Hypotony – Low Eye Pressure

Chat Highlights
Hypotony – Low Eye Pressure
July 5, 2000
Norma Devine, Editor

On Wednesday, July 5, 2000, Dr. Courtland Schmidt and Dr. Jonathan Myers, glaucoma specialists at Wills, and the glaucoma chat group discussed “Hypotony – Low Eye Pressure.” Dr. Myers joined us for the first half while Dr. Schmidt resolved a computer problem.

Moderator: Dr. Myers, tonight the topic is “Hypotony.”

Dr. Myers: Hypotony is an excellent topic. It is terribly ironic to suffer from elevated pressure for years, and then have problems with hypotony. Most people with glaucoma have original pressures of 20 or higher. In hypotony, the pressure is too low, usually at or below five. At low pressures, the eye becomes soft enough that just blinking can distort the shape of the eye and the vision. Also, at low pressures, fluid can collect behind the retina, interfering with the vision.

P: Is there a number that defines hypotony?

Dr. Myers: Low pressures are generally below five or so, but everyone is different. Just as some eyes are more sensitive to high pressure, some eyes are more easily troubled by low pressures.

P: The trabeculectomy that caused me to have hypotony followed use of Mitomycin C, which my specialist said had affected the bleb.

Dr. Myers: Mitomycin C reduces scarring, dramatically increasing surgical success. However, it may also lead to too much of a good thing: hypotony, pressure that is too low for the eye.

P: Is reaction to surgery the only cause of hypotony, or are there others?

Dr. Myers: The most common cause of low pressures is surgery. However, sometimes glaucoma medications can contribute to abnormally low pressures. Also, trauma to the eye or inflammation in the eye may lower (or raise) the pressure.

Moderator: When the fluid collects behind the retina, does that cause wrinkles in the retina?

Dr. Myers: Fluid under the retina can cause fine wrinkles, often called hypotony maculopathy (the macula is the center of the retina).

P: Would that be cystoid macular edema?

Dr. Myers: Cystoid macular edema is fluid in, not under the retina. It has similar effects on the vision. Fluid may also collect in larger lumps in the choroid under the retina, so called serous choroidals.

Moderator: What are the usual symptoms when the pressure is too low?

Dr. Myers: Low pressure may sometimes cause no symptoms. Or it may lead first to intermittent or constant blurring of the vision, either mild or more severe. As fluid collects, the vision is constantly cloudy. Sudden bleeding (hemorrhagic choroidals) beneath the retina may occur rarely and cause sudden pain and loss of vision.

Moderator: If the patient has low pressure, what action is needed and is it an emergency?

Dr. Myers: Low pressure is rarely an emergency. Often low pressures in the early period following surgery resolve as the eye heals. Low pressure which causes a loss of fluid in the front of the eye, a so-called shallow anterior chamber, may need to be addressed immediately. Shallow chambers can be treated with injection of thicker fluids to re-inflate the front of the eye, the anterior chamber.

Moderator: Like a malignant attack?

Dr. Myers: Malignant glaucoma is a good example of a serious problem with a shallow anterior chamber. It can be triggered by a low pressure. However, with malignant glaucoma the pressure then becomes elevated out of control.

P: Will you define “malignant glaucoma” for those who don’t know? It’s a different use of the word malignant than is used in cancer, yes?

Dr. Myers: Malignant glaucoma is an awkward term for aqueous misdirection. This is a type of angle closure glaucoma in which fluid flows toward the back of the eye, and the vitreous fluid is pushed forward, shallowing the anterior chamber. This type of glaucoma is difficult to treat medically and often has pressures into the 50’s and 60’s. Half of the patients with this condition require surgery.

Moderator: How do you inflate the eye?

Dr. Myers: Sometimes lasting hypotony requires surgery to reduce the amount of fluid draining from the eye through the glaucoma surgical site. This is typically done as an outpatient surgical procedure. Stitches (sutures) are placed to tighten the flap controlling the outflow of fluid from the eye.

Moderator: What is the needle injection that people with hypotony mention?

Dr. Myers: The needle injection for hypotony involves using a TINY needle to put a thicker fluid into the anterior chamber to re-inflate the eye and raise the pressure. This may be done in the office or minor-procedure room. Often the eye responds to this injection by making more fluid, increasing the pressure, resolving the problem of low pressure. Many people have low pressures immediately following surgery. Most resolve as the eye heals. Few require injections or more surgery.

Moderator: How does the injection work? Is it true the blood comes from the arm?

Dr. Myers: Sometimes blood from the arm is injected into the bleb, the area from the surgery where the fluid filters. The blood acts as a stop-leak. It helps to block the drainage channel and increase the pressure through healing.

P: Why is it difficult to eliminate all the wrinkles from long-standing hypotony?

Dr. Myers: Sometimes, when the fluid is under the retina a long, long time, the wrinkles in the retina become fixed. The wrinkles form some sort of scar tissue that holds them there even after the pressure comes up. This leaves the vision blurred. However, most times the wrinkles clear, even if they have been there six months or more. I’ve read of cases in which such wrinkles resolved two years later.

P: Why would the wrinkles be there that long without the hypotony being treated?

Dr. Myers: Sometimes the patient and the doctor both are trying everything possible to avoid more surgery.

Moderator: What is temporal injection and what causes it?

Dr. Myers: Temporal injection is superficial inflammation on the outside of the eye. That may be caused by dryness, allergies, a scrape, or eye drop reactions. Inflammation which affects eye pressure is inside the eye.

Note: Dr. Courtland Schmidt joins the group.

Dr. Schmidt: Sorry to have crashed the computer at the wrong time. Thanks, Jon, for pitching in.

Dr. Myers: Welcome, Dr. Schmidt. We’ve been talking about treatments of hypotony. Feel free to take it from here. Glad to see your computer decided to cooperate. Good night, everyone.

Dr. Schmidt: Thanks again, Jon. Any more questions about hypotony?

Moderator: Can too low eye pressure cause permanent damage?

Dr. Schmidt: Yes, too low IOP can definitely cause permanently decreased vision.

P: Can one go for years with IOPs of three or four with no adverse effects?

Dr. Schmidt: Some people can see 20/20 with a pressure of zero to one.

P: Really? Under what circumstances?

Dr. Schmidt: Usually, older people tolerate low pressure better.

P: How long after filtering surgery with anti-metabolites can bleb leaks and hypotony occur?

Dr. Schmidt: Bleb leaks can occur any time, early or late, even if no anti-metabolites were used.

P: Does hypotony only result from surgical intervention? Can you get it from “overdosing” with drops?

Dr. Schmidt: It is extremely rare to get too low an IOP using eye drops. We might see it once a year.

P: What fluid is used to put a thicker fluid into the anterior chamber to re-inflate the eye?

Dr. Schmidt: There are several viscous fluids, made of various substances, that can be used to re-inflate the anterior chamber, such as Healon, Viscoat, and Amvisc.

P: Are any of those silicone? I’ve heard of liquid silicone being used in eyes.

Dr. Schmidt: No, those are not silicone. That is used after retina or vitreous surgery.

Moderator: Silicone breast implants are said to cause problems. Can silicone in the eye cause problems?

Dr. Schmidt: Silicone in the eye can cause problems. As with any procedure, silicone is used when the benefits are felt to outweigh the risks.

P: If different surgeons apply Mitomycin C in different ways, how can results and complications from one study to another be compared?

Dr. Schmidt: We try to use standard techniques to control for that.

P: If a patient had a terribly damaged bleb after a trab with Mitomycin C and ended up with a shunt, would you use Mitomycin C on her other eye?

Dr. Schmidt: That depends again on how bad her glaucoma is, how low an IOP is necessary, etc. However, if there was a bad result with Mitomycin C, one would think twice before using it on the second eye. You might still have to bite the bullet, depending on the situation.

P: Why do wrinkles remain in the retina even when the IOP is raised again?

Dr. Schmidt: The wrinkles from low IOP can damage the retina, and the poor vision can persist even after the eye pressure rises.

P: My vision is 20/20 with pinhole, but I have a blind spot covering most of the upper portion of the visual field in my right eye. I had a trabeculectomy in that eye in 1995.

Dr. Schmidt: Presumably, the blind spot is the vision already lost to glaucoma before the IOP was lowered.

P: My most recent visual field test shows an increase in loss since the visual field test I took in March. I went to an ophthalmologist in 1985 because of a blind spot.

Dr. Schmidt: Did your doctor give you a reason for the increase in the defect in your visual field, such as errors in testing, too high an IOP, other possibilities?

P: One possibility the doctor mentioned was my upper eyelid drooped slightly during the test. The IOP in that eye is three. However, sometimes I lost fixation, which I understand can affect accuracy of the test.

Dr. Schmidt: Your doctor may want to repeat the field test.

P: I have a question about applying drops. We know we should occlude the tear duct for three minutes or so after applying drops. Dr. Spaeth recommends using a tissue to do this to absorb the excess. I didn’t do this before, because I would rarely feel any fluid outside the eye, but I have been trying it and the tissue is definitely moist. Is there any danger the tissue is “wicking” away too much medication?

Dr. Schmidt: No, if you can feel the eye get wet you have enough of the drop in. I usually have people block the tear duct for only one minute.

Moderator: Do you tell them to close the tear duct first?

Dr. Schmidt: No. I say, put the drop in, close the eye, block the tear duct, and keep the eye closed for one minute. That is most important if you are using beta blocker drops.

P: Dr. Rick says to keep the eye closed for three minutes, two at the least.

Dr. Schmidt: We’re all a little different. Like most things in life, if there is more than one way to do something, no particular way is probably much better than another.

Moderator: I try to keep my eye closed for at least one minute. After years and years, it gets harder, or am I just too hyper?

Dr. Schmidt: You can’t spend your whole life holding your tear duct closed.

Moderator: I really try hard when I use Betoptic. If I don’t, I feel tired later.

Dr. Schmidt: Beta blockers tend to have the most systemic side effects, and fatigue is common.

P: How long should one wait between two different kinds of drops?

Dr. Schmidt: I have patients wait five minutes minimum. Some say ten minutes but, again, you have to live your life.

P: Why are steroid eye drops for allergy (episcleritis) a risk for glaucoma?

Dr. Schmidt: Steroid eye drops can make the IOP rise dramatically.

P: Would a steroid-induced increase in IOP be immediate or could it happen long term?

Dr. Schmidt: It could be either.

P: What other side effects are there with steroid drops, such as Predforte?

Dr. Schmidt: The side effects can include cataract, infection, rebound inflammation, corneal thinning. It’s powerful stuff and should only be used on express direction by a doctor.

P: How much does IOP go up at night, if at all?

Dr. Schmidt: IOP usually drops at night, because the eye makes less fluid.

P: If IOP drops, say at night while you were sleeping, would you get any symptoms? Sometimes I get pain in my eyes that wakes me from a sound sleep. Is that significant?

Dr. Schmidt: Low IOP at night won’t cause eye pain. More likely, your eyes open slightly while you sleep and your cornea dries out.

P: That happened to my mother, and she wouldn’t believe me when I told her it was dryness. But it was! Celuvisc at night took care of it.

P: Sometimes, when I awaken in the morning, the eye with an IOP of three to four feels as though it’s swollen. When I put my fingertips on it, it feels very flat. Is that an indication of eye pressure?

Dr. Schmidt: If the IOP is always around three to four, the different feelings at different times of day are probably more related to surface (lid, cornea, bleb) issues than varying IOP.

P: Is a “funny looking” optic nerve in conjunction with visual field loss definitive for glaucoma?

Dr. Schmidt: No, not at all. In nearsighted people with, “funny looking” optic nerves can have a visual field defect unrelated to glaucoma.

P: What would distinguish nearsighted people with atypical optic nerves from actual glaucoma patients?

Dr. Schmidt: That depends on so many things: age, family history, eye pressure, other eye problems, refractive error, the kind of visual field defect. It has to be individualized. A visual field defect shouldn’t progress if it’s not glaucoma.

P: I have angle closure and shortly after waking I see faint haloes for about 30 minutes around some bright lights. I am then fine all day and evening. I am on Alphagan 2 times a day. Any clue to why I have these mild attacks in the a.m.?

Dr. Schmidt: Have you had iridectomies? If so, did your angle open afterwards?

P: Yes, I had iridectomies, but they don’t appear to still be open.

Dr. Schmidt: If your angle is open and you are having haloes, it would be good to get your IOP checked early in the morning. If the iridectomies are truly closed, then they need to be reopened.

P: The IOPs are about 31 during the halo events, then drop to 20. Could that be caused by a pupillary block, which dissipates when the pupil constricts?

Dr. Schmidt: The high IOP could be because of more fluid being made, which is often the case in the morning, or an outflow problem because of closed iridectomies. Your doctor should explain it to you.

P: He doesn’t seem very worried about it for now, since they are “mild.”

Dr. Schmidt: What is “mild?”

P: The attacks are mild compared to past attacks in the 80mm Hg range.

Dr. Schmidt: Frequent IOP rises to 31 could be capable of causing damage over time. Your doctor should document optic nerve appearance with photos and follow-up visual fields.

P: I have very tiny eyes and have had some real problems in the past year. We do have lots of photos, etc.

P: Are there risks with an iridectomy that a person should worry about?

Dr. Schmidt: There are risks with any surgical procedure, which one hopes your doctor will discuss with you. The risks include high eye pressure, inflammation, and infection if the iridectomy was done surgically, rather than with a laser.

P: My iridectomy would be done with a laser. Should I worry about risks? I’m age 43.

Dr. Schmidt: Risks are small, but not zero. Any eye doctor should discuss risks as well as benefits for any proposed procedure. There is no free lunch.

P: What are the benefits of an iridectomy when the angles are narrow?

Dr. Schmidt: To decrease the chance of the angle closing. Did your doctor explain what he or she wanted to do and why?

P: The iridectomy is being done to improve drainage. Will this lower my IOP?

Dr. Schmidt: If the angle isn’t already closed, the IOP should not change.

P: Is it unusual for one doctor to miss a drainage problem a week before another doctor saw it? I’m worried about an unnecessary iridectomy.

Dr. Schmidt: Narrow angles are often missed, and some doctors recommend unnecessary lasers. See a doctor you trust and follow his or her advice.

Moderator: I could not agree more. You have to trust your doctor.

Dr. Schmidt: But you can’t trust blindly (no pun intended) and you have to be informed.

P: Is an iridectomy painful?

Dr. Schmidt: Usually not. In an iridectomy, a hole is made in the iris either with a laser (the preferred way) or with surgery.

P: After an iridectomy, does the angle open because of better drainage?

Dr. Schmidt: The iridectomy allows the fluid behind the iris to come through, which decreases the forward pressure on the iris and allows it to fall back away from the cornea.

P: Can someone with open angle develop closed angle? I have heard “never,” then I have read “sometimes.”

Dr. Schmidt: The angle usually narrows slightly over time, so if it is wide open, it’s extremely rare for closed angle to develop. However, if the angle is open but slightly narrow, it can get more so over time, especially as cataract develops. That can close the angle.

P: Have you had patients with a funny-looking optic nerve that was mistaken for glaucoma?

Dr. Schmidt: Glaucoma specialists spend a lot of time trying to sort out who really has glaucoma and who has optic nerves that mimic glaucoma, so yes.

P: Can you recommend any glaucoma specialists in the Detroit or Ann Arbor (Michigan) area?

Dr. Schmidt: The University of Michigan in Ann Arbor should have good people. The glaucoma group of Dr. Hugh Beckmann and partners is also good.

P: Thanks, I think I’ll check out the University of Michigan. My present doctor seems to be making good decisions, but he never talks to me about them. I’d like to be kept informed of my treatment options.

Dr. Schmidt: You might let him know you want to know more. Unfortunately, some docs don’t explain as much as they might.

P: I think he feels a bit annoyed (maybe intimidated?) when I mention all the stuff I’ve learned through the Internet.

P: My doctor doesn’t like it either when I mention the Internet!

Dr. Schmidt: There is a lot of bad information on the Internet, so you need to use the information you gain to ask reasonable and informed questions. Some doctors are intimidated as patients know more.

P: Yes, but with the Glaucoma site and you and doctors Wilson, Spaeth, Myers, etc., our sources are the best! 🙂

Dr. Schmidt: I hope we provide good information, but it’s just a starting point for you with your doctor. Again, get a doctor you are comfortable with and trust, and go with it!

P: It was my hope that asking more informed questions — quoting specific research articles — would result in getting more information from my doctor. But it hasn’t happened.

Dr. Schmidt: Usually, quoting research is low yield. It’s better to use what you learn on the Net to ask informed and reasonable questions. If someone won’t answer reasonable questions, think twice.

P: I think “Internet” conjures up visions of a bunch of uninformed people exchanging information. That’s not what we have here. We have informed specialists answering thoughtful questions.

P: My doctor does not share my sense of urgency. He has a “let’s wait and see how this works” attitude. With optic nerves at .9 and 40% visual field loss, I feel near panic — and not inclined to wait until more damage occurs. Am I being unreasonable?

Dr. Schmidt: A reasonable question is, “am I stable or not?” If the answer is yes, the question is, “what is the evidence for this?” If the answer is no, the question is, “what are you going to do that is different to get me stable?”

Dr. Schmidt: I have to leave, folks. Best to all. Signing off now.

P: Goodnight doctor, and thank you for being here.

Dr. Schmidt: Glad to help.

End of highlights for July 5th chat.


About the Author:

The Glaucoma Service Foundation’s mission is to preserve or enhance the health of all people with glaucoma and to provide a model of medical care by supporting the educational and research efforts of the physicians on the Wills Eye Institute Glaucoma Service, the largest glaucoma diagnosis and treatment center in the country.
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