retina Problems Associated with Glaucoma
Chat Highlights
November 21, 2001

Norma Devine, Editor

On Wednesday, November 21, 2001, Dr. Arch McNamara, a retina specialist at Wills, and the glaucoma chat group discussed "Retina Problems Associated with Glaucoma."

Moderator:  Good evening Dr. McNamara.  Can you tell us a little about yourself before we start?  

Dr. Arch McNamara:  Good evening, folks.  I am an old hand at computing , but a newbie at chat rooms!   I am a retina specialist at Wills Eye Hospital.  I am involved in both medical and surgical problems of the retina.

Moderator:  What kind of retina problems do you see in some glaucoma patients?

Dr. Arch McNamara:  For starters, retinal diseases can co-exist with glaucoma unrelated to the underlying glaucoma.   For instance, many elderly glaucoma patients have associated age-related macular degeneration.  Cystoid macular edema (CME) is a vexing problem that can occur after any kind of intraocular surgery, such as trabeculectomy.

Moderator:  What is cystoid macular edema?

Dr. Arch McNamara:  Cystoid macular edema is a swelling in the retina.  In particular, it affects the center of the retina and causes decreased vision and distortion.  One cause is low-grade inflammation after surgery.  We try to manage it with anti-inflammatory medications.

P:  Is there supposed to be a gap between the hyaloid membrane and the retina?  If so, would cystoid macular edema cause a synechiae causing the membrane and the macula to attach?  

Dr. Arch McNamara:  The hyaloid (another word for vitreous) membrane is directly apposed to the retina in  youth. As we age, the vitreous degenerates and the posterior (back) hyaloid (vitreous) membrane often separates from the surface of the retina.  CME would not be associated with any synechiae.

P:  Are you saying that the vitreous is smack dab against the retina?

Dr. Arch McNamara:  Yes, the vitreous is up against the retina.

P:  Can folds in the retina be fixed? 

Dr. Arch McNamara:  Folds in the retina are tough to fix.  It depends on where the folds are, what is causing them, and whether or not they pose a visual threat.  

P:  Are retinal folds caused by the low pressure of hypotony difficult to fix?

Dr. Arch McNamara:  Yes, they present a real problem. The main problem is the hypotony itself.  If the pressure can be normalized, the folds should resolve, if they have not been present too long.

P:  Is there a solution to long-standing residual folds in the retina due to hypotony?  Will the vision remain distorted forever?   

Dr. Arch McNamara:  I regret to say that if the pressure has been normalized and the folds resolved, but the vision is still decreased due to macular problems (chronic retinal pigmentary changes), then the vision may not improve.

P:  After hypotony, if the IOP is normal, but some folds remain, what IOP would be needed to get rid of the folds? 

Dr. Arch McNamara:  That's a tough questions.  Folds should not really be present with IOPs greater than about 10 mm Hg.  It is important to rule out associated cystoid macular edema, which may be treatable.

P:  Do glaucoma and retinal tears go hand in hand?  How effective and long-lasting is it to use laser to repair a torn retina?  

Dr. Arch McNamara:  Glaucoma and retinal tears are not directly related.  Laser should permanently repair a torn retina.

P:  By what mechanism can miotics such as pilocarpine cause retinal detachments? Are there any particular types of glaucoma patients who are at higher risk for this side effect?  And what can be done about it?  

Dr. Arch McNamara:  The exact mechanism of the increased incidence of retinal detachment with miotics is not fully understood.  It is assumed that the forward displacement of the ciliary body causes traction on the retina,  which can cause retinal holes and hence retinal detachment.  Myopic glaucoma patients may be at greater risk for this complication.

P:  The IOP (intraocular pressure) in my left eye had gone up to 45 mm Hg.  I had had two trabs (trabeculectomies) and other procedures in that eye.  There was doubt about whether there was room for another trabeculectomy.  A specialist I consulted in another town used needling to open one of the old trabs.  First, however, he had sent me to a retina specialist, who said there was room for a shunt, rather than a trab.  Can you explain that?

Dr. Arch McNamara:  I am not sure why the retina doctor would make that determination.  The available area at the limbus would seem to be the determining factor, and the glaucoma. specialist could make that decision.

P:  Is it difficult to assess the retina in a glaucoma patient?  

Dr. Arch McNamara:  No, that is not difficult.  However, if the patient is on miotic drops (e.g., pilocarpine), the exam is more challenging since the pupil is small.  One can usually still get a good exam.

P:  I'm 53, with moderate lattice degeneration, and a family history of retinal detachment (father).  I am trying to weigh the risk of using pilocarpine regarding retinal detachment.  How would one assess the amount of  risk?

Dr. Arch McNamara:  There are so many new drugs to manage glaucoma these days that, i

n your case, I would try to stay away from using  miotics.  

P:  What is lattice degeneration?

Dr. Arch McNamara:  Lattice degeneration is a thinning of the peripheral retina. It is more common in myopic (near-sighted) people. It's present in about 7% of the population. The thinning can lead to holes and tears in the retina, which can lead to retinal detachment.

P:  I have been on pilocarpine for 12 years and have some lattice degeneration.  Would it be safe to say that if  I've had no retinal detachment it's okay for me to use this miotic?  

P:  What precautions should be taken for someone with lattice degeneration  to prevent retinal detachment?

Dr. Arch McNamara:  Avoiding miotics is a good start.  It is important to know the symptoms of retinal tear and detachment:  flashes, floaters and a peripheral visual field defect.  Avoiding direct trauma is also important.

P:  I've really been looking forward to this chat, Dr. McNamara.  I know a lot of glaucoma patients have worse problems than I do, but it's frustrating to see well before surgery and not see well for so long afterwards!  I had a trab in April, followed by two small bleb leaks and hypotony which cleared up fairly quickly.  However, now I have a lot of distorted vision in that eye.  

Dr. Arch McNamara:  No retinal pathology?  Did you have a fluorescein angiogram to check for, say, cystoid macular edema?

P:  A retinal specialist did a fluorescein angiogram,  and said my retinas are perfect.  But I see wavy vertical lines and jagged horizontal lines.  A circle is indented on the right side.   

Dr. Arch McNamara:  Perhaps there is some other explanation, such as a corneal problem or incipient cataract.  

P:  I have the beginning of a cataract in that eye, but the doctor  doesn't feel there's enough of it to be contributing to any vision problems.  I do have small dellen on the cornea.  

Dr. Arch McNamara:  Perhaps the combination of the small cataract and irregular astigmatism from the dellen may be ganging up on you.

Moderator:  I had an emergency pars plana vitrectomy (PPV) for aqueous misdirection.  Can you explain how a pars plana vitrectomy helps aqueous misdirection?  

Dr. Arch McNamara:  In aqueous misdirection, the fluid in the front of the eye is not allowed to drain through the normal channels (the angle) and builds up in the vitreous cavity, causing high pressure.  During a pars plana vitrectomy, instruments are inserted behind the cornea and into the cavity of the eye. The instruments are used to remove the vitreous gel and perform other necessary manipulations inside the eye.  The vitrectomy removes the fluid (the vitreous),  and re-establishes the proper drainage into the front of the eye.

Moderator:  I had a lot of pain after the PPV.   Why do you think that happened?

Dr. Arch McNamara:  I am not sure why you had pain after your PPV.  It is usually not so painful. Perhaps the pressure was persistently elevated in the post-op period.

Moderator:  The doctor said I was in a ciliary spasm.

Dr. Arch McNamara:  That is a possibility.  We can't see it to diagnose it, but if all else seems normal, then it's likely.  Cycloplegic drops (e.g., atropine) usually help ciliary spasm and that's why we usually prescribe it after some intraocular surgeries.

P:  Can HRT (Heidelberg Retinal Tomography) be used to diagnose retinal problems?

Dr. Arch McNamara:  There are exciting developments in the use of HRT for retinal disease. Very high-quality retinal imaging can be obtained,  and videoangiography is becoming very popular as a research and clinical tool.

P:  Would an HRT be better than a fluorescein  angiogram (FA)? 

Dr. Arch McNamara:  We have decades of experience with fluorescein angiograms, so it remains the gold standard.  As we gain more experience with technologies such as HRT, standard FA may be replaced.

P:  What can you tell us about vitamins and macular degeneration?

Dr. Arch McNamara:  Results of the Age-related Eye Disease Study were just published.  Briefly, it was an eight-year study concerning the use of nutritional supplements and the eye.  Patients with moderate "dry" age-related macular degeneration were found to have a lowered incidence of progression of their disease if the supplements in the study were used.

P:  What supplements were used in the study?

Dr. Arch McNamara:  Vitamins C, E and beta-carotene, and the minerals zinc and copper.

Moderator:  Will vitamins help "wet" macular degeneration?  Is  macular degeneration hereditary?  

Dr. Arch McNamara:  Vitamins will not help "wet" AMD.  It's too late.  There are hereditary aspects to AMD, but we do not fully understand them yet.

P:  Are you familiar with Berson's work using 15,000 IU (international unit) q.d. (every day) of vitamin-A to treat retinitis pigmentosa?  If so, can you explain why it was considered controversial and is this still the case?  I believe the progression of the disease seemed to be slowed by this treatment in those patients who weren't already too far advanced. 

Dr. Arch McNamara:  Dr. Berson's work remains somewhat controversial and a lot of experts in the field of hereditary retinal diseases do not recommend vitamin-A.  The disease itself was not noted to be slowed, but rather the progression of electroretinographic changes, which may not parallel the activity of clinical disease. The side effects of long-term, high-dose vitamin-A may be significant.

P:  Do eye exercises help?  

Dr. Arch McNamara:  In ophthalmological circles, eye exercises are not felt to be of any significant benefit.

P:  Sometimes I feel angry to have been kept on five glaucoma medications for over 20 years.  I never had a drug holiday, to see if I need so many drops. Do you blame me for being bewildered, doctor?  

Dr. Arch McNamara:  No, I sure don't blame you. Of course, I do not know the details of your case, but it is always prudent to manage any illness with the least medication necessary.

Moderator:  Thanks, Dr. McNamara, for all your help tonight.  Happy Thanksgiving from all of us. 

Dr. Arch McNamara:  Thank you! And thank you, too, for inviting me into your "room".   Wow!  You guys are lively!   Good night.  Happy Thanksgiving everyone!

Note:  Dr. Rick Wilson stopped by to thank Dr. McNamara and to wish everyone a happy Thanksgiving.  We were sorry to learn that Dr. Rick's 96-year-old father, who had Alzheimer's disease, had died.  Dr. Rick 's mother had died just three months ago. 

End of highlights for November 21, 2001.

On November 28, Dr. Spaeth joined the glaucoma chat support group to discuss "Diagnosing Glaucoma and Treatment Goals." Click here for highlights of that meeting.

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